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Safety of winch launch vrs. aero tow?



 
 
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  #11  
Old October 26th 03, 06:06 AM
Gary Boggs
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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


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  #12  
Old October 26th 03, 02:34 PM
Bill Daniels
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"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

  #13  
Old October 26th 03, 04:04 PM
JJ Sinclair
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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
  #15  
Old October 26th 03, 05:45 PM
Mark Navarre
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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
-
  #17  
Old October 26th 03, 08:30 PM
Bob Johnson
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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

  #18  
Old October 26th 03, 08:44 PM
Pete Brown
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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/



  #19  
Old October 26th 03, 10:36 PM
Mike Borgelt
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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



  #20  
Old October 27th 03, 12:09 AM
Bill Daniels
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"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


 




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