Safety of winch launch vrs. aero tow?

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

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

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

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.

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/saf...s/winching.pdf
or http://www.glidingmagazine.com/ListF...Dtl.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

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

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 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

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

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

"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