Winch Launch - Fatal

On Sunday, December 11, 2016 at 5:03:12 PM UTC-7, wrote:
1. Balance the wing, not just level it.
2. Point the glider EXACTLY at the winch.
3. PRECISELY center all controls and don't wag the stick around in the roll.
4. Above all, don't force a pilot to wobble along during an extended ground roll while struggling to keep the wings level.

I have an issue with points 2 and 3: you're of course right if the winch hook is on the center line of the glider. However, many gliders (e.g. Ka-6, ASK-13, ASK-21) have an off-centre winch hook. With a left of centre hook, the initial acceleration causes a marked yaw to the right. It is much better in this case to align the glider pointing slightly to the left of the winch, and giving left rudder at the start.

Swing due to an offset hook is minimal if the acceleration is high. Acceleration increases the download on the tail wheel forcing the glider to roll straight. In any event a slight drift to the side is of no consequence - you're not trying to fly formation on a winch.

On Tuesday, December 13, 2016 at 4:19:31 PM UTC+1, wrote:
On Sunday, December 11, 2016 at 5:03:12 PM UTC-7, wrote:
1. Balance the wing, not just level it.
2. Point the glider EXACTLY at the winch.
3. PRECISELY center all controls and don't wag the stick around in the roll.
4. Above all, don't force a pilot to wobble along during an extended ground roll while struggling to keep the wings level.

I have an issue with points 2 and 3: you're of course right if the winch hook is on the center line of the glider. However, many gliders (e.g. Ka-6, ASK-13, ASK-21) have an off-centre winch hook. With a left of centre hook, the initial acceleration causes a marked yaw to the right. It is much better in this case to align the glider pointing slightly to the left of the winch, and giving left rudder at the start.

Swing due to an offset hook is minimal if the acceleration is high. Acceleration increases the download on the tail wheel forcing the glider to roll straight. In any event a slight drift to the side is of no consequence - you're not trying to fly formation on a winch.

I can confirm that to be correct! I have flown everything from the K6,8,13 and the ASW-15 with an off-set CG hook and there was never any condition that could not be corrected or controlled with rudder input.
And before someone chimes in about the oh so dangerous L-13 Y-bridle CG hooks: no - launching on just one hook because the other one fell out does not cause a spectacular ground-loop, accident or male pattern hair-loss! ;-)

Uli

On Tuesday, December 6, 2016 at 7:15:05 AM UTC-7, Jock Proudfoot wrote:


You're right, relying on the pilot pulling the release doesn't work simply because it takes too long for the pilot to react.

I think there is just one cause of ground roll accidents and it's very simple - inadequate acceleration.

A glider just wants to fly and with the wing incidence angle at about 10 degrees with the tailwheel on the ground it will do so in about 2 seconds at 1G. Unless things are badly set up beforehand, the wings will stay balanced for at least that long. Once airborne. there is no risk of a ground roll accident.

The acceleration which worked with old wooden glider just doesn't get a heavy glass glider to aileron control speed and then airborne quickly enough.

Don, you brought up the old pitch-up myth so I'll go there.

Pitch-up on acceleration can only happen with the tailwheel in the air and that can only happen if the glider is slowly dragged into the air with feeble acceleration and THEN strong acceleration applied. It can't happen if strong acceleration is applied at the very start of the ground roll and maintained until the glider reaches the normal airspeed for rotating into the climb.

I could go on at length about this but I wrote a long paper on it available here https://dl.dropboxusercontent.com/u/...celeration.pdf Rather than take my word for it, I very strongly suggest the BGA and other national clubs do their own investigation using tension loggers. What you will see may terrify you.

Originally Posted by

On Tuesday, December 6, 2016 at 7:15:05 AM UTC-7, Jock Proudfoot wrote:


You're right, relying on the pilot pulling the release doesn't work simply because it takes too long for the pilot to react.

I think there is just one cause of ground roll accidents and it's very simple - inadequate acceleration.

A glider just wants to fly and with the wing incidence angle at about 10 degrees with the tailwheel on the ground it will do so in about 2 seconds at 1G. Unless things are badly set up beforehand, the wings will stay balanced for at least that long. Once airborne. there is no risk of a ground roll accident.

The acceleration which worked with old wooden glider just doesn't get a heavy glass glider to aileron control speed and then airborne quickly enough.

Don, you brought up the old pitch-up myth so I'll go there.

Pitch-up on acceleration can only happen with the tailwheel in the air and that can only happen if the glider is slowly dragged into the air with feeble acceleration and THEN strong acceleration applied. It can't happen if strong acceleration is applied at the very start of the ground roll and maintained until the glider reaches the normal airspeed for rotating into the climb.

I could go on at length about this but I wrote a long paper on it available here https://dl.dropboxusercontent.com/u/...celeration.pdf Rather than take my word for it, I very strongly suggest the BGA and other national clubs do their own investigation using tension loggers. What you will see may terrify you.

Hi Bill

An excellent paper and one that I will be sharing. It tallys with my own observations from watching multiple higher acceleration winch launches of a PW-5. In all cases the tail wheel hit the ground with the acceleration and with the stick neutral the glider lifted off in a shallow climb with a slow controlled rotation with increasing speed till it was in the full climb at around 150'

As described in your paper, the most dangerous winch launches I have seen and experienced have been ones with slow acceleration

Regards
Colin

At 09:35 14 December 2016, Ventus_a wrote:

;934125 Wrote:
On Tuesday, December 6, 2016 at 7:15:05 AM UTC-7, Jock
Proudfoot wrote:


You're right, relying on the pilot pulling the release doesn't wor
simply because it takes too long for the pilot to react

I think there is just one cause of ground roll accidents and it's
ver
simple - inadequate acceleration.

A glider just wants to fly and with the wing incidence angle at
about 1
degrees with the tailwheel on the ground it will do so in about
seconds at 1G. Unless things are badly set up beforehand, the
wing
will stay balanced for at least that long. Once airborne. there is
n
risk of a ground roll accident

The acceleration which worked with old wooden glider just
doesn't get
heavy glass glider to aileron control speed and then airborne
quickl
enough

Don, you brought up the old pitch-up myth so I'll go there

Pitch-up on acceleration can only happen with the tailwheel in
the ai
and that can only happen if the glider is slowly dragged into the
ai
with feeble acceleration and THEN strong acceleration applied.
It can'
happen if strong acceleration is applied at the very start of the
groun
roll and maintained until the glider reaches the normal airspeed
fo
rotating into the climb

I could go on at length about this but I wrote a long paper on i
available her

https://dl.dropboxusercontent.com/u/...celeration.pdf
Rathe
than take my word for it, I very strongly suggest the BGA and
othe
national clubs do their own investigation using tension loggers.
Wha
you will see may terrify you

Hi Bil

An excellent paper and one that I will be sharing. It tallys with m
own observations from watching multiple higher acceleration winc
launches of a PW-5. In all cases the tail wheel hit the ground with
th
acceleration and with the stick neutral the glider lifted off in
shallow climb with a slow controlled rotation with increasing speed
til
it was in the full climb at around 150

As described in your paper, the most dangerous winch launches I
hav
seen and experienced have been ones with slow acceleratio

Regard
Coli




--
Ventus_a


The tailwheel hitting the ground is normal for all gliders that sit on
a nosewheel and happens because the CofG is higher than the
winch hook. It has nothing to do with the rate of acceleration.
Taking off into a shallow climb with the elevator neutral is what I
would call normal acceleration.

Bill's pdf shows something completely different. The pilot is holding
the stick too far back in the early stages of launch & the elevator is
pushing the tailwheel down on to the ground even after the
mainwheel has taken off. That's just poor technique & usually
happens because the pilot is behind the aircraft & blindly pulling
back after the glider starts moving.

At 01:59 14 December 2016, wrote:

Don, you brought up the old pitch-up myth so I'll go there.

Pitch-up on acceleration can only happen with the tailwheel in the air
and
=
that can only happen if the glider is slowly dragged into the air with
feeb=
le acceleration and THEN strong acceleration applied. It can't happen if
s=
trong acceleration is applied at the very start of the ground roll and
main=
tained until the glider reaches the normal airspeed for rotating into the
c=
limb.

I could go on at length about this but I wrote a long paper on it
available=
here https://dl.dropboxusercontent.com/u/...celeration.pdf
Rather
=
than take my word for it, I very strongly suggest the BGA and other
nationa=
l clubs do their own investigation using tension loggers. What you will
se=
e may terrify you.


Hi Bill. If you follow URAS you will see that Don, whilst old and wise,
doesn't speak for the UK gliding community.

At 09:19 14 December 2016, Jim White wrote:
At 01:59 14 December 2016, wrote:

Don, you brought up the old pitch-up myth so I'll go there.

Pitch-up on acceleration can only happen with the tailwheel in the ai
and
=
that can only happen if the glider is slowly dragged into the air with
feeb=
le acceleration and THEN strong acceleration applied. It can't happen
if
s=
trong acceleration is applied at the very start of the ground roll and
main=
tained until the glider reaches the normal airspeed for rotating into
the
c=
limb.

I could go on at length about this but I wrote a long paper on it
available=
here https://dl.dropboxusercontent.com/u/...cceleration.pd
Rather
=
than take my word for it, I very strongly suggest the BGA and
other
nationa=
l clubs do their own investigation using tension loggers. What you will
se=
e may terrify you.


Hi Bill. If you follow URAS you will see that Don, whilst old and wise
doesn't speak for the UK gliding community.

Hi Bill,

The theory may be correct but I can assure you that a K18 ALWAYS needs the
application of almost full forward stck after lift off to prevent over
rotation. This is using a powerful V8 winch with about 2 seconds of ground
roll. Yes the accleration is still happening after lift off. With a narrow
steel drum throttle response is never instantaneous due to inertia of the
drum, even with the powerful (300 hp+) V8.

At 10:30 14 December 2016, Terry Walsh wrote:
At 09:19 14 December 2016, Jim White wrote:
At 01:59 14 December 2016,
wrote:

Don, you brought up the old pitch-up myth so I'll go there.

Pitch-up on acceleration can only happen with the tailwheel in
the ai
and
=
that can only happen if the glider is slowly dragged into the air
with
feeb=
le acceleration and THEN strong acceleration applied. It can't
happe
if
s=
trong acceleration is applied at the very start of the ground roll
and
main=
tained until the glider reaches the normal airspeed for rotating
int
the
c=
limb.

I could go on at length about this but I wrote a long paper on it
available=
here
https://dl.dropboxusercontent.com/u/...cceleration.pd
Rather
=
than take my word for it, I very strongly suggest the BGA and
other
nationa=
l clubs do their own investigation using tension loggers. What
you will
se=
e may terrify you.


Hi Bill. If you follow URAS you will see that Don, whilst old and
wise
doesn't speak for the UK gliding community.

Hi Bill,

The theory may be correct but I can assure you that a K18
ALWAYS needs th
application of almost full forward stck after lift off to prevent ove
rotation. This is using a powerful V8 winch with about 2 seconds
of groun
roll. Yes the accleration is still happening after lift off. With a
narro
steel drum throttle response is never instantaneous due to inertia
of th
drum, even with the powerful (300 hp+) V8.

I believe there is a solution to this, one which no one will like, but
which would reduce the frequency of the accidents, unfortunately it
may also very expensive and difficult to achieve on existing aircraft
and would result in a reduction in winch launch height. Move the
launch hook forward.

At 12:09 14 December 2016, Don Johnstone wrote:
At 10:30 14 December 2016, Terry Walsh wrote:
At 09:19 14 December 2016, Jim White wrote:
At 01:59 14 December 2016,
wrote:

Don, you brought up the old pitch-up myth so I'll go there.

Pitch-up on acceleration can only happen with the tailwheel in
the ai
and
=
that can only happen if the glider is slowly dragged into the air
with
feeb=
le acceleration and THEN strong acceleration applied. It can't
happe
if
s=
trong acceleration is applied at the very start of the ground roll
and
main=
tained until the glider reaches the normal airspeed for rotating
int
the
c=
limb.

I could go on at length about this but I wrote a long paper on it
available=
here
https://dl.dropboxusercontent.com/u/...cceleration.pd
Rather
=
than take my word for it, I very strongly suggest the BGA and
other
nationa=
l clubs do their own investigation using tension loggers. What
you will
se=
e may terrify you.


Hi Bill. If you follow URAS you will see that Don, whilst old and
wise
doesn't speak for the UK gliding community.

Hi Bill,

The theory may be correct but I can assure you that a K18
ALWAYS needs th
application of almost full forward stck after lift off to prevent ove
rotation. This is using a powerful V8 winch with about 2 seconds
of groun
roll. Yes the accleration is still happening after lift off. With a
narro
steel drum throttle response is never instantaneous due to inertia
of th
drum, even with the powerful (300 hp+) V8.

I believe there is a solution to this, one which no one will like, but
which would reduce the frequency of the accidents, unfortunately it
may also very expensive and difficult to achieve on existing aircraft
and would result in a reduction in winch launch height. Move the
launch hook forward.



I've picked this one up rather late, and probably like Don, I have many
thousands of winch launches, in vintage gliders, modern gliders, gliders
with compromise hooks, and with C of G hooks, initially on Tost, not
exactly underpowered, and for the last 20 years on Skylaunch, certainly not
underpowered.
To comment on something Bill said, I have analysed quite a few, from 1 sec
logger traces (perhaps not the most accurate way, but all I've got), and
find initial acceleration to be nearer .6g/.7g, rather than 1g. Tost weak
links are approximately 1.3 times auw, so should take 1g , at least when
new.
The problem with the wing going down is I think, that the pilot can be
unaware. A long time ago I had a 19m Jantar, with a compromise well forward
hook, and a loop of cord attached to the release toggle, because you could
not reach it. One day I took a launch, when I got back a few hours later, a
fellow instructor asked if I knew that the wing had gone down, so hard that
everyone at the launch point turned to look. I probably had 1500 hours on
that glider alone, and quite a few hundred launches in it, but hadn't a
clue anything had happened. To me it was a normal launch, and I got away
with it.
I totally agree though that high acceleration is good, the opposite is not.
Again, years ago, probably in the Jantar again, I had a very slow ground
run, but got away. When I got back, I found that a subsequent launch in an
ASW27, had had a wing down accident, substantial damage, fortunately no
injury. Though not there to see it, I always put that down to a slow ground
run like mine.
Most of the early Schleicher gliders, K8, K18, K6, do need a forward stick
position at the start, unlike most others, when neutral is best. The glider
will aviate when ready, it doesn't need encouraging by the pilot.
Winch launching is not inherently dangerous, any more than walking down the
street is dangerous, unless something goes wrong. Not sure without checking
how many are done in the UK each year without incident, but it runs into
hundreds of thousands. Just a very few go wrong.
What I would like to see is a re-think on launch speeds. High speed is
safe, low speed is not. Yet we have ridiculous situations like the Puchacz,
which I think is otherwise the best training glider available, with a
maximum of 59 kts, yet not really safe on a winch launch below 55 kts. This
is a fully aerobatic, inverted flight glider!!!
With the Skylaunch, perhaps others, the throttle stop is set to suit the
wind and the glider. The driver then advances the throttle lever to that
stop over a second or two. I would like to see a completely computerised
system, whereby the wind profile and the glider are selected, and the
driver just presses a button to launch, and all the parameters are built
in, including initial acceleration, surely not that difficult with modern
technology. Obviously there must be a dead man's handle.
Dave

It is pointless to enter into any sort of winch launching discussion here that is based on decades of experience by thousands of European pilots.