Safety of winch launch vrs. aero tow?

[Gary Boggs]

Someone must have already compared the safety of these tow launch methods.
What do the statistics show is the safer method of launch? Aero tow seems
to involve more inherent dangers to me. For one thing, there is just more
time for things to go wrong. What could be more dangerous than to tie tow
airplanes together and try to fly?

Gary Boggs

[Peter Seddon]

Hi

Having both winched and aerotowed several times!!! I find an aerotow less
demanding, everything happens very quickly on a winch wire.

Peter S
DLA


"Gary Boggs" > wrote in message
...
> Someone must have already compared the safety of these tow launch methods.
> What do the statistics show is the safer method of launch? Aero tow seems
> to involve more inherent dangers to me. For one thing, there is just more
> time for things to go wrong. What could be more dangerous than to tie tow
> airplanes together and try to fly?
>
> Gary Boggs
>
>

[Chris Nicholas]

It all depends on what you mean by statistics, and safer.

Harry Enfield (a UK comedian): "Flying is safe, you don't want to worry
about flying; it's crashing that's dangerous."

Winch launching and aerotowing are safe, it's the consequence of
mismanaging an abnormality that's dangerous.

Winch launches yield few accidents in themselves (e.g. occasional ground
loops); a competent pilot should have been trained in, and able to cope
with, a variety of abnormal situations such as cable breaks, too slow,
gradual power failure, etc. All of these are manageable with competent
handling. If badly handled, however, any can lead to a bad, even fatal,
accident. E.g. turning too low and slow after a cable break, leading to
a classic spin. But is that counted as a winch accident, or a failure to
monitor speed while turning close to the ground, i.e. a flight or
pre-landing accident? You may find that statistics are not compiled in
comparable ways over time, or between one club (or organisation, or
country) and another.

Aerotowing is more likely to kill the tug pilot than the glider pilot if
it goes wrong, i.e. the "tug upset" accident which seemed to start in
the 1970's. In terms of accidents per 100,000 launches, however, these
are rare. Oversimplifying to some extent, the only really dangerous
part of an aerotow where the competent glider pilot has little chance of
avoiding a bad accident is a rope break or power failure over bad
terrain, which is only applicable to a small proportion of sites (in my
experience).

Either method can lead very rarely to harm to second or third parties. I
know of one fatality to a ground handler associated with cable launch
operations (UK, 1970's). I know of other injuries from falling cables,
including one dead cow. There has probably been at least one instance
of somebody walking into a tug propellor, somewhere in the world. I
recall one tug accident where a child was a passenger in the tug and was
killed when it spun in (there is an argument for never carrying extra
people in the tug unless required for operational or training reasons -
it adds to the risk by reducing climb performance and increasing the
period of greatest hazard, as well as adding to the number of people at
risk in the operation - but many clubs seem to regard that as
acceptable).

There are some underlying causes of accidents that are more likely to be
found in the winch launch phase that in an aerotow - but could anyway
happen in the subsequent flight. A loose seat back leading to unintended
pitch up, and structural failure, are two I have heard of - winch
launches usually involve greater stresses and more extreme attitudes
than aerotows, unless the latter involve rotor or other adverse
conditions. But the subsequent flight could also have included
turbulence or other stress-inducing circumstances with equally tragic
results, if the problem had survived the launch phase - so should those
be counted as launch accidents?

Beware of the raw statistics.

Chris N.

[Mark Navarre]

Errors on the part of the winch driver may leave the glider pilot completely
"hung out to dry" with no risk whatsoever to the winch driver. During aerotow,
the tug pilot is not likely to make mistakes that might kill himself. The
incentive for a safe tow is thus higher for aerotow, because the tow pilot has
built-in accountability. I have driven the winch, and launched my glider by
tug, winch, and auto-tow. I prefer airtow over the other methods, but all can
be safe with proper training and pre-launch briefing.
-
Mark Navarre
ASW-20 OD
California, USA
-

[Eric Greenwell]

In article >,
says...
> Errors on the part of the winch driver may leave the glider pilot completely
> "hung out to dry" with no risk whatsoever to the winch driver. During aerotow,
> the tug pilot is not likely to make mistakes that might kill himself.

Of course, the winch operator can't make mistakes that will kill him
or her. In addition, I think a major advantage of the winch launch is
the glider pilot can't kill the winch operator! Unfortunately, tug
pilots have put themselves at risk (and been killed because of it)
because of a concern for the glider pilot that is putting the tug
pilot at risk. Sometimes this is just running out of fuel because they
don't want to slow down the launch line; sometimes it's hesitating to
pull the release when low over bad ground.

Personally, I suspect the glider pilot is a little better off behind a
towplane (might be my US training bias), but I have no idea if the
statistics agree with me. The UK and Europe might be able to do a good
comparison, but in the US, winch launching is done in only a few
places.
--
!Replace DECIMAL.POINT in my e-mail address with just a . to reply
directly

Eric Greenwell
Richland, WA (USA)

[Bob Johnson]

Mark,

I don't think the winch op can't leave anybody out to dry except maybe
himself. If the glider pilot doesn't like what's happening, pull
release, pull spoilers, land straight ahead.

BJ

Mark Navarre wrote:
>
> Errors on the part of the winch driver may leave the glider pilot completely
> "hung out to dry" with no risk whatsoever to the winch driver. During aerotow,
> the tug pilot is not likely to make mistakes that might kill himself. The
> incentive for a safe tow is thus higher for aerotow, because the tow pilot has
> built-in accountability. I have driven the winch, and launched my glider by
> tug, winch, and auto-tow. I prefer airtow over the other methods, but all can
> be safe with proper training and pre-launch briefing.
> -
> Mark Navarre
> ASW-20 OD
> California, USA
> -

[Bill Daniels]

"Gary Boggs" > wrote in message
...
> Someone must have already compared the safety of these tow launch methods.
> What do the statistics show is the safer method of launch? Aero tow seems
> to involve more inherent dangers to me. For one thing, there is just more
> time for things to go wrong. What could be more dangerous than to tie tow
> airplanes together and try to fly?
>
> Gary Boggs
>
>

I have done a whole lot of both and, given a choice, I'll take winch launch.

Yes, things happen fast on a winch launch but then the launch is over in
30-40 seconds so the risk exposure is short - with air tow, you are at risk
a least ten times as long. Air tow in turbulent air is fatiguing - you will
never get tired in a 35 second winch launch.

If you don't like the way a winch launch is going, release and land. You
can do that with a winch launch because you should always be in a position
to land back on the runway - I can't say that is always true with air tow.

Air tow is formation flying - involving two extremely mis-matched aircraft -
with a rope tying them together. This requires highly developed flying
skills to do safely. We teach this to pre-solo students. (I wonder how we
get away with it.) Winch launch can easily be taught to pre-solo pilots
since it is a simple, repetitive task.

Air tow has two aircraft at risk and at least two pilots - winch launch has
only one aircraft at risk.

Winch launch accelerates the glider far faster than air tow so dropping a
wing due to insufficient aileron control is unlikely. (Of course, you can
still drop a wing due to incompetence with unhappy results.)

In both cases, the training of the pilots and launch crews have a lot to due
with overall safety. There is ample opportunity for either to come to a bad
end. With equally good training, I think winch launch is safer.

But, lets face it - winch launch LOOKS scary to a pilot trained that a steep
nose-up attitude near the ground is dangerous. It isn't dangerous but it
sure looks that way.

Bill Daniels

[BTIZ]

and then you'll be nearer the winch operator for a little face to face
coordination..

BT

"Bob Johnson" > wrote in message
...
> Mark,
>
> I don't think the winch op can't leave anybody out to dry except maybe
> himself. If the glider pilot doesn't like what's happening, pull
> release, pull spoilers, land straight ahead.
>
> BJ
>
> Mark Navarre wrote:
> >
> > Errors on the part of the winch driver may leave the glider pilot
completely
> > "hung out to dry" with no risk whatsoever to the winch driver. During
aerotow,
> > the tug pilot is not likely to make mistakes that might kill himself.
The
> > incentive for a safe tow is thus higher for aerotow, because the tow
pilot has
> > built-in accountability. I have driven the winch, and launched my
glider by
> > tug, winch, and auto-tow. I prefer airtow over the other methods, but
all can
> > be safe with proper training and pre-launch briefing.
> > -
> > Mark Navarre
> > ASW-20 OD
> > California, USA
> > -

[Bob Johnson]

No man, you need to do one and then you'll understand what I'm saying.

BJ


BTIZ wrote:
>
> and then you'll be nearer the winch operator for a little face to face
> coordination..
>
> BT
>
> "Bob Johnson" > wrote in message
> ...
> > Mark,
> >
> > I don't think the winch op can't leave anybody out to dry except maybe
> > himself. If the glider pilot doesn't like what's happening, pull
> > release, pull spoilers, land straight ahead.
> >
> > BJ
> >
> > Mark Navarre wrote:
> > >
> > > Errors on the part of the winch driver may leave the glider pilot
> completely
> > > "hung out to dry" with no risk whatsoever to the winch driver. During
> aerotow,
> > > the tug pilot is not likely to make mistakes that might kill himself.
> The
> > > incentive for a safe tow is thus higher for aerotow, because the tow
> pilot has
> > > built-in accountability. I have driven the winch, and launched my
> glider by
> > > tug, winch, and auto-tow. I prefer airtow over the other methods, but
> all can
> > > be safe with proper training and pre-launch briefing.
> > > -
> > > Mark Navarre
> > > ASW-20 OD
> > > California, USA
> > > -

[Bob Johnson]

Here's an interesting point of reference:

Proper pilot life-saving reaction to winch line breaks, op inattention,
winch engine failure, or op incapacitation is routinely taught in ground
launch training.

How many airtow instructors pull the release on their student at 200 ft
over the outbound fence? Just once? Several times?

BJ

Gary Boggs wrote:
>
> Someone must have already compared the safety of these tow launch methods.
> What do the statistics show is the safer method of launch? Aero tow seems
> to involve more inherent dangers to me. For one thing, there is just more
> time for things to go wrong. What could be more dangerous than to tie tow
> airplanes together and try to fly?
>
> Gary Boggs

[Gary Boggs]

I like all these points and I suspect that because of the short time
required in a winch launch, and the faster acceleration, and the fact that
you are in a position to land on the runway that you are using at all times,
the winch launch would be safer, but I still see no statistics! Come on
folks, someone surly has crunched the numbers. Training is crucial in both,
but what I'm looking for is numbers, I have plenty of opinions myself.

Boggs


"Bill Daniels" > wrote in message
k.net...

"Gary Boggs" > wrote in message
...
> Someone must have already compared the safety of these tow launch methods.
> What do the statistics show is the safer method of launch? Aero tow seems
> to involve more inherent dangers to me. For one thing, there is just more
> time for things to go wrong. What could be more dangerous than to tie tow
> airplanes together and try to fly?
>
> Gary Boggs
>
>

I have done a whole lot of both and, given a choice, I'll take winch launch.

Yes, things happen fast on a winch launch but then the launch is over in
30-40 seconds so the risk exposure is short - with air tow, you are at risk
a least ten times as long. Air tow in turbulent air is fatiguing - you will
never get tired in a 35 second winch launch.

If you don't like the way a winch launch is going, release and land. You
can do that with a winch launch because you should always be in a position
to land back on the runway - I can't say that is always true with air tow.

Air tow is formation flying - involving two extremely mis-matched aircraft -
with a rope tying them together. This requires highly developed flying
skills to do safely. We teach this to pre-solo students. (I wonder how we
get away with it.) Winch launch can easily be taught to pre-solo pilots
since it is a simple, repetitive task.

Air tow has two aircraft at risk and at least two pilots - winch launch has
only one aircraft at risk.

Winch launch accelerates the glider far faster than air tow so dropping a
wing due to insufficient aileron control is unlikely. (Of course, you can
still drop a wing due to incompetence with unhappy results.)

In both cases, the training of the pilots and launch crews have a lot to due
with overall safety. There is ample opportunity for either to come to a bad
end. With equally good training, I think winch launch is safer.

But, lets face it - winch launch LOOKS scary to a pilot trained that a steep
nose-up attitude near the ground is dangerous. It isn't dangerous but it
sure looks that way.

Bill Daniels

[Bill Daniels]

"Gary Boggs" > wrote in message
...
> I like all these points and I suspect that because of the short time
> required in a winch launch, and the faster acceleration, and the fact that
> you are in a position to land on the runway that you are using at all
times,
> the winch launch would be safer, but I still see no statistics! Come on
> folks, someone surly has crunched the numbers. Training is crucial in
both,
> but what I'm looking for is numbers, I have plenty of opinions myself.
>
> Boggs

OK, the BGA accident database is available on the web. The database is
searchable for flights that began with a winch launch. Note, however, that
most of the accidents in this section do not relate directly to winch
launch.
I think that there were only three or four accidents over a ten year period
that actually happened during the winch launch. The rest were accidents
that happened later in a flight that began with a winch launch.

It seems to me that if winch launch accident data is hard to come by, that
in itself is good news. If accidents happened frequently, there would be
lots of hard data.

Bill Daniels

[JJ Sinclair]

Gary,
I suspect you are considering winch launching for your club and I would think
the biggest problem would be in getting club members, "Up to Speed" on winch
operations.

In way of illustrating my point, allow me to tell a little story about a local
soaring operation that is no longer in business. This outfit advertised, get
your "Aero-Tow Only" restriction, removed from your glider licence. Come to XXX
Soaring and we will check you out in about an hour, or so. This outfit had a
2-33 with only a nose tow hook (mistake no. 1) They didn't use radios (mistake
no. 2) The flight examiner weighed a good 300 lb. + your average student at 200
lb. = 500 lb's in the 2-33 (mistake no. 3)

I was going to take the course, but had to wait for the student in front of me
to get his check-out. The signal for "Start the launch" was, level the wings
and flash the lights in the car located near the right wing tip. It went
something like this:

1. Level the wings & flash the lights------------Glider rolled about 10 feet
and stopped. winch operator stalled the winch.

2. Level the wings & flash the lights---------- Cable went, but glider didn't
move. In the last attempt, wheel had rolled over cable and caused a reverse
release.

3.Level the wings & flash the lights---------------Glider went about 100 feet
and stopped. Cable had "Kinked" in previous 2 attempts and then broke at a
kink.

-------------30 minute delay while Nico-Press & sleves are found and cable is
spliced. With 3 attempts and no success, student is having second thoughts and
opens canopy and starts to climb out. Instructor tells him, everything will be
fine, this time, Get back in here.

4. Level the wings & flash the lights------------ Glider takes off, to the wild
applause of all those assembled. Glider only gets 400 feet due to nose tow hook
location. Glider makes a 90 right and a 180 left, lands and rolls right up to
the starting point.

Attempts 5, 6 & 7 come off without a hitch and the Flight Examiner is called
out (300 lbs)

Level the wings & flash the lights-------------- Glider takes off, but only
gets 300 feet, makes a modified 90/180 and plunks it down hard, way down the
runway.

I took this opportunity to silently disappear and my licence still reads,
Aero-Tow Only.
JJ Sinclair

[Andreas Maurer]

On 26 Oct 2003 15:04:10 GMT, (JJ Sinclair) wrote:


>I took this opportunity to silently disappear and my licence still reads,
>Aero-Tow Only.

I have to admit it: I'm impressed.
They really made every mistake that is possible. Thiw "insch launch"
attempts had as much in common with winch launching as a 2-33 has in
common with a Boeing 747.


Bye
Andreas

[Mark Navarre]

Bill Daniels writes:

>If you don't like the way a winch launch is going, release and land. You
>can do that with a winch launch because you should always be in a position
>to land back on the runway - I can't say that is always true with air tow.

This brings up a point I left out of my original post. The SITE must be
suitable for winch launching. If the site has a short runway, or obstructions,
then the option to release and land straight ahead may be limited. Of course
this applies to aerotow as well.

>Winch launch accelerates the glider far faster than air tow so dropping a
>wing due to insufficient aileron control is unlikely. (Of course, you can
>still drop a wing due to incompetence with unhappy results.)

If the winch operator does not apply adequate power for rotation and climb
early in the launch, the window of opportunity to abort safely closes quickly
and leaves unsuitable options.

>In both cases, the training of the pilots and launch crews have a lot to due
>with overall safety. There is ample opportunity for either to come to a bad
>end. With equally good training, I think winch launch is safer.

I wholeheartedly agree that training, and practice, are of great importance. I
had a winch launch accident early this year in which training played a large
part. Also reaction time, and the limited suitability of the site for winch
launching.
I will give a brief description of the accident:
I did not brief the winch driver on my launch requirements (mistake 1), my
glider had the highest wingloading of any there that day.
The initial acceleration from a stop was weak enough in comparison to all my
previous training on this winch to make the hair on the back of my neck stand
up. I had enough room to wait for more power (mistake 2) but was too low and
slow to wag wings. I briefly pulled back on the stick to see if there was any
tension on the cable, maybe the winch had redlined in a lower gear (the winch
in question has known issues, mistake 3). I felt the tension completely go
away, pulled the release and pushed the nose over. I was not aggressive with
the push over (mistake 4), but altitude was only 50-75 feet and the glider was
just above stall, so not enough room to gain speed, no room to land straight
ahead, and insufficient altitude to complete a turn to the right for a landing
on the abort runway.
I dragged the right wing and ground looped, breaking the tail boom of my
glider, and narrowly missed a Toyota truck that was parked in an unsafe area.
During debrief, I found out that the winch driver saw the retrieve chute
balloon immediately and thought I released so chopped the winch power. Chute
blossoming was common that day on previous launches due to improper chute
rigging (mistake 5) and this was probably exaggerated by the lack of full power
during the initial part of the launch. The site has about 1000 feet of usable
straight ahead runway, but it is downhill from glider to winch, and a portion
is steep enough so as to be impossible to walk uphill if the dirt is wet. The
abort runway is at a right angle to the launch runway, undulates in elevation
30-40 feet, and has a narrow spot about 60 feet wide bordered by trees and
bushes.
The dimensions of the site are such that there is a point in the launch when
you may be too high to land straight ahead, too low to continue into the ridge
lift, and too low to make the landable portion of the abort runway. The
situation is worse for higher wingloading gliders (I fly an ASW20) than are
typically flown at this site. Some of you may have guessed the site by now, it
is Torrey Pines, California. Having had this experience, I would fly there
again, but only after addressing the training and briefing issues mentioned.
The configuration of this site requires extra special attention to launch
procedures, but the satisfaction of flying at such a unique and historic
location is well worth it.


-
Mark Navarre
ASW-20 OD
California, USA
-

[Ralph Jones]

On 26 Oct 2003 15:04:10 GMT, (JJ Sinclair) wrote:
[snip]
>
>I took this opportunity to silently disappear and my licence still reads,
>Aero-Tow Only.

I have a co-worker who's still around because he made the same shrewd
decision in connection with a bungee-jumping operation...

rj

[Bob Johnson]

Anyone who is seriously interested in ground launches should read and
understand Derek Piggott's great book "Ground Launches".

Thanks, Derek!

BJ

Gary Boggs wrote:
>
> Someone must have already compared the safety of these tow launch methods.
> What do the statistics show is the safer method of launch? Aero tow seems
> to involve more inherent dangers to me. For one thing, there is just more
> time for things to go wrong. What could be more dangerous than to tie tow
> airplanes together and try to fly?
>
> Gary Boggs

[Pete Brown]

Try tying a glider to a truck to fly.

>
> Gary Boggs wrote:
>> What could be more dangerous than to tie two
>> airplanes together and try to fly?
>>
>>Gary Boggs

--

Peter D. Brown
http://home.gci.net/~pdb/
http://groups.yahoo.com/group/akmtnsoaring/

[Mike Borgelt]

On Sat, 25 Oct 2003 12:43:35 -0700, "Gary Boggs"
> wrote:

>Someone must have already compared the safety of these tow launch methods.
>What do the statistics show is the safer method of launch? Aero tow seems
>to involve more inherent dangers to me. For one thing, there is just more
>time for things to go wrong. What could be more dangerous than to tie tow
>airplanes together and try to fly?
>
>Gary Boggs
>

I've only done about two winch launches but have done several hundred
car tows and driven several hundred also.

Ground launches involve lots of wire, rope etc. It is probably a good
observation that the more rope you have the more trouble you can get
into! With one exception below.

I've had the glider run over the wire and tangle in the wheel well.
Not good as you now cannot release and depend on the tow driver..

Pilot reactions to a low altitude winch launch failure are utterly
critical. I suspect we've killed dozens if not hundreds over the years
this way around the world.

You may need more than one launch to get away(rare with aerotow). This
increases your launch risk exposure.

Someone mentioned the stresses in the wire and the glider. Both are
much lower in properly executed arotow.

Aero tow may have a higher exposure to an off airport landing in
unsuitable terrain but the failures seem to be much more rare than
winch wire breaks. If you don't use toy towplanes(less than 180HP)
then any place suitable for winching probably gives you the
opportunity to do a 180 or land straight ahead from an aerotow.

If you want gliding to be popular aerotow involves less running around
on the ground per flight hour.

Flying towplanes is more fun than driving a winch or tow
car.(Allegedly - I last sat in a towplane in 1971 writing down CHT's
for the cooling test for 4 tows in a row and haven't felt motivated to
get into a towplane since despite the aquisition of a PPL 9 years ago)

Aerotowing danger can be reduced by using a longer rope. One of the
local clubs around here tried it and liked it so much the towpilots
won't fly with short ropes. The long rope gives everyone more time to
handle upsets. I suspect the rise of the towplane upset accident
coincided with using shorter ropes.

Mike Borgelt

[Bill Daniels]

"JJ Sinclair" > wrote in message
...
> Gary,
> I suspect you are considering winch launching for your club and I would
think
> the biggest problem would be in getting club members, "Up to Speed" on
winch
> operations.
>
> In way of illustrating my point, allow me to tell a little story about a
local
> soaring operation that is no longer in business. This outfit advertised,
get
> your "Aero-Tow Only" restriction, removed from your glider licence. Come
to XXX
> Soaring and we will check you out in about an hour, or so. This outfit had
a
> 2-33 with only a nose tow hook (mistake no. 1) They didn't use radios
(mistake
> no. 2) The flight examiner weighed a good 300 lb. + your average student
at 200
> lb. = 500 lb's in the 2-33 (mistake no. 3)
>
> I was going to take the course, but had to wait for the student in front
of me
> to get his check-out. The signal for "Start the launch" was, level the
wings
> and flash the lights in the car located near the right wing tip. It went
> something like this:
>
> 1. Level the wings & flash the lights------------Glider rolled about 10
feet
> and stopped. winch operator stalled the winch.
>
> 2. Level the wings & flash the lights---------- Cable went, but glider
didn't
> move. In the last attempt, wheel had rolled over cable and caused a
reverse
> release.
>
> 3.Level the wings & flash the lights---------------Glider went about 100
feet
> and stopped. Cable had "Kinked" in previous 2 attempts and then broke at a
> kink.
>
> -------------30 minute delay while Nico-Press & sleves are found and cable
is
> spliced. With 3 attempts and no success, student is having second thoughts
and
> opens canopy and starts to climb out. Instructor tells him, everything
will be
> fine, this time, Get back in here.
>
> 4. Level the wings & flash the lights------------ Glider takes off, to the
wild
> applause of all those assembled. Glider only gets 400 feet due to nose tow
hook
> location. Glider makes a 90 right and a 180 left, lands and rolls right up
to
> the starting point.
>
> Attempts 5, 6 & 7 come off without a hitch and the Flight Examiner is
called
> out (300 lbs)
>
> Level the wings & flash the lights-------------- Glider takes off, but
only
> gets 300 feet, makes a modified 90/180 and plunks it down hard, way down
the
> runway.
>
> I took this opportunity to silently disappear and my licence still reads,
> Aero-Tow Only.
> JJ Sinclair

What JJ experienced is, unfortunately, an all too common experience in the
USA.

A bunch of guys, (it's usually guys) get together and decide to winch launch
gliders. ("How hard can it be?" "We can teach ourselves...") They start
with poor equipment, a bad site, no experience or training and proceed to
scare themselves badly...or worse.

They then decide that the problem is winch launch (It doesn't work, low
releases, lots of hassles, etc..) and then go back to air tow.

I've flown tugs and driven winches - I'll take winches for fun. I've flown
lots of air tow and been scared on plenty of occasions. I've flown lots of
winch launches and rarely had one go wrong. If anybody wants a winch
experienced CFI-G for a week of winch training, email me. I might be
available.

BTW, How about some of our British and European friends with lots of winch
experience jumping in here?

Bill Daniels

[Stefan]

Bill Daniels wrote:

>> BTW, How about some of our British and European friends with lots of winch
> experience jumping in here?

I can't speak for others, but I read this thread, shaked my head and
simply didn't feel like commenting. Seldom I have seen a discussion
which showed so clearly plain ignorance.

In a word: If done correctly, winch launching is safe, cheap and fun. It
is certainly much (much!) cheaper than aero-tow. It is certainly much
more fun. And it's easier, too.

The only dangerous moment for the pilot is at the very beginning of the
pull. It is very very very important not to pull too early or too
briskly. Stalling the glider at this altitude is lethal. Once
established in the climb, make sure you have always enough speed to pull
over if the rope breaks. Everything else is very easy and very safe.
There *are* rope breaks, but they are very much a non-event. Either you
have enough room to land straight, or you have enough altitude to do a
180 or a short circuit.

Winch launching has much more safety issues for the ground crew and
spectators than for the pilot. Be sure to have an experienced person
show you safe procedures.

Of course, an experienced winch driver helps a lot, too. At our club, a
new winch driver must do 50 launches under supervision befor he's
allowed to winch alone. We never had a winch accident in 40 years.

Stefan

[Stefan]

Bill Daniels wrote:

>> BTW, How about some of our British and European friends with lots of
winch
>
> experience jumping in here?


I can't speak for others, but I read this thread, shaked my head and
simply didn't feel like commenting. Seldom I have seen a discussion
which showed so clearly plain ignorance.

In a word: If done correctly, winch launching is safe, cheap and fun. It
is certainly much (much!) cheaper than aero-tow. It is certainly much
more fun. And it's easier, too.

The only dangerous moment for the pilot is at the very beginning of the
pull. It is very very very important not to pull too early or too
briskly. Stalling the glider at this altitude is lethal. Once
established in the climb, make sure you have always enough speed to push
over if the rope breaks. Everything else is very easy and very safe.
There *are* rope breaks, but they are very much a non-event. Either you
have enough room to land straight, or you have enough altitude to do a
180 or a short circuit.

Winch launching has much more safety issues for the ground crew and
spectators than for the pilot. Be sure to have an experienced person
show you safe procedures.

Of course, an experienced winch driver helps a lot, too. At our club, a
new winch driver must do 50 launches under supervision befor he's
allowed to winch alone. We never had a winch accident in 40 years.

Stefan

[Bill Daniels]

"Stefan" > wrote in message
...
> Bill Daniels wrote:
>
> >> BTW, How about some of our British and European friends with lots of
winch
> > experience jumping in here?
>
> I can't speak for others, but I read this thread, shaked my head and
> simply didn't feel like commenting. Seldom I have seen a discussion
> which showed so clearly plain ignorance.
>
> In a word: If done correctly, winch launching is safe, cheap and fun. It
> is certainly much (much!) cheaper than aero-tow. It is certainly much
> more fun. And it's easier, too.
>
> The only dangerous moment for the pilot is at the very beginning of the
> pull. It is very very very important not to pull too early or too
> briskly. Stalling the glider at this altitude is lethal. Once
> established in the climb, make sure you have always enough speed to pull
> over if the rope breaks. Everything else is very easy and very safe.
> There *are* rope breaks, but they are very much a non-event. Either you
> have enough room to land straight, or you have enough altitude to do a
> 180 or a short circuit.
>
> Winch launching has much more safety issues for the ground crew and
> spectators than for the pilot. Be sure to have an experienced person
> show you safe procedures.
>
> Of course, an experienced winch driver helps a lot, too. At our club, a
> new winch driver must do 50 launches under supervision befor he's
> allowed to winch alone. We never had a winch accident in 40 years.
>
> Stefan
>
Thanks, Stefan, we need to hear more of this sort of thing.

Bill Daniels

[E. A. Grens]

JJ -

I, as a power pilot, learned to fly sailplanes on the winch, overseas. I
now only fly aerotow, and am not signed off for ground launch. One thing I
have not seen mentioned is the qualification of winch operators. Tow plane
pilots ( I'm not one) have to meet certain standards and be signed off. I
became a winch operator by volunteering out of club spirit (stupidty?). I
was informally instructed by a winch operator who desparately wanted to
escape the exile of the winch. Then I was left to do the job, getting my
flights at the end of the day. They brought me food and drink
(nonalcholic), but no one "qualified" on the winch would come near for
hours. I'm sure I never endangered any aircraft or pilot, but I'm also sure
that some achieved less than optimal release altitude. There was no
tensionmeter, and throttle control was based on visual evaluation of
aircraft attitude and cable sag.

Many years later I had the chance to observe the operator of a modern
six-reel winch at Terlet. He was an artist at work, and he had the best
equipment.

I think winch launches are safe, as long as you have a cg hook. But, in any
comparison to aerotow, the increased number of launches necessary to achieve
sustained flight must be taken into account.

Ed Grens

[John Giddy]

"Bill Daniels" > wrote in message
ink.net...
| A bunch of guys, (it's usually guys) get together and
decide to winch launch
| gliders. ("How hard can it be?" "We can teach
ourselves...") They start
| with poor equipment, a bad site, no experience or training
and proceed to
| scare themselves badly...or worse.
|
| They then decide that the problem is winch launch (It
doesn't work, low
| releases, lots of hassles, etc..) and then go back to air
tow.
|
| I've flown tugs and driven winches - I'll take winches for
fun. I've flown
| lots of air tow and been scared on plenty of occasions.
I've flown lots of
| winch launches and rarely had one go wrong. If anybody
wants a winch
| experienced CFI-G for a week of winch training, email me.
I might be
| available.
|
| BTW, How about some of our British and European friends
with lots of winch
| experience jumping in here?

Not from UK or Europe, but Australia:
There are a number of clubs, ours included that usually
launch by winch.
In Oz, all gliding is controlled by The Gliding Federation
of Australia, under a delegation from CASA (the Aussie FAA)
GFA has a regulation setting the minimum length of field for
winch launching to 1200 metres (approx 4000 ft). This is to
avoid the possibility of a "non-manoeuvring" area, where, if
the cable breaks, there is insufficient length to land
straight ahead, and not high enough to do a modified circuit
and land normally.
There are standard procedures which are taught, involving
signals between the pilot and the winch driver, and
procedure for dealing with cable breaks. These are taught
and practiced during the winch launch training. There is an
agreed minimum number of launches (12) before sign-off for
anyone converting from aerotow.
Provided you have a good winch, with sufficient power, and
an experienced driver, it is a very safe and efficient way
to get into the air.
It is also quiet, which is a boon for those fields close to
built-up areas.
Cheers, John G.

[tango4]

"Mike Borgelt" > wrote in message
...
>
> If you want gliding to be popular aerotow involves less running around
> on the ground per flight hour.
>

A cable retrieve winch such as the one in use at the Long Mynd in the UK
makes a winch operation even slicker than aerotowing!

Ian

[John Mason]

A good place for statistics is:

http://www.esgc.co.uk/BGAdata.htm

Search and study the reports. There is much written between the lines. If
you look at the number of accidents where the launch was originally a winch
launch you will find that a lot of accidents occur soon after the launch is
completed and are attributed to other factors but which would really not
have happened if they had aerotowed. (Rigging errors not found in the speed
of the launch, not watching airspeed and spinning after the launch because
of distraction with the high workload of the winch and not dealing with the
angle of attack in the launch properly and so on). It is not possible to
give clear cut statistics without a significant degree of human
interpretation and you will really need to make your own mind up. I am
certain winching is a lot more dangerous. There are more things that can go
wrong and if they can go wrong, they will given time.


"Gary Boggs" > wrote in message
...
> I like all these points and I suspect that because of the short time
> required in a winch launch, and the faster acceleration, and the fact that
> you are in a position to land on the runway that you are using at all
times,
> the winch launch would be safer, but I still see no statistics! Come on
> folks, someone surly has crunched the numbers. Training is crucial in
both,
> but what I'm looking for is numbers, I have plenty of opinions myself.
>
> Boggs
>

[Jona]

"Bob Johnson" > wrote in message
...
> Here's an interesting point of reference:
>
> Proper pilot life-saving reaction to winch line breaks, op inattention,
> winch engine failure, or op incapacitation is routinely taught in ground
> launch training.
>
> How many airtow instructors pull the release on their student at 200 ft
> over the outbound fence? Just once? Several times?
>
> BJ
>
> Gary Boggs wrote:
> >
> > Someone must have already compared the safety of these tow launch
methods.
> > What do the statistics show is the safer method of launch? Aero tow
seems
> > to involve more inherent dangers to me. For one thing, there is just
more
> > time for things to go wrong. What could be more dangerous than to tie
tow
> > airplanes together and try to fly?
> >
> > Gary Boggs

Bob;
Right, I thik this is really imprtant.
On tow, at 200 ft over the far-boundary you need the confidence to
know the right thing to do and do it straight away while retaing air-speed.
On tows we take of saying to oursevles 'land-ahead if it breaks now' from 0
to 150 feet
but there is a sweaty bit between150 and 300 ft where the choices are less
attractive.
In a winch lanuch (probably becauseof more experience) I am never in this
sweaty "hope it don't break at just this second" position.


--

Jonathan

[Mike Borgelt]

On Mon, 27 Oct 2003 05:41:06 +0000 (UTC), "tango4"
> wrote:

>
>"Mike Borgelt" > wrote in message
...
>>
>> If you want gliding to be popular aerotow involves less running around
>> on the ground per flight hour.
>>
>
>A cable retrieve winch such as the one in use at the Long Mynd in the UK
>makes a winch operation even slicker than aerotowing!
>
>Ian
>


So how many winch operations involve two people?
I've had tows where the only people present were the tow pilot and the
glider pilot. Least I got with auto tow was three. Both were no radio
ops.

And for you guys who operate on nice green grass airfields which allow
things like cable retrieve winches - it don't happen in Oz.

And lastly we did have a winch driver killed during a winch launch a
few years ago. The wire (basically high tensile single strand fencing
wire) shattered as it was being reeled in after the glider released
and one of the pieces of shrapnel hit the winch driver in the upper
torso and he died shortly thereafter before anyone got to the winch.
The lexan shield had been bought but not installed.

My favourite launch method involves a motor in the glider.

Mike Borgelt

[Silent Flyer]

> >"Mike Borgelt" > wrote in message
> ...
>
> And for you guys who operate on nice green grass airfields which allow
> things like cable retrieve winches - it don't happen in Oz.
>
***********
You have obviously never been to the Long Mynd - I have heard it described
rather unkindly) as " a barely levelled granite hilltop".

The retrieve system ( a small winch pulls the cable back to the launch
point) originated out of necessity many many years ago when the airfield was
much smaller and the winch had to be positioned outside the boundary. The
cable crossed a deep, (approx 15/20 ft) gully at the airfield boundary and
then on up along a slope covered in bracken and heather, any other method of
retrieving the cable was impracticable. However the system was so efficient
in terms of launch rates that it has continued to this day even though the
airfield is now big enough to site the winch within the boundary. There is
of course a small penalty in terms of launch height but this is of little
significance.

[Owain Walters]

I have about 1800 hours and I would say that 80% of
my flying is from winch launching.

My club operates primarily from the winch launch. When
our club was a bit busier we completed anything up
to 120 winch launches a day.

Winch launching, like anything in flying, is completely
safe if people are trained properly. I am not going
to teach people how to winch launch over the internet
but I will say that the number one rule is never to
get yourself into a situation from which you can not
recover with the energy (whether kinetic or potential)
you have. Put simply - never climb steeply from the
ground, always maintain an shallow 'initial' climb
until you reach a safe height and speed.

Winch launching is more Labour intensive than aerotowing
as you need a winch-driver, a cable retrieve driver,
a competent and experienced person making the decisions
and supervising and a wingrunner. However, for a training
environment it is certainly much, much cheaper and
fosters a 'club' atmosphere as everyone relies on eachother
to make things happen.

I do not know any statistics of winching vs. aerotowing
and frankly I think that statistics are, in general,
irrelevant in gliding (just look at the US contest
finish stats, I counted 4 in the last 17 years but
people think this is an area out of control in the
US). But what I do know is that I have never been in
a situation where I could not land safely on the airfield
in the event of a launch failure and I have never just
cleared the boundary hedge by a matter of inches (my
gratitude to the tug pilot for not dumping me has been
expressed many times in the form of beer) in a Duo
full of water on a winch launch either.

Having said that,I also feel that aerotows are also
safe when given that the equipment is regularly inspected
(whether it be the tug or rope) and that the landing
options are fully researched/explained prior to take
off. I have never not considered an aerotow because
I felt it was unsafe.

I guess my point is that both types are utterly safe
if people are trained and have a plan if things go
wrong, again like most situations in flying.

[Bill Daniels]

"John Mason" > wrote in message
...
> A good place for statistics is:
>
> http://www.esgc.co.uk/BGAdata.htm
>
> Search and study the reports. There is much written between the lines.
If
> you look at the number of accidents where the launch was originally a
winch
> launch you will find that a lot of accidents occur soon after the launch
is
> completed and are attributed to other factors but which would really not
> have happened if they had aerotowed. (Rigging errors not found in the
speed
> of the launch, not watching airspeed and spinning after the launch because
> of distraction with the high workload of the winch and not dealing with
the
> angle of attack in the launch properly and so on). It is not possible to
> give clear cut statistics without a significant degree of human
> interpretation and you will really need to make your own mind up. I am
> certain winching is a lot more dangerous. There are more things that can
go
> wrong and if they can go wrong, they will given time.
>

John, the only way to see the data in the way you suggest is with a
prejudiced eye. If a pilot can't fly a glider under stress or rig it
properly, he's just an accident looking for a place to happen. It doesn't
matter how the glider is launched.

Bill Daniels

[Bert Willing]

A winch driver won't get killed if the winch is equipped properly. And a
cable breaking near the winch under full power is something very, very
dangerous, so sitting on a winch without shielding is asking to be killed.

The min team for winch launches is the pilot, the winch driver and the wing
runner (the winch driver can retrieve the cables on his own if the winch has
properly working brakes on the drums). If pilot and winch driver are
suffiencently experienced, a chair may well replace the wingrunner (although
stating that in public may not be politically correct :-)

During winch launch, any accident is related to pilot errors so you can
basically keep the accident rate fairly low.

On aerotows you may have situations were a cable break *will* induce an
accident, and the pilot may just be able to influence the damage.

--
Bert Willing

ASW20 "TW"


"Mike Borgelt" > a écrit dans le message de
...
> On Mon, 27 Oct 2003 05:41:06 +0000 (UTC), "tango4"
> > wrote:
>
> >
> >"Mike Borgelt" > wrote in message
> ...
> >>
> >> If you want gliding to be popular aerotow involves less running around
> >> on the ground per flight hour.
> >>
> >
> >A cable retrieve winch such as the one in use at the Long Mynd in the UK
> >makes a winch operation even slicker than aerotowing!
> >
> >Ian
> >
>
>
> So how many winch operations involve two people?
> I've had tows where the only people present were the tow pilot and the
> glider pilot. Least I got with auto tow was three. Both were no radio
> ops.
>
> And for you guys who operate on nice green grass airfields which allow
> things like cable retrieve winches - it don't happen in Oz.
>
> And lastly we did have a winch driver killed during a winch launch a
> few years ago. The wire (basically high tensile single strand fencing
> wire) shattered as it was being reeled in after the glider released
> and one of the pieces of shrapnel hit the winch driver in the upper
> torso and he died shortly thereafter before anyone got to the winch.
> The lexan shield had been bought but not installed.
>
> My favourite launch method involves a motor in the glider.
>
> Mike Borgelt

[Martin Gregorie]

On Mon, 27 Oct 2003 09:16:58 +0000 (UTC), "John Mason"
> wrote:

....snippage...

>(Rigging errors not found in the speed
>of the launch, not watching airspeed and spinning after the launch because
>of distraction with the high workload of the winch and not dealing with the
>angle of attack in the launch properly and so on).


....snippage...

None of these points are unique to winching.

- I've seen many more comments on r.a.s about failed aero tows
due to rigging errors than I've heard about for winching. To me this
says more about the safety culture (or lack of it) at different
sites than anything to do with the launch method.
- incorrect airspeed and stall/spin after release is just as possible
at the end of an aero tow if you overcook the climbing turn.
- AOA mis-management will be *much* more serious during an aero tow
on a CG hook than during a winch launch provided the appropriate
weak link is used. Think tug upset.

I launch both ways though I'll admit to many more winch than aero-tow
starts. I see very little difference in pilot stress levels or
workload between the launch methods in good conditions, but the
overall stress from an aero tow is larger, simply because you're on
tow for 5 minutes or more compared with the 30 seconds to get to the
top of the cable. If I'm flying something as sluggish in roll as a
G.103A in turbulent, windy conditions then winching has a much lower
work load than aero-tow.

This is my opinion entirely: I'm not speaking for anybody else or
trying to put words in their mouth.

--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

[Bill Daniels]

"Bert Willing" > wrote in
message ...
> A winch driver won't get killed if the winch is equipped properly. And a
> cable breaking near the winch under full power is something very, very
> dangerous, so sitting on a winch without shielding is asking to be killed.
>
> The min team for winch launches is the pilot, the winch driver and the
wing
> runner (the winch driver can retrieve the cables on his own if the winch
has
> properly working brakes on the drums). If pilot and winch driver are
> suffiencently experienced, a chair may well replace the wingrunner
(although
> stating that in public may not be politically correct :-)
>
> During winch launch, any accident is related to pilot errors so you can
> basically keep the accident rate fairly low.
>
> On aerotows you may have situations were a cable break *will* induce an
> accident, and the pilot may just be able to influence the damage.
>
> --
> Bert Willing
>
> ASW20 "TW"
>

I was recently shown (very discretely) a wing runner replacement by a pilot
who uses ground launch.

I was comprised of a long tripod made of PVC pipe, topped with an inverted,
felt lined, ski-type runner, on which the wing tip slid. It would hold the
wings level for the first 2 meters of the takeoff roll. It could be
dismantled and stored in the glider trailer.

The successful use of this device depended on excellent radio communication
between the glider pilot and the tow car/winch driver plus a very good wheel
brake on the glider so that the pilot could prevent being pulled off the
tripod as the slack was slowly pulled out. I was told that it worked very
well.

Way back in the 1960's a friend and I would trailer our gliders out to
remote dry lakes in the Mojave Desert. We would take turns auto-towing the
other into the air. The obvious problem is that the pilot driving the tow
car was left on the ground with his glider if the other found lift.

On one occasion, I caught a thermal and soared away leaving my friend on the
ground. I felt bad about leaving him on the ground but thought - but hey, I
have lift. Shortly afterward, my friend joined my thermal in his glider.
He had talked a curious passer by into driving the tow car.

We just started the launch with the wingtip on the ground. Ground launch
crews can be very small.

Bill Daniels

[Christian Husvik]

Hei,

John Mason wrote:

> (Rigging errors not found in the speed of the launch,

Whit??

Do forgive my clearly insufficient knowledge of the English
language, but what exactly does "rigging errors not found in the speed
of the launch" mean? And how would those have been found and corrected
if the launch subsequent to rigging had been by areotow rather than by
winch?

I mean: The fact that an aerotow takes longer time to complete does not
give you any more time _prior_ to launch, does it?

Christian 8-)

[Mike Borgelt]

On Mon, 27 Oct 2003 11:59:17 -0000, "Silent Flyer" ]>
wrote:

>
>> >"Mike Borgelt" > wrote in message
>> ...
>>
>> And for you guys who operate on nice green grass airfields which allow
>> things like cable retrieve winches - it don't happen in Oz.
>>
>***********
>You have obviously never been to the Long Mynd - I have heard it described
> rather unkindly) as " a barely levelled granite hilltop".
>
Actually I have in 1988.
The surface looked pretty good compared to most Oz airfields. There
are one or two which I've jokingly said you would fail an outlanding
check if you picked the airfield.

I'm sure there are good statistics available for the safety of winch
vs aerotow but nobody has come up with them.

Winching is cheaper for training but has anyone noticed that gliding
is shrinking worldwide? Perhaps the old way of doing business is no
longer successful?

I think we need to realise that gliding is a sport for *pilots*.

First turn a newcomer into a pilot.

There is a wonderful array of small light aircraft and /or
motorgliders available nowadays at very reasonable prices. In Oz a
Pipistrel Sinus costs about the same as a new ASK21 and for the
purposes the K21 would be mostly used for (primary training) the Sinus
might be not quite as good a sailplane but will more than adequately
do the job and lets you teach cross country navigation, outlanding
field selection etc as well as being a not bad two seat bugsmasher.
Combine training in one of these with motivational rides with cross
country pilots in high performance two seat gliders(minimum - Janus,
Duo etc preferably with self launch or turbo to prevent outlandings)
and I think you might have a 21st Century soaring movement that might
have a fighting chance of actually retaining the people that come to
it.

Mike Borgelt

[Marry Daniel or David Grah]

This sounds like the place I learned to ground launch. Well, actually I
guess I got the basics down during a visit to New Zealand. In any event my
experience at the place was more positive as was the success of all of the
launches than your experience. "Lights on!" and all. I liked the rustic
feel of things, felt clear on and comfortable with the safety measures and
procedures in use, and my license no longer says aero tow only.

David Grah
Bishop, California

"JJ Sinclair" > wrote in message
...
> Gary,
> I suspect you are considering winch launching for your club and I would
think
> the biggest problem would be in getting club members, "Up to Speed" on
winch
> operations.
>
> In way of illustrating my point, allow me to tell a little story about a
local
> soaring operation that is no longer in business. This outfit advertised,
get
> your "Aero-Tow Only" restriction, removed from your glider licence. Come
to XXX
> Soaring and we will check you out in about an hour, or so. This outfit had
a
> 2-33 with only a nose tow hook (mistake no. 1) They didn't use radios
(mistake
> no. 2) The flight examiner weighed a good 300 lb. + your average student
at 200
> lb. = 500 lb's in the 2-33 (mistake no. 3)
>
> I was going to take the course, but had to wait for the student in front
of me
> to get his check-out. The signal for "Start the launch" was, level the
wings
> and flash the lights in the car located near the right wing tip. It went
> something like this:
>
> 1. Level the wings & flash the lights------------Glider rolled about 10
feet
> and stopped. winch operator stalled the winch.
>
> 2. Level the wings & flash the lights---------- Cable went, but glider
didn't
> move. In the last attempt, wheel had rolled over cable and caused a
reverse
> release.
>
> 3.Level the wings & flash the lights---------------Glider went about 100
feet
> and stopped. Cable had "Kinked" in previous 2 attempts and then broke at a
> kink.
>
> -------------30 minute delay while Nico-Press & sleves are found and cable
is
> spliced. With 3 attempts and no success, student is having second thoughts
and
> opens canopy and starts to climb out. Instructor tells him, everything
will be
> fine, this time, Get back in here.
>
> 4. Level the wings & flash the lights------------ Glider takes off, to the
wild
> applause of all those assembled. Glider only gets 400 feet due to nose tow
hook
> location. Glider makes a 90 right and a 180 left, lands and rolls right up
to
> the starting point.
>
> Attempts 5, 6 & 7 come off without a hitch and the Flight Examiner is
called
> out (300 lbs)
>
> Level the wings & flash the lights-------------- Glider takes off, but
only
> gets 300 feet, makes a modified 90/180 and plunks it down hard, way down
the
> runway.
>
> I took this opportunity to silently disappear and my licence still reads,
> Aero-Tow Only.
> JJ Sinclair

[Fred Blair]

As many times as it takes for the student to react properly. In our club,
it happens often, especially if the student fails to call 200ft.
Fred
>
> How many airtow instructors pull the release on their student at 200 ft
> over the outbound fence? Just once? Several times?
>

[F.L. Whiteley]

"E. A. Grens" > wrote in message
...
> JJ -
>
> I, as a power pilot, learned to fly sailplanes on the winch, overseas. I
> now only fly aerotow, and am not signed off for ground launch. One thing
I
> have not seen mentioned is the qualification of winch operators. Tow
plane
> pilots ( I'm not one) have to meet certain standards and be signed off. I
> became a winch operator by volunteering out of club spirit (stupidty?). I
> was informally instructed by a winch operator who desparately wanted to
> escape the exile of the winch. Then I was left to do the job, getting my
> flights at the end of the day. They brought me food and drink
> (nonalcholic), but no one "qualified" on the winch would come near for
> hours. I'm sure I never endangered any aircraft or pilot, but I'm also
sure
> that some achieved less than optimal release altitude. There was no
> tensionmeter, and throttle control was based on visual evaluation of
> aircraft attitude and cable sag.
>
> Many years later I had the chance to observe the operator of a modern
> six-reel winch at Terlet. He was an artist at work, and he had the best
> equipment.
>
> I think winch launches are safe, as long as you have a cg hook. But, in
any
> comparison to aerotow, the increased number of launches necessary to
achieve
> sustained flight must be taken into account.
>
> Ed Grens
>
If it's soarable, one launch should do most days. Most seasons I winch
launched regularly I can count on one hand the number second snaps taken per
season to soar away. Of course, _big wings_ do help, but that's another
thread;^) This season, I only took two aerotows to 2000agl. My other AT
releases were 1200 to 1700agl, that is, at or below winch height and near
enough to the airfield to presume had we been winching, getting away was
pretty likely. For a number of reasons we didn't winch much this season,
but when we did, we soared. This included thermals on New Year's Day and
wave on Feb 1 and thermals each subsequent winch day this season. Looks
like snow for November 1st though. Last Saturday would have been perfect as
lift was 10kts to 12K in a stiff NW breeze. The kind of day we get 2500+agl
on the wire.

Frank Whiteley

[F.L. Whiteley]

"Stefan" > wrote in message
...
> Bill Daniels wrote:
>
> >> BTW, How about some of our British and European friends with lots of
> winch
> >
> > experience jumping in here?
>
>
<SNIP>
> Winch launching has much more safety issues for the ground crew and
> spectators than for the pilot. Be sure to have an experienced person
> show you safe procedures.
>
> Of course, an experienced winch driver helps a lot, too. At our club, a
> new winch driver must do 50 launches under supervision befor he's
> allowed to winch alone. We never had a winch accident in 40 years.
>
> Stefan
>
We do 40, 20 as observer/helper, and 20 supervised, but our winch is a
simple
single-drummed affair.

Frank Whiteley

[F.L. Whiteley]

"F.L. Whiteley" > wrote in message
...
>
> "Stefan" > wrote in message
> ...
> > Bill Daniels wrote:
> >
> > >> BTW, How about some of our British and European friends with lots of
> > winch
> > >
> > > experience jumping in here?
> >
> >
> <SNIP>
> > Winch launching has much more safety issues for the ground crew and
> > spectators than for the pilot. Be sure to have an experienced person
> > show you safe procedures.
> >
> > Of course, an experienced winch driver helps a lot, too. At our club, a
> > new winch driver must do 50 launches under supervision befor he's
> > allowed to winch alone. We never had a winch accident in 40 years.
> >
> > Stefan
> >
> We do 40, 20 as observer/helper, and 20 supervised, but our winch is a
> simple
> single-drummed affair.
>
> Frank Whiteley
>
Let me amend this to say a minimum of 40. To that end, you may have driven
a winch hundreds or thousands of times and still not have seen it all, and
hopefully, never will.

Frank Whiteley

[Bert Willing]

In Germany, the requirement is 100 supervised launches on at least 10
different days.

--
Bert Willing

ASW20 "TW"


"F.L. Whiteley" > a écrit dans le message de
...
> Let me amend this to say a minimum of 40. To that end, you may have
driven
> a winch hundreds or thousands of times and still not have seen it all, and
> hopefully, never will.
>
> Frank Whiteley
>
>

[Eggert Ehmke]

Bill Daniels wrote:

> BTW, How about some of our British and European friends with lots of winch
> experience jumping in here?

I have done some 1500 winch launches and about 50 aerotows. Beside some
cable breaks, I can't remember any uncomfortable situation during a winch
launch. I can't tell this of the aerotows.

In Germany, winch drivers have to do at least 100 launches on 10 different
days under supervision of an experienced driver. The 10 days rule is to
ensure different weather/wind situations during the training. We expect
every pilot to get his winch driver licence. The driver will get a
replacement after some hours and normally can choose his favorite glider
after his shift.

As for unexperienced winch drivers: anything that can happen (cable breaks,
engine problems, other launch interruptions) can be and must be handled by
the pilot.

On our 1200 m strip, we normally get 350-600 m after release. On good
thermal days, this is pretty enough to get away. With students we can do
easily lots of patterns of 6-10 minutes.
Eggert

[Bob Johnson]

Mr. Ehmke --

Your ability to get 600 m releases with a winch on a 1200 m strip seems
extraordinary. Is your cable length just 1200 m also or is it greater
than your strip length?

Thanks for your input.

BJ

Eggert Ehmke wrote:
>
> Bill Daniels wrote:
>
> > BTW, How about some of our British and European friends with lots of winch
> > experience jumping in here?
>
> I have done some 1500 winch launches and about 50 aerotows. Beside some
> cable breaks, I can't remember any uncomfortable situation during a winch
> launch. I can't tell this of the aerotows.
>
> In Germany, winch drivers have to do at least 100 launches on 10 different
> days under supervision of an experienced driver. The 10 days rule is to
> ensure different weather/wind situations during the training. We expect
> every pilot to get his winch driver licence. The driver will get a
> replacement after some hours and normally can choose his favorite glider
> after his shift.
>
> As for unexperienced winch drivers: anything that can happen (cable breaks,
> engine problems, other launch interruptions) can be and must be handled by
> the pilot.
>
> On our 1200 m strip, we normally get 350-600 m after release. On good
> thermal days, this is pretty enough to get away. With students we can do
> easily lots of patterns of 6-10 minutes.
> Eggert

[Bill Gribble]

Bob Johnson > writes
>Your ability to get 600 m releases with a winch on a 1200 m strip seems
>extraordinary. Is your cable length just 1200 m also or is it greater
>than your strip length?

350-600m is between 1155' and 1980' (approximately)?

Our own main strip is 1500m. In my somewhat limited experience, the
typical winch launch releases a K13 at 1600'. With an appropriate
head-wind, I've read that launches of up to 3000' (910m ?) can be
achieved from this particular strip (though possibly not in a K13!),
though that could well be just innocent boasting.

In that context, is 600m from a 1200m strip quite so extraordinary?
Especially as it was cited as the outside boundary of a range (ie. 350
to 600).

From a complete layman's point of view (well, one with 12 winch launches
so far and 1 aerotow to his name) I'd say that the winch was a good deal
more exhilarating than a tow and thus feels a damn sight more risky. But
I understand that if you fly the launch by the book then the winch is
perfectly safe.

That said, I've also read somewhere that the main contributors to
gliding fatalities in the UK are mainly mid-airs and "spin-ins" from
steeply initiated winch launches.

If that's the case, then perhaps the fact that a pilot launching on
winch only has himself to worry about, as opposed to one on tow who also
has the tug pilot's safety as a concern and responsibility, might leave
the former more predisposed to taking chances with his personal safety?

And perhaps the fact that you do need to fly a winch launch aggressively
(by comparison) if you want to make the maximum possible height out of
it, whereas with a tow, failing pilot error, mechanical failure or other
eventuality, you are going to make the release height you want
regardless. A winch has a 30 second window at best. A tow can take as
long as it needs within reason.

Of course, none of this contributes the stats and figures requested. And
all of this could be attributed to the flawed mis-interpretations of a
complete newbie who has read far too much in the last three months to
possibly retain any of it with a reasonable degree of accuracy ...

--
Bill Gribble

/----------------------------------\
| http://www.cotswoldgliding.co.uk |
| http://members.aol.com/annsweb |
| http://www.shatteredkingdoms.org |
\----------------------------------/

[Stefan]

Bob Johnson wrote:

> Your ability to get 600 m releases with a winch on a 1200 m strip seems
> extraordinary.

It all depends on the wind. With zero wind, the rule of thumb is that
you get approximately 1/3 the cable lengh. More with headwind, much more
with strong headwind. With extraordirarily strong headwind, you can even
kite. (Yes, it has been done.)

Stefan

[Bill Gribble]

Stefan > writes
> With extraordirarily strong headwind, you can even kite. (Yes, it has
>been done.)

Whilst I have no trouble believing that, it does conjure up some curious
mental images ... Though perhaps that speaks more of my own mental
imbalance than that of the suggestion <g>

--
Bill Gribble

/----------------------------------\
| http://www.cotswoldgliding.co.uk |
| http://members.aol.com/annsweb |
| http://www.shatteredkingdoms.org |
\----------------------------------/

[Eggert Ehmke]

Bob Johnson wrote:

> Mr. Ehmke --
>
> Your ability to get 600 m releases with a winch on a 1200 m strip seems
> extraordinary. Is your cable length just 1200 m also or is it greater
> than your strip length?

That's 1200 m of cable laid out, with a V8 240 HP engine at the other end.
What I told is the normal range - with strong wind aligned to the runway we
had 750 m (2460 feet) agl with a double seated ASK21. I did not see this
launch, but it sounds reasonable. 650 m I have experienced myself.
Eggert

[Gary Boggs]

I really appreciate all this good input, thank you all for responding. Now
for a new twist, one of our members has built a "pay out winch". A pay out
winch is a drum with a break on it. The glider hooks up about 200' behind
the tow vehicle, and as the glider climbs, the line spools out. Does
anybody have any experience with this type of launch? How much runway do
you need for this type of launch, how high can you get, ect?

Boggs

"Stefan" > wrote in message
...
Bob Johnson wrote:

> Your ability to get 600 m releases with a winch on a 1200 m strip seems
> extraordinary.

It all depends on the wind. With zero wind, the rule of thumb is that
you get approximately 1/3 the cable lengh. More with headwind, much more
with strong headwind. With extraordirarily strong headwind, you can even
kite. (Yes, it has been done.)

Stefan

[Mike Borgelt]

On Tue, 28 Oct 2003 10:26:06 -0800, "Gary Boggs"
> wrote:

>I really appreciate all this good input, thank you all for responding. Now
>for a new twist, one of our members has built a "pay out winch". A pay out
>winch is a drum with a break on it. The glider hooks up about 200' behind
>the tow vehicle, and as the glider climbs, the line spools out. Does
>anybody have any experience with this type of launch? How much runway do
>you need for this type of launch, how high can you get, ect?
>
>Boggs

Don't know about that one but car tows generally aren't as good as a
winch as the initial accleration is much slower. You are accelerating
the car as well as the glider. The winch motor only accelerates the
glider and wire.

The car doesn't last very long in that sort of duty either.

Mike Borgelt

[John Galloway]

Your on your own there I think.

John Galloway


At 18:36 28 October 2003, Gary Boggs wrote:
>I really appreciate all this good input, thank you
>all for responding. Now
>for a new twist, one of our members has built a 'pay
>out winch'. A pay out
>winch is a drum with a break on it. The glider hooks
>up about 200' behind
>the tow vehicle, and as the glider climbs, the line
>spools out. Does
>anybody have any experience with this type of launch?
> How much runway do
>you need for this type of launch, how high can you
>get, ect?
>
>Boggs
>

[Bill Daniels]

"Gary Boggs" > wrote in message
...
> I really appreciate all this good input, thank you all for responding.
Now
> for a new twist, one of our members has built a "pay out winch". A pay
out
> winch is a drum with a break on it. The glider hooks up about 200' behind
> the tow vehicle, and as the glider climbs, the line spools out. Does
> anybody have any experience with this type of launch? How much runway do
> you need for this type of launch, how high can you get, ect?
>
> Boggs
>

I've done lots of auto tows and winch launches but no payout winch launches.
But, I have done some back of the envelope calculating for payout winches.
Payout winches seem to work fine for hang gliders where the towing speeds
are far lower than sailplanes. The speeds needed for sailplanes really jack
up the numbers.

Assuming no wind, (Given enough wind, anything works - even a large stake.)
the tow car has to accelerate to the normal towing speed plus the payout
rate. The normal glider airspeed at the beginning of the climb will be
about 55 - 60 Knots. Correcting this for True Airspeed, depending on
density altitude, may be 70 - 75 MPH on the tow car speedometer. To pay out
enough wire to make the effort worthwhile, (Say, 2500 feet in 60 seconds)
the payout rate will be about 45FPS or 30MPH which brings the tow car speed
to 105MPH - a bit fast for my taste. Now the tow car speed will decrease as
the glider climbs so the distance required will be less than that covered at
100MPH for one minute. But you have to add in the distance to accelerate
and stop the tow car.

Juggle the numbers for yourself but it looks like you will need a 12,000
foot runway and really fast car - or lots of headwind. Consider also that a
heavy two-seater will demand nearly 250 HP at the tow hook and a wire
tension of about 1300 pounds. Your tow car had better be heavy as well as
fast.

This starts to make a standard winch launch look good.

Bill Daniels

[Bob Mowry]

> Beware of the raw statistics.

How about this one:

100% of 2003 US glider fatalities occur after aerotow.

Sounds like a good tag line for a winch manufacturer advertisement :)

-bob

[Adrian Jansen]

I was lucky enough to get a kite launch one day. We had about 35 Kts of
wind on the ground, and someone suggested we try a launch. An instructor
and I climbed into a Blanick L13, launched ( *very* short run ! ) and
climbed to 4300 ft still on the wire. Of course we needed the expert
cooperation of the winch driver, who eased off the power as we got about 500
ft, then payed out cable to let us climb. At the end, it was mostly the
weight of cable ( single strand high tensile steel wire ) which determined
the max height, although there wasnt much wire left on the drum.

--
Regards,

Adrian Jansen
J & K MicroSystems
Microcomputer solutions for industrial control
"Stefan" > wrote in message
...
> Bob Johnson wrote:
>
> > Your ability to get 600 m releases with a winch on a 1200 m strip seems
> > extraordinary.
>
> It all depends on the wind. With zero wind, the rule of thumb is that
> you get approximately 1/3 the cable lengh. More with headwind, much more
> with strong headwind. With extraordirarily strong headwind, you can even
> kite. (Yes, it has been done.)
>
> Stefan
>

[Tim Ward]

"Gary Boggs" > wrote in message
...
> I really appreciate all this good input, thank you all for responding.
Now
> for a new twist, one of our members has built a "pay out winch". A pay
out
> winch is a drum with a break on it. The glider hooks up about 200' behind
> the tow vehicle, and as the glider climbs, the line spools out. Does
> anybody have any experience with this type of launch? How much runway do
> you need for this type of launch, how high can you get, ect?
>
> Boggs

I have quite a bit -- in hang gliders. It works best with lots of road,
runway, or dry lake.
We typically got about 2/3 of the paid-out line in altitude. With 6000 feet
of 3/16 inch polyprop, we could get 4000 feet.
More typically, we'd tow until we hit a thermal somewhere above 500 feet.

If you don't have a dry lake handy, you can "step tow". The tow car stops
at the end of the road, and turns around (either a U turn or a "Y" turn), as
the glider also turns around, being careful not to wrap the rope around the
wing.
When the glider is more-or-less turned around, the tow car starts again.
Rinse, lather, repeat. The downwind run takes much less time.
This might not work in sailplanes. In hang gliders, we were using a
three-ring release, which doesn't back-release.

Tim Ward

[Eric Greenwell]

In article >, mowry86
@hotmail.com says...
> > Beware of the raw statistics.
>
> How about this one:
>
> 100% of 2003 US glider fatalities occur after aerotow.
>
> Sounds like a good tag line for a winch manufacturer advertisement :)

Unfortunately, not true: some have occurred after self-launch, and I
know there have been some ground launch fatalities (how recently, I
can't remember)
--
!Replace DECIMAL.POINT in my e-mail address with just a . to reply
directly

Eric Greenwell
Richland, WA (USA)

[Bob Johnson]

Eggert --

Those are really good numbers for your winch.

With V8 300 HP (GMC 454 c.i., 7.4 L), and 5000 ft (1550 m) Plasma line
laid out, we are getting the rule of thumb 1/3 cable length releases of
1700 ft (525 m). This is into 10-15 kt wind. Much over that, we leave
the Blanik in the barn!

BJ
Midland, Texas







Eggert Ehmke wrote:
>
> Bob Johnson wrote:
>
> > Mr. Ehmke --
> >
> > Your ability to get 600 m releases with a winch on a 1200 m strip seems
> > extraordinary. Is your cable length just 1200 m also or is it greater
> > than your strip length?
>
> That's 1200 m of cable laid out, with a V8 240 HP engine at the other end.
> What I told is the normal range - with strong wind aligned to the runway we
> had 750 m (2460 feet) agl with a double seated ASK21. I did not see this
> launch, but it sounds reasonable. 650 m I have experienced myself.
> Eggert

[Shirley]

wrote:

>How about this one:
>100% of 2003 US glider fatalities occur
>after aerotow.

Occur *after* aerotow? or *as a direct result of* aerotow?

[soarski]

Good Morning!

I Think Gary had a similar question or topic here, a year ago or
longer.
Seems to me, he likes winches, but his club has doubts.

I was trained with winch launches to solo in Germany, after I had
already learnt to fly airplanes in the US. Subsequently I got into
soaring in CO with aerotow, the going thing. Visiting Germany through
the years, I realize how much more experience there is about that
method. There are many places, where there is winch launch only! There
are pilots with two years experience of flying who have never seen an
aero tow!

One canot make any comparison or have statistics! It all depends who
does it, and his knowledge. When I look at modern winches and
everything that goes with it, winch launching is really quite
complicated and specialized.

Take a good Towplane, a good instructor, a talented pilot, and in no
time one has a towing operation going. In the US, to start a winch
operation, which is as perfect as Oerlinghausen or similar would take
a lot. To my knowledge, there is not a decent winch in the US, by
comparison to Germany and what they have.

Bill Daniels knows his stuff, but I think he is the exeption in the
US.

As for Gary Boggs, the only thing I can suggest is to go to Germany
for a summer and learn the trade. Winches, how to run them, including
the infrastructure. (Telephone)

On the other hand, with more reasonable selflaunchers coming out, the
winch effort may not be the answer anymore in the US. There are enough
reasons mentioned in this thread.

Happy Halloween

[Christian Husvik]

Gary Boggs wrote:
> I really appreciate all this good input, thank you all for responding. Now
> for a new twist, one of our members has built a "pay out winch".

Haven't heard about that, but I _have_ heard about a hairy thing called
"step towing", which is something the hang-glider pilots do from small
fields. They winch up to say 150m, have the winch pay out as the fly
back, turn and take another winch launch from altitude! This can of
course be repeated for as many times as practical, and some respectable
altitudes can be gained.

Imagine this done with a glider and dyneema or spectra cord for wire.
You would of course have to modify the tow-hook to not automatically
back-release (shudder, gulp!)...

Well, if someone actually tries this with a sailplane I'm not sure I'd
want to know. They would certainly not be allowed to fly _my_ glider
anyway.

Christian 8-)

[Slingsby]

"F.L. Whiteley" > wrote in message >...

> If it's soarable, one launch should do most days. Most seasons I winch
> launched regularly I can count on one hand the number second snaps taken per
> season to soar away. Of course, _big wings_ do help, but that's another
> thread;^) This season, I only took two aerotows to 2000agl. My other AT
> releases were 1200 to 1700agl, that is, at or below winch height and near
> enough to the airfield to presume had we been winching, getting away was
> pretty likely. For a number of reasons we didn't winch much this season,
> but when we did, we soared. This included thermals on New Year's Day and
> wave on Feb 1 and thermals each subsequent winch day this season. Looks
> like snow for November 1st though. Last Saturday would have been perfect as
> lift was 10kts to 12K in a stiff NW breeze. The kind of day we get 2500+agl
> on the wire.
>
> Frank Whiteley
************************************************** ********************************
You guys should get a really good winch and pay someone to operate it
during the week. During the summer you could become a vacation
destination. Since there are nonstop flights from Europe to Denver
every day, you could probably get enough Brits and others to pay for
your winch and some rental gliders in a few summers.

[F.L. Whiteley]

"Eric Greenwell" > wrote in message
.. .
> In article >, mowry86
> @hotmail.com says...
> > > Beware of the raw statistics.
> >
> > How about this one:
> >
> > 100% of 2003 US glider fatalities occur after aerotow.
> >
> > Sounds like a good tag line for a winch manufacturer advertisement :)
>
> Unfortunately, not true: some have occurred after self-launch, and I
> know there have been some ground launch fatalities (how recently, I
> can't remember)
> --
> !Replace DECIMAL.POINT in my e-mail address with just a . to reply
> directly
>
> Eric Greenwell
> Richland, WA (USA)

The following occured in the launch phase

Two fatals I'm aware of. A homebuilt failed structurally in a winch launch
in Colorado some years ago and apparently another homebuilt crashed in North
Carolina in the past couple of weeks on auto tow. Not clear whether the NC
accident pilot was even trained in ground launch. Perhaps someone in that
neck of the woods can offer more information.

A Russia was damaged in Wyoming a few years back on auto tow at a private
ranch strip, however, the grapevine reported the pilot had no specific
ground launch training and cart-wheeled the glider. IIRC, it was properly
repaired and sold.

A sometimes RAS poster was seriously injured in a winch launch accident
involving a Phoebus C in Georgia a few years ago. (stalled all-flying tail
to excessive pitch-up to wing stall, wing-drop, and rolled inverted to
impact)

Any others? Certainly there have been a few at Torrey Pines over the
decades, though environmental factors have been a big player there.

Frank Whiteley

[F.L. Whiteley]

The HG community used (has used) pay-out winches for a number of years. At
least one major auto maker produced a limited production launch vehicle
pick-up truck as advertised on national TV. Others were retro-fits or home
grown. The current generation of US UL gliders, Sparrowhawk and Lighthawk,
could probably use these as supplied. The Apis and Silent might need
something a bit more stout.

Frank Whiteley


"Gary Boggs" > wrote in message
...
> I really appreciate all this good input, thank you all for responding.
Now
> for a new twist, one of our members has built a "pay out winch". A pay
out
> winch is a drum with a break on it. The glider hooks up about 200' behind
> the tow vehicle, and as the glider climbs, the line spools out. Does
> anybody have any experience with this type of launch? How much runway do
> you need for this type of launch, how high can you get, ect?
>
> Boggs
>
> "Stefan" > wrote in message
> ...
> Bob Johnson wrote:
>
> > Your ability to get 600 m releases with a winch on a 1200 m strip seems
> > extraordinary.
>
> It all depends on the wind. With zero wind, the rule of thumb is that
> you get approximately 1/3 the cable lengh. More with headwind, much more
> with strong headwind. With extraordirarily strong headwind, you can even
> kite. (Yes, it has been done.)
>
> Stefan
>
>

[Robert Ehrlich]

Bob Johnson wrote:
>
> Eggert --
>
> Those are really good numbers for your winch.
>
> With V8 300 HP (GMC 454 c.i., 7.4 L), and 5000 ft (1550 m) Plasma line
> laid out, we are getting the rule of thumb 1/3 cable length releases of
> 1700 ft (525 m). This is into 10-15 kt wind. Much over that, we leave
> the Blanik in the barn!
>
> BJ
> Midland, Texas
>
>
>
> Eggert Ehmke wrote:
> >
> > Bob Johnson wrote:
> >
> > > Mr. Ehmke --
> > >
> > > Your ability to get 600 m releases with a winch on a 1200 m strip seems
> > > extraordinary. Is your cable length just 1200 m also or is it greater
> > > than your strip length?
> >
> > That's 1200 m of cable laid out, with a V8 240 HP engine at the other end.
> > What I told is the normal range - with strong wind aligned to the runway we
> > had 750 m (2460 feet) agl with a double seated ASK21. I did not see this
> > launch, but it sounds reasonable. 650 m I have experienced myself.
> > Eggert


1/3 cable length seems low. There was in France an experiment showing
40% cable length without wind with cable length from 1000 to 2000 m.
See HTTP://www.gliderforum.com/thread-view.asp?threadid=385&MessageID=1466#1466

[Robert Ehrlich]

soarski wrote:
> ...
> As for Gary Boggs, the only thing I can suggest is to go to Germany
> for a summer and learn the trade. Winches, how to run them, including
> the infrastructure. (Telephone)
>

Why telephone rather than radio? Radio let everybody know what is
happening, rather than only the two persons at bot end of telephone.
Likely mandatory when there is some other activity in parallel (aero
tow, power flying ...).

> On the other hand, with more reasonable selflaunchers coming out, the
> winch effort may not be the answer anymore in the US. There are enough
> reasons mentioned in this thread.
>

What does "reasonable" mean here? Selflaunchers are a way to increase
the cost of flying, winch is a way to decrease it.

[Bob Johnson]

Robert --

I would like to learn how they do this. Our Blanik has perhaps the best
located CG hook on any sailplane I'm aware of, although some would say
the bridle is somewhat awkward to use.
On a typical tow, with the Blanik weighing about 1100 lb, the 300 hp
winch engine throttle is advanced to the forward stop in 3 seconds and
at this time the engine is already rapidly approaching redline 5000 RPM.
At this point the Blanik is already beginning its climb and the throttle
is eased.

This quick takeoff and climb performance is still not fast enough to
load the ship and its occupants to more than about 0.8 - 0.9 G
horizontal acceleration, which I think one would have do to attain any
more than the 1/3 line length releases we are attaining.

We limit our climb airspeed to 55-60 kt, which I believe is the POH
recommendation. Very little if any back stick is necessary, and the
Blanik attains the 55 kt climb pretty much on its own until the last
part of the 45 second tow, when some back stick is applied to counter
the downward (with respect to the ground) pull of the rope. Our
Spectra/Dyneema/Plasma plastic rope weighs less than its full 66 lb when
partially wound on the drum, so line weight (and its necessary
acceleration and ground contact friction) for us is practically
negligible.

If there is a better setup anywhere in the world, I would sure
appreciate a description.

Thanks for your reply,

BJ
Midland, Texas
http://www.permiansoaring.us/

Robert Ehrlich wrote:
>
> Bob Johnson wrote:
> >
> > Eggert --
> >
> > Those are really good numbers for your winch.
> >
> > With V8 300 HP (GMC 454 c.i., 7.4 L), and 5000 ft (1550 m) Plasma line
> > laid out, we are getting the rule of thumb 1/3 cable length releases of
> > 1700 ft (525 m). This is into 10-15 kt wind. Much over that, we leave
> > the Blanik in the barn!
> >
> > BJ
> > Midland, Texas
> >
> >
> >
> > Eggert Ehmke wrote:
> > >
> > > Bob Johnson wrote:
> > >
> > > > Mr. Ehmke --
> > > >
> > > > Your ability to get 600 m releases with a winch on a 1200 m strip seems
> > > > extraordinary. Is your cable length just 1200 m also or is it greater
> > > > than your strip length?
> > >
> > > That's 1200 m of cable laid out, with a V8 240 HP engine at the other end.
> > > What I told is the normal range - with strong wind aligned to the runway we
> > > had 750 m (2460 feet) agl with a double seated ASK21. I did not see this
> > > launch, but it sounds reasonable. 650 m I have experienced myself.
> > > Eggert
>
> 1/3 cable length seems low. There was in France an experiment showing
> 40% cable length without wind with cable length from 1000 to 2000 m.
> See HTTP://www.gliderforum.com/thread-view.asp?threadid=385&MessageID=1466#1466

[Marcel Duenner]

Mike Borgelt > wrote in message >...
> On Sat, 25 Oct 2003 12:43:35 -0700, "Gary Boggs"
> > wrote:
>
> >Someone must have already compared the safety of these tow launch methods.
> >What do the statistics show is the safer method of launch? Aero tow seems
> >to involve more inherent dangers to me. For one thing, there is just more
> >time for things to go wrong. What could be more dangerous than to tie tow
> >airplanes together and try to fly?
> >
> >Gary Boggs
> >
>
> I've only done about two winch launches but have done several hundred
> car tows and driven several hundred also.

Two winch launches. Helps to understand why you say what you say later
on.

>
> Ground launches involve lots of wire, rope etc. It is probably a good
> observation that the more rope you have the more trouble you can get
> into! With one exception below.
>
> I've had the glider run over the wire and tangle in the wheel well.
> Not good as you now cannot release and depend on the tow driver..
>
> Pilot reactions to a low altitude winch launch failure are utterly
> critical. I suspect we've killed dozens if not hundreds over the years
> this way around the world.

Yes, the reaction is critical. But even more important is the correct
attitude corresponding to airspeed and altitude at all times. This
does make the reaction when something goes wrong a quite a bit less
critical.
I guess we have about 0.5 cable breaks and 2 or 3 weak link breaks per
1000 launches. We do about 3500 winch launches a year. It can happen
and if the pilot is properly instructed he knows this and is prepared.
I do not consider cable break or engine failure to be a _problem_ when
launching even when it happens.

>
> You may need more than one launch to get away(rare with aerotow).

Normally not.

> Someone mentioned the stresses in the wire and the glider. Both are
> much lower in properly executed arotow.

Stresses are normally higher, but where's the problem in that? The
glider is built to easily take those stresses and we change the wire
once a year anyway.

>
> Aero tow may have a higher exposure to an off airport landing in
> unsuitable terrain but the failures seem to be much more rare than
> winch wire breaks. If you don't use toy towplanes(less than 180HP)
> then any place suitable for winching probably gives you the
> opportunity to do a 180 or land straight ahead from an aerotow.

Definite 'No' on the 'probably gives you' bit.
From a winch launch you should _always_ be able to land on the
runwyay. I know lots of airfields where you have a certain time,
sometimes only two or three seconds, sometimes ages, in the aero tow
when you definitely do _not_ want _anything_ to go wrong. The
suitability of the airfield for whinch launching has no relevance
here.

>
> If you want gliding to be popular aerotow involves less running around
> on the ground per flight hour.

Don't see why. Only thing to do additionally is retrieveing the winch
cable. And the guy drives, he doesn't run.
And: If you want gliding to be more popular among the people living
near the airfield you should stop making such a racket with those
ancient technology fuel to noise converters. Instead we do 80% of our
launches with 0.4 litres of Diesel.

>
> Flying towplanes is more fun than driving a winch or tow
> car.(Allegedly - I last sat in a towplane in 1971 writing down CHT's
> for the cooling test for 4 tows in a row and haven't felt motivated to
> get into a towplane since despite the aquisition of a PPL 9 years ago)
>
> Aerotowing danger can be reduced by using a longer rope. One of the
> local clubs around here tried it and liked it so much the towpilots
> won't fly with short ropes. The long rope gives everyone more time to
> handle upsets. I suspect the rise of the towplane upset accident
> coincided with using shorter ropes.

Agree to all that.

Regards
Marcel

[Andreas Maurer]

On Wed, 29 Oct 2003 10:02:06 +0000, Robert Ehrlich
> wrote:


>Why telephone rather than radio? Radio let everybody know what is
>happening, rather than only the two persons at bot end of telephone.
>Likely mandatory when there is some other activity in parallel (aero
>tow, power flying ...).

Nothing worse than someone else interfering during the critical phase
of a winch launch (initial acceleration).

Bye
Andreas

[Eggert Ehmke]

Bob Johnson wrote:

> I would like to learn how they do this. Our Blanik has perhaps the best
> located CG hook on any sailplane I'm aware of, although some would say
> the bridle is somewhat awkward to use.
> On a typical tow, with the Blanik weighing about 1100 lb, the 300 hp
> winch engine throttle is advanced to the forward stop in 3 seconds and
> at this time the engine is already rapidly approaching redline 5000 RPM.
> At this point the Blanik is already beginning its climb and the throttle
> is eased.

As a winch driver, I allways try to leave the throttle in the position it
has when the plane leaves the ground, for about the first 1/3 of the climb.
Then I slightly slow down, depending on the wind and the climb angle of the
plane. This can mean full throttle for a double seater and almost idle for
a Ka8 with strong headwind. This method works in all wind conditions.

With an ASK21 or Grob G103, the ground roll is not longer than 2 or 3
seconds. The first ca. 100 feet we keep a flat attitude, than we go
slightly into a climb angle of about 40 degrees.

> We limit our climb airspeed to 55-60 kt, which I believe is the POH
> recommendation.

This seems a bit slow for me, but may be correct for the Blanik. The ASK21
has a recommended speed of about 60 kt, and 65 is no problem. More speed
means more lift too.

> Very little if any back stick is necessary, and the
> Blanik attains the 55 kt climb pretty much on its own until the last
> part of the 45 second tow, when some back stick is applied to counter
> the downward (with respect to the ground) pull of the rope.

In the last part of the climb it is even important to give the stick a
little forward, so the angle between cable and plane does not exceed the
point where the backrelease is triggered. That way you can stay longer on
the rope, getting higher. Also the release is much softer.

Just my 2 cents...
Eggert

[Robert Ehrlich]

Bob Johnson wrote:
>
> Robert --
>
> I would like to learn how they do this.

The experiment I was talking about was done in another club,
so I have no direct information about it. However, when our winch
correctly delivers its power, we also get about 40% of cable length,
i.e. 400m with 1000m cable.

> Our Blanik has perhaps the best
> located CG hook on any sailplane I'm aware of, although some would say
> the bridle is somewhat awkward to use.
> On a typical tow, with the Blanik weighing about 1100 lb, the 300 hp
> winch engine throttle is advanced to the forward stop in 3 seconds and
> at this time the engine is already rapidly approaching redline 5000 RPM.
> At this point the Blanik is already beginning its climb and the throttle
> is eased.

There are some differences with what happens in my club: the reduction
ratio is not the same by us, engine RPM is 1800-2000. We never get
near redline, although the throttle is kept to the forward stop for
2 seaters (ASK21) until the glider seen from the winch crosses the
angle between the front window and the top window, i.e. cable angle
near 45 degrees. Our engine has only 200 hp.
>
> This quick takeoff and climb performance is still not fast enough to
> load the ship and its occupants to more than about 0.8 - 0.9 G
> horizontal acceleration, which I think one would have do to attain any
> more than the 1/3 line length releases we are attaining.
>
> We limit our climb airspeed to 55-60 kt, which I believe is the POH
> recommendation. Very little if any back stick is necessary, and the
> Blanik attains the 55 kt climb pretty much on its own until the last
> part of the 45 second tow, when some back stick is applied to counter
> the downward (with respect to the ground) pull of the rope. Our
> Spectra/Dyneema/Plasma plastic rope weighs less than its full 66 lb when
> partially wound on the drum, so line weight (and its necessary
> acceleration and ground contact friction) for us is practically
> negligible.
>
> If there is a better setup anywhere in the world, I would sure
> appreciate a description.
>

Maybe a reduction ratio on the engine allowing full throttle without
crossing redline, keeping full throtte longer during the climb, climbing
at 60 kt rather than 55 kt. And probably a higher nose up attitude during
the first part of the climb, which would be allowed with more power and
speed during this phase. But maybe the difference is only due to the
better aerodynamic of the ASK21 compared to the Blanik. I don't remember what gliders
were used in the experiment I reported about, but probably modern
gliders, certainly not Blaniks (almost unknown in France).

> Thanks for your reply,
>

[Robert Ehrlich]

Andreas Maurer wrote:
>
> On Wed, 29 Oct 2003 10:02:06 +0000, Robert Ehrlich
> > wrote:
>
> >Why telephone rather than radio? Radio let everybody know what is
> >happening, rather than only the two persons at both end of telephone.
> >Likely mandatory when there is some other activity in parallel (aero
> >tow, power flying ...).
>
> Nothing worse than someone else interfering during the critical phase
> of a winch launch (initial acceleration).
>

A worse thing would be someone interfering not to the communication but
to the launch itself because he is not aware of the launch. Of course
this is a discipline that everybody has to observe, i.e. don't use
the radio for anything else when a winch launch is in progress. This
also implies that every glider or tow plane has a working radio, which
is the case by us.

[Martin Gregorie]

On Wed, 29 Oct 2003 14:48:37 +0100, Andreas Maurer
> wrote:

>On Wed, 29 Oct 2003 10:02:06 +0000, Robert Ehrlich
> wrote:
>
>
>>Why telephone rather than radio? Radio let everybody know what is
>>happening, rather than only the two persons at bot end of telephone.
>>Likely mandatory when there is some other activity in parallel (aero
>>tow, power flying ...).
>
>Nothing worse than someone else interfering during the critical phase
>of a winch launch (initial acceleration).
>
True enough, and you wouldn't want the continuous stream of "take up
slack....take up slack....all out...all out" occupying a common-use
channel either. We use radio to control launch but its on a dedicated
channel (sorry - I don't know the frequency) that is separate from our
tugging frequency and is one that I've never heard interference on.
One benefit is that as well as the winch, the cable truck, golf
buggy[1] and office are all on the channel so the launch marshal can
talk to anybody he needs to.

[1] an excellent and economical way of moving gliders about.


--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

[JJ Sinclair]

>
>Any others? Certainly there have been a few at Torrey Pines over the
>decades, though environmental factors have been a big player there.
>
>Frank Whiteley

Its been a long time now, but a group was auto-towing a Cherokee at Air
Sailing, NV. The initial flights were made with a pulley attached to a stake in
the ground and car driver heading straight for the glider. After several
flights they decided to put the pilley on the car and NOBODY knew that would
DOUBLE the glider speed. The driver "Stood on it " hard and finally obtained
his briefed 50 mph. The glider was now doing 100 and pilot was unable to
release due to excessive tow line pressure. The wings came off and pilot was
killed.

About 20 years back, a group was auto-towing a Monarch at Kingdon, Ca. That
went so well, they decided to hook it up to a tow plane. The ship did several
PIO's as the pilot tried in vain, to release. He survived, but doesen't
remember anything after the 3rd grade.

My pilot licence still reads, "Aero-Tow- Only"
JJ Sinclair

[Bill Daniels]

"Bob Johnson" > wrote in message
...
> Eggert --
>
> Those are really good numbers for your winch.
>
> With V8 300 HP (GMC 454 c.i., 7.4 L), and 5000 ft (1550 m) Plasma line
> laid out, we are getting the rule of thumb 1/3 cable length releases of
> 1700 ft (525 m). This is into 10-15 kt wind. Much over that, we leave
> the Blanik in the barn!
>
> BJ
> Midland, Texas

Bob, When winching, the wind is your friend. Quitting at 15 knots is not
necessary. I have winched into 35 knots and higher winds and the results
are spectacular. Each 10 knots of headwind is the equivalent of about 40
additional HP.

The thing that often severely limits the altitude gained is a slow pitch-up
profile at the start of the launch. The final height achieved is largely
determined by the profile flown in the first few seconds of the launch.

Now, as everyone has pointed out, you need to be careful here. Safety at
the start of the climb is a combination of airspeed, altitude and attitude.
The more you have of the first, the faster you can get the second two and
the higher you will get.

I've done calculations, simulator runs (X-Plane) and flight test to prove
the following point. If you have 60 knots in a glider with a stalling
airspeed of 40 knots, you can be in full climb attitude at zero altitude and
still have a large safety margin. Practice this way - at several thousand
feet AGL, zoom the glider into a 50 degree nose-up attitude. As the
airspeed decays to 60 knots, yell "WIRE BREAK", delay 0.5 seconds
(simulating reaction time) and pitch forward at zero G. Watch the airspeed
and altitude, you'll see what I mean. (For winch CFI-G's, this is a great
way to teach how to handle wire breaks.)

If you have (or simulate) a wire break at this point and start a zero G
pitch over after a .5 second delay, the minimum airspeed during the
parabolic ballistic trajectory will be about 50 - 55 knots when the glider
reaches apogee at an altitude of about 100 feet AGL. So there you are at
100 feet and 55 knots in a normal gliding attitude - not exactly a
problematic situation, just land straight ahead. The reason this works is
that the glider's induced drag at zero G is minimal so the airspeed decay is
mainly just due to gravity and the glider follows a parabolic trajectory
until the pilot re-establishes one G at the normal glide attitude.

I need to repeat that I am not advocating a rocket blast-off kind of climb
profile but a smooth transition into the full climb without undue delay
equipped with a full understanding of the safety margins.

Bill Daniels

[Bert Willing]

Nothing worse than an additional communication step between pilot and winch
driver. Did that for 10 years in Germany, happy to do it by radio ever since
I left Germany, hadn't had an interference from others on the same
frequencies for the last 13 years :-)

--
Bert Willing

ASW20 "TW"


"Andreas Maurer" > a écrit dans le message de
...
> On Wed, 29 Oct 2003 10:02:06 +0000, Robert Ehrlich
> > wrote:
>
>
> >Why telephone rather than radio? Radio let everybody know what is
> >happening, rather than only the two persons at bot end of telephone.
> >Likely mandatory when there is some other activity in parallel (aero
> >tow, power flying ...).
>
> Nothing worse than someone else interfering during the critical phase
> of a winch launch (initial acceleration).
>
> Bye
> Andreas

[Bill Daniels]

"JJ Sinclair" > wrote in message
...
> >
> >Any others? Certainly there have been a few at Torrey Pines over the
> >decades, though environmental factors have been a big player there.
> >
> >Frank Whiteley
>
> Its been a long time now, but a group was auto-towing a Cherokee at Air
> Sailing, NV. The initial flights were made with a pulley attached to a
stake in
> the ground and car driver heading straight for the glider. After several
> flights they decided to put the pilley on the car and NOBODY knew that
would
> DOUBLE the glider speed. The driver "Stood on it " hard and finally
obtained
> his briefed 50 mph. The glider was now doing 100 and pilot was unable to
> release due to excessive tow line pressure. The wings came off and pilot
was
> killed.
>
> About 20 years back, a group was auto-towing a Monarch at Kingdon, Ca.
That
> went so well, they decided to hook it up to a tow plane. The ship did
several
> PIO's as the pilot tried in vain, to release. He survived, but doesen't
> remember anything after the 3rd grade.
>
> My pilot licence still reads, "Aero-Tow- Only"
> JJ Sinclair

JJ, you've had some bad experiences and I'm sorry for that. But you have to
realize that there are hundreds of thousands, if not millions of winch
launches all around the world that go off without a hitch simply because the
people involved know what they are doing.

If we take the trouble to learn from them and not try to re-invent the
wheel, ground launch becomes very safe and enjoyable. (The first thing to
learn is not to use a Schweitzer-type tow release for anything at all,
period.)

Bill Daniels

[Tjeerd Mulder]

On our field communication between pilot and winch driver is mostly by 4.6mm
steel cable. Works fine and very direct :-)
And in germany communication between winch and start point on air band radio
(only) is not allowed, you may use a radio on some other frequency.

Tjeerd


"Bert Willing" > schrieb im
Newsbeitrag ...
> Nothing worse than an additional communication step between pilot and
winch
> driver. Did that for 10 years in Germany, happy to do it by radio ever
since
> I left Germany, hadn't had an interference from others on the same
> frequencies for the last 13 years :-)
>
> --
> Bert Willing
>
> ASW20 "TW"
>
>
> "Andreas Maurer" > a écrit dans le message de
> ...
> > On Wed, 29 Oct 2003 10:02:06 +0000, Robert Ehrlich
> > > wrote:
> >
> >
> > >Why telephone rather than radio? Radio let everybody know what is
> > >happening, rather than only the two persons at bot end of telephone.
> > >Likely mandatory when there is some other activity in parallel (aero
> > >tow, power flying ...).
> >
> > Nothing worse than someone else interfering during the critical phase
> > of a winch launch (initial acceleration).
> >
> > Bye
> > Andreas
>
>

[Bob Johnson]

Eggert -

You are exactly right with those finer points of flying the launch.
Thanks for adding those to the thread.

Also we will want to try maybe 60-65 kt in the climb next time we go
out.

Cheers,

BJ

Eggert Ehmke wrote:
>
> Bob Johnson wrote:
>
> > I would like to learn how they do this. Our Blanik has perhaps the best
> > located CG hook on any sailplane I'm aware of, although some would say
> > the bridle is somewhat awkward to use.
> > On a typical tow, with the Blanik weighing about 1100 lb, the 300 hp
> > winch engine throttle is advanced to the forward stop in 3 seconds and
> > at this time the engine is already rapidly approaching redline 5000 RPM.
> > At this point the Blanik is already beginning its climb and the throttle
> > is eased.
>
> As a winch driver, I allways try to leave the throttle in the position it
> has when the plane leaves the ground, for about the first 1/3 of the climb.
> Then I slightly slow down, depending on the wind and the climb angle of the
> plane. This can mean full throttle for a double seater and almost idle for
> a Ka8 with strong headwind. This method works in all wind conditions.
>
> With an ASK21 or Grob G103, the ground roll is not longer than 2 or 3
> seconds. The first ca. 100 feet we keep a flat attitude, than we go
> slightly into a climb angle of about 40 degrees.
>
> > We limit our climb airspeed to 55-60 kt, which I believe is the POH
> > recommendation.
>
> This seems a bit slow for me, but may be correct for the Blanik. The ASK21
> has a recommended speed of about 60 kt, and 65 is no problem. More speed
> means more lift too.
>
> > Very little if any back stick is necessary, and the
> > Blanik attains the 55 kt climb pretty much on its own until the last
> > part of the 45 second tow, when some back stick is applied to counter
> > the downward (with respect to the ground) pull of the rope.
>
> In the last part of the climb it is even important to give the stick a
> little forward, so the angle between cable and plane does not exceed the
> point where the backrelease is triggered. That way you can stay longer on
> the rope, getting higher. Also the release is much softer.
>
> Just my 2 cents...
> Eggert

[Bob Johnson]

Robert -

Those are all good points, see my reply to Eggert.

Our engine is petrol fueled. Despite Google's best efforts, I have not
yet located a Torque/HP/RPM curve for our very common 7.4 L engine, but
have heard that it develops max torque and HP at about 3000 RPM and
further that the curves are fairly flat at this point.

Our drum speed is around 400 RPM for about a 7-8/1 overall reduction
using first gear of our automatic tranny. We have lately begun bringing
in the parachute in second gear, which reduces engine wear and tear
considerably.

In addition to raising the unflapped climb speed to 65 kt, we also have
the option on our Blanik L-13 model to let out the Fowler flaps and
climb at a reduced airspeed. We have not yet tried the flaps during tow
to my knowledge.

You may be using a Diesel, which could account for your good performance
at lower revs.

Thanks,
BJ

Robert Ehrlich wrote:
>
> Bob Johnson wrote:
> >
> > Robert --
> >
> > I would like to learn how they do this.
>
> The experiment I was talking about was done in another club,
> so I have no direct information about it. However, when our winch
> correctly delivers its power, we also get about 40% of cable length,
> i.e. 400m with 1000m cable.
>
> > Our Blanik has perhaps the best
> > located CG hook on any sailplane I'm aware of, although some would say
> > the bridle is somewhat awkward to use.
> > On a typical tow, with the Blanik weighing about 1100 lb, the 300 hp
> > winch engine throttle is advanced to the forward stop in 3 seconds and
> > at this time the engine is already rapidly approaching redline 5000 RPM.
> > At this point the Blanik is already beginning its climb and the throttle
> > is eased.
>
> There are some differences with what happens in my club: the reduction
> ratio is not the same by us, engine RPM is 1800-2000. We never get
> near redline, although the throttle is kept to the forward stop for
> 2 seaters (ASK21) until the glider seen from the winch crosses the
> angle between the front window and the top window, i.e. cable angle
> near 45 degrees. Our engine has only 200 hp.
> >
> > This quick takeoff and climb performance is still not fast enough to
> > load the ship and its occupants to more than about 0.8 - 0.9 G
> > horizontal acceleration, which I think one would have do to attain any
> > more than the 1/3 line length releases we are attaining.
> >
> > We limit our climb airspeed to 55-60 kt, which I believe is the POH
> > recommendation. Very little if any back stick is necessary, and the
> > Blanik attains the 55 kt climb pretty much on its own until the last
> > part of the 45 second tow, when some back stick is applied to counter
> > the downward (with respect to the ground) pull of the rope. Our
> > Spectra/Dyneema/Plasma plastic rope weighs less than its full 66 lb when
> > partially wound on the drum, so line weight (and its necessary
> > acceleration and ground contact friction) for us is practically
> > negligible.
> >
> > If there is a better setup anywhere in the world, I would sure
> > appreciate a description.
> >
>
> Maybe a reduction ratio on the engine allowing full throttle without
> crossing redline, keeping full throtte longer during the climb, climbing
> at 60 kt rather than 55 kt. And probably a higher nose up attitude during
> the first part of the climb, which would be allowed with more power and
> speed during this phase. But maybe the difference is only due to the
> better aerodynamic of the ASK21 compared to the Blanik. I don't remember what gliders
> were used in the experiment I reported about, but probably modern
> gliders, certainly not Blaniks (almost unknown in France).
>
> > Thanks for your reply,
> >

[Bob Johnson]

Hi Bill --

I 'member my O-Nine Two oil field piano wire breaking at the half way
point during a tow in Roy Schlemeyer's old SGS 2-22. I yelled "Oh, line
break" or something to that effect and recall the glider innards debris
collected since the last ice age floating up and dancing before my eyes
as I dumped the stick full forward. Was it half a second before I
reacted? Can't believe I waited that long. And when the astronauts tell
you that zero-g is exhilarating, believe it.

Luckily, I had been well briefed by Roy as to what to expect. It has
been theorized that some people are "allergic" to zero-g and they
instinctively jerk the stick full back instead of push full forward.
Unfortunately, this is the last mistake they ever make and we can no
longer interview them as to why they did this.

There, we're back to the original question, "Is winch launch safer than
aerotow?" The answer? -- scroll down


















IT DEPENDS!


Thanks and good to hear from you again.

BJ



Bill Daniels wrote:
>
> "Bob Johnson" > wrote in message
> ...
> > Eggert --
> >
> > Those are really good numbers for your winch.
> >
> > With V8 300 HP (GMC 454 c.i., 7.4 L), and 5000 ft (1550 m) Plasma line
> > laid out, we are getting the rule of thumb 1/3 cable length releases of
> > 1700 ft (525 m). This is into 10-15 kt wind. Much over that, we leave
> > the Blanik in the barn!
> >
> > BJ
> > Midland, Texas
>
> Bob, When winching, the wind is your friend. Quitting at 15 knots is not
> necessary. I have winched into 35 knots and higher winds and the results
> are spectacular. Each 10 knots of headwind is the equivalent of about 40
> additional HP.
>
> The thing that often severely limits the altitude gained is a slow pitch-up
> profile at the start of the launch. The final height achieved is largely
> determined by the profile flown in the first few seconds of the launch.
>
> Now, as everyone has pointed out, you need to be careful here. Safety at
> the start of the climb is a combination of airspeed, altitude and attitude.
> The more you have of the first, the faster you can get the second two and
> the higher you will get.
>
> I've done calculations, simulator runs (X-Plane) and flight test to prove
> the following point. If you have 60 knots in a glider with a stalling
> airspeed of 40 knots, you can be in full climb attitude at zero altitude and
> still have a large safety margin. Practice this way - at several thousand
> feet AGL, zoom the glider into a 50 degree nose-up attitude. As the
> airspeed decays to 60 knots, yell "WIRE BREAK", delay 0.5 seconds
> (simulating reaction time) and pitch forward at zero G. Watch the airspeed
> and altitude, you'll see what I mean. (For winch CFI-G's, this is a great
> way to teach how to handle wire breaks.)
>
> If you have (or simulate) a wire break at this point and start a zero G
> pitch over after a .5 second delay, the minimum airspeed during the
> parabolic ballistic trajectory will be about 50 - 55 knots when the glider
> reaches apogee at an altitude of about 100 feet AGL. So there you are at
> 100 feet and 55 knots in a normal gliding attitude - not exactly a
> problematic situation, just land straight ahead. The reason this works is
> that the glider's induced drag at zero G is minimal so the airspeed decay is
> mainly just due to gravity and the glider follows a parabolic trajectory
> until the pilot re-establishes one G at the normal glide attitude.
>
> I need to repeat that I am not advocating a rocket blast-off kind of climb
> profile but a smooth transition into the full climb without undue delay
> equipped with a full understanding of the safety margins.
>
> Bill Daniels

[Bob Kuykendall]

Earlier, JJ Sinclair wrote:

> Its been a long time now, but a group was
> auto-towing a Cherokee at Air Sailing, NV...

I'm not sure, but I believe that was actually a Don Mitchell design
called the Nimbus III-B (no relation to the later Schempp-Hirth
product of similar name). That was in 1973:

http://www.ntsb.gov/NTSB/brief.asp?ev_id=85473&key=0

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com

[Marcel Duenner]

"Bert Willing" > wrote in message >...
> Nothing worse than an additional communication step between pilot and winch
> driver. Did that for 10 years in Germany, happy to do it by radio ever since
> I left Germany, hadn't had an interference from others on the same
> frequencies for the last 13 years :-)
>


Agree, the way they often do it in Germany is useless. Glider having
to tell the guy at the phone what he's supposed to then tell the
winch. It's so simple if the winch has a radio.

Our winch has had a radio for decades. Even when we used to give the
lauch signals with a flag! About fifteen years ago we switched to
telephone to give the launching commands but as soon as the glider has
left the ground the guy at the phone says _nothing_ more. Then only
the glider pilot says either 'faster' or 'slower' over the radio.
Since we have the wire tension indicated to the winch driver these
commands have become very rare and so have cable breaks.

[Bob Johnson]

As long as we're sitting around the campfire and also to show you I can
go both ways, I 'member a time only a couple of years ago that I
experienced the dreaded aerotow line break at 200 ft and 60 kt over the
outbound fence.

I looked out front and it wasn't too exiting, so I gingerly turned
ninety to the left and the scenery looked some better, but not the
greatest, so I REALlY gingerly gave it another ninety to the left and
was really impressed this time as I found I was perfectly lined up with
the takeoff runway. And I recall I hadn't lost too much of my original
60 kt. Will wonders never cease!!

I thought "OK now God, you've made it possible for me to do this little
magic trick perfectly the first time I tried it in front of all my
friends and hangar bums, give me your hand again and let's try just one
more."

So I pulled spoilers, checked gear down and rolled up to my exact
takeoff spot.

And as I popped the canopy, my good friend who shall remain nameless,
said "S--t!, you've gone and lost us another Tost ring, somebody go back
to the hangar and see if they can find another tow rope". It was his
turn to tow, so I pushed back. Nobody else said a word.

Safety lecture from a dummy follows:

I don't remember to this day why I ninetied to the left. During the
previous year's biannual when Juan Batch pulled the plug on me over his
outbound fence, turning right was the correct choice because in that
direction lay the wind, which blows one back over the airport. This
improves the scenery like you wouldn't believe.

When I tried the trick for real solo, the wind lay to my left. I'd like
to think it was instinct. But I believe it was a coin toss.

Anyway, thank God. And Juan.

It Depends

BJ






Bob Johnson wrote:
>
> Hi Bill --
>
> I 'member my O-Nine Two oil field piano wire breaking at the half way
> point during a tow in Roy Schlemeyer's old SGS 2-22. I yelled "Oh, line
> break" or something to that effect and recall the glider innards debris
> collected since the last ice age floating up and dancing before my eyes
> as I dumped the stick full forward. Was it half a second before I
> reacted? Can't believe I waited that long. And when the astronauts tell
> you that zero-g is exhilarating, believe it.
>
> Luckily, I had been well briefed by Roy as to what to expect. It has
> been theorized that some people are "allergic" to zero-g and they
> instinctively jerk the stick full back instead of push full forward.
> Unfortunately, this is the last mistake they ever make and we can no
> longer interview them as to why they did this.
>
> There, we're back to the original question, "Is winch launch safer than
> aerotow?" The answer? -- scroll down
>
> IT DEPENDS!
>
> Thanks and good to hear from you again.
>
> BJ
>
>
>
> Bill Daniels wrote:
> >
> > "Bob Johnson" > wrote in message
> > ...
> > > Eggert --
> > >
> > > Those are really good numbers for your winch.
> > >
> > > With V8 300 HP (GMC 454 c.i., 7.4 L), and 5000 ft (1550 m) Plasma line
> > > laid out, we are getting the rule of thumb 1/3 cable length releases of
> > > 1700 ft (525 m). This is into 10-15 kt wind. Much over that, we leave
> > > the Blanik in the barn!
> > >
> > > BJ
> > > Midland, Texas
> >
> > Bob, When winching, the wind is your friend. Quitting at 15 knots is not
> > necessary. I have winched into 35 knots and higher winds and the results
> > are spectacular. Each 10 knots of headwind is the equivalent of about 40
> > additional HP.
> >
> > The thing that often severely limits the altitude gained is a slow pitch-up
> > profile at the start of the launch. The final height achieved is largely
> > determined by the profile flown in the first few seconds of the launch.
> >
> > Now, as everyone has pointed out, you need to be careful here. Safety at
> > the start of the climb is a combination of airspeed, altitude and attitude.
> > The more you have of the first, the faster you can get the second two and
> > the higher you will get.
> >
> > I've done calculations, simulator runs (X-Plane) and flight test to prove
> > the following point. If you have 60 knots in a glider with a stalling
> > airspeed of 40 knots, you can be in full climb attitude at zero altitude and
> > still have a large safety margin. Practice this way - at several thousand
> > feet AGL, zoom the glider into a 50 degree nose-up attitude. As the
> > airspeed decays to 60 knots, yell "WIRE BREAK", delay 0.5 seconds
> > (simulating reaction time) and pitch forward at zero G. Watch the airspeed
> > and altitude, you'll see what I mean. (For winch CFI-G's, this is a great
> > way to teach how to handle wire breaks.)
> >
> > If you have (or simulate) a wire break at this point and start a zero G
> > pitch over after a .5 second delay, the minimum airspeed during the
> > parabolic ballistic trajectory will be about 50 - 55 knots when the glider
> > reaches apogee at an altitude of about 100 feet AGL. So there you are at
> > 100 feet and 55 knots in a normal gliding attitude - not exactly a
> > problematic situation, just land straight ahead. The reason this works is
> > that the glider's induced drag at zero G is minimal so the airspeed decay is
> > mainly just due to gravity and the glider follows a parabolic trajectory
> > until the pilot re-establishes one G at the normal glide attitude.
> >
> > I need to repeat that I am not advocating a rocket blast-off kind of climb
> > profile but a smooth transition into the full climb without undue delay
> > equipped with a full understanding of the safety margins.
> >
> > Bill Daniels

[JJ Sinclair]

>JJ, you've had some bad experiences and I'm sorry for that. But you have to
>realize that there are hundreds of thousands, if not millions of winch
>launches all around the world that go off without a hitch simply because the
>people involved know what they are doing.

The subject under discussion is a club that is thinking about trying a new
launch system, winch launching and now pay-out winch. My point in posting on
this subject is to show what can happen when unskilled club members try a new
system.
JJ Sinclair

[Bill Daniels]

"JJ Sinclair" > wrote in message
...
>
>
> >JJ, you've had some bad experiences and I'm sorry for that. But you have
to
> >realize that there are hundreds of thousands, if not millions of winch
> >launches all around the world that go off without a hitch simply because
the
> >people involved know what they are doing.
>
> The subject under discussion is a club that is thinking about trying a new
> launch system, winch launching and now pay-out winch. My point in posting
on
> this subject is to show what can happen when unskilled club members try a
new
> system.
> JJ Sinclair

OK, JJ, If they are unskilled and insist on REMAINING unskilled, I'll give
you the point. Everybody starts out unskilled, however - I don't hold that
against them.

I don't think you are dissing ground launch, you're just warning that any
group needs to realize that there is a steep learning curve ahead of them.
I'll agree with that.

They've learned to fly gliders however, so they can't be dumb. I think they
can learn to operate a winch safely and enjoyably IF they take the trouble
to learn the art and science of it. There are lots of books to read and
this medium, the internet, connects us with the world where there is a
wealth of knowledge about ground launch.

If someone wanted to do the world of ground launch a great favor, they would
start a web site where the collective wisdom of the world could be displayed
so that anyone wishing to undertake winch launch could go there and get an
education.

Any volunteers?

Bill Daniels

I say learn and enjoy.

Bill Daniels

[Andreas Maurer]

On Wed, 29 Oct 2003 16:48:38 +0100, "Bert Willing"
> wrote:

>Nothing worse than an additional communication step between pilot and winch
>driver. Did that for 10 years in Germany, happy to do it by radio ever since
>I left Germany, hadn't had an interference from others on the same
>frequencies for the last 13 years :-)

Don't forget that you rarely do 100 launches per day at your current
airfield with "Vent arriere" messages each 3 minutes, interfering with
launches... :)

(Yes - I'm envious!)

Of course you are correct - it's nice to have a direct connection
between pilot and winch driver.
My club at Landau has never had such a (radio) communication, and we
seldom miss it. Sometimes the Ka-8 gets too fast (and releases early),
but otherwise I cannot remember and disadvantages of not having a
glider-winch connection.
It's more a question of winch driver practice - drivers with little
practice tend to judge the speed wrong and need corrections.

To add some spice - I personally watched two bad winch accidents, each
had to do with power failure of the winch/too low airspeed. In both
cases there was direct radio communication between glider and winch.






Bye
Andreas

[Bruce Hoult]

In article >,
Bob Johnson > wrote:

> Our engine is petrol fueled. Despite Google's best efforts, I have not
> yet located a Torque/HP/RPM curve for our very common 7.4 L engine, but
> have heard that it develops max torque and HP at about 3000 RPM and
> further that the curves are fairly flat at this point.

You are making some totally contradictory and inconsistent claims there.

If max torque and max HP occur close together then they must both drop
off precipitously after that.

If the torque curve is flat then HP will be increasing linearly with
RPM, max torque and max HP will be very far apart.


It is quite likely that you do have maximum torque at around 3000 RPM,
but if for example the torque curve is flat enough that the torque at
the 5000 RPM redline is still 60% or more of that at 3000 RPM then that
(redline) is exactly where maximum power will be.

-- Bruce

[Marcel Duenner]

> To add some spice - I personally watched two bad winch accidents, each
> had to do with power failure of the winch/too low airspeed. In both
> cases there was direct radio communication between glider and winch.
>

Of course having radio connection does not mean you can just let the
launch happen. You still have to fly it and react to whatever
situation arises. First, you have to use the radio. Second you have to
use it before it's to late and third and most important: never rely on
the use of radio of having any effect on the launch.
I still fail to understand why any winch or cabel failure should lead
to an accident. With or without radio. With or without wind. With or
without water ballast.
Be prepared.

Marcel

[Robert Ehrlich]

Bob Johnson wrote:
>
> As long as we're sitting around the campfire and also to show you I can
> go both ways, I 'member a time only a couple of years ago that I
> experienced the dreaded aerotow line break at 200 ft and 60 kt over the
> outbound fence.
>
> I looked out front and it wasn't too exiting, so I gingerly turned
> ninety to the left and the scenery looked some better, but not the
> greatest, so I REALlY gingerly gave it another ninety to the left and
> was really impressed this time as I found I was perfectly lined up with
> the takeoff runway. And I recall I hadn't lost too much of my original
> 60 kt. Will wonders never cease!!
>
> I thought "OK now God, you've made it possible for me to do this little
> magic trick perfectly the first time I tried it in front of all my
> friends and hangar bums, give me your hand again and let's try just one
> more."
>
> So I pulled spoilers, checked gear down and rolled up to my exact
> takeoff spot.
>
> And as I popped the canopy, my good friend who shall remain nameless,
> said "S--t!, you've gone and lost us another Tost ring, somebody go back
> to the hangar and see if they can find another tow rope". It was his
> turn to tow, so I pushed back. Nobody else said a word.
>
> Safety lecture from a dummy follows:
>
> I don't remember to this day why I ninetied to the left. During the
> previous year's biannual when Juan Batch pulled the plug on me over his
> outbound fence, turning right was the correct choice because in that
> direction lay the wind, which blows one back over the airport. This
> improves the scenery like you wouldn't believe.
>
> When I tried the trick for real solo, the wind lay to my left. I'd like
> to think it was instinct. But I believe it was a coin toss.
>
> Anyway, thank God. And Juan.
>
> It Depends
>
> BJ
>

This raises the interesting question of the height loss during a 180 degrees
turn in a glider or an airplane with a dead engine. I recently had a dicsussion
about that with a friend who is a power pilot and on this occasion made again a
small computation I had already made on this matter. As I never have seen
these results elsewhere, I think it may useful to show that here. Assume
you fly your turn wit an angle of attack which correspond to the speed V
when flying straight and wings level, and that the vertical sink speed
in the same conditions wuold be Vz, then during this 180 degrees turn
flown with a bank angle phi, the height loss is pi*V*Vz/(g*sin(phi)*cos(phi)),
and the turn is flown at speed V/sqrt(cos(phi)). The optimum (minimal
height loss) is when sin(phi)*cos(phi) is maximum, i.e. phi = 45 degrees,
and the product V*Vz is minimum. A glance on a typical glider polar will
show that this last thing is obtained with V just below min sink speed, but
as it is not easy to find how many below, let's assume the turn is done
at min sink speed, this is not very far from the optimum. For a typical
glider with min sink of .6 m/s at 80 km/h (22.2 m/s) the height loss is
8.5 m, for a typical airplane with min sink of 3 m/s at 120 km/h (33.3 m/s)
the height loss is 64 m. This explains why the 180 degrees turn back to
the runway over the outbound fence succeeds in a glider but not in a power
plane.

In the case mentioned above, the speed (60kt) was far over the optimum,
however the result is as expected not catastrophic. Assuming a bank angle
of 45 degrees, the equivalent speed in straight flight would be multiplied
by 1.18, this gives 26 m/s or 93 km/h. Assuming the sink speed is 1 m/s in these
conditions, we get a height loss of 16.6m. This is for a poor glider (L/D =
26 at 93 km/h).

[Martin Gregorie]

On Thu, 30 Oct 2003 10:11:18 +0000, Robert Ehrlich
> wrote:

>Bob Johnson wrote:
>>
>> As long as we're sitting around the campfire and also to show you I can
>> go both ways, I 'member a time only a couple of years ago that I
>> experienced the dreaded aerotow line break at 200 ft and 60 kt over the
>> outbound fence.
>>
>> I looked out front and it wasn't too exiting, so I gingerly turned
>> ninety to the left and the scenery looked some better, but not the
>> greatest, so I REALlY gingerly gave it another ninety to the left and
>> was really impressed this time as I found I was perfectly lined up with
>> the takeoff runway. And I recall I hadn't lost too much of my original
>> 60 kt. Will wonders never cease!!
>>
>> I thought "OK now God, you've made it possible for me to do this little
>> magic trick perfectly the first time I tried it in front of all my
>> friends and hangar bums, give me your hand again and let's try just one
>> more."
>>
>> So I pulled spoilers, checked gear down and rolled up to my exact
>> takeoff spot.
>>
>> And as I popped the canopy, my good friend who shall remain nameless,
>> said "S--t!, you've gone and lost us another Tost ring, somebody go back
>> to the hangar and see if they can find another tow rope". It was his
>> turn to tow, so I pushed back. Nobody else said a word.
>>
>> Safety lecture from a dummy follows:
>>
>> I don't remember to this day why I ninetied to the left. During the
>> previous year's biannual when Juan Batch pulled the plug on me over his
>> outbound fence, turning right was the correct choice because in that
>> direction lay the wind, which blows one back over the airport. This
>> improves the scenery like you wouldn't believe.
>>
>> When I tried the trick for real solo, the wind lay to my left. I'd like
>> to think it was instinct. But I believe it was a coin toss.
>>
>> Anyway, thank God. And Juan.
>>
>> It Depends
>>
>> BJ
>>
>
>This raises the interesting question of the height loss during a 180 degrees
>turn in a glider or an airplane with a dead engine. I recently had a dicsussion
>about that with a friend who is a power pilot and on this occasion made again a
>small computation I had already made on this matter. As I never have seen
>these results elsewhere, I think it may useful to show that here. Assume
>you fly your turn wit an angle of attack which correspond to the speed V
>when flying straight and wings level, and that the vertical sink speed
>in the same conditions wuold be Vz, then during this 180 degrees turn
>flown with a bank angle phi, the height loss is pi*V*Vz/(g*sin(phi)*cos(phi)),
>and the turn is flown at speed V/sqrt(cos(phi)). The optimum (minimal
>height loss) is when sin(phi)*cos(phi) is maximum, i.e. phi = 45 degrees,
>and the product V*Vz is minimum. A glance on a typical glider polar will
>show that this last thing is obtained with V just below min sink speed, but
>as it is not easy to find how many below, let's assume the turn is done
>at min sink speed, this is not very far from the optimum. For a typical
>glider with min sink of .6 m/s at 80 km/h (22.2 m/s) the height loss is
>8.5 m, for a typical airplane with min sink of 3 m/s at 120 km/h (33.3 m/s)
>the height loss is 64 m. This explains why the 180 degrees turn back to
>the runway over the outbound fence succeeds in a glider but not in a power
>plane.
>
>In the case mentioned above, the speed (60kt) was far over the optimum,
>however the result is as expected not catastrophic. Assuming a bank angle
>of 45 degrees, the equivalent speed in straight flight would be multiplied
>by 1.18, this gives 26 m/s or 93 km/h. Assuming the sink speed is 1 m/s in these
>conditions, we get a height loss of 16.6m. This is for a poor glider (L/D =
>26 at 93 km/h).

Thanks for that. A most informative calculation and certainly matches
my most recent relevant experience.

The last time I was having a supervised aero-tow refresher in our
Puchacz I was doing a running commentary for the instructors benefit
and as soon as I said "400 ft - no problem now from a rope break" BANG
as he pulled the release. We had a touch over 60 kts and as soon as I
saw the rope go I pulled a 45 degree banked 180, keeping the 60 kts
just as Bob described, and was amazed at how easily we got in over the
fence. In fact, once I'd rolled out it looked like a normal approach,
so I opened the brakes and did a typical Puchacz approach and landing.

--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

[Brian Case]

> If someone wanted to do the world of ground launch a great favor, they would
> start a web site where the collective wisdom of the world could be displayed
> so that anyone wishing to undertake winch launch could go there and get an
> education.

Ok it may not be the collective wisdom of the world. But there is
quite a bit of information on winch launching at:

http://www.northwestsoaring.com/sitemap.shtml

Let me know if I am missing anything really important about Winch
Launching here.

Brian Case
CFIIG/ASEL

[Bill Daniels]

"Brian Case" > wrote in message
om...
> > If someone wanted to do the world of ground launch a great favor, they
would
> > start a web site where the collective wisdom of the world could be
displayed
> > so that anyone wishing to undertake winch launch could go there and get
an
> > education.
>
> Ok it may not be the collective wisdom of the world. But there is
> quite a bit of information on winch launching at:
>
> http://www.northwestsoaring.com/sitemap.shtml
>
> Let me know if I am missing anything really important about Winch
> Launching here.
>
> Brian Case
> CFIIG/ASEL

Good site - congratulations.

About your 2003 procedures - you must have had a bad experience with gusty
wind conditions. This is why I have been advocating airspeed telemetry.

Bill Daniels

[John Galloway]

About 20 years ago I was doing an aerotow from the
front seat of a Janus at Lasham with Derek Piggot in
the back during a cross country course. We were just
off the deck within the airfield waiting for the tug
to start to climb and I heard Derek say '60 knots'.
Later I asked him why he said that out loud and he
told me that he always made a note of when the speed
reached 60 knots because he reckoned that at that speed
he could pull up and turn back without loss of height.

John Galloway


At 14:00 30 October 2003, Martin Gregorie wrote:
>On Thu, 30 Oct 2003 10:11:18 +0000, Robert Ehrlich
> wrote:
>
>>Bob Johnson wrote:
>>>
>>> As long as we're sitting around the campfire and also
>>>to show you I can
>>> go both ways, I 'member a time only a couple of years
>>>ago that I
>>> experienced the dreaded aerotow line break at 200
>>>ft and 60 kt over the
>>> outbound fence.
>>>
>>> I looked out front and it wasn't too exiting, so I
>>>gingerly turned
>>> ninety to the left and the scenery looked some better,
>>>but not the
>>> greatest, so I REALlY gingerly gave it another ninety
>>>to the left and
>>> was really impressed this time as I found I was perfectly
>>>lined up with
>>> the takeoff runway. And I recall I hadn't lost too
>>>much of my original
>>> 60 kt. Will wonders never cease!!
>>>
>>> I thought 'OK now God, you've made it possible for
>>>me to do this little
>>> magic trick perfectly the first time I tried it in
>>>front of all my
>>> friends and hangar bums, give me your hand again and
>>>let's try just one
>>> more.'
>>>
>>> So I pulled spoilers, checked gear down and rolled
>>>up to my exact
>>> takeoff spot.
>>>
>>> And as I popped the canopy, my good friend who shall
>>>remain nameless,
>>> said 'S--t!, you've gone and lost us another Tost
>>>ring, somebody go back
>>> to the hangar and see if they can find another tow
>>>rope'. It was his
>>> turn to tow, so I pushed back. Nobody else said a
>>>word.
>>>
>>> Safety lecture from a dummy follows:
>>>
>>> I don't remember to this day why I ninetied to the
>>>left. During the
>>> previous year's biannual when Juan Batch pulled the
>>>plug on me over his
>>> outbound fence, turning right was the correct choice
>>>because in that
>>> direction lay the wind, which blows one back over
>>>the airport. This
>>> improves the scenery like you wouldn't believe.
>>>
>>> When I tried the trick for real solo, the wind lay
>>>to my left. I'd like
>>> to think it was instinct. But I believe it was a coin
>>>toss.
>>>
>>> Anyway, thank God. And Juan.
>>>
>>> It Depends
>>>
>>> BJ
>>>
>>
>>This raises the interesting question of the height
>>loss during a 180 degrees
>>turn in a glider or an airplane with a dead engine.
>>I recently had a dicsussion
>>about that with a friend who is a power pilot and on
>>this occasion made again a
>>small computation I had already made on this matter.
>>As I never have seen
>>these results elsewhere, I think it may useful to show
>>that here. Assume
>>you fly your turn wit an angle of attack which correspond
>>to the speed V
>>when flying straight and wings level, and that the
>>vertical sink speed
>>in the same conditions wuold be Vz, then during this
>>180 degrees turn
>>flown with a bank angle phi, the height loss is pi*V*Vz/(g*sin(ph
>>>i)*cos(phi)),
>>and the turn is flown at speed V/sqrt(cos(phi)). The
>>optimum (minimal
>>height loss) is when sin(phi)*cos(phi) is maximum,
>>i.e. phi = 45 degrees,
>>and the product V*Vz is minimum. A glance on a typical
>>glider polar will
>>show that this last thing is obtained with V just below
>>min sink speed, but
>>as it is not easy to find how many below, let's assume
>>the turn is done
>>at min sink speed, this is not very far from the optimum.
>>For a typical
>>glider with min sink of .6 m/s at 80 km/h (22.2 m/s)
>>the height loss is
>>8.5 m, for a typical airplane with min sink of 3 m/s
>>at 120 km/h (33.3 m/s)
>>the height loss is 64 m. This explains why the 180
>>degrees turn back to
>>the runway over the outbound fence succeeds in a glider
>>but not in a power
>>plane.
>>
>>In the case mentioned above, the speed (60kt) was far
>>over the optimum,
>>however the result is as expected not catastrophic.
>>Assuming a bank angle
>>of 45 degrees, the equivalent speed in straight flight
>>would be multiplied
>>by 1.18, this gives 26 m/s or 93 km/h. Assuming the
>>sink speed is 1 m/s in these
>>conditions, we get a height loss of 16.6m. This is
>>for a poor glider (L/D =
>>26 at 93 km/h).
>
>Thanks for that. A most informative calculation and
>certainly matches
>my most recent relevant experience.
>
>The last time I was having a supervised aero-tow refresher
>in our
>Puchacz I was doing a running commentary for the instructors
>benefit
>and as soon as I said '400 ft - no problem now from
>a rope break' BANG
>as he pulled the release. We had a touch over 60 kts
>and as soon as I
>saw the rope go I pulled a 45 degree banked 180, keeping
>the 60 kts
>just as Bob described, and was amazed at how easily
>we got in over the
>fence. In fact, once I'd rolled out it looked like
>a normal approach,
>so I opened the brakes and did a typical Puchacz approach
>and landing.
>
>--
>martin@ : Martin Gregorie
>gregorie : Harlow, UK
>demon :
>co : Zappa fan & glider pilot
>uk :
>
>

[Eric Greenwell]

In article >,
says...
> I still fail to understand why any winch or cabel failure should lead
> to an accident. With or without radio. With or without wind. With or
> without water ballast.
> Be prepared.

I seem to recall some launches where the cable became tangled in the
main wheel, when the winch jerked the glider forward, then paused very
briefly. This is caused the glider to pitch up too fast at the start,
and the pilot was unable to release, leading to a crash. Perhaps this
is not what you mean by a winch failure?

--
!Replace DECIMAL.POINT in my e-mail address with just a . to reply
directly

Eric Greenwell
Richland, WA (USA)

[Andreas Maurer]

On 29 Oct 2003 23:17:50 -0800, (Marcel
Duenner) wrote:


>I still fail to understand why any winch or cabel failure should lead
>to an accident. With or without radio. With or without wind. With or
>without water ballast.
>Be prepared.

100% agree.

I sometimes get the impression that in case of a glider-winch radio
connection the glider pilot tends to rely on his radio commands
("faster" - "slower") to correct a sub-optimum situation. Which
obviously not works in all cases and then might lead to an even worse
situation.

In case of no glider-winch connection the glider pilot completely
relies on himself and takes the according action if a certain
parameter (e-g. speed) exceeds the (his) limits.
Bye
Andreas

[Chris Nicholas]

What Eric describes has happened, but the way to eliminate that event is
to sheathe the cable with plastic hosepipe of suitable size at the
glider end, so it is too stiff to wrap round the axle (or even enter
the wheel box area). It is one of many things where the technology and
operational procedures have been modified and developed over the years
to reduce accidents and incidents to the minumum, leaving only pilot
error/failure to act as trained as the remiaining significant factor.

Chris N.


Eric G: "I seem to recall some launches where the cable became tangled
in the
main wheel, when the winch jerked the glider forward, then paused very
briefly. This is caused the glider to pitch up too fast at the start,
and the pilot was unable to release, leading to a crash. [snip]"

[Bob Johnson]

Hi Bruce --

That's a very welcome correction to my hazily-remembered version of a
second-hand report of what the 454 c.i. engine torque/hp/rpm chart looks
like. This is the kind of info I was looking for and thanks for providing it!

In all our past kicking around of the ideal winch prime mover, here's one
that sounds silly but might rate at least an engineering investigation -- a
recip steam engine! If I recall correctly, the steam engine develops max
torque at stall.

What got me thinking about that was the fact that the Navy gets 66,000 lb
Super Hornets flying in about the same three seconds that it takes us to get
airborne. And they do it with steam, not because it's handy, but that's
probably the only practical way to get it done.

BJ

Bruce Hoult wrote:

> In article >,
> Bob Johnson > wrote:
>
> > Our engine is petrol fueled. Despite Google's best efforts, I have not
> > yet located a Torque/HP/RPM curve for our very common 7.4 L engine, but
> > have heard that it develops max torque and HP at about 3000 RPM and
> > further that the curves are fairly flat at this point.
>
> You are making some totally contradictory and inconsistent claims there.
>
> If max torque and max HP occur close together then they must both drop
> off precipitously after that.
>
> If the torque curve is flat then HP will be increasing linearly with
> RPM, max torque and max HP will be very far apart.
>
> It is quite likely that you do have maximum torque at around 3000 RPM,
> but if for example the torque curve is flat enough that the torque at
> the 5000 RPM redline is still 60% or more of that at 3000 RPM then that
> (redline) is exactly where maximum power will be.
>
> -- Bruce

[Martin Gregorie]

On Thu, 30 Oct 2003 07:49:51 -0800, Eric Greenwell
> wrote:

>In article >,
says...
>> I still fail to understand why any winch or cabel failure should lead
>> to an accident. With or without radio. With or without wind. With or
>> without water ballast.
>> Be prepared.
>
>I seem to recall some launches where the cable became tangled in the
>main wheel, when the winch jerked the glider forward, then paused very
>briefly. This is caused the glider to pitch up too fast at the start,
>and the pilot was unable to release, leading to a crash. Perhaps this
>is not what you mean by a winch failure?

That should be a recoverable situation provided that the signalling
channel between launch point and winch can convey three messages:

- take up slack
- all out
- STOP

If, as it appears to be the case at Torrey Pines, the headlamp signals
can't be used to signal STOP then you have an accident waiting to
happen. The launch marshal must ALWAYS be able to signal STOP and be
obeyed without question. Doesn't matter whether the channel is radio,
telephone, coded light flashes or signalling bat provided that it can
transmit those three commands unambiguously.

On the sites where I've winch launched an immediate STOP is signalled
if the glider overruns the cable for any reason. The reason we use the
three phrases listed above (repeated continuously) is that they have
three, two and one syllable and so can be distinguished despite noise
in the winch cab and/or wind noise in the launch marshall's
microphone.

--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

[Robert Ehrlich]

Bob Johnson wrote:
>
> Robert -
> ...
> You may be using a which could account for your good performance
> at lower revs.
> ...

Yes, it's a Diesel, with no gearbox, only a reduction box and and
hydraulic (or should be called "oilic" :-) couple converter.

[Bill Daniels]

Actually, I read somewhere that the US Navy is converting its steam
catapults to linear electric motors to get finer control over the launch. I
also suspect that it reduces the manpower required to operate the "cat".

Bill Daniels

"Bob Johnson" > wrote in message
...
> Hi Bruce --
>
> That's a very welcome correction to my hazily-remembered version of a
> second-hand report of what the 454 c.i. engine torque/hp/rpm chart looks
> like. This is the kind of info I was looking for and thanks for providing
it!
>
> In all our past kicking around of the ideal winch prime mover, here's one
> that sounds silly but might rate at least an engineering investigation --
a
> recip steam engine! If I recall correctly, the steam engine develops max
> torque at stall.
>
> What got me thinking about that was the fact that the Navy gets 66,000 lb
> Super Hornets flying in about the same three seconds that it takes us to
get
> airborne. And they do it with steam, not because it's handy, but that's
> probably the only practical way to get it done.
>
> BJ
>
> Bruce Hoult wrote:
>
> > In article >,
> > Bob Johnson > wrote:
> >
> > > Our engine is petrol fueled. Despite Google's best efforts, I have not
> > > yet located a Torque/HP/RPM curve for our very common 7.4 L engine,
but
> > > have heard that it develops max torque and HP at about 3000 RPM and
> > > further that the curves are fairly flat at this point.
> >
> > You are making some totally contradictory and inconsistent claims there.
> >
> > If max torque and max HP occur close together then they must both drop
> > off precipitously after that.
> >
> > If the torque curve is flat then HP will be increasing linearly with
> > RPM, max torque and max HP will be very far apart.
> >
> > It is quite likely that you do have maximum torque at around 3000 RPM,
> > but if for example the torque curve is flat enough that the torque at
> > the 5000 RPM redline is still 60% or more of that at 3000 RPM then that
> > (redline) is exactly where maximum power will be.
> >
> > -- Bruce
>

[Jack]

in article , Robert Ehrlich at
wrote on 2003/10/30 4:11:

> Bob Johnson wrote:

>> I 'member a time only a couple of years ago that I experienced the
>> dreaded aerotow line break at 200 ft and 60 kt over the...fence.

> This raises the interesting question of the height loss during a 180
> degree turn in a glider or an airplane with a dead engine.

The considerations are not so different for a power plane or a glider, but
the parameters are different. See the cites/sites below in their entirety at
the inlcuded URLs for the discussion as applied to Genral Aviation ASEL
types:

--------------------

Should You Turnback?
or
The Possible `Impossible' Turn
by
David F. Rogers, PhD

Copyright (C) 1991 by David F. Rogers. All rights reserved.


"Most of us fly single engine aircraft. If the engine quits
on takeoff, should you attempt to turnback to land on the
runway? The turnback problem is extremely complex. Like many
complex problems, there is no single right answer. Each
situation must be judged individually. Thus, the answer is
a qualified maybe or the classical `it depends'. It depends
on the Conditions, the Aircraft, the Altitude, the
Proficiency of the pilot and on Planning. CAAPP for short."

http://web.usna.navy.mil/~dfr/flying/possible.html

================================================== ==========

The Possible `Impossible' Turn

David F. Rogers
United States Naval Academy
Annapolis, Maryland 21402

Copyright 1994 David F. Rogers, All rights reserved.
Originally published in the AIAA Journal of Aircraft, Vol. 32,
pp. 392-397, 1995 with permission.

"Turning back after engine failure during the take-off phase
of flight in a single engine aircraft is examined using a
simplified analytical model. The important parameters are
identified. The analysis shows that the optimum flight path
is teardrop shaped with a 45-degree bank angle at stall
velocity during the turn. The effects of engine failure
altitude, wind direction and velocity, and bank angle on
the required runway length are examined. The results show
that the typical recommendations for general aviation
single engine aircraft are not optimum."

http://web.usna.navy.mil/~dfr/flying/aiaa1col.pdf

================================================== ==========

[tango4]

I love it! The boiler could provide the permanent thermal off the top of the
launch too!

Ian

"Bob Johnson" > wrote in message
...
> Hi Bruce --
>
> That's a very welcome correction to my hazily-remembered version of a
> second-hand report of what the 454 c.i. engine torque/hp/rpm chart looks
> like. This is the kind of info I was looking for and thanks for providing
it!
>
> In all our past kicking around of the ideal winch prime mover, here's one
> that sounds silly but might rate at least an engineering investigation --
a
> recip steam engine! If I recall correctly, the steam engine develops max
> torque at stall.
>
> What got me thinking about that was the fact that the Navy gets 66,000 lb
> Super Hornets flying in about the same three seconds that it takes us to
get
> airborne. And they do it with steam, not because it's handy, but that's
> probably the only practical way to get it done.
>
> BJ
>
> Bruce Hoult wrote:
>
> > In article >,
> > Bob Johnson > wrote:
> >
> > > Our engine is petrol fueled. Despite Google's best efforts, I have not
> > > yet located a Torque/HP/RPM curve for our very common 7.4 L engine,
but
> > > have heard that it develops max torque and HP at about 3000 RPM and
> > > further that the curves are fairly flat at this point.
> >
> > You are making some totally contradictory and inconsistent claims there.
> >
> > If max torque and max HP occur close together then they must both drop
> > off precipitously after that.
> >
> > If the torque curve is flat then HP will be increasing linearly with
> > RPM, max torque and max HP will be very far apart.
> >
> > It is quite likely that you do have maximum torque at around 3000 RPM,
> > but if for example the torque curve is flat enough that the torque at
> > the 5000 RPM redline is still 60% or more of that at 3000 RPM then that
> > (redline) is exactly where maximum power will be.
> >
> > -- Bruce
>

[Bob Johnson]

OK, the threads on this topic are branching out pretty good, so again I feel the
need to post that most if not all of the collected wisdom in the world concerning
ground launch in all of its phases is already available in one place.

This place is between the covers of one slim volume by the same name and was
authored by the great Derek Piggott. I just Googled "ground launch piggott" and
up popped maybe a half dozen people who wanted to sell me one. The first was NSM,
our National Soaring Museum:

http://www.soaringmuseum.org/estore/loaditem.html?itempage=item353463656.html

Get one today! (Book, that is)

And after you read it, don't go out and "do this at home" as they say. Get
somebody that knows how to show you the ropes (har, har) and then the book will
make much more sense.

Disclaimer--- I own stock in both Piggott Enterprises and NSM.

Just kidding

BJ

Brian Case wrote:

> > If someone wanted to do the world of ground launch a great favor, they would
> > start a web site where the collective wisdom of the world could be displayed
> > so that anyone wishing to undertake winch launch could go there and get an
> > education.
>
> Ok it may not be the collective wisdom of the world. But there is
> quite a bit of information on winch launching at:
>
> http://www.northwestsoaring.com/sitemap.shtml
>
> Let me know if I am missing anything really important about Winch
> Launching here.
>
> Brian Case
> CFIIG/ASEL

[Bob Johnson]

Gonna take a California Governor-sized battery and alternator combo down there
in the nuclear engine room!

Using my handy-dandy winch horsepower spreadsheet, solving for required
launching force is an incredible 218,000 pounds and over 50,000 horsepower! Of
course the engines are in full AB, but still ---

Other numbers are a "ground run" of 306 ft and a peak acceleration of 3.3G in
2.4 sec.

I can see that they have already provided the Super Hornet with a pretty stout
nosegear. That's where their "cg hook" is, I believe.

BJ

Bill Daniels wrote:

> Actually, I read somewhere that the US Navy is converting its steam
> catapults to linear electric motors to get finer control over the launch. I
> also suspect that it reduces the manpower required to operate the "cat".
>
> Bill Daniels
>
> "Bob Johnson" > wrote in message
> ...
> > Hi Bruce --
> >
> > That's a very welcome correction to my hazily-remembered version of a
> > second-hand report of what the 454 c.i. engine torque/hp/rpm chart looks
> > like. This is the kind of info I was looking for and thanks for providing
> it!
> >
> > In all our past kicking around of the ideal winch prime mover, here's one
> > that sounds silly but might rate at least an engineering investigation --
> a
> > recip steam engine! If I recall correctly, the steam engine develops max
> > torque at stall.
> >
> > What got me thinking about that was the fact that the Navy gets 66,000 lb
> > Super Hornets flying in about the same three seconds that it takes us to
> get
> > airborne. And they do it with steam, not because it's handy, but that's
> > probably the only practical way to get it done.
> >
> > BJ
> >
> > Bruce Hoult wrote:
> >
> > > In article >,
> > > Bob Johnson > wrote:
> > >
> > > > Our engine is petrol fueled. Despite Google's best efforts, I have not
> > > > yet located a Torque/HP/RPM curve for our very common 7.4 L engine,
> but
> > > > have heard that it develops max torque and HP at about 3000 RPM and
> > > > further that the curves are fairly flat at this point.
> > >
> > > You are making some totally contradictory and inconsistent claims there.
> > >
> > > If max torque and max HP occur close together then they must both drop
> > > off precipitously after that.
> > >
> > > If the torque curve is flat then HP will be increasing linearly with
> > > RPM, max torque and max HP will be very far apart.
> > >
> > > It is quite likely that you do have maximum torque at around 3000 RPM,
> > > but if for example the torque curve is flat enough that the torque at
> > > the 5000 RPM redline is still 60% or more of that at 3000 RPM then that
> > > (redline) is exactly where maximum power will be.
> > >
> > > -- Bruce
> >

[Bruce Hoult]

In article >,
Bob Johnson > wrote:

> In all our past kicking around of the ideal winch prime mover, here's one
> that sounds silly but might rate at least an engineering investigation -- a
> recip steam engine! If I recall correctly, the steam engine develops max
> torque at stall.

That is true, and it is also true of many electric motors.

Unfortunately, I suspect that if they are strong enough with the glider
flying at 60 knots then they will be far *too* strong at the start!

-- Bruce

[Bob Johnson]

I believe a German club has recently built themselves a DC winch using
dozens of automotive type batteries. Haven't heard how they have done
with it, though.

BJ

Bruce Hoult wrote:
>
> In article >,
> Bob Johnson > wrote:
>
> > In all our past kicking around of the ideal winch prime mover, here's one
> > that sounds silly but might rate at least an engineering investigation -- a
> > recip steam engine! If I recall correctly, the steam engine develops max
> > torque at stall.
>
> That is true, and it is also true of many electric motors.
>
> Unfortunately, I suspect that if they are strong enough with the glider
> flying at 60 knots then they will be far *too* strong at the start!
>
> -- Bruce

[Andrew Warbrick]

Yes, but would you get up at 3am to stoke it :)

At 20:24 30 October 2003, Tango4 wrote:
>I love it! The boiler could provide the permanent thermal
>off the top of the
>launch too!
>
>Ian
>
>'Bob Johnson' wrote in message
...
>> Hi Bruce --
>>
>> That's a very welcome correction to my hazily-remembered
>>version of a
>> second-hand report of what the 454 c.i. engine torque/hp/rpm
>>chart looks
>> like. This is the kind of info I was looking for and
>>thanks for providing
>it!
>>
>> In all our past kicking around of the ideal winch
>>prime mover, here's one
>> that sounds silly but might rate at least an engineering
>>investigation --
>a
>> recip steam engine! If I recall correctly, the steam
>>engine develops max
>> torque at stall.
>>
>> What got me thinking about that was the fact that
>>the Navy gets 66,000 lb
>> Super Hornets flying in about the same three seconds
>>that it takes us to
>get
>> airborne. And they do it with steam, not because it's
>>handy, but that's
>> probably the only practical way to get it done.
>>
>> BJ
>>
>> Bruce Hoult wrote:
>>
>> > In article ,
>> > Bob Johnson wrote:
>> >
>> > > Our engine is petrol fueled. Despite Google's best
>>>>efforts, I have not
>> > > yet located a Torque/HP/RPM curve for our very common
>>>>7.4 L engine,
>but
>> > > have heard that it develops max torque and HP at
>>>>about 3000 RPM and
>> > > further that the curves are fairly flat at this
>>>>point.
>> >
>> > You are making some totally contradictory and inconsistent
>>>claims there.
>> >
>> > If max torque and max HP occur close together then
>>>they must both drop
>> > off precipitously after that.
>> >
>> > If the torque curve is flat then HP will be increasing
>>>linearly with
>> > RPM, max torque and max HP will be very far apart.
>> >
>> > It is quite likely that you do have maximum torque
>>>at around 3000 RPM,
>> > but if for example the torque curve is flat enough
>>>that the torque at
>> > the 5000 RPM redline is still 60% or more of that
>>>at 3000 RPM then that
>> > (redline) is exactly where maximum power will be.
>> >
>> > -- Bruce
>>
>
>
>

[Guy Byars]

> Yes, but would you get up at 3am to stoke it :)

Who would't want to stroke the wench at 3am?

[F.L. Whiteley]

There once was a non-BGA soaring site/club in East Anglia in the UK. The
operator was named Fred, but the surname escapes me and I believe he passed
away in the 1980's. By all accounts he operated a steam winch though I
never met him nor saw it in action. I believe that operation was dwindling
and may have ceased operations about 1980. Any stories out there?

Frank Whiteley

"Bob Johnson" > wrote in message
...
> Hi Bruce --
>
> That's a very welcome correction to my hazily-remembered version of a
> second-hand report of what the 454 c.i. engine torque/hp/rpm chart looks
> like. This is the kind of info I was looking for and thanks for providing
it!
>
> In all our past kicking around of the ideal winch prime mover, here's one
> that sounds silly but might rate at least an engineering investigation --
a
> recip steam engine! If I recall correctly, the steam engine develops max
> torque at stall.
>
> What got me thinking about that was the fact that the Navy gets 66,000 lb
> Super Hornets flying in about the same three seconds that it takes us to
get
> airborne. And they do it with steam, not because it's handy, but that's
> probably the only practical way to get it done.
>
> BJ
>
> Bruce Hoult wrote:
>
> > In article >,
> > Bob Johnson > wrote:
> >
> > > Our engine is petrol fueled. Despite Google's best efforts, I have not
> > > yet located a Torque/HP/RPM curve for our very common 7.4 L engine,
but
> > > have heard that it develops max torque and HP at about 3000 RPM and
> > > further that the curves are fairly flat at this point.
> >
> > You are making some totally contradictory and inconsistent claims there.
> >
> > If max torque and max HP occur close together then they must both drop
> > off precipitously after that.
> >
> > If the torque curve is flat then HP will be increasing linearly with
> > RPM, max torque and max HP will be very far apart.
> >
> > It is quite likely that you do have maximum torque at around 3000 RPM,
> > but if for example the torque curve is flat enough that the torque at
> > the 5000 RPM redline is still 60% or more of that at 3000 RPM then that
> > (redline) is exactly where maximum power will be.
> >
> > -- Bruce
>

[Chris OCallaghan]

A related remembrance...

Years ago I attended a mid-summer's eve cookout at Ridge Soaring in
central PA. For entertainment we were armchairing the end o'day
training flights. A glider released just after take-off, landing at
the far end of the field. The tow plane landed, then taxied down to
launch the glider in the opposite direction. As the tug passed us,
2-33 in tow, KS asked what was going on. I explained that a series of
rope breaks were practiced as a student got close to solo. They had
just completed a straight ahead release and recovery and would now
practice a 180 for return to the runway. As the tow plane and glider
reached 20 feet above the ground, still short of the runway boundary,
Karl said, "Now! It would be hairy, but you could do it."

Karl and a handfull of other pilots probably could. The rest of us
wait until we have enough altitude to more than measure the sins we're
likely to commit as the emergency unfolds -- 200 feet being an
appropriate indulgence.

For those who need to know to the inch, don't forget to include 35% of
your wingspan, lest you bury a tip. And don't forget that anytime the
controls are not neutral, your sink rate goes well below the arc of
the polar.

So far, of the math I've seen, success would only be achieved for
gliders of zero span requiring no control input (and resulting drag)
to initiate a bank or roll out of it.

[Bill Daniels]

"Chris OCallaghan" > wrote in message
om...
> A related remembrance...
>
> Years ago I attended a mid-summer's eve cookout at Ridge Soaring in
> central PA. For entertainment we were armchairing the end o'day
> training flights. A glider released just after take-off, landing at
> the far end of the field. The tow plane landed, then taxied down to
> launch the glider in the opposite direction. As the tug passed us,
> 2-33 in tow, KS asked what was going on. I explained that a series of
> rope breaks were practiced as a student got close to solo. They had
> just completed a straight ahead release and recovery and would now
> practice a 180 for return to the runway. As the tow plane and glider
> reached 20 feet above the ground, still short of the runway boundary,
> Karl said, "Now! It would be hairy, but you could do it."
>
> Karl and a handfull of other pilots probably could. The rest of us
> wait until we have enough altitude to more than measure the sins we're
> likely to commit as the emergency unfolds -- 200 feet being an
> appropriate indulgence.
>
> For those who need to know to the inch, don't forget to include 35% of
> your wingspan, lest you bury a tip. And don't forget that anytime the
> controls are not neutral, your sink rate goes well below the arc of
> the polar.
>
> So far, of the math I've seen, success would only be achieved for
> gliders of zero span requiring no control input (and resulting drag)
> to initiate a bank or roll out of it.

Not to belabor the obvious, but a 180 return to the runway from a 200 foot
airtow rope break is not always possible. We tend to talk as if it were
true but if believe it, we may be setting up a disaster. With a heavy
glider, weak tug, high density altitude and unfavorable wind (and maybe a
thick headed tug pilot) you may need as much as 1000 feet to be in a
position for a safe return to the airfield.

There have been many occasions when my left hand hovered near the release in
preparation for a simulated rope break. But, looking back over my shoulder
at the airfield, I thought, "I don't theeenk so" and let the student
continue.

Over the last year a young friend of mine (A CFI-G) suffered two low
altitude rope breaks (weak link failures) and each incident resulted in an
off-airfield landing. (To his credit - no damage)

Bill Daniels

[Chris Nicholas]

Frank Whiteley wrote[snip]
There once was a non-BGA soaring site/club in East Anglia in the UK. The
operator was named Fred, but the surname escapes me and I believe he
passed
away in the 1980's. By all accounts he operated a steam winch [snip]

Freddie Wiseman was the man, and the winch was not steam powered, but
diesel. It was remarkable in that it was a converted combine harvester.
I have a photo of it somewhere. I saw it working. It was rather low
powered, and operated via huge canvas belt drives which were
"interesting". Not technology I would suggest repeating elsewhere.

The site was Ridgewell (ex 381st BG base 1943-45), where I now fly
from - see http://www.essexgliding.org/index.htm

The winch was fairly lethal, potentially - I knew one of the drivers who
had to contend with a broken cable still under power thrashing around in
the cab. After Freddie's death in 1984 a few people revived the club
and continued to use the combine winch until 1988. When my club bought
the site the winch was still intact and was brought back, but we decided
not to use it and instead bought other winches. The only time I know of
using it in our time was as a towing vehicle, when we moved two huts and
the tractors got bogged down (don't ask - it's a long story). It did
the rescue but burnt out its clutch in the process. It was eventually
scrapped about three years ago.

Relevance to the subject line - it was dangerous to the operator, but
never hurt a pilot - instead gave lots of practice, as is only right, in
"premature terminations of launch" and "too low in circuit".

Chris N.

[Jack]

in article et, Bill
Daniels at wrote on 2003/10/31 11:39:



> ...a 180 return to the runway from a 200 foot airtow rope break
> is not always possible.

> ...you may need as much as 1000 feet to be in a position for
> a safe return to the airfield.

> ...two low altitude rope breaks (weak link failures) and...resulted
> in...off-airfield landing[s].


More specifics please for those off-airport landings. Otherwise your "1000
feet" may be taken by some as a bit of an exageration.



Jack

[Bill Daniels]

"Jack" > wrote in message
...
> in article et, Bill
> Daniels at wrote on 2003/10/31 11:39:
>
>
>
> > ...a 180 return to the runway from a 200 foot airtow rope break
> > is not always possible.
>
> > ...you may need as much as 1000 feet to be in a position for
> > a safe return to the airfield.
>
> > ...two low altitude rope breaks (weak link failures) and...resulted
> > in...off-airfield landing[s].
>
>
> More specifics please for those off-airport landings. Otherwise your "1000
> feet" may be taken by some as a bit of an exageration.
>
>
>
> Jack
>

In my friends case, the first break came shortly after crossing the field
boundary at about 50 feet. This was a case of insufficient climb angle to
reach 200 feet while still in range of the runway. The other, as I
understand it, was at about 300 feet but still out of gliding range of the
airport.

My comment about 1000 feet referred to a situation that happened to me
because the tug pilot turned downwind at 100 feet AGL with a heavy glider
and strayed still further downwind as the air tow ground on despite urgent
radio calls. It was only at 1000 feet AGL that I felt that I could release
and get back. (and get another tug pilot) This has happened to me too many
times to recall all of them.

Understand, I fly in an area where density altitude at takeoff can exceed
10,000 feet. It takes a strong tug to keep a heavy two seater constantly in
range of the runway.

My point with the original post is that there is no guarantee that the magic
200 feet AGL will always get you back.

Bill Daniels

[Jack]

in article . net, Bill
Daniels at wrote on 2003/10/31 19:45:

>
> "Jack" > wrote in message
> ...

>> More specifics please for those off-airport landings. Otherwise your "1000
>> feet" may be taken by some as a bit of an exaggeration.

> ...in an area where density altitude at takeoff can exceed
> 10,000 feet...[i]t takes a strong tug to keep a heavy two seater
> constantly in range of the runway.

> ...there is no guarantee that the magic 200 feet AGL will
> always get you back.

Very good point, and thanks much for the additional information.

You have a much greater challenge then we do here at DA ~2000 feet. The
winds here make every day different.



Jack

[Chris Reed]

Indeed, aerotow can sometimes be interesting! Some years ago I was flying in
a local club competition and found myself behind an underpowered Rallye,
piloted by a man with a recently diagnosed heart condition who therefore
needed a safety pilot with him. (Yes, I know the correct response is to
refuse the tow, but competitions soften the safety cells in the brain, even
local club competitions).

We climbed (very slowly) to 400ft and then stayed there while we flew in a
straight line at least 3 miles from the airfield. It's the only time I've
been field spotting on tow for such a long time.

Not suprisingly, I failed to soar once we reached the release height of
2,000 ft (partly because I only had time for once centreing turn if I was to
remain within gliding range of the field). My relight was a winch launch!

"Bill Daniels" > wrote in message
ink.net...
>
> "Chris OCallaghan" > wrote in message
> om...
> > A related remembrance...
> >
> > Years ago I attended a mid-summer's eve cookout at Ridge Soaring in
> > central PA. For entertainment we were armchairing the end o'day
> > training flights. A glider released just after take-off, landing at
> > the far end of the field. The tow plane landed, then taxied down to
> > launch the glider in the opposite direction. As the tug passed us,
> > 2-33 in tow, KS asked what was going on. I explained that a series of
> > rope breaks were practiced as a student got close to solo. They had
> > just completed a straight ahead release and recovery and would now
> > practice a 180 for return to the runway. As the tow plane and glider
> > reached 20 feet above the ground, still short of the runway boundary,
> > Karl said, "Now! It would be hairy, but you could do it."
> >
> > Karl and a handfull of other pilots probably could. The rest of us
> > wait until we have enough altitude to more than measure the sins we're
> > likely to commit as the emergency unfolds -- 200 feet being an
> > appropriate indulgence.
> >
> > For those who need to know to the inch, don't forget to include 35% of
> > your wingspan, lest you bury a tip. And don't forget that anytime the
> > controls are not neutral, your sink rate goes well below the arc of
> > the polar.
> >
> > So far, of the math I've seen, success would only be achieved for
> > gliders of zero span requiring no control input (and resulting drag)
> > to initiate a bank or roll out of it.
>
> Not to belabor the obvious, but a 180 return to the runway from a 200 foot
> airtow rope break is not always possible. We tend to talk as if it were
> true but if believe it, we may be setting up a disaster. With a heavy
> glider, weak tug, high density altitude and unfavorable wind (and maybe a
> thick headed tug pilot) you may need as much as 1000 feet to be in a
> position for a safe return to the airfield.
>
> There have been many occasions when my left hand hovered near the release
in
> preparation for a simulated rope break. But, looking back over my
shoulder
> at the airfield, I thought, "I don't theeenk so" and let the student
> continue.
>
> Over the last year a young friend of mine (A CFI-G) suffered two low
> altitude rope breaks (weak link failures) and each incident resulted in an
> off-airfield landing. (To his credit - no damage)
>
> Bill Daniels
>

[Shirley]

Chris Reed wrote:

>We climbed (very slowly) to 400ft and then
>stayed there while we flew in a straight line at
>least 3 miles from the airfield. It's the only time
>I've been field spotting on tow for such a long time.
>
>Not suprisingly, I failed to soar once we reached
>the release height of 2,000 ft

Was it not possible for you to use the in-air signals to steer the tow pilot
back toward the field?

[Martin Eiler]

Should we assume that these two rope breaks were during aero tow?
The next obvious question is how strong were the weak links and
why did they break.

The fact that this individual had two weak links break at a low enough
altitude that it resulted in his landing off field, does make us wonder
what the complete story is. Was he solo in a single place glider? Or
was it a result of letting a student get too far out of position? Inquiring
minds would like to know.

M Eiler

> > More specifics please for those off-airport landings. Otherwise your
"1000
> > feet" may be taken by some as a bit of an exageration.
> > Jack
> >
>
> In my friends case, the first break came shortly after crossing the field
> boundary at about 50 feet. This was a case of insufficient climb angle to
> reach 200 feet while still in range of the runway. The other, as I
> understand it, was at about 300 feet but still out of gliding range of the
> airport.
>
> My comment about 1000 feet referred to a situation that happened to me
> because the tug pilot turned downwind at 100 feet AGL with a heavy glider
> and strayed still further downwind as the air tow ground on despite urgent
> radio calls. It was only at 1000 feet AGL that I felt that I could
release
> and get back. (and get another tug pilot) This has happened to me too
many
> times to recall all of them.
>
> Understand, I fly in an area where density altitude at takeoff can exceed
> 10,000 feet. It takes a strong tug to keep a heavy two seater constantly
in
> range of the runway.
>
> My point with the original post is that there is no guarantee that the
magic
> 200 feet AGL will always get you back.
>
> Bill Daniels
>

[W.J. \(Bill\) Dean \(U.K.\).]

Those interested in wire launch safety may like to read an article by
John Hoskins, BGA Accident Investigator, which has just been published.

See http://www.gliding.co.uk/bgainfo/safety/bulletins/winching.pdf
or http://www.glidingmagazine.com/ListFeatureArticleDtl.asp?id=370 .

There have been many accidents of the types described,
insufficient energy to avoid a heavy landing after a launch failure,
and a spin entry after stalling during the first part of the launch.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.

>
> "Gary Boggs" > wrote in message
> ...
>
> Someone must have already compared the safety of these tow launch methods.
> What do the statistics show is the safer method of launch? Aero tow
> seems to involve more inherent dangers to me. For one thing, there is
> just more time for things to go wrong. What could be more dangerous than
> to tie two airplanes together and try to fly?
>
> Gary Boggs
>

[Andreas Maurer]

On Sun, 2 Nov 2003 00:05:21 -0000, "W.J. \(Bill\) Dean \(U.K.\)."
> wrote:

>There have been many accidents of the types described,
>insufficient energy to avoid a heavy landing after a launch failure,
>and a spin entry after stalling during the first part of the launch.

See this example:
http://www.alexburger.de/sf/seilriss.avi

Pilot suffered only minor injury.

Bye
Andreas

[Bill Daniels]

Marty, I'm going to top post here since I can't figure out which way this
thread is expanding.

In the first case, the weak link at the tug failed because the tugee
modified it without our knowledge or approval. In the second case the rope
itself was the weak link and it most likely failed because it was left
laying on the ground in the path of a landing 2-33 which cut some of the
strands with its razor sharp metal skid.

I know that in the first case, the glider was in perfect position - the link
just fell apart. In the second, the student was flying but was not badly
out of position. In both cases the failure was a complete surprise to the
CFI-G.

These incidents happened at different airports under different conditions
and operating procedures but to the same CFI-G in the same month. One could
argue, as I did, that the CFI-G shared responsibility with the tug pilot to
check the integrity of the rope and weak links . As we know, this is hard
to do for each flight at a busy operation and we rely on the operating
procedures and ground personnel to insure the rope is usable. Sometimes
your luck just runs out.

My original point was that with airtow stuff happens and sometimes you
aren't in position for a return to the runway. In winch launching, you are.

Bill Daniels

"Martin Eiler" > wrote in message
...
> Should we assume that these two rope breaks were during aero tow?
> The next obvious question is how strong were the weak links and
> why did they break.
>
> The fact that this individual had two weak links break at a low enough
> altitude that it resulted in his landing off field, does make us wonder
> what the complete story is. Was he solo in a single place glider? Or
> was it a result of letting a student get too far out of position?
Inquiring
> minds would like to know.
>
> M Eiler
>
> > > More specifics please for those off-airport landings. Otherwise your
> "1000
> > > feet" may be taken by some as a bit of an exageration.
> > > Jack
> > >
> >
> > In my friends case, the first break came shortly after crossing the
field
> > boundary at about 50 feet. This was a case of insufficient climb angle
to
> > reach 200 feet while still in range of the runway. The other, as I
> > understand it, was at about 300 feet but still out of gliding range of
the
> > airport.
> >
> > My comment about 1000 feet referred to a situation that happened to me
> > because the tug pilot turned downwind at 100 feet AGL with a heavy
glider
> > and strayed still further downwind as the air tow ground on despite
urgent
> > radio calls. It was only at 1000 feet AGL that I felt that I could
> release
> > and get back. (and get another tug pilot) This has happened to me too
> many
> > times to recall all of them.
> >
> > Understand, I fly in an area where density altitude at takeoff can
exceed
> > 10,000 feet. It takes a strong tug to keep a heavy two seater
constantly
> in
> > range of the runway.
> >
> > My point with the original post is that there is no guarantee that the
> magic
> > 200 feet AGL will always get you back.
> >
> > Bill Daniels
> >
>
>

[W.J. \(Bill\) Dean \(U.K.\).]

Not always.

I learnt to fly at the London Gliding Club, Dunstable Downs some 40 years
ago, entirely on the winch, and on the T21b.

There was one run for which I was taught that the correct procedure for a
launch failure at a certain height was to land beyond the airfield boundary
in the farmer's field.

The point surely is that before the launch starts the pilot should have in
mind all the possible options to cope with any launch failure; this may
include an off-airfield landing for either a wire or an aerotow launch.

Incidentally, the London Club now has more land, and outlandings after a
winch launch failure are not now required.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.

>
> "Bill Daniels" > wrote in message
> nk.net...
>
> <snip>
>
> My original point was that with airtow stuff happens and sometimes you
> aren't in position for a return to the runway. In winch launching, you
> are.
>
> Bill Daniels
>

[Chris Nicholas]

The film clip posted by Andreas shows another sort of accident, i.e. it
seems not to have been caused by rotating too much and hence
insufficient energy to avoid a heavy landing. Instead it is one of the
accidents relatively common in winch launching - we do not see the
glider leaving the cable, but it clearly flies at an adequate airspeed
for some distance before spinning off a turn which is too steep, too
close to the ground, in the wind gradient, and too slow for that set of
circumstances. Without knowing the site one cannot say what the pilot
should have done instead, but it is rare for there not to be a "land
ahead" option with less serious potential after a low cable break or
launch failure.

As I remarked before, it is not the winch launch itself that usually
produces the accident, it is pilot mismanagement of the subsequent
flightpath.

The too-little-energy syndrome this thread had been discussing most
recently is pilot mismanagement during the launch - not having learned
properly how to avoid having too little energy to cope with any
eventuality.

Both kinds of pilot error seem hard to eradicate in civilian gliding
clubs, which leads to considerable numbers of "winch launch" related
statistics.

My understanding is that the Air Cadets in the UK, who do huge amounts
of winch launching, have a much better safety record. It is rumoured
that they achieve this by teaching in a more regimented fashion. However
they do it, it demonstrates that winch launching CAN be safe - the
problem is the human element, not the technology itself. The only way
the human element can be made safer is by better training etc.

If a wave of winch launching were to commence in the USA, I think it
would be difficult to avoid a wave of accidents following, unless the
training and conversion of pilots were done better than we often manage
in the UK civilian gliding world. I wish every success to the
instigators of the project, and I hope they can pick up enough know-how
to climb the learning curve safely.

Chris N.

[Chris OCallaghan]

Of course. When we say 200 feet, it's the first 199 that are
important. As a rule, you should only attempt to land in what you can
see up to 200 feet agl. You've already been planning your landing
during the tow, now you need only execute.

Above 200 feet you have more options, one of which is to recognize the
conditions (wind shear, sink, low airspeed, tailwind on takeoff, etc.)
which may not favor a rote return to the airfield. But above 200 you
can start planning landings to known fields that you cannot see (not
necessarily the airport).

[Mike Lindsay]

In article >, F.L. Whiteley
> writes
>There once was a non-BGA soaring site/club in East Anglia in the UK. The
>operator was named Fred, but the surname escapes me and I believe he passed
>away in the 1980's. By all accounts he operated a steam winch though I
>never met him nor saw it in action. I believe that operation was dwindling
>and may have ceased operations about 1980. Any stories out there?
>
>Frank Whiteley
>
In the 60s there was an instructor at the Midland GC who had the idea of
building a steam winch.

Because the Long Mynd is largely peat, we thought we might use the
terrain as a fuel source.

The project never got off the ground; we never got any steam driven,
Mynd fuelled launches.
>

--
Mike Lindsay
n

[Bill Daniels]

"Chris Nicholas" > wrote in message
...
> The film clip posted by Andreas shows another sort of accident, i.e. it
> seems not to have been caused by rotating too much and hence
> insufficient energy to avoid a heavy landing. Instead it is one of the
> accidents relatively common in winch launching - we do not see the
> glider leaving the cable, but it clearly flies at an adequate airspeed
> for some distance before spinning off a turn which is too steep, too
> close to the ground, in the wind gradient, and too slow for that set of
> circumstances. Without knowing the site one cannot say what the pilot
> should have done instead, but it is rare for there not to be a "land
> ahead" option with less serious potential after a low cable break or
> launch failure.
>
> As I remarked before, it is not the winch launch itself that usually
> produces the accident, it is pilot mismanagement of the subsequent
> flightpath.
>
> The too-little-energy syndrome this thread had been discussing most
> recently is pilot mismanagement during the launch - not having learned
> properly how to avoid having too little energy to cope with any
> eventuality.
>
> Both kinds of pilot error seem hard to eradicate in civilian gliding
> clubs, which leads to considerable numbers of "winch launch" related
> statistics.
>
> My understanding is that the Air Cadets in the UK, who do huge amounts
> of winch launching, have a much better safety record. It is rumoured
> that they achieve this by teaching in a more regimented fashion. However
> they do it, it demonstrates that winch launching CAN be safe - the
> problem is the human element, not the technology itself. The only way
> the human element can be made safer is by better training etc.
>
> If a wave of winch launching were to commence in the USA, I think it
> would be difficult to avoid a wave of accidents following, unless the
> training and conversion of pilots were done better than we often manage
> in the UK civilian gliding world. I wish every success to the
> instigators of the project, and I hope they can pick up enough know-how
> to climb the learning curve safely.
>
> Chris N.
>
>
Chris makes a good point.

There does seem to be a condition experienced by some people who find it
hard to make fast mental adjustments from one set of conditions to another.
One moment they are setting on the ground and 35 seconds later then are high
in the sky at the controls of a glider and struggling to cope. The rush of
a winch launch may create a sensory overload beyond their ability to manage.

This may be analogous to a well known condition experienced by some
motorists who enter a high speed expressway and find it hard to adjust to
the fast traffic for a while. (and, of course, the reverse when leaving the
expressway and entering slow surface traffic.) I have never experienced
this and know of relatively few who do.

If we were more alert to this possibility we might intervene and ask a pilot
showing these symptoms to get a little more recurrent training. Perhaps
this is something we instructors should emphasize in training. Instructors
should be alert to sensory overload in their students and pace their lessons
accordingly but things do happen quickly in a winch launch.

Bill Daniels

[BAToulson]

In article >, "Adrian Jansen"
> writes:

>I was lucky enough to get a kite launch one day. We had about 35 Kts of
>wind on the ground, and someone suggested we try a launch. An instructor
>and I climbed into a Blanick L13, launched ( *very* short run ! ) and
>climbed to 4300 ft still on the wire. Of course we needed the expert
>cooperation of the winch driver, who eased off the power as we got about 500
>ft, then payed out cable to let us climb. At the end, it was mostly the
>weight of cable ( single strand high tensile steel wire ) which determined
>the max height, although there wasnt much wire left on the drum.

Yessss, but!!

I suggest you now estimate the wing loading with 4300 ft of high tensile steel
plus the down pull of the winch. Because you cannot feel the "G" loading on a
winch does not mean it is not there and two effects occur.

1) Your stalling speed increases with the weight of cable dangling below you,
and,

2) the G loading increases by the weight of cable attached to your glider so
you MAY be far exceding your all up "weight".

Beware, whilst this may be great fun, you get much closer to the envelope
limits than you know.Care is needed.

Barney
UK

[Andreas Maurer]

On Sun, 02 Nov 2003 15:03:18 GMT, "Bill Daniels"
> wrote:


>There does seem to be a condition experienced by some people who find it
>hard to make fast mental adjustments from one set of conditions to another.
>One moment they are setting on the ground and 35 seconds later then are high
>in the sky at the controls of a glider and struggling to cope. The rush of
>a winch launch may create a sensory overload beyond their ability to manage.

Hmmm... I never saw this during a winch launch yet. The work load
during a winch launch is very low compared to an aerotow - the only
thing you really need to watch is airspeed and the "bang" of a rope
break.

The situation you describe (when the pilot gets behind the plane)
happens much more often during very low maneuvering (like low
approaches) - suddenly pilot looses track of airspeed and stalls, for
example (just as the clip I posted shows).



Bye
Andreas

[Stefan]

> On Sun, 02 Nov 2003 15:03:18 GMT, "Bill Daniels"
> > wrote:
>
>>There does seem to be a condition experienced by some people who find it
>>hard to make fast mental adjustments from one set of conditions to another.
>>One moment they are setting on the ground and 35 seconds later then are high
>>in the sky at the controls of a glider and struggling to cope. The rush of
>>a winch launch may create a sensory overload beyond their ability to manage.

Hmm... If their sensory is overloaded so easily, then they should
consider to quit flying immediately.

Stefan

[Bill Daniels]

"Andreas Maurer" > wrote in message
...
> On Sun, 02 Nov 2003 15:03:18 GMT, "Bill Daniels"
> > wrote:
>
>
> >There does seem to be a condition experienced by some people who find it
> >hard to make fast mental adjustments from one set of conditions to
another.
> >One moment they are setting on the ground and 35 seconds later then are
high
> >in the sky at the controls of a glider and struggling to cope. The rush
of
> >a winch launch may create a sensory overload beyond their ability to
manage.
>
> Hmmm... I never saw this during a winch launch yet. The work load
> during a winch launch is very low compared to an aerotow - the only
> thing you really need to watch is airspeed and the "bang" of a rope
> break.
>
> The situation you describe (when the pilot gets behind the plane)
> happens much more often during very low maneuvering (like low
> approaches) - suddenly pilot looses track of airspeed and stalls, for
> example (just as the clip I posted shows).
>
>
>
> Bye
> Andreas

It's probably because you and your friends are accustomed to winch launch as
a normal way to get gliders into the air. In the USA, winch launch is still
a novelty for most glider pilots. I very much agree that the workload is
far less during a winch launch as compared to airtow, but the sensations are
quite novel for the uninitiated.

I once gave a 747 captain his first glider ride on a winch. After release,
I asked him what he thought of the launch. His answer, "I have no idea what
just happened" - "I have never felt so far behind an aircraft".

Bill Daniels

[Mark James Boyd]

In power planes I often wondered how high I would need to turn around,
and the biggest difference seemed to be how well I was climbing.
In a heavy Piper Arrow on a hot day, We couldn't climb fast enough
to ever glide back regardless how high we went if we did a
straight out or 45 departure. Departing downwind was another story,
of course.

On hot days with heavy loads at Avenal, the tug sometimes turns very
gently at low altitudes to downwind. I recall flying a two seater open
cockpit on a very hot day and seeing miserable climb out of us
and the 150/150. In our case not a problem with all the
flat ground, but still a bit disconcerting to be
so far out and low...

"Bill Daniels" > wrote in message
nk.net...
> I once gave a 747 captain his first glider ride on a winch. After
release,
> I asked him what he thought of the launch. His answer, "I have no idea
what
> just happened" - "I have never felt so far behind an aircraft".
>
> Bill Daniels
>

He probably missed not having his co-pilot to do the flying for him.

Pat Barfield :-)

[Andreas Maurer]

On Sun, 02 Nov 2003 19:05:17 GMT, "Bill Daniels"
> wrote:


>It's probably because you and your friends are accustomed to winch launch as
>a normal way to get gliders into the air. In the USA, winch launch is still
>a novelty for most glider pilots. I very much agree that the workload is
>far less during a winch launch as compared to airtow, but the sensations are
>quite novel for the uninitiated.

Sure this is the case. But it's nothing that coud not be trained away
with 30 winch launches...
Bye
Andreas

[Chris Reed]

What in-air signals? I had no radio, but even if I had it was clear that the
tug pilot was having an interesting day, so I wouldn't have wanted to
distract him.

Fortunately this was in East Anglia in the UK, so there was a constant set
of fields each about the size of a normal gliding club site.

"Shirley" > wrote in message
...
> Chris Reed wrote:
>
> >We climbed (very slowly) to 400ft and then
> >stayed there while we flew in a straight line at
> >least 3 miles from the airfield. It's the only time
> >I've been field spotting on tow for such a long time.
> >
> >Not suprisingly, I failed to soar once we reached
> >the release height of 2,000 ft
>
> Was it not possible for you to use the in-air signals to steer the tow
pilot
> back toward the field?
>

[Bill Daniels]

"Mark James Boyd" > wrote in message
news:3fa5f571$1@darkstar...
> In power planes I often wondered how high I would need to turn around,
> and the biggest difference seemed to be how well I was climbing.
> In a heavy Piper Arrow on a hot day, We couldn't climb fast enough
> to ever glide back regardless how high we went if we did a
> straight out or 45 departure. Departing downwind was another story,
> of course.
>
> On hot days with heavy loads at Avenal, the tug sometimes turns very
> gently at low altitudes to downwind. I recall flying a two seater open
> cockpit on a very hot day and seeing miserable climb out of us
> and the 150/150. In our case not a problem with all the
> flat ground, but still a bit disconcerting to be
> so far out and low...

Back in around 1970 a power instructor who had witnessed glider 200 foot 180
turns back to the runway wanted to try some in a Cessna 150. I rode with
him as we tried a few at a safe altitude. The 150 was one of the old ones
with a straight tail and manual flaps.

The glider technique of a 45 degree banked turn was very marginal. We then
experimented with some more aggressive maneuvers. The best seem to be a
sort of diving 180 degree rolling turn with a pullout from the dive on the
reciprocal heading. We came out of the dive headed towards the runway at
high airspeed but in ground effect which got us to the runway with ease.

Once we were confident of our technique, we tried a few at Caddo Mills, TX.
At the time, Caddo Mills was just abandoned runways with no buildings or
fences and surrounded by alfalfa fields. The 45 degree turn never made it
back but the diving roll did work if you were quick and aggressive.

We both agreed that the conventional instruction of not trying a 180 below
about 500 feet was best.

Bill Daniels

[Tony Verhulst]

Chris Reed wrote:
> What in-air signals? I had no radio,

Well, in the US we have this
http://home.comcast.net/~verhulst/GBSC/student/signals.html

> it was clear that the tug pilot was having an
> interesting day, so I wouldn't have wanted to
> distract him.

A valid point.

Tony V.

[Colin]

"Bill Daniels" > wrote:

>
>"Mark James Boyd" > wrote in message
>news:3fa5f571$1@darkstar...
>> In power planes I often wondered how high I would need to turn around,
>> and the biggest difference seemed to be how well I was climbing.
>> In a heavy Piper Arrow on a hot day, We couldn't climb fast enough
>> to ever glide back regardless how high we went if we did a
>> straight out or 45 departure. Departing downwind was another story,
>> of course.
>>
>> On hot days with heavy loads at Avenal, the tug sometimes turns very
>> gently at low altitudes to downwind. I recall flying a two seater open
>> cockpit on a very hot day and seeing miserable climb out of us
>> and the 150/150. In our case not a problem with all the
>> flat ground, but still a bit disconcerting to be
>> so far out and low...
>
>Back in around 1970 a power instructor who had witnessed glider 200 foot 180
>turns back to the runway wanted to try some in a Cessna 150. I rode with
>him as we tried a few at a safe altitude. The 150 was one of the old ones
>with a straight tail and manual flaps.
>
>The glider technique of a 45 degree banked turn was very marginal. We then
>experimented with some more aggressive maneuvers. The best seem to be a
>sort of diving 180 degree rolling turn with a pullout from the dive on the
>reciprocal heading. We came out of the dive headed towards the runway at
>high airspeed but in ground effect which got us to the runway with ease.
>
>Once we were confident of our technique, we tried a few at Caddo Mills, TX.
>At the time, Caddo Mills was just abandoned runways with no buildings or
>fences and surrounded by alfalfa fields. The 45 degree turn never made it
>back but the diving roll did work if you were quick and aggressive.
>
>We both agreed that the conventional instruction of not trying a 180 below
>about 500 feet was best.
>
>Bill Daniels

Many years ago a highly respected aerobatic pilot in UK (still working
today) wrote an article in our Pilot magazine on this subject. He
reminded us that three things were required:
1. A rapid 180 degree change of heading.
2. Minimum loss of height.
3. Normal airspeed at the end of the manoever.
Controversially, he maintained that a highly banked slipping turn
satisfies all three criteria. The rate of decent is very high during
the turn, but the duration is so short that it results in less height
loss than either of the two alternatives (eg:slow and gentle or fast
and furious), and the airspeed is normal throughout.
Just don't forget to keep loads of top rudder on.

- Colin

[Chris Reed]

From a UK perspective the signals are unexpected! We have one signal from
glider to tug (Can't release) and two from tug to glider (release now,
spoilers out). These are the same as the US signals.

UK tug pilots are an independent breed - I imagine that trying to tell them
where to go could leave you dropped in fierce sink. On the other hand, prior
negotiation coupled with flattery can get you to that good thermal
(especially if you repay the tow in the bar later on).


"Tony Verhulst" > wrote in message
...
> Chris Reed wrote:
> > What in-air signals? I had no radio,
>
> Well, in the US we have this
> http://home.comcast.net/~verhulst/GBSC/student/signals.html
>
> > it was clear that the tug pilot was having an
> > interesting day, so I wouldn't have wanted to
> > distract him.
>
> A valid point.
>
> Tony V.
>

[Robert Ehrlich]

Colin wrote:
>
> Many years ago a highly respected aerobatic pilot in UK (still working
> today) wrote an article in our Pilot magazine on this subject. He
> reminded us that three things were required:
> 1. A rapid 180 degree change of heading.
> 2. Minimum loss of height.
> 3. Normal airspeed at the end of the manoever.
> Controversially, he maintained that a highly banked slipping turn
> satisfies all three criteria. The rate of decent is very high during
> the turn, but the duration is so short that it results in less height
> loss than either of the two alternatives (eg:slow and gentle or fast
> and furious), and the airspeed is normal throughout.
> Just don't forget to keep loads of top rudder on.
>
> - Colin


I don't see why the turn should be a slipping one, you certainly will
loose more height in a slipping turn than in a normal one. And height
loss is what make the turn possible or not.

[Stephen Haley]

I still fly at dunstable and can say that there can still be a problem on
very still days off the Winch where you have too much height to land
straight ahead but not enough to turn safely. This is especially true for
abinitios/early solos. Unfortunately Dunstable is still far from flat and
still has a horrendous dip to the downs side over half the field with the
aver half having being filled in with spoil from the M1 making diagonal
landings in that direction difficult/impossible unless you want to do a
lemming act off the cliff edge that bisects part of the field but at least
the hedge has been partially removed on part of the southern edge leaving
the option of running on into a ploughed field. While I have never seen an
outfield landing following a winch break I could see it happening a calm
days with certain glider types.
Areotowing in Strong Easterly winds out towards the downs - that is best
confined to the horror vault. The wind coming across the top of the downs
produces a very violent wave pattern across the field and just as you are
getting to the roughest part where it feels like the wind is almost vertical
and trying to slam you back into the field the tug has to execute a sharp
right turn at V low altitude. There are parts of the field where the wave
effect produces a complete wind shadow.
As for being pulled off at 200ft - I wish. One of JJs (who probably taught
the previous poster) last acts before retiring for the winter was to pull me
off over the sw hedge - luckily we have a dip a bit further on that gives
another 40 ft and somehow I got it down back on the field after a 270. When
I asked him later if it was circa 150ft I was given the laconic comment -
"Not as much as that - remember each wing is only 30ft so you dont need a
lot providing you remember you already have flying speed and fly the turn
precisely". I never did have the courage to ask him exactly how high we
were.


"W.J. (Bill) Dean (U.K.)." > wrote in message
...
> Not always.
>
> I learnt to fly at the London Gliding Club, Dunstable Downs some 40 years
> ago, entirely on the winch, and on the T21b.
>
> There was one run for which I was taught that the correct procedure for a
> launch failure at a certain height was to land beyond the airfield
boundary
> in the farmer's field.
>
> The point surely is that before the launch starts the pilot should have in
> mind all the possible options to cope with any launch failure; this may
> include an off-airfield landing for either a wire or an aerotow launch.
>
> Incidentally, the London Club now has more land, and outlandings after a
> winch launch failure are not now required.
>
> W.J. (Bill) Dean (U.K.).
> Remove "ic" to reply.
>
> >
> > "Bill Daniels" > wrote in message
> > nk.net...
> >
> > <snip>
> >
> > My original point was that with airtow stuff happens and sometimes you
> > aren't in position for a return to the runway. In winch launching, you
> > are.
> >
> > Bill Daniels
> >
>
>
>
>
>
>

[W.J. \(Bill\) Dean \(U.K.\).]

Yes, JJ was one of my two instructors at Dunstable 40 years ago (John
Jeffries, not to be confused with some young whippersnapper from Nevada who
has hijacked these initials).

I remember the way he used to fly, and it is obvious that some things don't
change.

My other instructor was Mike Till, I flew with him mostly, I see he is on
the current roster.

As to launch failures generally, aerotow failures will often involve
outlandings, fortunately such failures are rare compared with wire launch
failures.

There has been considerable discussion as to how aerotow failures should be
taught, since it is important that the pupil should not assume that the
airfield can always be reached. It maybe that JJ could get back, but this
does not mean that you can when it happens for real. Instructors are apt
to pull a simulated failure when it is still possible to get back, though
only just with JJ. There is a lot to be said for using a motor-glider for
teaching aerotow landing options, though JJ won't like this idea!

In real life some aerotow operations are carried out where an aerotow
failure may result at best in a controlled crash. Remember that if the tug
has an engine problem it may operate at low power before failing, so you
will be slower and lower than on a normal tow before you abandon the tow or
it abandons you.

As to wire launch failures at Dunstable, yes there is often a very narrow
gap between being too low to turn and too high to get in straight ahead.
It is certainly a good idea to have fields outside the airfield in mind when
reviewing the options while doing the launch failure bit of "eventualities"
before starting the launch. Often the field is partly blocked by gliders
awaiting retrieve, and tractors on their way to do the retrieve. If you do
not think of an option when reviewing options before starting, you are
unlikely to think of it when conducting a very high pressure recovery which
is by definition not expected (though it must be thought about).

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.

>
>"Stephen Haley" > wrote in message
> ...
>
> I still fly at Dunstable and can say that there can still be a problem on
> very still days off the winch where you have too much height to land
> straight ahead but not enough to turn safely. This is especially true
> for abinitios/early solos. Unfortunately Dunstable is still far from
> flat and still has a horrendous dip to the downs side over half the field
> with the other half having being filled in with spoil from the M1 making
> diagonal landings in that direction difficult/impossible unless you want
> to do a lemming act off the cliff edge that bisects part of the field but
> at least the hedge has been partially removed on part of the southern edge
> leaving the option of running on into a ploughed field. While I have
> never seen an outfield landing following a winch break I could see it
> happening a calm days with certain glider types.
>
> Aerotowing in strong easterly winds out towards the downs - that is best
> confined to the horror vault. The wind coming across the top of the
> downs produces a very violent wave pattern across the field and just as
> you are getting to the roughest part where it feels like the wind is
> almost vertical and trying to slam you back into the field the tug has to
> execute a sharp right turn at v low altitude. There are parts of the
> field where the wave effect produces a complete wind shadow.
>
> As for being pulled off at 200ft - I wish. One of JJs (who probably
> taught the previous poster) last acts before retiring for the winter was
> to pull me off over the sw hedge - luckily we have a dip a bit further on
> that gives another 40 ft and somehow I got it down back on the field after
> a 270. When I asked him later if it was circa 150ft I was given the
> laconic comment - "Not as much as that - remember each wing is only 30ft
> so you dont need a lot providing you remember you already have flying
> speed and fly the turn precisely". I never did have the courage to ask
> him exactly how high we were.
>
> >
> > "W.J. (Bill) Dean (U.K.)." > wrote in message
> > ...
> >
> > Not always.
> >
> > I learnt to fly at the London Gliding Club, Dunstable Downs some 40
> > years ago, entirely on the winch, and on the T21b.
> >
> > There was one run for which I was taught that the correct procedure for
> > a launch failure at a certain height was to land beyond the airfield
> > boundary in the farmer's field.
> >
> > The point surely is that before the launch starts the pilot should have
> > in mind all the possible options to cope with any launch failure; this
> > may include an off-airfield landing for either a wire or an aerotow
> > launch.
> >
> > Incidentally, the London Club now has more land, and outlandings after a
> > winch launch failure are not now required.
> >
> > W.J. (Bill) Dean (U.K.).
> >
> > >
> > > "Bill Daniels" > wrote in message
> > > nk.net...
> > >
> > > <snip>
> > >
> > > My original point was that with airtow stuff happens and sometimes you
> > > aren't in position for a return to the runway. In winch launching,
> > > you are.
> > >
> > > Bill Daniels
> > >
> >
>

[Robert Ehrlich]

"W.J. (Bill) Dean (U.K.)." wrote:
> ...
> There is a lot to be said for using a motor-glider for
> teaching aerotow landing options, though JJ won't like this idea!
>

I agree with JJ's opinion. My computation identified the minumum of
Vz*V as an important factor in the possibility of turning back, and
this values is usually much higher in a motor-glider, due to higher
wing loading and worse aerodynamic.

> ...
> As to wire launch failures at Dunstable, yes there is often a very narrow
> gap between being too low to turn and too high to get in straight ahead.

I don't understand clearly what is the problem at Dunstable. What is the
length of runway ahead of you when you reach 150m?

> ...
> Often the field is partly blocked by gliders
> awaiting retrieve, and tractors on their way to do the retrieve.

In this case, if they don't allow a sufficient free space to land
in case of a cable break, you should delay the start.

[W.J. \(Bill\) Dean \(U.K.\).]

Teaching aerotow launch failure options with a motor glider.

JJ has always disliked the idea of using a motor glider for any purpose
whatever, and he has the same opinion of turbo and self-launching gliders
(unless old age is getting to him and he has changed his opinion recently).
His opinion is purist, aesthetic and emotional, and I can remember him
admitting this. Dunstable never used a motor glider for training while he
was running things, they got one after he retired from the club management.
It is a matter of what is most fun, flying with JJ has always been fun
(unlike some instructors I could name).

It is now a BGA requirement that glider pilots get a "Cross-Country
Endorsement" to their Gliding Certificate before deliberately flying
cross-country. See "Laws and Rules for Glider Pilots" edition 14 (BGA),
page 44 section 17.12. In the section on Field Landings it states: "The
candidate must make a minimum of two successful approaches, selected by
himself in a motor glider. .....". The motor glider is used of course so
that an approach can be made without actually landing.

The use of motor gliders for glider pilot training generally has always been
controversial in he U.K., the strongest advocate was always Derek Piggott.
However whenever a club has got used to using a motor glider for teaching
the cross country skills of Navigation, Field Selection and Field Landings
it has always been accepted as being valuable, and its use for teaching
Field Landings is now mandatory.

In the case of aerotow launch failures the training I had in mind was for
the cases where turning back to the airfield is not a safe option. This
then becomes an exercise like any field landing, except that the decision to
land is immediate and unexpected, but should be into a field already known
about.

As for the case where it is possible to turn back to the airfield, if it is
not possible in a motor glider with a very experienced instructor
supervising, and the exercise known about in advance; would it be sensible
for a rather inexperienced pilot solo and taken by surprise?

The type of motor glider almost invariably used for this area of training in
the U.K. is one of the Falke series.

Winch launching at Dunstable.

I flew 917 launches at Dunstable as instructor between 1992 and 1994, almost
all of them by winch, most in the K21 the remainder in the K13. I did many
launch failure exercises (we all did) and none of them finished in a field.

The field is fairly small, and roughly rectangular in shape so all the winch
runs are short. I recall that 1,200ft was a good launch, and sometimes on
some runs we got 800ft or less. 150m or 450ft would be far too high to
land ahead unless the wind was strong, on a no wind day such a height would
be considered easy for a short circuit.

As for congestion on the airfield, of course one would not launch if there
were nowhere to land, it is simply that one seldom had the whole area
available.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.

>
> "Robert Ehrlich" > wrote in message
> ...
>
> >
> > "W.J. (Bill) Dean (U.K.)." wrote:
> > ...
> > There is a lot to be said for using a motor-glider for
> > teaching aerotow landing options, though JJ won't like this idea!
> >
>
> I agree with JJ's opinion. My computation identified the minimum of
> Vz*V as an important factor in the possibility of turning back, and
> this values is usually much higher in a motor-glider, due to higher
> wing loading and worse aerodynamic.
>
> > ...
> > As to wire launch failures at Dunstable, yes there is often a very
> > narrow gap between being too low to turn and too high to get in straight
> > ahead.
> >
>
> I don't understand clearly what is the problem at Dunstable. What is the
> length of runway ahead of you when you reach 150m?
>
> > ...
> > Often the field is partly blocked by gliders
> > awaiting retrieve, and tractors on their way to do the retrieve.
> >
>
> In this case, if they don't allow a sufficient free space to land
> in case of a cable break, you should delay the start.
>

[Stephen Haley]

> I don't understand clearly what is the problem at Dunstable. What is the
> length of runway ahead of you when you reach 150m?

Simple answer is not really enough when launching in flat calm conditions
which aggravate matters in 2 ways
1) Lack of wind reduces the overall height gained by upto 30% which means
you will be substantially further down the field @ 150ft.
2) Lack of headwind means that the landing will be longer.
10kts of wind changes everything and produces a reasonable overlap.

The ordinance survey shows the field at about 1k in length
As for runway we are a grass field which is far from level.

"Robert Ehrlich" > wrote in message
...
> "W.J. (Bill) Dean (U.K.)." wrote:
> > ...
> > There is a lot to be said for using a motor-glider for
> > teaching aerotow landing options, though JJ won't like this idea!
> >
>
> I agree with JJ's opinion. My computation identified the minumum of
> Vz*V as an important factor in the possibility of turning back, and
> this values is usually much higher in a motor-glider, due to higher
> wing loading and worse aerodynamic.
>
> > ...
> > As to wire launch failures at Dunstable, yes there is often a very
narrow
> > gap between being too low to turn and too high to get in straight ahead.
>
> I don't understand clearly what is the problem at Dunstable. What is the
> length of runway ahead of you when you reach 150m?
>
> > ...
> > Often the field is partly blocked by gliders
> > awaiting retrieve, and tractors on their way to do the retrieve.
>
> In this case, if they don't allow a sufficient free space to land
> in case of a cable break, you should delay the start.

[Colin]

Robert Ehrlich > wrote:

>Colin wrote:
>>
>> Many years ago a highly respected aerobatic pilot in UK (still working
>> today) wrote an article in our Pilot magazine on this subject. He
>> reminded us that three things were required:
>> 1. A rapid 180 degree change of heading.
>> 2. Minimum loss of height.
>> 3. Normal airspeed at the end of the manoever.
>> Controversially, he maintained that a highly banked slipping turn
>> satisfies all three criteria. The rate of decent is very high during
>> the turn, but the duration is so short that it results in less height
>> loss than either of the two alternatives (eg:slow and gentle or fast
>> and furious), and the airspeed is normal throughout.
>> Just don't forget to keep loads of top rudder on.
>>
>> - Colin
>
>
>I don't see why the turn should be a slipping one, you certainly will
>loose more height in a slipping turn than in a normal one. And height
>loss is what make the turn possible or not.

1. A slipping turn can be made at a high bank angle and low airspeed.
2. Rate of turn is dependent on angle of bank and airspeed, such that
the highest rate of turn is achieved with a high bank angle and a low
airspeed.
Brian illustrated this by inviting us to compare the rate of turn
achieved by a C150 and a jet fighter at the same angle of bank.
It has to be a slipping turn or we would stall, so the maximum bank
which can be used is dependent on the amount of top rudder available.

- Colin

[Eric Greenwell]

Colin wrote:

>>
>>I don't see why the turn should be a slipping one, you certainly will
>>loose more height in a slipping turn than in a normal one. And height
>>loss is what make the turn possible or not.
>
>
> 1. A slipping turn can be made at a high bank angle and low airspeed.

I don't understand this: at any given bank angle, how can you achieve a
lower airspeed when you are slipping? Doesn't that require more elevator
power? How would a slipping turn enable that?

[Robert Ehrlich]

Stephen Haley wrote:
>
> > I don't understand clearly what is the problem at Dunstable. What is the
> > length of runway ahead of you when you reach 150m?
>
> Simple answer is not really enough when launching in flat calm conditions
> which aggravate matters in 2 ways
> 1) Lack of wind reduces the overall height gained by upto 30% which means
> you will be substantially further down the field @ 150ft.
> 2) Lack of headwind means that the landing will be longer.
> 10kts of wind changes everything and produces a reasonable overlap.
>
> The ordinance survey shows the field at about 1k in length

I was talking of 150m, not 150ft. If your 1k length is also in feet,
this is pretty short (~ 300m), i.e. the winch is probably far beyond the
landable area, which is unusual. If it is 1km, even if you had a very
poor climb and you are at mid field (500m) at 150m, 500m seems highly
sufficient in any condition of wind for a landing straight ahead.

[Robert Ehrlich]

Robert Ehrlich wrote:
> ...
> In this case our common conclusion
> is again that the optimal (aerodynamic) bank angle is 90 degrees,
> ...

Corrcting myself: should be 45 degrees.

[Ian Forbes]

On Thu, 06 Nov 2003 00:02:30 +0000, Colin wrote:

> 1. A slipping turn can be made at a high bank angle and low airspeed.

I believe in (and teach) a few basic principles when flying close to the
ground.

- Stall/spin accidents kill more pilots than any other single cause.

- Stalls occur when you fly too slowly.

- Spins occur when you stall and the glider is not "co-ordinated" ie
either slipping or skidding.

Therefore if you are flying close to the ground, keep the airspeed
comfortably above stalling speed. And if you can't do that, keep the
aircraft co-ordinated.

(When instructing, close to the ground, if the student can't maintain a
steady airspeed, I take over control at the first sign of loss of
co-ordination).

Using a low airspeed slipping turn to turn 180 deg when less than 200 ft
above the ground sounds like the advice that a legendary grandmother is
once said to have given "now son, be careful when you go flying, don't fly
to high and don't fly too fast!"

Maybe some aerobatic super pilot can prove me wrong, but if you have to
resort to these measures to get back to the field then I think you would
probably be better off taking your chances going in straight ahead.


Ian

(I have seen gliders “land� in some unusual places and get away with
relatively minor damage and no injuries. Provided the glider is flown in a
controlled manner to the point of touch down, and the landing is done with
lowest possible energy - full flaps, into wind, air brakes closed - damage
is often minor. On the other hand I have seen two crashes where the glider
went in wing tip first and cartwheeled. Both were right-offs with serious
injuries.)

[Colin]

Robert Ehrlich > wrote:

>Colin wrote:
>> ...
>> 1. A slipping turn can be made at a high bank angle and low airspeed.
>> 2. Rate of turn is dependent on angle of bank and airspeed, such that
>> the highest rate of turn is achieved with a high bank angle and a low
>> airspeed.
>> Brian illustrated this by inviting us to compare the rate of turn
>> achieved by a C150 and a jet fighter at the same angle of bank.
>> It has to be a slipping turn or we would stall, so the maximum bank
>> which can be used is dependent on the amount of top rudder available.
>> ...
>
>Ok, if you use the lift provided by the fuselage in a slipping turn,
>you can devote more of the lift provided by the wings for generating
>the centripetal force, by increasing the bank angle, and so the horizontal
>component of the wing lift. But you pay this by an increase in drag, i.e.
>more height loss. It is not obvious if the gain in time to turn override
>the increased rate of sink, but I have some argument that should show that
>the answer is no.
>
>The analysis of Dr. Rogers as well as my own one can be used in the case
>of a slipping turn can be used if you consider as bank angle not the
>geometric bank angle, i.e. the angle between the wing plane and the
>horizontal plane, but the aerodynamic bank angle, i.e. the angle between
>the total lift vector (wings + fuselage) and the vertical (well as we consider
>a glide it is rather total aerodynamic force than lift, but the difference
>between both angles can be neglected). In this case our common conclusion
>is again that the optimal (aerodynamic) bank angle is 90 degrees, although
>the geometric bank angle is higher, and we have to maximize Cl/(Cd^2) in
>Dr. Rogers' analysis, minimize Vz*V in my analysis. It is difficult to determine
>if you may have a higher max Cl/(Cd^2) with slip, but I have a good argument
>that we can't lower Vz*V. Remember in this analysis Vz and V are the horizontal
>and vertical speed at zero (aerodynamic) bank angle and the same angle of attack,
>i.e. what you find in an usual glider polar. In the case of a slipped turn,
>we should use a polar showing Vz versus V for a straight flight with the
>same slip angle. I never saw such a polar, but I think it is obvioous that
>at any speed V the vertical speed Vz is higher with slip than without it.
>i.e. the polar with slip is entirely below the polar without slip. Now the
>minimum of Vz*V for the polar without slip is where this polar is tangent
>to one of the hyperbolas Vz*V = constant, and except for the point of
>contact, the polar is entirely below this hyperbola. So the polar with
>slip is also entirely below this hyperbola, and no point of it can
>provide a value for Vz*V that is lower or equal to the the value on
>the hyperbola, i.e. the minimum of Vz*V obtained without slip cannot
>be obtained with slip.

Er, yes ...
But how does the result compare with a large tear-drop flown at normal
glide speed, or for that matter, a smaller tear-drop flown with higher
airspeed and more bank ?
The point is how to complete a rapid 180 without spinning-in, and a
full sideslip with small angle of attack precludes a spin.
The author also encourages us to go out and try it, high up to begin
with of course.
- Colin.

[Eric Greenwell]

Ian Forbes wrote:

> On Thu, 06 Nov 2003 00:02:30 +0000, Colin wrote:

>
> - Spins occur when you stall and the glider is not "co-ordinated" ie
> either slipping or skidding.

I used to think this, but I soon discovered our club Blanik would
happily spin from a coordinated turn by using a shallow bank and simply
reducing the airspeed. Since then, I've done this with other gliders.

A coordinated turn doesn't prevent the inner wing from flying at a
higher angle of attack than the outer wing, which is why it stalls
first, and a spin can begin. I haven't experimented with it enough to be
certain, but I suspect a slipping turn would reduce the tendency for the
inner wing to stall first.

[Chris OCallaghan]

Eric,

Point of interest: did you let the spin fully develop after the
coordinated turning stall? There is an aerodynamic tipping point --
that is the self-righting tendency of the tail that would typically
favor a spiral over a spin assuming that the only deflected control
surface was the elevator. Of course a wing drops when in a turning
stall, but without aileron deflection generating drag my guess would
be that designed yaw stability would prevent spin development.

There is a significant difference in the assymetric drag profile with
and without aileron deflection. Remember that most modern aircraft
begin their stall at the root. That means less torque and less
disposition to overpower yaw stability and enter a spin. Slapping an
aileron down to pick up the low wing adds significat drag at the tip.
Add some rudder (cross-controls), and now you have a greater
disposition to get the aircraft spinning rather than spiralling.

I'll give this a try over the weekend -- that is, making no recovery
to a coordinated turning stall to see how it develops. My Ventus spins
happily if aggrevated. It should prove a good test bed.

Eric Greenwell > wrote in message >...
> Ian Forbes wrote:
>
> > On Thu, 06 Nov 2003 00:02:30 +0000, Colin wrote:
>
> >
> > - Spins occur when you stall and the glider is not "co-ordinated" ie
> > either slipping or skidding.
>
> I used to think this, but I soon discovered our club Blanik would
> happily spin from a coordinated turn by using a shallow bank and simply
> reducing the airspeed. Since then, I've done this with other gliders.
>
> A coordinated turn doesn't prevent the inner wing from flying at a
> higher angle of attack than the outer wing, which is why it stalls
> first, and a spin can begin. I haven't experimented with it enough to be
> certain, but I suspect a slipping turn would reduce the tendency for the
> inner wing to stall first.

[Mark James Boyd]

>Most pilots instinctively recover long before they can
>tell the difference between a stall -- recovery -- spiral dive
>scenario and a stall -- spin. This often causes confusion about which
>is which.

I personally intentionally tried a spin entry once in a glass
glider and got a surprise and made an immediate spin recovery.

It seems the airspeed indicator rotates all the way around, so
80 knots indicated is the same as 20 knots indicated.

Imagine my surprise when the glider stalls, the nose drops,
and the ASI wobbles and then indicates ???
I tried it a few more times and by god could never
tell the difference, so I was too scared to do
anything but recover immediately (release the cross-controlled
inputs). Whichever it was, the glider sure picked up
speed like lightning when nose down.

I still wonder if this killed the Nimbus4DM pilots in Reno.
Imagine looking at the ASI and not knowing if
you should be doing a spin recovery or a spiral recovery
(two very different things).

[Chris OCallaghan]

A clarification...

When I ask did you let the spin fully develop, I mean through one or
more full turns, ie, to the point where it is easily differentiated
from a spiral. The initial turning stall very often self-recovers
within a quarter turn (yaw stability). If the stick is not moved
forward, the glider will continue to turn in a steepening bank and
accelerate. Most pilots instinctively recover long before they can
tell the difference between a stall -- recovery -- spiral dive
scenario and a stall -- spin. This often causes confusion about which
is which. I'm quibbling a little here, but there is a difference in
recovery times and altitude loss between the two. Your underlying
message, "Don't trust the yaw string alone to prevent a spin" is a
good one. Airspeed/AOA is the primary concern. A straight yaw string a
close second.

There is some value in understanding that a straight yaw string helps
a sailplane resist spinning. If we can be certain of this, low
altitude stalls can be more confidently addressed with greater control
and less loss of altitude. I'm thinking principally of wind shear
while turning base to low final. If the pilot doesn't detect the loss
of airspeed, he will certainly notice that the nose pitches down
(position of the elevator will try to return the glider to the lower
angle of attack) and may respond, initially, by trying to raise the
nose, aggrevating the situation. If a stall develops a quick glance
at the yaw string can help determine appropriate action, that is,
release back pressure and raise the lower wing using coordinated stick
and rudder, versus ailerons neutral, stick aggressively forward and
hard-over opposite rudder, then recovery from the ensuing dive.



(Chris OCallaghan) wrote in message >...
> Eric,
>
> Point of interest: did you let the spin fully develop after the
> coordinated turning stall? There is an aerodynamic tipping point --
> that is the self-righting tendency of the tail that would typically
> favor a spiral over a spin assuming that the only deflected control
> surface was the elevator. Of course a wing drops when in a turning
> stall, but without aileron deflection generating drag my guess would
> be that designed yaw stability would prevent spin development.
>
> There is a significant difference in the assymetric drag profile with
> and without aileron deflection. Remember that most modern aircraft
> begin their stall at the root. That means less torque and less
> disposition to overpower yaw stability and enter a spin. Slapping an
> aileron down to pick up the low wing adds significat drag at the tip.
> Add some rudder (cross-controls), and now you have a greater
> disposition to get the aircraft spinning rather than spiralling.
>
> I'll give this a try over the weekend -- that is, making no recovery
> to a coordinated turning stall to see how it develops. My Ventus spins
> happily if aggrevated. It should prove a good test bed.
>
> Eric Greenwell > wrote in message >...
> > Ian Forbes wrote:
> >
> > > On Thu, 06 Nov 2003 00:02:30 +0000, Colin wrote:
>
> > >
> > > - Spins occur when you stall and the glider is not "co-ordinated" ie
> > > either slipping or skidding.
> >
> > I used to think this, but I soon discovered our club Blanik would
> > happily spin from a coordinated turn by using a shallow bank and simply
> > reducing the airspeed. Since then, I've done this with other gliders.
> >
> > A coordinated turn doesn't prevent the inner wing from flying at a
> > higher angle of attack than the outer wing, which is why it stalls
> > first, and a spin can begin. I haven't experimented with it enough to be
> > certain, but I suspect a slipping turn would reduce the tendency for the
> > inner wing to stall first.

[Bruce Hoult]

In article >,
(Chris OCallaghan) wrote:

> Point of interest: did you let the spin fully develop after the
> coordinated turning stall? There is an aerodynamic tipping point --
> that is the self-righting tendency of the tail that would typically
> favor a spiral over a spin assuming that the only deflected control
> surface was the elevator. Of course a wing drops when in a turning
> stall, but without aileron deflection generating drag my guess would
> be that designed yaw stability would prevent spin development.

Even with the string in the middle, the elevator will *not* be the only
deflected control surface.

The Blanik makes this very obvious. As you slow down in a shallow turn
(10 degrees, say) you need more and more out of turn aileron in order to
prevent the turn from steepening, and you need more and more into turn
rudder to keep the string in the middle. Both controls can get a
significant way towards their limits in what seems like a perfectly
normal turn. When the inner wing eventually stalls everything is
perfectly set up for a rapid departure and spin.

-- Bruce

[Eric Greenwell]

Chris OCallaghan wrote:
> Eric,
>
> Point of interest: did you let the spin fully develop after the
> coordinated turning stall?

No, but there didn't seem to be any need to, as the inner wing dropped
and rotation began.

There is an aerodynamic tipping point --
> that is the self-righting tendency of the tail that would typically
> favor a spiral over a spin assuming that the only deflected control
> surface was the elevator. Of course a wing drops when in a turning
> stall, but without aileron deflection generating drag my guess would
> be that designed yaw stability would prevent spin development.
>

As Mark points out, the ailerons on the Blanik are significantly
deflected with "down" aileron on the inner wing, which is part of the
reason the inner wing stalls first. They are also deflected this way on
other gliders, but perhaps not as much.

> There is a significant difference in the assymetric drag profile with
> and without aileron deflection. Remember that most modern aircraft
> begin their stall at the root.

At least, for a straight ahead stall. I don't think this is true for
many gliders in a turn.

That means less torque and less
> disposition to overpower yaw stability and enter a spin. Slapping an
> aileron down to pick up the low wing adds significat drag at the tip.
> Add some rudder (cross-controls), and now you have a greater
> disposition to get the aircraft spinning rather than spiralling.
>
> I'll give this a try over the weekend -- that is, making no recovery
> to a coordinated turning stall to see how it develops. My Ventus spins
> happily if aggrevated. It should prove a good test bed.

We await your report with interest!

[Eric Greenwell]

In my first reply to Chris, I should've said "as Bruce Hoult points out"
instead of Mark Boyd.

Chris OCallaghan wrote:

> Eric,
>
> Point of interest: did you let the spin fully develop after the
> coordinated turning stall? There is an aerodynamic tipping point --
> that is the self-righting tendency of the tail that would typically
> favor a spiral over a spin assuming that the only deflected control
> surface was the elevator. Of course a wing drops when in a turning
> stall, but without aileron deflection generating drag my guess would
> be that designed yaw stability would prevent spin development.
>

[tango4]

"Mark James Boyd" > wrote in message
news:3fac007b$1@darkstar...

> tell the difference, so I was too scared to do
> anything but recover immediately (release the cross-controlled
> inputs).

With all due respect ......

That is not a spin recovery, never was and never will be although I'll admit
that in the right circumstances it will occasionally work.

If you are intentionally trying to spin not knowing how to recover properly
then you either have balls the size of footballs or are seriously mentally
challenged.

A STANDARD recovery is

CENTRALISE AILERONS
FULL OPPOSITE RUDDER.
SLIGHT PAUSE
STICK PROGRESSIVELY FORWARD UNTIL THE SPINNING STOPS.
CENTRALISE THE RUDDER.
RECOVER FROM THE RESULTING DIVE.

Very occasionally there may be a 'non standard' method in the POH but they
are few and far between. To be certified a glider should recover reliably
using the standard proceedure.

There is an excellent post by Bill Dean ( and others ) about this in the
archives ( a year ago )
http://groups.google.co.uk/groups?q=spin+recovery+group:rec.aviation.soaring&hl=en&lr=&ie=UTF-8&oe=UTF-8&group=rec.aviation.soaring&selm=1037116407.16021.0%40iapetus.uk.clara.net&rnum=2

Ian

[Slingsby]

> I still wonder if this killed the Nimbus4DM pilots in Reno.
> Imagine looking at the ASI and not knowing if
> you should be doing a spin recovery or a spiral recovery
> (two very different things).
************************************************** ******************************
What really killed them were wings which, by design, are only good for
3.5 g (+50% if the glue holds) when you get into a stall/spin
situation.

[Chris OCallaghan]

You've just described a cross-control stall. I think Eric's point was
that the additional drag at the wingtip wasn't necessary to initiate
auto rotation. The control inputs you've described are counter
intuitive. Is this a peculiarity of the Blanik? I only have a couple
of flights in them.

Typically, shallow banked turns like to roll level, especially if
there is any tendency to slip (dihedral). In most of the models I've
flown, overbanking doesn't become noticeable until you reach 30+
degrees.

Bruce Hoult > wrote in message >...
> In article >,
> (Chris OCallaghan) wrote:
>
> > Point of interest: did you let the spin fully develop after the
> > coordinated turning stall? There is an aerodynamic tipping point --
> > that is the self-righting tendency of the tail that would typically
> > favor a spiral over a spin assuming that the only deflected control
> > surface was the elevator. Of course a wing drops when in a turning
> > stall, but without aileron deflection generating drag my guess would
> > be that designed yaw stability would prevent spin development.
>
> Even with the string in the middle, the elevator will *not* be the only
> deflected control surface.
>
> The Blanik makes this very obvious. As you slow down in a shallow turn
> (10 degrees, say) you need more and more out of turn aileron in order to
> prevent the turn from steepening, and you need more and more into turn
> rudder to keep the string in the middle. Both controls can get a
> significant way towards their limits in what seems like a perfectly
> normal turn. When the inner wing eventually stalls everything is
> perfectly set up for a rapid departure and spin.
>
> -- Bruce

[Chris OCallaghan]

Your original post suggested a coordinated turn. See my response
regarding crossed controls. It sounds like the Blanik has an odd
tendency to want to overbank from a shallow turn, leading to an
aileron/rudder deflection that establishes the drag profile needed to
enter a fully developed spin.

In a turning stall, there is a tendency to rotate at stall break due
to assymetric drag. However, if there is no aileron input to aggrevate
the situation, the glider will typically drop its nose (lowering angle
of attack) and gain speed. This lowers the drag on the low wing and
envigorates the self-righting tendency of the vertical stabilizer.
This is why the first second or two after stall break scream SPIN, but
in fact the glider has self recovered and is now in a spiral.

Hopefully we'll have enough altitude to play with this today. Dr. Jack
isn't very optimistic. I might even get access to a CAP Blanik over
the next few weeks. I'll be interested to see how it behaves.


Eric Greenwell > wrote in message >...
> Chris OCallaghan wrote:
> > Eric,
> >
> > Point of interest: did you let the spin fully develop after the
> > coordinated turning stall?
>
> No, but there didn't seem to be any need to, as the inner wing dropped
> and rotation began.
>
> There is an aerodynamic tipping point --
> > that is the self-righting tendency of the tail that would typically
> > favor a spiral over a spin assuming that the only deflected control
> > surface was the elevator. Of course a wing drops when in a turning
> > stall, but without aileron deflection generating drag my guess would
> > be that designed yaw stability would prevent spin development.
> >
>
> As Mark points out, the ailerons on the Blanik are significantly
> deflected with "down" aileron on the inner wing, which is part of the
> reason the inner wing stalls first. They are also deflected this way on
> other gliders, but perhaps not as much.
>
> > There is a significant difference in the assymetric drag profile with
> > and without aileron deflection. Remember that most modern aircraft
> > begin their stall at the root.
>
> At least, for a straight ahead stall. I don't think this is true for
> many gliders in a turn.
>
> That means less torque and less
> > disposition to overpower yaw stability and enter a spin. Slapping an
> > aileron down to pick up the low wing adds significat drag at the tip.
> > Add some rudder (cross-controls), and now you have a greater
> > disposition to get the aircraft spinning rather than spiralling.
> >
> > I'll give this a try over the weekend -- that is, making no recovery
> > to a coordinated turning stall to see how it develops. My Ventus spins
> > happily if aggrevated. It should prove a good test bed.
>
> We await your report with interest!

[Chris OCallaghan]

We're taught (in fact, it's hammered into us) to recover immediately
from the insipient phase of any stall. Hanging in there to allow the
condition to fully develop is an exercise that takes practice, and
probably one that you don't want to get too used to.

Given the confusion of your asi, the next best way to differentiate is
by g load. In a spin, the loading quickly stabilizes to 1.5 to 2g. In
a spiral dive it builds quickly beyond this. Visually, the yaw string
goes right over in a spin, but since a spiral dive needn't be
coordinated, this too can be confusing.

Spinning or spiral diving are both unusual maneuvers. Because of that,
each of us will perceive them a little differently, based on our
personal idiosyncracies. For most of us, a canopy full of mother earth
screams acceleration, overpowering any other cues.

I am reminded of an experience I relive at least once every winter:
the first application of brakes on ice. When I step on the brakes, I
expect the reassurance of weight into my shoulder belt. When that
doesn't happen, I get the oddest feeling that instead of decelerating
I am accelerating, which, of course, makes me want to mash the brake
pedal down even harder. It takes a second or two to break through the
misperception and get my foot back up off the brake. I suspect that we
are all subject to varying degrees of a similar effect when we explore
parts of the envelope we don't often visit. Practice makes perfect,
but why do we need to be perfect unless we're aerobatic pilots.

We should focus instead on the insipient phase. Much more subtle, but
much more valuable in gleaning out every last ounce of performance
when it counts most.




(Mark James Boyd) wrote in message news:<3fac007b$1@darkstar>...
> >Most pilots instinctively recover long before they can
> >tell the difference between a stall -- recovery -- spiral dive
> >scenario and a stall -- spin. This often causes confusion about which
> >is which.
>
> I personally intentionally tried a spin entry once in a glass
> glider and got a surprise and made an immediate spin recovery.
>
> It seems the airspeed indicator rotates all the way around, so
> 80 knots indicated is the same as 20 knots indicated.
>
> Imagine my surprise when the glider stalls, the nose drops,
> and the ASI wobbles and then indicates ???
> I tried it a few more times and by god could never
> tell the difference, so I was too scared to do
> anything but recover immediately (release the cross-controlled
> inputs). Whichever it was, the glider sure picked up
> speed like lightning when nose down.
>
> I still wonder if this killed the Nimbus4DM pilots in Reno.
> Imagine looking at the ASI and not knowing if
> you should be doing a spin recovery or a spiral recovery
> (two very different things).

[Andreas Maurer]

On 7 Nov 2003 23:40:26 -0800, (Slingsby)
wrote:

>> I still wonder if this killed the Nimbus4DM pilots in Reno.
>> Imagine looking at the ASI and not knowing if
>> you should be doing a spin recovery or a spiral recovery
>> (two very different things).
>************************************************** ******************************
>What really killed them were wings which, by design, are only good for
>3.5 g (+50% if the glue holds) when you get into a stall/spin
>situation.


The official conclusion sounds a little different:


The maximum maneuvering load factor limits (in units of gravity or
g's) change with variations in glider speed and flap/airbrake
configuration. From a "flaps up" configuration at Va to the condition
of airbrakes and flaps extended at Vne, the maximum maneuvering load
factor limits decrease from positive 5.3 to a positive 3.5.



In other words: If the pilots had not extended the airbrakes, the
Nimbus would not have disintegrated.

This is what NTSB thinks about what killed them:


The National Transportation Safety Board determines that the probable
cause of this accident was the pilot's excessive use of the elevator
control during recovery from an inadvertently entered spin and/or
spiral dive during which the glider exceeded the maximum permissible
speed, which resulted in the overload failure of the wings at loadings
beyond the structure's ultimate design loads.



Note the term "at loadings beyond the structure's ultimate design
loads".




Bye
Andreas

[Eric Greenwell]

Chris OCallaghan wrote:
> You've just described a cross-control stall. I think Eric's point was
> that the additional drag at the wingtip wasn't necessary to initiate
> auto rotation. The control inputs you've described are counter
> intuitive. Is this a peculiarity of the Blanik? I only have a couple
> of flights in them.

Bruce's point, and mine, is that the controls ARE crossed in a
coordinated turn, and the crossing becomes greater as you slow down.
This is not a peculiarity of the Blanik, but is true for all the 20+
gliders I've flown.

>
> Typically, shallow banked turns like to roll level, especially if
> there is any tendency to slip (dihedral).

Yes, a slip will tend to roll level, but then you are not flying a
coordinated turn. A slipping turn will allow you to use less "top
aileron" (stick opposite the turn).

In most of the models I've
> flown, overbanking doesn't become noticeable until you reach 30+
> degrees.

Try it again at 15 to 20 degrees, and notice the control position as you
slow down. Top aileron becomes more pronounced as you near stall, but
it's there even at the usual thermalling speeds.

>
> Bruce Hoult > wrote in message >...

snip

>>
>>Even with the string in the middle, the elevator will *not* be the only
>>deflected control surface.
>>
>>The Blanik makes this very obvious. As you slow down in a shallow turn
>>(10 degrees, say) you need more and more out of turn aileron in order to
>>prevent the turn from steepening, and you need more and more into turn
>>rudder to keep the string in the middle. Both controls can get a
>>significant way towards their limits in what seems like a perfectly
>>normal turn. When the inner wing eventually stalls everything is
>>perfectly set up for a rapid departure and spin.
>>
>>-- Bruce

[W.J. \(Bill\) Dean \(U.K.\).]

About the Minden accident on 13 July 1999 to a Nimbus 4DM (LAX99MA251
http://www.ntsb.gov/publictn/2002/AAB0206.htm ).

Note that at the time the NTSB report was published there was discussion
about it on RAS. One of the things reported by posters with experience of
the Nimbus 3/4 models (I have none) was that the airbrakes have been known
to deploy uncommanded by the pilot. So the brakes may have deployed
themselves, and it is possible that this is what killed the pilots.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.

>
> "Andreas Maurer" > wrote in message
> ...
>
> >>
> >> On 7 Nov 2003 23:40:26 -0800, (Slingsby)
> >> wrote:
> >>
> >> I still wonder if this killed the Nimbus4DM pilots in Reno.
> >> Imagine looking at the ASI and not knowing if
> >> you should be doing a spin recovery or a spiral recovery
> >> (two very different things).
> >>
> >
> > What really killed them were wings which, by design, are only good for
> > 3.5 g (+50% if the glue holds) when you get into a stall/spin
> > situation.
> >
>
> The official conclusion sounds a little different:
>
>
> The maximum manoeuvring load factor limits (in units of gravity or
> g's) change with variations in glider speed and flap/airbrake
> configuration. From a "flaps up" configuration at Va to the condition
> of airbrakes and flaps extended at Vne, the maximum manoeuvring load
> factor limits decrease from positive 5.3 to a positive 3.5.
>
>
> In other words: If the pilots had not extended the airbrakes, the
> Nimbus would not have disintegrated.
>
> This is what NTSB thinks about what killed them:
>
>
> The National Transportation Safety Board determines that the probable
> cause of this accident was the pilot's excessive use of the elevator
> control during recovery from an inadvertently entered spin and/or
> spiral dive during which the glider exceeded the maximum permissible
> speed, which resulted in the overload failure of the wings at loadings
> beyond the structure's ultimate design loads.
>
>
>
> Note the term "at loadings beyond the structure's ultimate design
> loads".
>
> Bye
> Andreas
>

[Eric Greenwell]

Chris OCallaghan wrote:

> Your original post suggested a coordinated turn. See my response
> regarding crossed controls. It sounds like the Blanik has an odd
> tendency to want to overbank from a shallow turn, leading to an
> aileron/rudder deflection that establishes the drag profile needed to
> enter a fully developed spin.

It is not an oddity of the Blanik (in fact, it is an excellent trainer
for spins, because it does them so normally), but a consequence of a
coordinated turn. Because the inner wing is traveling more slowly than
the outer wing, it must have a higher lift coefficent to develop the
same lift as the outer wing. It achieves this with a downward deflected
aileron (and flap in many flapped gliders). This downward deflected
aileron produces a wing tip that stalls at a lower angle of attack than
the outer wingtip, which has an upward deflected wing tip.

>
> In a turning stall, there is a tendency to rotate at stall break due
> to assymetric drag.

The asymetric drag is due to a partially stalled inner wing, and
generally in the aileron area.

However, if there is no aileron input to aggrevate
> the situation, the glider will typically drop its nose (lowering angle
> of attack) and gain speed.

This is true, and is the reason the spin recovery includes centralizing
the ailerons. On some gliders, this is enough to unstall the inner wing
tip, and stop the incipient spin.

This lowers the drag on the low wing and
> envigorates the self-righting tendency of the vertical stabilizer.

I don't think "lowers the drag" is the best way to think of this, but
instead, think of it as unstalling the wing tip (of course, a stalled
wing tip does have higher drag than the unstalled one). No stall, no spin.

> This is why the first second or two after stall break scream SPIN, but
> in fact the glider has self recovered and is now in a spiral.

The situation Bruce and I describe has no discernible stall "break". THe
inner wing begins to drop, and it can't be held up with the aileron. If
the pilot doesn't recognize this is a spin entry, he will continue
adding top aileron, which deepens the stall on the inner wing tip, and
very quickly has a fully developed spin. There never is a "break", as
you get with a straight ahead stall, but a smooth entry into a spin.

[Chris OCallaghan]

November 9, 2003
Turning Stalls and Insipient Spins

As promised, apropos to this discussion on spin entry from coordinated
turning stalls, I took a tow this morning to 5000 feet agl and
performed a series of coordinated and cross control turning stalls.

The aircraft used was a Ventus 2bx, delivered this year. I have
approximately 75 hours in this aircraft and about 525 hours total in
the model. I flew the glider at approximately 70% of the aft cg limit.
Wing loading was 7.8 lbs per square foot. All stalls were entered in
the first positive flap position.

My intention was as follows: to perform a series of turning stalls,
both coordinated and cross controlled, to determine the departure and
post departure characteristics of a modern fiberglass sailplane.
Stalls were entered gently and in a shallow bank (lower wingtip on
horizon). Whether coordinated or cross controlled, I fixed the
controls in the pre-departure position for three full seconds after
departure (that is, no attempt was made to recover immediately after
the stall break).

Once off tow I completed two clearing turns, then stalled the glider
wings level twice to establish attitude. I then entered a coordinated
shallow left turn and gently eased back on the stick. The stall broke
cleanly. The glider initially yawed about 30 degrees to the left,
dropped its nose through the horizon, then began to increase its bank
angle and gain speed. G forces accumulated and I recovered from the
spiral dive at about 80 knots and roughly 70 degrees of bank. (As
noted above, the elevator was held firmly aft and aileron and rudder
neutral until recovery was initiated.

I repeated the same maneuver to the right. The stall break was less
clean (more mushy). Development of the ensuing spiral dive was slower,
but airspeed and bank angle both accumulated until I released the
controls and initiated a recovery.

I repeated this sequence with like results.

I then entered a shallow bank turning stall (left) while skidding
slightly. As the low wing began to drop, I applied about ½ stick
travel to the right, ostensibly to raise the dropping wing. Entry into
the spin was immediate and dramatic. The glider yawed approximately
ninety degrees while dropping it nose to about 60 degrees below the
horizon. I left the controls in this position for a count of three
(one one thousand, two one thousand…) The glider completed
approximately 1.25 rotations before I initiated a recovery (stick
forward, ailerons neutral, opposite rudder, pull up from dive).

I repeated this process to the right. However, this time, I gently
accelerated the stall (achieving a slightly higher nose attitude
before departure). Once again, I skidded the turn (10 to 20 degrees),
and tried to pick up the low wing as it stalled, this time with full
deflection of the aileron. The ensuing spin entry was even more
dramatic. I was unable to measure rotation rate (even roughly) because
the glider's nose went immediately past vertical. As I lost the
horizon I became disoriented, until I looked out at the wingtip and
found the horizon again. I nonetheless fixed the controls for a count
of three. There was no noticeable g build up until I initiated a spin
recovery. Max speed during the dive was just above 120 knots, about 20
knots more than I typically see for a recovery from a fully developed
spin.

It should be noted that my glider has a flap redline of 80 knots. In
all cases, if airspeed exceeded 80 knots, I moved the flap handle to
the first negative position.

My interpretation: while the glider exhibited a yawing motion during
the coordinated turning stall, it did not auto rotate, nor did it show
any such propensity. Some pilots may find the dropping wing, yaw
motion, and reduced g force of a coordinated turning stall
disquieting, but when compared in sequence to an actual autorotation
leading to a fully developed spin, the prior is patently docile.
Height loss after an immediate recovery from a coordinated turning
stall using a release of back pressure and coordinated ailerons and
rudder could be measured in 10s of feet. The spin, however, from entry
to the bottom of the dive recovery was measured in hundreds. Loss of
height for the first spin, from entry, through development, to the
bottom of the recovery dive was 475 feet. The second: 750 feet.

Conclusions: draw your own.

I wish I could say something interesting about the task we flew in the
afternoon (blue, weak, and manky), but what I've described above was
the highlight of my Sunday.

[Eric Greenwell]

Todd Pattist wrote:

>>In other words: If the pilots had not extended the airbrakes, the
>>Nimbus would not have disintegrated.
>
>
> I don't think this is quite the correct way to look at it.
> It implies that opening the brakes was the direct cause. I
> don't see it that way.
>
> Each part of the wing can produce a certain lifting force.
> The g-force you feel is the result of the total lifting
> force produced - applied to the mass of the glider.
> Opening the brakes prevents portions of the wing from
> producing their share of the lifting force. For structural
> reasons, the remaining parts (tips especially) cannot safely
> produce any more lift than they were producing before the
> brakes were opened, so the total lift force is reduced and
> the g-force drops automatically. Thus, it's not so much
> opening the brakes that breaks the wings, it's the use of
> the elevator to increase the AOA after the brakes are opened
> to try to hold the higher g-force.

I think this may not be a correct analysis. In my ASW 20, during steady
straight flight, I could open the spoilers while holding the stick
steady. The glider would maintain it's attitude, but begin sinking. The
G force was reduced very momentarily, then returned to 1 G. The wing
tips would bend upwards, indicating they were producing additional lift.
The additional sink rate increased the angle of attack of the wing, and
this caused the additional loading on the wing tips. In other words, the
lift tends to shift to the wing tips without the pilot doing anything
besides opening the spoilers.

I haven't tried it, but I assume this would also happen in a 3 G turn.
If true, the only way to avoid exceeding the "open spoiler G limit"
would be reduce the G loading before opening the spoilers.

[Slingsby]

Andreas Maurer > wrote in message >...
> On 7 Nov 2003 23:40:26 -0800, (Slingsby)
> wrote:
>
> >> I still wonder if this killed the Nimbus4DM pilots in Reno.
> >> Imagine looking at the ASI and not knowing if
> >> you should be doing a spin recovery or a spiral recovery
> >> (two very different things).
> >************************************************** ******************************
> >What really killed them were wings which, by design, are only good for
> >3.5 g (+50% if the glue holds) when you get into a stall/spin
> >situation.
>
>
> The official conclusion sounds a little different:
>
>
> The maximum maneuvering load factor limits (in units of gravity or
> g's) change with variations in glider speed and flap/airbrake
> configuration. From a "flaps up" configuration at Va to the condition
> of airbrakes and flaps extended at Vne, the maximum maneuvering load
> factor limits decrease from positive 5.3 to a positive 3.5.
>
>
> Right. By design they are ONLY good for 3.5 g. Exceed that amount by a paltry 50% and the wings WILL snap off like toothpicks. Guaranteed. They will, and did, snap off together. Both wings were equally weak by design and construction technique AND, they used enough glue.

> In other words: If the pilots had not extended the airbrakes, the
> Nimbus would not have disintegrated.
>
> This is what NTSB thinks about what killed them:
>
>
> The National Transportation Safety Board determines that the probable
> cause of this accident was the pilot's excessive use of the elevator
> control during recovery from an inadvertently entered spin and/or
> spiral dive during which the glider exceeded the maximum permissible
> speed, which resulted in the overload failure of the wings at loadings
> beyond the structure's ultimate design loads.
>
>
Remove the word "excessive" and the description becomes more realistic.

> Note the term "at loadings beyond the structure's ultimate design
> loads".

> Bye
> Andreas

[Robert Ehrlich]

Todd Pattist wrote:
> ..
> We're not talking about a "turn," but rather a pullup from
> nose down attitude. You can't really compare the situation
> where gravity imposes 1 g to the case where the g-load is
> not externally imposed.
> ...


A similar effect arises even in this situation: when the lift
is reduced due to the extended brakes, the radius of curvature
increases. By rotational inertia the glider will tend to keep
the same rate of rotation around the pitch axis, so that the
AOA increases, i.e. the g-load increases and the radius of curvature
decreases. Of course the rotational inertia will not have a total
success in trying to keep the rotational rate, as the AOA increases
this also changes the AOA at the tail plane, providing the moment
which is going to reduce the rotational rate. However the radius
obtained in this way is not what would be obtained by just reducing
the lift, there is still a (partial) load transfer to the wing tips.

[Andreas Maurer]

On 11 Nov 2003 14:41:02 -0800, (Slingsby)
wrote:

>>
>> The National Transportation Safety Board determines that the probable
>> cause of this accident was the pilot's excessive use of the elevator
>> control during recovery from an inadvertently entered spin and/or
>> spiral dive during which the glider exceeded the maximum permissible
>> speed, which resulted in the overload failure of the wings at loadings
>> beyond the structure's ultimate design loads.
>>
>>
> Remove the word "excessive" and the description becomes more realistic.

Ask that the NTSB... ;)

If the pilot pulls too hard, creating g-forces that overload the
aircraft, the term "excessive" sounds appropriate for someone like me
whose mother language is not English.

Bye
Andreas

[Eric Greenwell]

In article >,
says...
> Eric Greenwell > wrote:
>
>
> >I think this may not be a correct analysis. In my ASW 20, during steady
> >straight flight, I could open the spoilers while holding the stick
> >steady. The glider would maintain it's attitude, but begin sinking. The
> >G force was reduced very momentarily, then returned to 1 G.
>
> Correct. In steady straight flight, as the brakes destroy
> lift in the wing central area, the glider begins to
> accelerate towards the ground under the influence of
> gravity. The change in path causes an increase in AOA
> everywhere until lift has increased to equal weight.
>
> However, we aren't talking about "steady straight flight" at
> 1g but curved flight at >1g and the only question is how
> much greater than 1g we're going to impose on the structure.
>
> >The wing
> >tips would bend upwards, indicating they were producing additional lift.
>
> Agreed.
>
>
> >The additional sink rate increased the angle of attack of the wing, and
> >this caused the additional loading on the wing tips. In other words, the
> >lift tends to shift to the wing tips without the pilot doing anything
> >besides opening the spoilers.
>
> Correct - in the case of "steady straight flight" at 1g.
> However, in the case of nose down curving high-g pullup,
> there is no force corresponding to gravity that will cause
> the glider's path to automatically change to increase the
> AOA.

I haven't tried it, but I think the glider will change it's path; in
fact, it must, since the lift on the wings has changed. How could it
continue in the same direction with one of the forces on it cut by a
large amount?

I don't think it matters if the glider is in a turn or pulling out
from a dive, what matters is the reduction in lift force. Because of
this reduction, the glider will accelerate "downward" (relative to the
lift on the wing). This change in path will increase the AOA on the
wing, increasing the lift at the tips, and increasing the load on
them.

If this analysis is correct, simply opening the spoilers will result
in shifting some of the lift to the wing tips. It isn't necessary to
change the elevator position to make this happen.

> That would only happen if there was a 5 g force
> outside the curve of the pullup pulling the glider outward.
> There isn't. If the pilot has an AOA set to produce 5 g's
> and opens the brakes, he suddenly loses a major part of the
> lift and gets 3 g's and a larger radius pullup. There's no
> 5 g gravitational force outside the pullup path imposing 5
> g's on the structure. The glider is happy to fly at the
> larger radius reduced g path produced when the wing remains
> at the original AOA with the brakes open.
>
> The "trap" for the pilot is that we tend to hold a constant
> g-level by modulating back pressure on the stick. As the
> brakes are opened, we will automatically pull back to
> increase AOA and shift the load to the tips, even if the
> glider doesn't do it automatically.

This may also happen, which would make the situation worse, of course.

>
> >I haven't tried it, but I assume this would also happen in a 3 G turn.
> >If true, the only way to avoid exceeding the "open spoiler G limit"
> >would be reduce the G loading before opening the spoilers.
>
> We're not talking about a "turn," but rather a pullup from
> nose down attitude.

The basic forces on a glider in a 2 G turn (for example) are
indistinguishable from a 2 G pullup.

> You can't really compare the situation
> where gravity imposes 1 g to the case where the g-load is
> not externally imposed.

I think you can. Aren't the forces on a glider pulling 1 G at the top
of a loop the same as a glider gliding steadily and upright? Of
course, there are some minor differences because the airflow in
curving flight isn't exactly the same as straight flight, so the
elevator would have a slightly different force on it. The influence of
gravity is to change the path of the glider, but the forces on the
structure depend on the G loading, not the orientation of the glider.

--
!Replace DECIMAL.POINT in my e-mail address with just a . to reply
directly

Eric Greenwell
Richland, WA (USA)