Spin

[K.P. Termaat]

This happened trying to land back at the field after a cable break. Very sad
indeed.
www.fsv-unterjesingen.de/DnLoads/Seilriss.avi

Karel, NL

[Mal]

Is the pilot alive.

Tail wind landing too slow and the combination of pulling the air brakes
into a spin looks like a Jantar 2 !

"K.P. Termaat" > wrote in message
...
> This happened trying to land back at the field after a cable break. Very
sad
> indeed.
> www.fsv-unterjesingen.de/DnLoads/Seilriss.avi
>
> Karel, NL
>
>

[Nick Gilbert]

wow, that is sobering.

Nick.


"Mal" > wrote in message
...
> Is the pilot alive.
>
> Tail wind landing too slow and the combination of pulling the air brakes
> into a spin looks like a Jantar 2 !
>
> "K.P. Termaat" > wrote in message
> ...
> > This happened trying to land back at the field after a cable break. Very
> sad
> > indeed.
> > www.fsv-unterjesingen.de/DnLoads/Seilriss.avi
> >
> > Karel, NL
> >
> >
>
>

[Mal]

Sure is.

Its National no Alcohol week

Nick where are the pictures from the SA Nationals ?

You seen the weekend pictures http://www.mals.net/camden/ DG1000

"Nick Gilbert" > wrote in message
...
> wow, that is sobering.
>
> Nick.
>
>
> "Mal" > wrote in message
> ...
> > Is the pilot alive.
> >
> > Tail wind landing too slow and the combination of pulling the air brakes
> > into a spin looks like a Jantar 2 !
> >
> > "K.P. Termaat" > wrote in message
> > ...
> > > This happened trying to land back at the field after a cable break.
Very
> > sad
> > > indeed.
> > > www.fsv-unterjesingen.de/DnLoads/Seilriss.avi
> > >
> > > Karel, NL
> > >
> > >
> >
> >
>
>

[Bill Daniels]

"K.P. Termaat" > wrote in message
...
> This happened trying to land back at the field after a cable break. Very
sad
> indeed.
> www.fsv-unterjesingen.de/DnLoads/Seilriss.avi
>
> Karel, NL
>
Note that the departure occurred with the nose well below the horizon. It
appeared that the glider was stalled and sinking toward the ground for most
of the turn before the departure. Perhaps the pilot ignored airspeed
pre-stall warnings because the perceived priority was to get lined up with
the runway.

Question, was this low altitude turn-back necessary because there not enough
landable area into the wind?

One wonders if the maneuver would have been successful if the glider had
been accurately flown.

Bill Daniels

[C.Fleming]

My condolences to the family and friends. Very sad.

I write an instructor's column for our club's newsletter, and this month's
subject is about flying in windy conditions. The wind sock in the video
appears to indicate the windspeed was in excess of 15knots (assuming a
standard windsock). Before every flight, but especially in windy
conditions, an emergency plan needs to be considered! If you have a large
crosswind, a turn in the wrong direction after a rope break may blow you
helplessly too far away from the runway. If you have a strong headwind on
takeoff, a turn back to the runway may not even be an option! The resulting
tailwind landing may cause you to completely overfly the runway, or may
cause you to lose control during the landing rollout. Every situation is
different, but you need to make this decision before you close the canopy,
not at 300 feet.

Finally, if you ever find yourself in a situation where you are
low-and-slow, "fly the glider!" An off-field landing under control is
always better than an on-field landing out of control. Aim for something
soft and cheap. Ignore your ego, kiss the glider good-bye, and save your
butt!

Chris Fleming



"Bill Daniels" > wrote in message
...
> Note that the departure occurred with the nose well below the horizon. It
> appeared that the glider was stalled and sinking toward the ground for
most
> of the turn before the departure. Perhaps the pilot ignored airspeed
> pre-stall warnings because the perceived priority was to get lined up with
> the runway.
>
> Question, was this low altitude turn-back necessary because there not
enough
> landable area into the wind?
>
> One wonders if the maneuver would have been successful if the glider had
> been accurately flown.
>
> Bill Daniels
>

[Bert Willing]

From what I heard on the German forum, there was no fatality involved in
this accident.

--
Bert Willing

ASW20 "TW"


"C.Fleming" > a écrit dans le message de
...
> My condolences to the family and friends. Very sad.
>
> I write an instructor's column for our club's newsletter, and this month's
> subject is about flying in windy conditions. The wind sock in the video
> appears to indicate the windspeed was in excess of 15knots (assuming a
> standard windsock). Before every flight, but especially in windy
> conditions, an emergency plan needs to be considered! If you have a large
> crosswind, a turn in the wrong direction after a rope break may blow you
> helplessly too far away from the runway. If you have a strong headwind on
> takeoff, a turn back to the runway may not even be an option! The
resulting
> tailwind landing may cause you to completely overfly the runway, or may
> cause you to lose control during the landing rollout. Every situation is
> different, but you need to make this decision before you close the canopy,
> not at 300 feet.
>
> Finally, if you ever find yourself in a situation where you are
> low-and-slow, "fly the glider!" An off-field landing under control is
> always better than an on-field landing out of control. Aim for something
> soft and cheap. Ignore your ego, kiss the glider good-bye, and save your
> butt!
>
> Chris Fleming
>
>
>
> "Bill Daniels" > wrote in message
> ...
> > Note that the departure occurred with the nose well below the horizon.
It
> > appeared that the glider was stalled and sinking toward the ground for
> most
> > of the turn before the departure. Perhaps the pilot ignored airspeed
> > pre-stall warnings because the perceived priority was to get lined up
with
> > the runway.
> >
> > Question, was this low altitude turn-back necessary because there not
> enough
> > landable area into the wind?
> >
> > One wonders if the maneuver would have been successful if the glider had
> > been accurately flown.
> >
> > Bill Daniels
> >
>
>

[Marcel Duenner]

"Mal" > wrote in message >...
> Is the pilot alive.

Yes. Only minor injuries.

>
> Tail wind landing too slow and the combination of pulling the air brakes
> into a spin looks like a Jantar 2 !

No, it's a DG500

[C.Fleming]

That's great news!


"Bert Willing" > wrote in
message ...
> From what I heard on the German forum, there was no fatality involved in
> this accident.
>
> --
> Bert Willing
>
> ASW20 "TW"
>
>
> "C.Fleming" > a écrit dans le message de
> ...
> > My condolences to the family and friends. Very sad.
> >
> > Chris Fleming
> >
> >

[Shawn Curry]

Bert Willing wrote:
> From what I heard on the German forum, there was no fatality involved in
> this accident.
>

Good to hear he's OK. I've only been able to play the audio of this
clip and it didn't sound good. Anyone else w/similar problems? I'm
loading a Quicktime update to see if that helps. Newest winblows media
playa gags on it totally.

Shawn

[Stefan]

Shawn Curry wrote:

> Good to hear he's OK. I've only been able to play the audio of this
> clip and it didn't sound good.

Actually, it sounds very good: "Für den Piloten endete dieser Crash mit
ein paar Schnittwunden."

Stefan

[Shawn Curry]

Stefan wrote:
> Shawn Curry wrote:
>
>> Good to hear he's OK. I've only been able to play the audio of this
>> clip and it didn't sound good.
>
>
> Actually, it sounds very good: "Für den Piloten endete dieser Crash mit
> ein paar Schnittwunden."
>
> Stefan
>
OooKaaay. Sorry not much help. Bit of French maybe but German? Nope.
The concerned sounding voice of a woman (?) and lots of crunching
sounds is all I could decipher. That and the word "crash"

Shawn

[Stefan]

Shawn Curry wrote:

>> Actually, it sounds very good: "Für den Piloten endete dieser Crash
>> mit ein paar Schnittwunden."

> OooKaaay. Sorry not much help. Bit of French maybe but German? Nope.
> The concerned sounding voice of a woman (?) and lots of crunching
> sounds is all I could decipher. That and the word "crash"

Ok. The woman basically says. "Oh ****! Let's go there!"

The commentator says that it was a sunday routine flight, then the cable
broke, and then the abovementioned sentence which basically means: "The
pilot suffered a couple of cuts."

Stefan

[Fredrik Thörnell]

K.P. Termaat > skrev den Wed, 04 Feb 2004 10:07:21 GMT:

> This happened trying to land back at the field after a cable break. Very
> sad
> indeed.
> www.fsv-unterjesingen.de/DnLoads/Seilriss.avi

What does the commentator say about 18 meter (high?) something? Or is that
a reference to the span? Or am I mishearing completely? Should have spent
less time communication with the cute girls outside the window during
German class... ;)

Cheers,
Fred

[CV]

Fredrik Thörnell wrote:
> What does the commentator say about 18 meter (high?) something? Or is

He is saying that the cable broke at 80 meters height. (200 odd feet)
CV

[Bill Daniels]

"CV" > wrote in message
...
> Fredrik Thörnell wrote:
> > What does the commentator say about 18 meter (high?) something? Or is
>
> He is saying that the cable broke at 80 meters height. (200 odd feet)
> CV
>
Perhaps someone familiar with the incident could explain why the pilot tried
to turn back from a height of 80 meters. I would expect that, with a wire
break at 80 meters, the pilot would have 75% or more of the airfield
straight ahead for a safe landing. In fact, a 180 degree turn from an 80
meter wire break would leave no place to land at most winch sites.

Bill Daniels

[Stefan]

Bill Daniels wrote:

> Perhaps someone familiar with the incident could explain why the pilot tried
> to turn back from a height of 80 meters. I would expect that, with a wire
> break at 80 meters, the pilot would have 75% or more of the airfield
> straight ahead for a safe landing

Stress? Overtax? Panic? Blackout? It's happened before.

Stefan

[ir. K.P. Termaat]

Stefan > wrote in message >...
> Bill Daniels wrote:
>
> > Perhaps someone familiar with the incident could explain why the pilot tried
> > to turn back from a height of 80 meters. I would expect that, with a wire
> > break at 80 meters, the pilot would have 75% or more of the airfield
> > straight ahead for a safe landing
>
> Stress? Overtax? Panic? Blackout? It's happened before.
>
> Stefan


The commentator says:

"Sunday afternoon in Magdenburg.
It was a routine start with winch, but at 80m the cable breaks.
For the pilot this crash ends with a couple of cutting wounds"

The glider is a 2-seater DG500. Probabbly with only the pilot on
board.
The commentator's voice is very professional. A story by the media for
the general public?. Not very good for our sport.
If standard rules (e.g. landing straight ahead after this low cable
break) had been performed nothing seriously would have happened. And
why did the cable break anyway (weak cable, heavy glider, to steep a
take off, to much force on the cable by the winchman and what have
you).

Karel, NL

[Jon Meyer]

I haven't followed this thread, so I don't know if
anyone has already mentioned this, but It is clear
from the video that the pilot was performaing a downwind
turn in a fairly strong wind (windsock almost straight).
Why he decided to turn downwind at this height is anyone's
guess. You may also note that at the point of spin
entry the airbrakes are opened fully, I suspect that
the pilot had cracked the brakes open (again god knows
why), resulting in the wing stalling. The fact that
he opened the brakes fully upon spinning seems to suggest
his brain was switched to 'landing lever mode' if it
was switched on at all. Another reminder that eventualities
should be considered before every winch launch. This
guy was very lucky to only suffer minor injuries.

J.

I don't mean to sound 'holier than thou'. We've all
run out of ideas at some time or another and gotten
away with it by sheer luck. Its interesting to see
the chain of events that led to this guy not getting
away with it tho.

[Janos Bauer]

> If standard rules (e.g. landing straight ahead after this low cable
> break) had been performed nothing seriously would have happened.

What are the standards altitudes for such incident? Here are the list
I learnt: <50 straight landing, 50<&<100 one 180 degree turn, 180< two
turns or small circle. Of course in strong wind I would increase these
values.


/Janos

[Bert Willing]

There are no worldwide standards but rather local procedures (depending on
the terrain) with daily adjustments (depending on wind conditions).

--
Bert Willing

ASW20 "TW"


"Janos Bauer" > a écrit dans le message de
...
>
> > If standard rules (e.g. landing straight ahead after this low cable
> > break) had been performed nothing seriously would have happened.
>
> What are the standards altitudes for such incident? Here are the list
> I learnt: <50 straight landing, 50<&<100 one 180 degree turn, 180< two
> turns or small circle. Of course in strong wind I would increase these
> values.
>
>
> /Janos
>

[Chris OCallaghan]

I once watched a pilot turn an ASW 20 through 360 degrees after a 75
foot rope break. With each successive 90 degree turn, I heaved a sigh
of relief, until he rolled into the next one. The pilot made three 90
degree left hand turns, at one point dropping slightly below the level
of the runway, until he was lined up to land across the runway. He
made his last 90 degree right turn in ground effect, using rudder
only. I didn't see much of the touchdown or rollout, as I was running
for life and limb. The glider was undamaged. The pilot, on the other
hand...

To my knowledge, he never flew another glider.



"Bill Daniels" > wrote in message >...
> "CV" > wrote in message
> ...
> > Fredrik Thörnell wrote:
> > > What does the commentator say about 18 meter (high?) something? Or is
> >
> > He is saying that the cable broke at 80 meters height. (200 odd feet)
> > CV
> >
> Perhaps someone familiar with the incident could explain why the pilot tried
> to turn back from a height of 80 meters. I would expect that, with a wire
> break at 80 meters, the pilot would have 75% or more of the airfield
> straight ahead for a safe landing. In fact, a 180 degree turn from an 80
> meter wire break would leave no place to land at most winch sites.
>
> Bill Daniels

[Janos Bauer]

Sorry, meters.

/Janos

Todd Pattist wrote:
> Janos Bauer > wrote:
>
>
>> What are the standards altitudes for such incident? Here are the list
>>I learnt: <50 straight landing, 50<&<100 one 180 degree turn, 180< two
>>turns or small circle. Of course in strong wind I would increase these
>>values.
>
>
> Units? Meters or feet?
>
> Todd Pattist - "WH" Ventus C
> (Remove DONTSPAMME from address to email reply.)

[David Pye]

Please would someone post a url if this clip is online.

Thanks



At 15:36 05 February 2004, Todd Pattist wrote:
>Janos Bauer wrote:
>
>>Sorry, meters.
>
>Thanks. I thought it was meters, but I wanted to be
>sure.
>Todd Pattist - 'WH' Ventus C
>(Remove DONTSPAMME from address to email reply.)
>
David Pye
Kent Gliding Club
Charing

Mob: 07946-302975
Home: 01732-873088
East Malling, Kent, UK

[Jon Meyer]

At 23:12 05 February 2004, David Pye wrote:
>Please would someone post a url if this clip is online.
>

http://www.fsv-unterjesingen.de/DnLoads/Seilriss.avi

[Arnold Pieper]

>He made his last 90 degree right turn in ground effect, using rudder
> only. I didn't see much of the touchdown or rollout, as I was running
> for life and limb. The glider was undamaged. The pilot, on the other
> hand...
>
> To my knowledge, he never flew another glider.

A turn at low speed with rudder only is an invitation for a spin.
At low altitude, it will usually end exactly the way we saw in this video,
with the glider spinning right into the ground.

If your collegue performed that last turn at very high speed the glider
wouldn't turn with rudder only.
If it was at low speed, and below 2 feet altitude, one of the wingtips
certainly touched first and it wasn't very pretty.

If he was above 2 feet, the result would have been some glider damage.

[Robert Ehrlich]

Bert Willing wrote:
>
> There are no worldwide standards but rather local procedures (depending on
> the terrain) with daily adjustments (depending on wind conditions).
>
> --
> Bert Willing
>
> ASW20 "TW"
>
> "Janos Bauer" > a écrit dans le message de
> ...
> >
> > > If standard rules (e.g. landing straight ahead after this low cable
> > > break) had been performed nothing seriously would have happened.
> >
> > What are the standards altitudes for such incident? Here are the list
> > I learnt: <50 straight landing, 50<&<100 one 180 degree turn, 180< two
> > turns or small circle. Of course in strong wind I would increase these
> > values.
> >

I had a reminder last summer during a check flight on a new field, and
then tried to pass the message to my first students during my first flights
as instructor: as long as landing straight ahead is possible, do it, don't
try anything else. If it is not possible, then you should have a height
sufficient for an abbreviated pattern. What I would like to add is some
rule of thumb for estimating if landing straight ahead is possible, not
based on looking on instruments if possible, like "First push the stick
in order to reach a normal flight attitude and speed. Then if you can see
the last 300m of the runway, you can land ahead". The value of 300m is
of course subject to discussion and change. The advantage of such a strategy
is that it could be well planned before take-off by having a well-known ground
feature mark the point you must see for deciding to land straight ahead.

[Mark James Boyd]

Janos Bauer > wrote:
>
> What are the standards altitudes for such incident? Here are the list
>I learnt: <50 straight landing, 50<&<100 one 180 degree turn, 180< two
>turns or small circle. Of course in strong wind I would increase these
>values.

I have been VERY surprised a few times by the effect of a slight
tailwind on my rope break practice. Since then I pay a lot
more attention to when the towplane rotates. If he rotates
much further down the strip, then I know I have either
a tailwind, heavy glider, high density altitude, etc.

Of course this assumes the towplane pilot rotates at the same speed
each time (in my experience they are very consistent).

In the cases when this happens
I know we ain't doin' very much "up" for the amount
"forward." So I SWAG a higher 180 altitude (maybe 300 or 400 feet).
The worst was an open canopy L-13 with two people on a hot
day with a 3-5 knot tailwind and only 180hp towplane. I dunno
if even 400 feet AGL woulda been enough.

Anybody else use the point of towplane rotation as
a hint?

I've wondered why airliners don't have some spot on the
ground (GPS) some distance down the runway, and abort
at that spot if they haven't reached a certain airspeed.
Seems simpler than doing all them calculamications for
wind, density altitude, etc. which may have changed since
you did them. Why not observe instead of predicting?

It doesn't work if you have ice/frost on the wings,
or if the ASI malfunctions (reads too high AS),
or you're misconfigured, but otherwise it seems to make
sense to me...

Of course when's the last time anybody de-iced a towplane or
glider, for goodness sakes! ;O

[Mark James Boyd]

Arnold Pieper > wrote:
>>He made his last 90 degree right turn in ground effect, using rudder
>> only. I didn't see much of the touchdown or rollout, as I was running
>> for life and limb. The glider was undamaged. The pilot, on the other
>> hand...
>>
>> To my knowledge, he never flew another glider.
>
>A turn at low speed with rudder only is an invitation for a spin.
>At low altitude, it will usually end exactly the way we saw in this video,
>with the glider spinning right into the ground.

I wonder if this was use of rudder, or coarse use of rudder.
I suspect the steep bank and different wing airspeeds set it up,
and then an accelerated use of rudder caused the wingtip speeds
to be that much more (a skidding stab at the rudder seems like
it would have a different effect than slowly putting in rudder).

>
>If your collegue performed that last turn at very high speed the glider
>wouldn't turn with rudder only.
>If it was at low speed, and below 2 feet altitude, one of the wingtips
>certainly touched first and it wasn't very pretty.

I've done quite a few turns with level wings and using rudder
to turn below 2 feet. I've done it both on the takeoff
roll (to line up from being way off) behind the towplane, and
after landing to line up with the takeoff runway (about
120 degrees left).

In the first case I probably should have simply released immediately.
In the second case I should have stopped straight ahead.
Not because this was necessary (it wasn't, since de facto
everything worked out fine) but because it would
be better practice for flying a higher performance glider,
where both of these circumstances could possibly create a
ground loop.

The competition pilots stay REAL straight at low airspeeds.
I suspect a few ground loops have convinced them not to
put in adverse yaw (and rudder to turn) during taxi.

[Bill Daniels]

Mark, I think Janos was talking about winch launch. The land ahead/turn
height for winch launch depends greatly on the winch site although at 25% of
the altitude expected without a wire break, say 500 feet or 150 meters, a
landing straight ahead on the runway should be possible. The ideal,
available at most sites, is an overlap between the two options where a 360
degree turn with a landing into the wind can be made from 300 feet AGL and a
straight ahead landing can be successful at 450 feet.

For airtow, there are certainly conditions where a low altitude rope break
will not allow the glider to get back to the airfield. Tailwinds, high
density altitudes and heavy gliders make conditions worse for rope breaks.
I have often been at 1000'AGL (300 Meters) before I felt comfortable about a
return to the runway. Under these conditions, airtow weak link strength
becomes a life or death matter.

Conditions like these make me far more comfortable with winch launch where I
can be sure of landing the glider on the airfield without a scratch.

Bill Daniels


"Mark James Boyd" > wrote in message
news:4023f76a$1@darkstar...
> Janos Bauer > wrote:
> >
> > What are the standards altitudes for such incident? Here are the list
> >I learnt: <50 straight landing, 50<&<100 one 180 degree turn, 180< two
> >turns or small circle. Of course in strong wind I would increase these
> >values.
>
> I have been VERY surprised a few times by the effect of a slight
> tailwind on my rope break practice. Since then I pay a lot
> more attention to when the towplane rotates. If he rotates
> much further down the strip, then I know I have either
> a tailwind, heavy glider, high density altitude, etc.
>
> Of course this assumes the towplane pilot rotates at the same speed
> each time (in my experience they are very consistent).
>
> In the cases when this happens
> I know we ain't doin' very much "up" for the amount
> "forward." So I SWAG a higher 180 altitude (maybe 300 or 400 feet).
> The worst was an open canopy L-13 with two people on a hot
> day with a 3-5 knot tailwind and only 180hp towplane. I dunno
> if even 400 feet AGL woulda been enough.
>
> Anybody else use the point of towplane rotation as
> a hint?
>
> I've wondered why airliners don't have some spot on the
> ground (GPS) some distance down the runway, and abort
> at that spot if they haven't reached a certain airspeed.
> Seems simpler than doing all them calculamications for
> wind, density altitude, etc. which may have changed since
> you did them. Why not observe instead of predicting?
>
> It doesn't work if you have ice/frost on the wings,
> or if the ASI malfunctions (reads too high AS),
> or you're misconfigured, but otherwise it seems to make
> sense to me...
>
> Of course when's the last time anybody de-iced a towplane or
> glider, for goodness sakes! ;O

[Bill Daniels]

"Mark James Boyd" > wrote in message
news:4023fa90$1@darkstar...
> Arnold Pieper > wrote:
> I've done quite a few turns with level wings and using rudder
> to turn below 2 feet. I've done it both on the takeoff
> roll (to line up from being way off) behind the towplane, and
> after landing to line up with the takeoff runway (about
> 120 degrees left).
>
> In the first case I probably should have simply released immediately.
> In the second case I should have stopped straight ahead.
> Not because this was necessary (it wasn't, since de facto
> everything worked out fine) but because it would
> be better practice for flying a higher performance glider,
> where both of these circumstances could possibly create a
> ground loop.
>
> The competition pilots stay REAL straight at low airspeeds.
> I suspect a few ground loops have convinced them not to
> put in adverse yaw (and rudder to turn) during taxi.
>

Sometimes you have no choice. I had a tow pilot suddenly brake to a halt
just as I lifted off. My choice was to try a flat turn and risk a ground
loop or hit the tug. My wheel brake was useless for the task of stopping
short of the tug and anyway, my wheel wasn't on the runway. Fortunately, I
succeeded in turning the Lark 45 degrees before touchdown using rudder
only - and avoiding a groundloop. (Then I had an eyeball to eyeball talk
with the tug pilot.)

Bill Daniels

[Jack]

On 2/6/04 1:22 PM, in article 4023f76a$1@darkstar, "Mark James Boyd"
> wrote:


> I've wondered why airliners don't have some spot on the
> ground (GPS) some distance down the runway, and abort
> at that spot if they haven't reached a certain airspeed.
> Seems simpler than doing all them calculamications for
> wind, density altitude, etc. which may have changed since
> you did them. Why not observe instead of predicting?

We can't afford not to do both, Mark. The calculations would still be
required in every case, making the "spot" different for each takeoff.

Airlines conduct operations on many different runways under all conditions
of weather, ambient lighting, loading, runway slope, braking coefficients,
etc., and many of these factors will vary from flight to flight even at the
same field, on the same day, in the same aircraft. In some cases a crew
member may fly in as many as three or four variations of a single type
(e.g., DC-9-10, DC-9-30, DC-9-40, DC-9-50), with a significant range of
performance and handling characteristics, within the same 24-hour period. I
think you can see that calculations for each flight with go/no-go decisions
made according to predetermined speeds for the anticipated conditions, with
adjustments when conditions change (there's your "observation") is the only
way we can safely operate.

With hundreds, or thousands, of pilots on the roster, and scores or hundreds
of destinations across the country and around the world, the idea of trying
to train every pilot to the visual cues at every runway would leave the
training department using far more assets than the revenue side of the
operation could likely produce.

I'd much prefer to make split-second decisions based upon the well
understood performance of the aircraft, than on the often vague cues
provided by the environment in which we operate the aircraft. In contrast to
the typical sailplane flight, we operate big fast moving machines often
under conditions in which I would prefer not to have to walk to my car, let
alone drive it to the airport.

If visual cues are to comprise the primary reference for takeoff
performance, by all means let it be at 30 to 50 mph in a 1-26 or in a
Pawnee, on a sunny day from 2500 feet of grass, where I am familiar with
every bump and soft spot, and not from the cockpit of a 180,000 lb
(relatively light, at that) Boeing 757 on a snowy February night from 6500
feet of wet runway at Midway, on the south side of Chicago.

Flying sailplanes well, I suspect, will be complicated enough.


-----
Jack
-----

[Mark James Boyd]

Bill Daniels > wrote:
>Mark, I think Janos was talking about winch launch. The land ahead/turn
>height for winch launch depends greatly on the winch site although at 25% of
>the altitude expected without a wire break, say 500 feet or 150 meters, a
>landing straight ahead on the runway should be possible. The ideal,
>available at most sites, is an overlap between the two options where a 360
>degree turn with a landing into the wind can be made from 300 feet AGL and a
>straight ahead landing can be successful at 450 feet.

Aha! An excellent point. I hadn't considered the advantages of
the steep climb from ground-launch and the increased options it
provides. Thanks for pointing this out (since ground-launch is
rare in this part of the gliding community i.e. west coast USA).

[Chris OCallaghan]

In fact, he did exactly what you said can't be done. He had some help
from the main gear, which touched the runway several times assiting
his skidding turn. If memory serves, he wound up pretty much where he
started, pointing in the opposite direction. There were many, many
witnesses. What parts I didn't see while running, I had recounted to
me in excrutiating detail, mainly because it was my glider. (The pilot
of the 20F, by the way, nearly hit my other glider, a parked Pegase.
The only two French gliders on the airport. Proof again that like
seeks like.)

Better, I think, to start with observed facts rather than to try to
deduce them.

As for owning two French gliders, you are welcome to exercise your
powers of induction.

[Mark James Boyd]

Jack > wrote:
>On 2/6/04 1:22 PM, in article 4023f76a$1@darkstar, "Mark James Boyd"
> wrote:
>
>> I've wondered why airliners don't have some spot on the
>> ground (GPS) some distance down the runway, and abort
>> at that spot if they haven't reached a certain airspeed.
>> Seems simpler than doing all them calculamications for
>> wind, density altitude, etc. which may have changed since
>> you did them. Why not observe instead of predicting?
>
>We can't afford not to do both, Mark. The calculations would still be
>required in every case, making the "spot" different for each takeoff.

OK, then both. From my point of view, however, if I had to choose
between 1. point on the ground and ASI and timing to acceleration vs.
2. just look at the engine gauges and interpret them, I'd take #1
first.

http://www.avweb.com/news/safety/182403-1.html

>Airlines conduct operations on many different runways under all conditions
>of weather, ambient lighting, loading, runway slope, braking coefficients,
>etc., and many of these factors will vary from flight to flight even at the
>same field, on the same day, in the same aircraft. In some cases a crew
>member may fly in as many as three or four variations of a single type
>(e.g., DC-9-10, DC-9-30, DC-9-40, DC-9-50), with a significant range of
>performance and handling characteristics, within the same 24-hour period. I
>think you can see that calculations for each flight with go/no-go decisions
>made according to predetermined speeds for the anticipated conditions, with
>adjustments when conditions change (there's your "observation") is the only
>way we can safely operate.

Yep. So add in a calculation for time to airspeed. And add in
a calculation for ground distance to airspeed. If one detects
that the acceleration and airspeed aren't coming up at that point,
abort the takeoff (presumably that point is calculated to be
the point of safe abort).

The simplicity of this is one doesn't need to deal with the complexity
of diagnosing what CAUSED the lack of acceleration. Was it the
RPM or the EPR that was wrong? Is it the RPM or that the prop is
worn thin? Did I leave the hand brake on for takeoff? Is the
nosewheel flat? Did they put a second passenger in the glider and
now it's too heavy? So many factors (some known, some not).
I prefer simplicity...

Of course the simple answer is just to have much more power
available than you could possibly need (RJs with 8000fpm climb,
a nice 400hp stearman) so really I'm talking about using this
as a tool to provide the same level of safety with less training
and less cost, rather than improving safety...

>With hundreds, or thousands, of pilots on the roster, and scores or hundreds
>of destinations across the country and around the world, the idea of trying
>to train every pilot to the visual cues at every runway would leave the
>training department using far more assets than the revenue side of the
>operation could likely produce.

Umm...I didn't say anything yet about visual cues. GPS, a stopwatch,
and marking the point when the takeoff roll starts. For jets,
an automated calculation and "low acceleration" warning
light.

For towplanes, probably a visual cue is easier, though,
and simpler than for an airline, because one tows off the same field
again and again. Another possibility is to simply walk the
field (or taxi up the taxiway) with the GPS and measure the
visual cue distance and the safe takeoff runway.
I've used GPS to measure a short strip before and declined to
takeoff there. Useful things, these little gadgets. Better than
my golfing range estimating eyeball...

If I towed out of a farm field or a "new to me" airstrip, and
I had some questions about whether I could make it over the
power lines, I might use this technique as an "extra tool in my bag"
to improve my confidence and capability. How much does the 1" thick
soft dirt slow me down? Am I light enough on fuel? I can do all
the calculations, but it's never the things I know that hurt me,
it's the things I don't know that I don't know...

>
>If visual cues are to comprise the primary reference for takeoff
>performance, by all means let it be at 30 to 50 mph in a 1-26 or in a
>Pawnee, on a sunny day from 2500 feet of grass, where I am familiar with
>every bump and soft spot, and not from the cockpit of a 180,000 lb
>(relatively light, at that) Boeing 757 on a snowy February night from 6500
>feet of wet runway at Midway, on the south side of Chicago.
>-----
>Jack
>-----
>

The last time I even dreamed that an airline pilot looked out
the window was at Ontario in low overcast when the tower called

"Delta XYZ traffic 2 O'clock 1 mile below you an experimental
with no transponder tight left base will pass behind you..."

And a real nervous co-pilot "XYZ looking for traffic"

....and I suspect a few expletives from the captain
"Who lets a f***ing no-squawk ragwing fly around in OUR
go***mn airport?"

Again, for any airline guys, I wouldn't DREAM of asking you
to look outside the cockpit for a visual cue of anything.
(Now, now, don't get yer panties in a bunch, I'm jus'
hasslin' ya, with yer umpteen item checklists, and yer
bells and whistles, and yer big cozy pilot chairs, and
yer Datsun 280Z's :PPP)

For you guys, I just thought maybe a nice shiny new
"acceleration" computer might be an extra takeoff tool... :P
Something to go with the pre-calculated trim settings and
"gee ya almost hit the tail" printouts?

But you are right, perhaps try it a while in the pawnee towing
an extra heavy ballasted two seat glider a few times first
and see how it affects the rotation point, and then
come up with some takeoff abort scenarios, and see how
much runway you REALLY have.

I actually really also liked the discussion about how longer
towropes allow an abort where the glider doesn't ram into the
back of the tug, too...

[Mark James Boyd]

Bill Daniels > wrote:
>
>Sometimes you have no choice. I had a tow pilot suddenly brake to a halt
>just as I lifted off. My choice was to try a flat turn and risk a ground
>loop or hit the tug. My wheel brake was useless for the task of stopping
>short of the tug and anyway, my wheel wasn't on the runway. Fortunately, I
>succeeded in turning the Lark 45 degrees before touchdown using rudder
>only - and avoiding a groundloop. (Then I had an eyeball to eyeball talk
>with the tug pilot.)

>Bill Daniels

A real good reason to use a little longer rope, eh?
I'm glad you weren't hurt, and I hope you got a good reason and
a beer from the tuggie.

I must say though, when I was taught to aerotow, and to drive a tug,
both instructors said "you don't owe a damn thing to the other guy.
If you have a problem, you release immediately and save your own
arse."

Don't get me wrong, release and potential release at rotation
is one of my greatest fears (it's happened to me a few times,
never initiated by me on purpose). But it is so scary
I didn't even practice a tuggie abort while actually hooked up
during any of my training...

Even if I rehearsed this one on the ground first, I'd still be
pretty apprehensive of practicing this abnormal procedure...

[Mark James Boyd]

Bill Daniels > wrote:
>
>A longer rope will just move the tug further down the runway where he has
>even less room. I'm pretty comfortable with 250 foot ropes.

Yes, I really meant longer "within reason." I'm really just saying
even as a tug pilot I'd rather have a 250 foot rope and less
runway in front of me, than the extra 150 feet in front of me and
some guy on a 100 foot rope, if I had to abort. I can't imagine
anyone could abort takeoff and release successfully with a 100
foot towrope without scraping metal...I wouldn't even consider
practicing this as an abnormal during training...

A tuggie
>always has the right to abort a takeoff roll any time being on the ground
>will be preferable to being in the air. What I would like is a review of
>the runway abort procedures. As far as I know, the following is not in the
>"How to be a Tuggie" comic book.
>
>The first step is for the tug to release the rope - that gives the glider
>pilot the unmistakable sign that this is an abort. Just as in the air, the
>tug must turn left and the glider right. There may be room to leave the
>runway completely or just move as far to the edge as safety allows. If
>there are runway lights, there may be clearance for the tug wing to pass
>over them - use all the room available. The tug should try to maintain
>speed and not brake until reaching the departure end of the runway or when
>it's clear that a collision is not possible.
>
>Again, you see why I like winch launch.
>
>Bill Daniels
>

Bill,

excellent review. Just as with power training, aborts are
too rarely discussed or trained, IMHO.

I'd add the one point from our local tuggie/CFI, that if a certain
tire flattens, the tuggie may not be able to abort to the "correct"
side. I guess this is rare, but has happened to him...

[Bill Daniels]

"Mark James Boyd" > wrote in message
news:40252327$1@darkstar...
>
> I actually really also liked the discussion about how longer
> towropes allow an abort where the glider doesn't ram into the
> back of the tug, too...

A longer rope will just move the tug further down the runway where he has
even less room. I'm pretty comfortable with 250 foot ropes. A tuggie
always has the right to abort a takeoff roll any time being on the ground
will be preferable to being in the air. What I would like is a review of
the runway abort procedures. As far as I know, the following is not in the
"How to be a Tuggie" comic book.

The first step is for the tug to release the rope - that gives the glider
pilot the unmistakable sign that this is an abort. Just as in the air, the
tug must turn left and the glider right. There may be room to leave the
runway completely or just move as far to the edge as safety allows. If
there are runway lights, there may be clearance for the tug wing to pass
over them - use all the room available. The tug should try to maintain
speed and not brake until reaching the departure end of the runway or when
it's clear that a collision is not possible.

Again, you see why I like winch launch.

Bill Daniels

[Andreas Maurer]

On 7 Feb 2004 09:40:55 -0700, (Mark James Boyd)
wrote:

>Yep. So add in a calculation for time to airspeed. And add in
>a calculation for ground distance to airspeed. If one detects
>that the acceleration and airspeed aren't coming up at that point,
>abort the takeoff (presumably that point is calculated to be
>the point of safe abort).

Add a little data about brake authority (wet runway, maximum wheel
brake temperatures depending on OAT), wind conditions, flap setting
(affects acceleration due to drag), and you get the complex scheme
that is being used today.

FYI: In the early days of jet aviation the pilots of the B-47 bomber
indeed used a stop watch. If a certain speed was not achieved after a
certain time, the takeoff was aborted.

Bye
Andreas

[ir. K.P. Termaat]

Did some simple calculations to get an idea of what caused the spin of
the DG500.
If the glider flew initially with an IAS of 100km/h and had a headwind
of say 25 km/h then its speed relative to the ground is 75km/h. If
after making the 180° turn back to the airfield the glider flew again
with an IAS of 100km/h but now with a tailwind of 25km/h, then its
speed relative to the ground is 125km/h. This means that during the
180° turn the glider had to be accellerated from 75km/h to 125km/h
relative to the ground.

For a banking angle of 45° and an IAS of 100km/h one finds from simple
mathematics that a 180° turn takes 8.9 secs when properly flown. The
forward accellaration of the glider during the 180° turn must then be
(125-75)/(3.6)/8.9=1.56m/s2 to come out at the same speed of 100km/h.
Suppose the mass of the glider (including the pilot) is 650kg, then
the force needed to accelarate the glider with 1.56m/s2 is 650x1.56 =
1014kgm/s2 or 1014N.

Where does this force come from. Indeed, from gravity. The glider must
pitch down to keep its IAS up. With a glider mass of 650kg, its weight
is 650x9.8=6370N. The pitch down angle must then be
arc(sin)1014/6370=9.2°. Add to this a normal glide angle of 1.4° (for
a glide ratio of 40), then the total pitch down angle during the 180°
turn of the DG500 should have been over 10°.

If the pilot does not move his stick quite a bit forward to achieve
this relative large pitch angle, the glider will loose its IAS, then
stall and spin. This looks to me what happened unfortunately with the
DG500 at Magdenburg.

Karel, NL

[tango4]

Looking at the windsock I'd say there was also a considerable wind gradient.
The aircraft had one wingtip within 1 span of the ground and the other a
good 15 to 20 m above that.

This little clip really is a classic, so many things wrong in one 10 second
period!

Ian




"ir. K.P. Termaat" > wrote in message
om...
> Did some simple calculations to get an idea of what caused the spin of
> the DG500.
> If the glider flew initially with an IAS of 100km/h and had a headwind
> of say 25 km/h then its speed relative to the ground is 75km/h. If
> after making the 180° turn back to the airfield the glider flew again
> with an IAS of 100km/h but now with a tailwind of 25km/h, then its
> speed relative to the ground is 125km/h. This means that during the
> 180° turn the glider had to be accellerated from 75km/h to 125km/h
> relative to the ground.
>
> For a banking angle of 45° and an IAS of 100km/h one finds from simple
> mathematics that a 180° turn takes 8.9 secs when properly flown. The
> forward accellaration of the glider during the 180° turn must then be
> (125-75)/(3.6)/8.9=1.56m/s2 to come out at the same speed of 100km/h.
> Suppose the mass of the glider (including the pilot) is 650kg, then
> the force needed to accelarate the glider with 1.56m/s2 is 650x1.56 =
> 1014kgm/s2 or 1014N.
>
> Where does this force come from. Indeed, from gravity. The glider must
> pitch down to keep its IAS up. With a glider mass of 650kg, its weight
> is 650x9.8=6370N. The pitch down angle must then be
> arc(sin)1014/6370=9.2°. Add to this a normal glide angle of 1.4° (for
> a glide ratio of 40), then the total pitch down angle during the 180°
> turn of the DG500 should have been over 10°.
>
> If the pilot does not move his stick quite a bit forward to achieve
> this relative large pitch angle, the glider will loose its IAS, then
> stall and spin. This looks to me what happened unfortunately with the
> DG500 at Magdenburg.
>
> Karel, NL

[Z Goudie]

At 10:00 08 February 2004, Ir. K.P. Termaat wrote:
>Did some simple calculations to get an idea of what
>caused the spin of
>the DG500.
>If the glider flew initially with an IAS of 100km/h
>and had a headwind
>of say 25 km/h then its speed relative to the ground
>is 75km/h. If
>after making the 180° turn back to the airfield the
>glider flew again
>with an IAS of 100km/h but now with a tailwind of 25km/h,
>then its
>speed relative to the ground is 125km/h. This means
>that during the
>180° turn the glider had to be accellerated from 75km/h
>to 125km/h
>relative to the ground.

That old red herring again!

The glider is flying in an airmass which is moving
over the ground at a constant rate. No additional
acceleration is required apart from that normally needed
in a turn to supply the turning force.

There may be some effect caused by descending/putting
the lower wing down through any wind gradient but this
actually improves the situation as the air is moving
'away' from the path of the glider more slowly and
will consequently cause some increase in airspeed.
(You can try the opposite of that effect by pulling
up from a downwind racing finish through a strong wind
gradient; watch the airspeed decay at an alarming rate).

The biggest problem is that the apparent speed over
the ground in say a 15kt wind jumps by 30kts and results
in people trying to reduce the ground rush by raising
the nose with no reference to the ASI.

[Shawn Curry]

ir. K.P. Termaat wrote:

> Did some simple calculations to get an idea of what caused the spin of
> the DG500.
> If the glider flew initially with an IAS of 100km/h and had a headwind
> of say 25 km/h then its speed relative to the ground is 75km/h. If
> after making the 180° turn back to the airfield the glider flew again
> with an IAS of 100km/h but now with a tailwind of 25km/h, then its
> speed relative to the ground is 125km/h. This means that during the
> 180° turn the glider had to be accellerated from 75km/h to 125km/h
> relative to the ground.
>
> For a banking angle of 45° and an IAS of 100km/h one finds from simple
> mathematics that a 180° turn takes 8.9 secs when properly flown. The
> forward accellaration of the glider during the 180° turn must then be
> (125-75)/(3.6)/8.9=1.56m/s2 to come out at the same speed of 100km/h.
> Suppose the mass of the glider (including the pilot) is 650kg, then
> the force needed to accelarate the glider with 1.56m/s2 is 650x1.56 =
> 1014kgm/s2 or 1014N.
>
> Where does this force come from. Indeed, from gravity. The glider must
> pitch down to keep its IAS up. With a glider mass of 650kg, its weight
> is 650x9.8=6370N. The pitch down angle must then be
> arc(sin)1014/6370=9.2°. Add to this a normal glide angle of 1.4° (for
> a glide ratio of 40), then the total pitch down angle during the 180°
> turn of the DG500 should have been over 10°.
>
> If the pilot does not move his stick quite a bit forward to achieve
> this relative large pitch angle, the glider will loose its IAS, then
> stall and spin. This looks to me what happened unfortunately with the
> DG500 at Magdenburg.
>
> Karel, NL

You need to have a good long talk with your instructor.

[BAToulson]

In article >, Janos Bauer
> writes:

> What are the standards altitudes for such incident? Here are the list
>I learnt: <50 straight landing, 50<&<100 one 180 degree turn, 180< two
>turns or small circle. Of course in strong wind I would increase these
>values.
>

Best rules, and those now taught in the UK are, if you can land safely ahead,
then you should do so.

Heights are not a good guide as they can mislead you into all sorts of trouble.
The higher the wind, the greater the land ahead opportunities up to heights
well above those where it is clearly safe to do a reasonably normal short
circuit. The tricky situation on a short run is a hot, nil wind day when the
margin between landing ahead and adequate height for a short circuit is very
narrow.

However, the GOLDEN RULE is first fly the aeroplane. i.e if both options are
marginal, recover from nose high and get into stable flight at correct speed,
then assess your options. there is usually ample time.

Barney
UK

[Rich Carr]

> There may be some effect caused by descending/putting
> the lower wing down through any wind gradient but this
> actually improves the situation as the air is moving
> 'away' from the path of the glider more slowly and
> will consequently cause some increase in airspeed.
> (You can try the opposite of that effect by pulling
> up from a downwind racing finish through a strong wind
> gradient; watch the airspeed decay at an alarming rate).
>
> The biggest problem is that the apparent speed over
> the ground in say a 15kt wind jumps by 30kts and results
> in people trying to reduce the ground rush by raising
> the nose with no reference to the ASI.

There is also the potential of poor turn coordination caused by the
perceptual changes that occur when maneuvering below pivotal altitude,
although that didn't appear to be the case in the video. The
suddenness of the departure was a bit surprising, but it seemed to be
triggered by the opening of the spoilers rather than by any obvious
lack of coordination.

- Rich Carr

[ir. K.P. Termaat]

Hi Shawn.

Since 1978 I am an instructor myself and teach aerodynamics to new
pilots as
well as new instructors since then. Next month we will have a
discussion in
our instructor's team on the matter of spinning and especially on how
to
avoid this killing phenomenon when happening at low altitude. If you
don't
understand my wordings please let me know; I am quite willing to
elucidate
on what I sayd. If you think my interpretation of the Magdenburg crash
with the DG500 is wrong please explain, I am quite willing to listen
to better theories about this. Something like "you need .... " doesn't
help much Shawn.

Karel, NL


Shawn Curry > wrote in message . net>...
> ir. K.P. Termaat wrote:
>
> > Did some simple calculations to get an idea of what caused the spin of
> > the DG500.
> > If the glider flew initially with an IAS of 100km/h and had a headwind
> > of say 25 km/h then its speed relative to the ground is 75km/h. If
> > after making the 180° turn back to the airfield the glider flew again
> > with an IAS of 100km/h but now with a tailwind of 25km/h, then its
> > speed relative to the ground is 125km/h. This means that during the
> > 180° turn the glider had to be accellerated from 75km/h to 125km/h
> > relative to the ground.
> >
> > For a banking angle of 45° and an IAS of 100km/h one finds from simple
> > mathematics that a 180° turn takes 8.9 secs when properly flown. The
> > forward accellaration of the glider during the 180° turn must then be
> > (125-75)/(3.6)/8.9=1.56m/s2 to come out at the same speed of 100km/h.
> > Suppose the mass of the glider (including the pilot) is 650kg, then
> > the force needed to accelarate the glider with 1.56m/s2 is 650x1.56 =
> > 1014kgm/s2 or 1014N.
> >
> > Where does this force come from. Indeed, from gravity. The glider must
> > pitch down to keep its IAS up. With a glider mass of 650kg, its weight
> > is 650x9.8=6370N. The pitch down angle must then be
> > arc(sin)1014/6370=9.2°. Add to this a normal glide angle of 1.4° (for
> > a glide ratio of 40), then the total pitch down angle during the 180°
> > turn of the DG500 should have been over 10°.
> >
> > If the pilot does not move his stick quite a bit forward to achieve
> > this relative large pitch angle, the glider will loose its IAS, then
> > stall and spin. This looks to me what happened unfortunately with the
> > DG500 at Magdenburg.
> >
> > Karel, NL
>
> You need to have a good long talk with your instructor.

[Robert John]

Hi Karel,
I do not follow your explanation.
If I carry out the same 180 degree manouver at 5000
feet, even in a 50kt wind, both I and the glider are
quite unaware of groundspeed. No change in attitude
is required or made.
The only difference in doing it at 100 feet is surely
the close view of the ground and the APPEARANCE of
changing speed which may cause me to lower or raise
the nose when I should not.
Regards
Robert
At 19:06 09 February 2004, Ir. K.P. Termaat wrote:
>Hi Shawn.
>
>Since 1978 I am an instructor myself and teach aerodynamics
>to new
>pilots as
>well as new instructors since then. Next month we will
>have a
>discussion in
>our instructor's team on the matter of spinning and
>especially on how
>to
>avoid this killing phenomenon when happening at low
>altitude. If you
>don't
>understand my wordings please let me know; I am quite
>willing to
>elucidate
>on what I sayd. If you think my interpretation of the
>Magdenburg crash
>with the DG500 is wrong please explain, I am quite
>willing to listen
>to better theories about this. Something like 'you
>need .... ' doesn't
>help much Shawn.
>
>Karel, NL
>
>
>Shawn Curry wrote in message news:...
>> ir. K.P. Termaat wrote:
>>
>> > Did some simple calculations to get an idea of what
>>>caused the spin of
>> > the DG500.
>> > If the glider flew initially with an IAS of 100km/h
>>>and had a headwind
>> > of say 25 km/h then its speed relative to the ground
>>>is 75km/h. If
>> > after making the 180° turn back to the airfield the
>>>glider flew again
>> > with an IAS of 100km/h but now with a tailwind of
>>>25km/h, then its
>> > speed relative to the ground is 125km/h. This means
>>>that during the
>> > 180° turn the glider had to be accellerated from
>>>75km/h to 125km/h
>> > relative to the ground.
>> >
>> > For a banking angle of 45° and an IAS of 100km/h
>>>one finds from simple
>> > mathematics that a 180° turn takes 8.9 secs when
>>>properly flown. The
>> > forward accellaration of the glider during the 180°
>>>turn must then be
>> > (125-75)/(3.6)/8.9=1.56m/s2 to come out at the same
>>>speed of 100km/h.
>> > Suppose the mass of the glider (including the pilot)
>>>is 650kg, then
>> > the force needed to accelarate the glider with 1.56m/s2
>>>is 650x1.56 =
>> > 1014kgm/s2 or 1014N.
>> >
>> > Where does this force come from. Indeed, from gravity.
>>>The glider must
>> > pitch down to keep its IAS up. With a glider mass
>>>of 650kg, its weight
>> > is 650x9.8=6370N. The pitch down angle must then
>>>be
>> > arc(sin)1014/6370=9.2°. Add to this a normal glide
>>>angle of 1.4° (for
>> > a glide ratio of 40), then the total pitch down angle
>>>during the 180°
>> > turn of the DG500 should have been over 10°.
>> >
>> > If the pilot does not move his stick quite a bit
>>>forward to achieve
>> > this relative large pitch angle, the glider will
>>>loose its IAS, then
>> > stall and spin. This looks to me what happened unfortunately
>>>with the
>> > DG500 at Magdenburg.
>> >
>> > Karel, NL
>>
>> You need to have a good long talk with your instructor.
>

[Jim]

I'm certainly not speaking for Shawn, but what feels wrong-headed to
me about your description of acceleration RELATIVE TO THE GROUND,
and the need then to find forces to account for that apparent
acceleration, is that, in my view of things, no such acceleration of
the glider is occurring at all and thus no forces need be conjured.

The changes in groundspeed are not accompanied by changes in airspeed
and are a result of the movement over the ground of the air in which
the glider is turning.



On 9 Feb 2004 11:01:42 -0800, (ir. K.P. Termaat) wrote:

>Hi Shawn.
>
>Since 1978 I am an instructor myself and teach aerodynamics to new
>pilots as
>well as new instructors since then. Next month we will have a
>discussion in
>our instructor's team on the matter of spinning and especially on how
>to
>avoid this killing phenomenon when happening at low altitude. If you
>don't
>understand my wordings please let me know; I am quite willing to
>elucidate
>on what I sayd. If you think my interpretation of the Magdenburg crash
>with the DG500 is wrong please explain, I am quite willing to listen
>to better theories about this. Something like "you need .... " doesn't
>help much Shawn.
>
>Karel, NL
>
>
>Shawn Curry > wrote in message . net>...
>> ir. K.P. Termaat wrote:
>>
>> > Did some simple calculations to get an idea of what caused the spin of
>> > the DG500.
>> > If the glider flew initially with an IAS of 100km/h and had a headwind
>> > of say 25 km/h then its speed relative to the ground is 75km/h. If
>> > after making the 180° turn back to the airfield the glider flew again
>> > with an IAS of 100km/h but now with a tailwind of 25km/h, then its
>> > speed relative to the ground is 125km/h. This means that during the
>> > 180° turn the glider had to be accellerated from 75km/h to 125km/h
>> > relative to the ground.
>> >
>> > For a banking angle of 45° and an IAS of 100km/h one finds from simple
>> > mathematics that a 180° turn takes 8.9 secs when properly flown. The
>> > forward accellaration of the glider during the 180° turn must then be
>> > (125-75)/(3.6)/8.9=1.56m/s2 to come out at the same speed of 100km/h.
>> > Suppose the mass of the glider (including the pilot) is 650kg, then
>> > the force needed to accelarate the glider with 1.56m/s2 is 650x1.56 =
>> > 1014kgm/s2 or 1014N.
>> >
>> > Where does this force come from. Indeed, from gravity. The glider must
>> > pitch down to keep its IAS up. With a glider mass of 650kg, its weight
>> > is 650x9.8=6370N. The pitch down angle must then be
>> > arc(sin)1014/6370=9.2°. Add to this a normal glide angle of 1.4° (for
>> > a glide ratio of 40), then the total pitch down angle during the 180°
>> > turn of the DG500 should have been over 10°.
>> >
>> > If the pilot does not move his stick quite a bit forward to achieve
>> > this relative large pitch angle, the glider will loose its IAS, then
>> > stall and spin. This looks to me what happened unfortunately with the
>> > DG500 at Magdenburg.
>> >
>> > Karel, NL
>>
>> You need to have a good long talk with your instructor.

[Shawn Curry]

ir. K.P. Termaat wrote:

> Shawn Curry > wrote in message . net>...
>
>>ir. K.P. Termaat wrote:
>>
>>
>>>Did some simple calculations to get an idea of what caused the spin of
>>>the DG500.
>>>If the glider flew initially with an IAS of 100km/h and had a headwind
>>>of say 25 km/h then its speed relative to the ground is 75km/h. If
>>>after making the 180° turn back to the airfield the glider flew again
>>>with an IAS of 100km/h but now with a tailwind of 25km/h, then its
>>>speed relative to the ground is 125km/h. This means that during the
>>>180° turn the glider had to be accellerated from 75km/h to 125km/h
>>>relative to the ground.
>>>
>>>For a banking angle of 45° and an IAS of 100km/h one finds from simple
>>>mathematics that a 180° turn takes 8.9 secs when properly flown. The
>>>forward accellaration of the glider during the 180° turn must then be
>>>(125-75)/(3.6)/8.9=1.56m/s2 to come out at the same speed of 100km/h.
>>>Suppose the mass of the glider (including the pilot) is 650kg, then
>>>the force needed to accelarate the glider with 1.56m/s2 is 650x1.56 =
>>>1014kgm/s2 or 1014N.
>>>
>>>Where does this force come from. Indeed, from gravity. The glider must
>>>pitch down to keep its IAS up. With a glider mass of 650kg, its weight
>>>is 650x9.8=6370N. The pitch down angle must then be
>>>arc(sin)1014/6370=9.2°. Add to this a normal glide angle of 1.4° (for
>>>a glide ratio of 40), then the total pitch down angle during the 180°
>>>turn of the DG500 should have been over 10°.
>>>
>>>If the pilot does not move his stick quite a bit forward to achieve
>>>this relative large pitch angle, the glider will loose its IAS, then
>>>stall and spin. This looks to me what happened unfortunately with the
>>>DG500 at Magdenburg.
>>>
>>>Karel, NL
>>
>>You need to have a good long talk with your instructor.


> Hi Shawn.
>
> Since 1978 I am an instructor myself and teach aerodynamics to new
> pilots as
> well as new instructors since then. Next month we will have a
> discussion in
> our instructor's team on the matter of spinning and especially on how
> to
> avoid this killing phenomenon when happening at low altitude. If you
> don't
> understand my wordings please let me know; I am quite willing to
> elucidate
> on what I sayd. If you think my interpretation of the Magdenburg crash
> with the DG500 is wrong please explain, I am quite willing to listen
> to better theories about this. Something like "you need .... " doesn't
> help much Shawn.
>
> Karel, NL
>

Your description of the situation sounded naive. If you were
considering wind shear (decreasing wind velocity with altitude) you
didn't note that. As Robert noted in another response a turn is a turn,
as far as the aircraft is concerned, whether at 80 meters or 2000 unless
the wind changes during the turn.
I assumed you did not understand this, and figured a "usenet education"
is a poor (perhaps deadly) substitute for time spent with an instructor.
Thus my response.

Shawn

[ir. K.P. Termaat]

Robert John > wrote in message >...
> Hi Karel,
> I do not follow your explanation.
> If I carry out the same 180 degree manouver at 5000
> feet, even in a 50kt wind, both I and the glider are
> quite unaware of groundspeed. No change in attitude
> is required or made.
> The only difference in doing it at 100 feet is surely
> the close view of the ground and the APPEARANCE of
> changing speed which may cause me to lower or raise
> the nose when I should not.
> Regards
> Robert

Hi Robert,

You are right Robert. The glider is unaware of groundspeed.
Looked several times at the short film of the crash where it is
obvious that the DG500 is flying to slow relative to the fast moving
air rather then to slow relative to the ground while having a lot of
tailwind (which is not very fast either).
During standard circling no accelleration forces in the longitudinal
direction of the glider are required to keep the IAS constant when the
glider makes perfect circles relative to the moving layer of air. From
the ground this looks quite different of course. But that is indeed
irrelevant.

Regards and thanks for your comment,
Karel

[ir. K.P. Termaat]

>
> Hi Robert,
>
> You are right Robert. The glider is unaware of groundspeed.
> Looked several times at the short film of the crash where it is
> obvious that the DG500 is flying to slow relative to the fast moving
> air rather then to slow relative to the ground while having a lot of
> tailwind (which is not very fast either).


I showed the film to one of our airobatic pilots.
His comment was:
- the airflow may have been very turbulent at low altitude due to
several obstructions in the field
- at the last moment the pilot tried to line up the glider with the
runway or his selected landing spot and therefore applied a lot of
right rudder and some right stick input
- when he observed the right wingtip to get rather low he tried to
move it up using left stick input
- so then you had the classic spin inputs: low speed and crossed
controls
- the right wing stalled first because of the aileron deflection
downwards; the full rudder deflection to the right made it worse; a
spin became unavoidable.
- undisciplined glider pilot

Though my calculation of pitch down input during the 180° turn back
curve to the field was based on a wrong supposition (sorry for that)
it would have helped the pilot a lot to speed up his glider which
might have been just enough to make a safe landing. No excuse though.

Karel, NL

[ir. K.P. Termaat]

Z Goudie > wrote in message >...
>
> That old red herring again!
>
> The glider is flying in an airmass which is moving
> over the ground at a constant rate. No additional
> acceleration is required apart from that normally needed
> in a turn to supply the turning force.
>
> There may be some effect caused by descending/putting
> the lower wing down through any wind gradient but this
> actually improves the situation as the air is moving
> 'away' from the path of the glider more slowly and
> will consequently cause some increase in airspeed.
> (You can try the opposite of that effect by pulling
> up from a downwind racing finish through a strong wind
> gradient; watch the airspeed decay at an alarming rate).
>
> The biggest problem is that the apparent speed over
> the ground in say a 15kt wind jumps by 30kts and results
> in people trying to reduce the ground rush by raising
> the nose with no reference to the ASI.

We have very nice herring in NL, not red however.

Indeed I made a wrong supposition in my calculation of a 10° pitch
angle required during the turn back curve of the DG500 to the
airfield.

A steeper pitch angle then the pilot obviously applied would have
helped him a lot though to keep the glider from stalling and spinning
in.
The comment of one of our aerobatic pilots is that the DG-pilot flew
to slow in the last part of the flight and a full spin with crossed
controls (right rudder and left stick) evolved. The air may have been
very turbulent in the lower layer because of several obstructions on
the field.

Karel

[Robert Ehrlich]

"ir. K.P. Termaat" wrote:
> ...
> During standard circling no accelleration forces in the longitudinal
> direction of the glider are required to keep the IAS constant when the
> glider makes perfect circles relative to the moving layer of air. From
> the ground this looks quite different of course. But that is indeed
> irrelevant.
>

You may consider it as irrelevant but it nevertheless complies with the
same laws of dynamics as seen from the air. An observer moving with
the airmass sees a glider with a bank angle generating an horizontal
component of the lift which remains perpendicular to the speed and has
no effect on the magnitude of the speed but only on its direction:
the glider circles. An observer on the ground sees the same horizontal
force but it does not remains perpendicular to the speed and so has an effect
on its magnitude as well as on its direction. The final resulting effect
is that the glider has increased its speed relative to the ground.
The force needed for this longitudinal acceleration that you were calling
for in your previous post is just the horizontal component of the lift.

[K.P. Termaat]

"Robert Ehrlich" > schreef in bericht
...
> "ir. K.P. Termaat" wrote:
> > ...
> > During standard circling no accelleration forces in the longitudinal
> > direction of the glider are required to keep the IAS constant when the
> > glider makes perfect circles relative to the moving layer of air. From
> > the ground this looks quite different of course. But that is indeed
> > irrelevant.
> >
>
> You may consider it as irrelevant but it nevertheless complies with the
> same laws of dynamics as seen from the air. An observer moving with
> the airmass sees a glider with a bank angle generating an horizontal
> component of the lift which remains perpendicular to the speed and has
> no effect on the magnitude of the speed but only on its direction:
> the glider circles. An observer on the ground sees the same horizontal
> force but it does not remain perpendicular to the speed and so has an
effect
> on its magnitude as well as on its direction. The final resulting effect
> is that the glider has increased its speed relative to the ground.
> The force needed for this longitudinal acceleration that you were calling
> for in your previous post is just the horizontal component of the lift.

I think your reasoning for an observer on the ground is o.k.

However my approach to this would be to add the speedvector Vg(x,y,t) of the
glider in the moving airmass plane (constant in strength with direction
tangent to the circle) to the windvector Vw(x,y) in the groundplane
(constant in strength and direction).

The result would be a trajectory in the ground plane in the shape of open
loops moving in the direction of the wind. This is what the observer on the
ground would see and can be described as a function of time mathematically.
Then one could calculate accellarations of the glider relative to the ground
from this. However, though this is a nice observation I do not see at the
moment an application of this knowledge. So it is a little academic I guess.

All what happens to the glider is controlled by Lift and Drag (aerodynamic
forces) and the Weight of the glider (gravity force). Movements of the
glider as a result of these forces can best be described relative to a
horizontal plane moving with the wind. The glider making coördinated turns
with constant IAS will produce perfect circles as a trajectory on this plane
with a constant radial accelleration in the direction of the center of the
circle and without longitudenal accelleration.

But I guess you know this all already.

Karel

[Derrick Steed]

What puzzles me about this discussion is the lack of any appeal to inertial reference frames:

In what follows I am not taking into account any factors relating to windshear - the main assumption is that the windspeed is constant right down to the ground, but the analysis can be extended to take account of that.

What is an inertial reference frame? One in which Newtons laws apply

In this discussion there are two reference frames: one attached to the ground, one attached to the the moving airmass

One frame (the airmass one) is moving linearly (i.e. not accelerated) with the respect to the other (the ground)

The discussions of the particle (glider) motions observed as occurring in the airmass reference frame can be related to the motions observed as occurring in the ground reference frame by the additional of constant equal to the speed of motion of the airmass (e.g. the uniform rate at which the airmass is moving over the ground)

So what is the problem? No accelerations are involved other than that of the the glider due to it's circular motion.

Rgds,

Derrick.s
"Robert Ehrlich" schreef in bericht
> ...
> "ir. K.P. Termaat" wrote:
> > ...
> > During standard circling no accelleration forces in the longitudinal
> > direction of the glider are required to keep the IAS constant when the
> > glider makes perfect circles relative to the moving layer of air. From
> > the ground this looks quite different of course. But that is indeed
> > irrelevant.
> >
>
> You may consider it as irrelevant but it nevertheless complies with the
> same laws of dynamics as seen from the air. An observer moving with
> the airmass sees a glider with a bank angle generating an horizontal
> component of the lift which remains perpendicular to the speed and has
> no effect on the magnitude of the speed but only on its direction:
> the glider circles. An observer on the ground sees the same horizontal
> force but it does not remain perpendicular to the speed and so has an
effect
> on its magnitude as well as on its direction. The final resulting effect
> is that the glider has increased its speed relative to the ground.
> The force needed for this longitudinal acceleration that you were calling
> for in your previous post is just the horizontal component of the lift.

I think your reasoning for an observer on the ground is o.k.

However my approach to this would be to add the speedvector Vg(x,y,t) of the
glider in the moving airmass plane (constant in strength with direction
tangent to the circle) to the windvector Vw(x,y) in the groundplane
(constant in strength and direction).

The result would be a trajectory in the ground plane in the shape of open
loops moving in the direction of the wind. This is what the observer on the
ground would see and can be described as a function of time mathematically.
Then one could calculate accellarations of the glider relative to the ground
from this. However, though this is a nice observation I do not see at the
moment an application of this knowledge. So it is a little academic I guess.

All what happens to the glider is controlled by Lift and Drag (aerodynamic
forces) and the Weight of the glider (gravity force). Movements of the
glider as a result of these forces can best be described relative to a
horizontal plane moving with the wind. The glider making coördinated turns
with constant IAS will produce perfect circles as a trajectory on this plane
with a constant radial accelleration in the direction of the center of the
circle and without longitudenal accelleration.

But I guess you know this all already.

Karel

[Z Goudie]

At 11:00 11 February 2004, Derrick Steed wrote:
>So what is the problem? No accelerations are involved
>other than that of the the glider due to it's circular
motion.

I think they're suffering from 'Last week I coodn't
spell the word injuneer - now I is one' syndrome.

[Shawn Curry]

Z Goudie wrote:
> At 11:00 11 February 2004, Derrick Steed wrote:
>
>>So what is the problem? No accelerations are involved
>>other than that of the the glider due to it's circular
>
> motion.
>
> I think they're suffering from 'Last week I coodn't
> spell the word injuneer - now I is one' syndrome.

Thats why I said he should talk to his instructor instead of going into
frames of reference. Cuz I be a biolygyst not no train driver ;-)

Shawn