Wing
Drop During Glider Launch
A Schleicher ASW 20L glider
suffered a right wing drop as it became airborne during a winch launch. The
glider yawed and then rolled uncontrollably to the right. The winch cable was
not released by the pilot and the glider rolled inverted and struck the ground.
The pilot suffered severe head injuries and died four days later.
The surface wind at the time of launch was
115/10kt giving a crosswind component of 3kt, well below the aircraft
crosswind limitation of 13.5kt. Full cable release checks were conducted
prior to beginning the launch and the cable release operated correctly during
these checks. The winch launch was conducted normally with the assistance of
a wing walker to hold the wings level until the pilot was able to do so using
aerodynamic controls. The first launch attempt was aborted when the glider
overran the winch cable. The winch cable was reattached with the glider at
the position where it had come to rest, some 50m ahead of the original start
point. During the second launch attempt the wing walker had to push downward
on the left wing to keep the wings level. He continued to do so until he
could no longer keep pace with the accelerating glider. The glider became
airborne almost immediately and rolled to the right. The right wingtip struck
soft ground causing the glider to yaw and roll rapidly to the right, pitch
nose down and somersault inverted. The tail broke off causing the top of the
canopy to bear most of the impact. The pilot, who was restrained by a
four-point harness, suffered severe injuries to his unprotected head.
The winch driver stated
that the glider appeared to drop its right wing as it became airborne. In
accordance with his training he maintained power to continue the launch until
the glider reached 90 degrees bank and the nose began to drop. He then cut
power and applied the winch brake. The cable remained attached to the glider
throughout the accident sequence. There was no evidence that the winch or its
operation had any adverse effect on this launch.
The cockpit cable release control of the Schleicher ASW 20L is
situated to the left of the aircraft centreline low down at the base of the
instrument panel and just ahead of the base of the control column. An
identical control to allow rudder pedal adjustment is mounted just to the
right of the cable release. The cable release terminates in a spherical
yellow knob about 30mm in diameter. The rudder adjustment knob is identical
in size, but coloured brown.
There was no evidence of any pre-impact failure to any of the controls or
of the airframe. An imprint on the upper wing skin from part of the right
aileron bellcrank that probably occurred during impact indicated that there
was a right aileron deflection of 15 to 27 degrees trailing edge down at
impact. Full aileron deflection was measured at 31 degrees trailing edge
down. The cable release mechanism was examined and found to operate normally.
BGA Guidance
The issue of wing drop during launch is the
subject of guidance produced by the British Gliding Association (BGA) and
discussed in several articles published in UK gliding magazines. The
consensus is that even gentle contact of the wingtip with the ground can
result in considerable yaw leading very quickly to unrecoverable rates of
roll. Pilots are taught to release the cable immediately a wingtip makes even
slight contact with the ground. The BGA Instructors manual contains the
following guidance:
”Release the cable immediately if a wing goes down or
anything else goes wrong during the ground run, e.g. an overrun. Keep the
left hand near to the release knob, or, depending on its position – for
example if applying left aileron will make it awkward to reach – actually
take hold of it.”
The BGA leaflet ‘Safe Winch Launching’ includes:
”The demonstration might include patter such as the
following:
* As the cable tightens, ensure your left hand is close to, or on the
release.
* As the glider moves forward, keep the wings level using the ailerons.
Large deflections may be needed initially.
* If a wing goes down, release.”
The
control ergonomics of the accident aircraft may have made it difficult, or
impossible, for the pilot to get his left hand to the cable release knob and
to operate it immediately while he had the control column deflected far to
the left of the cockpit to counteract the initial right roll. The initial
right roll, and the fact that the wing walker had to hold the left wing down
at the start of the launch, may indicate that the pilot had inadvertently
applied right roll control at the start of the launch.
The BGA sent all gliding clubs a revised edition of the “Safe Winch
Launching” leaflet that all glider pilots and those responsible for safe
operations should read again to refresh their memory. The BGA also sent a
letter to all BGA gliding instructors that included the following advice:
”There is inevitably a healthy level of debate on winch
launching techniques which should be encouraged to aid better understanding
of what is a complex task. One point that really does need to be emphasised
however is the need for the pilot to keep his/her left hand firmly on the
release during the initial part of the launch.”
The gliding club where this particular fatal
accident occurred conducted a trial in which the person assisting the launch
(usually the wing walker) will, after connecting the cable, look inside the
cockpit to see if the pilot’s hand is on the cable release. If not the
assistant will remind the pilot to do so.
In my
experience there are two types of lead-in to an accident. One is where things
gradually go wrong and a chain of minor incidents is allowed to develop until
the whole thing is out of control and an accident happens. Another lead-in is
where things go disastrously wrong in a very few seconds and unless you are
fully prepared and have planned and practised your immediate action you may
well become another statistic. I have Martin-Baker to thank for saving my
life in one of the latter situations. You don’t have the option in a glider
of pulling a handle and leaving the scene in a rapid vertical direction so
you must prepare for what can go wrong.
A winch launch can very quickly go wrong. Give yourself a chance by
deciding on your immediate actions and following them on each and every winch
launch.
The facts relating to this accident are taken from AAIB Field
Investigation reference EW/C2006/09/06 which source is gratefully
acknowledged. Any conclusions and comments are those of the Gremline Managing
Editor and do not seek to reflect AAIB or BGA views.
Traps
for Beginners — And Experienced Pilots, Too!
A Few Samples from an Endless
List.
Take our safety test. Add up the number of
statements you have used at one time or another. Be honest. Check your score
at the end of the test.
” I took off from this strip yesterday, without
any problem.”
” The plane was perfectly serviceable yesterday.”
” The cloud will lift once I get past these hills.”
“ There’s plenty of fuel on board. I’ve only done
a couple of short trips since refuelling.”
” A couple of small children in the back won’t make much difference.”
” I’ll have that checked next time I see an engineer.”
” Fred said it’s OK and he’s an experienced pilot.”
” It’ll save time if I take off from the intersection.
” I should get there before dark.”
” The fuel sample is perfectly clear so that’s OK.”
” I can sort the speed out before touchdown.”
” That sounds different – probably my imagination.”
” It doesn’t really matter all that much.”
” I’ll connect jump leads and the battery will charge as we go
along.”
” That must be that disused airfield near Bedford.”
” I can always climb above the cloud.”
” I can’t be off track already.”
” It’s up to the engineer to check the tyre pressures.”
“ I don’t need to check the ident every
time.”
” Why doesn’t that idiot stop talking on this frequency?”
“ I don’t need to be checked by an
instructor.”
” I just managed to scrape in before it clamped.”
” I can’t be bothered with all that stuff.”
” Fred said he has rolled one of these. I’ll give it a try.”
” Acceleration’s a bit slow but I can make it.”
” I can get onto the runway before that clown.”
“ I have the right of way.”
” I’ll show you some really low flying.”
“ Come on! Come on! I haven’t got all day.”
” You jump in and start the checks. I’ll be there in a minute.”
” All this paperwork is a load of rubbish.”
” I’ll sort it out once we are airborne.”
” I’m late so we will debrief your lesson tomorrow.”
If your score is one or more, you’ve failed!
Text and Photographs © 2009 Gremline & Hill House
Publications, unless otherwise stated.
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