Winch Launch - Fatal

On Sunday, December 11, 2016 at 3:15:02 AM UTC-7, Peter Whitehead wrote:
On Tuesday, 6 December 2016 14:15:05 UTC, Jock Proudfoot wrote:


Modern winches are powerful so the ground run is shorter, and it is this which allows greater height on launch (you are effectively lengthening the airfield compared to those with "anaemic winches"). The problem is the acceleration and reduction in time to sort out the problem with wing drop on the ground, and also a stall and wing drop (to inverted ) in the rotation (to climb).This can all happen too quickly for human responses. It kills "smart" people.

Please do read and digest (and disseminate) the following link from experts in the field, the BGA. This programme of "safe winching" has shown reduction (evidence based) in accidents and fatalities in this mode of launching..

https://www.bfgc.co.uk/Documents/Winching.pdf

Pete Whitehead

I read every new issue of the BGA safe winching and note a slow movement toward scientific rationality such as the deletion of the ridiculous graphic showing a glider pitching up due to acceleration.

There is NO time to "sort out problems" in the ground roll - the only option is to prevent them in the first place.

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.

A normal winch acceleration is 19 knots per second (1G) which gets the glider to aileron control airspeed in less than a second and airborne in about two seconds. If rules 1 - 3 above are followed it's almost impossible to imagine a wing drop before the glider is airborne and out of danger.

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.

On Sun, 11 Dec 2016 16:03:09 -0800, stephanevdv 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.

There was a discussion about this during my club's launch marshal meeting
today. The consensus was that there is a potential problem with point 3
because many pilots think 'balanced turn' and also add some aileron, thus
inviting wing drop, when leaving the ailerons centralised and just
applying rudder is the correct course. Centralising all controls avoids
this. I should add that we use SZD Juniors, which have a larger left hook
offset than any of the gliders you mention and consequently a stronger
tendency to swing right, especially if there is a cross-wind from the
right!

I start winch launches with controls centred regardless of whether I'm
flying my Libelle or one of the club's fleet (Junior, ASK-21, Puchacz or
Grob G103). In all cases you can get rudder on fast enough to control a
swing if you're paying attention, and what are you doing as PIC if you
aren't paying attention?


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

At 00:44 12 December 2016, Martin Gregorie wrote:
On Sun, 11 Dec 2016 16:03:09 -0800, stephanevdv 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.

There was a discussion about this during my club's launch
marshal meeting
today. The consensus was that there is a potential problem with
point 3
because many pilots think 'balanced turn' and also add some
aileron, thus
inviting wing drop, when leaving the ailerons centralised and just
applying rudder is the correct course. Centralising all controls
avoids
this. I should add that we use SZD Juniors, which have a larger
left hook
offset than any of the gliders you mention and consequently a
stronger
tendency to swing right, especially if there is a cross-wind from
the
right!

I start winch launches with controls centred regardless of whether
I'm
flying my Libelle or one of the club's fleet (Junior, ASK-21,
Puchacz or
Grob G103). In all cases you can get rudder on fast enough to
control a
swing if you're paying attention, and what are you doing as PIC if
you
aren't paying attention?


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

You are absolutely right Martin and the point you make is crucial.
Whatever the glider, the crosswind or any other factor the controls
should all be centered, or in the case of the elevator, neutral to the
trim setting or takeoff position (I find a T21 needs the stick well
forward). The controls should only ever be used to correct a
departure from the attitude required, or to select an attitude
required, never, in the context of a winch launch, to anticipate a
perceived or potential problem.
If any force is needed by the wing tip runner to hold the wings level
with the ailerons central this can be corrected by lifting or lowering
the wing by a small amount to balance, a Bill has said. If however
balance cannot be achieved with a small lowering or lifting then
serious thought should be given as to if the launch should be
attempted.

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 13, 2016 at 1:32:58 PM UTC-6, AS wrote:
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

Uli and Bill D beat me to it: that's exactly my experience. The offset hook myth is just that, an old wifes tale, to be used for bedtime stories to scare your children.
Herb

On Tuesday, December 13, 2016 at 3:37:14 PM UTC-7, wrote:
On Tuesday, December 13, 2016 at 1:32:58 PM UTC-6, AS wrote:
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

Uli and Bill D beat me to it: that's exactly my experience. The offset hook myth is just that, an old wifes tale, to be used for bedtime stories to scare your children.
Herb

Actually, just to be obstinate, there is a scenario where an offset hook will induce a swing to the side. That's under ridiculously low acceleration where the glider swings a bit each time the tailwheel bounces. Increase the acceleration to a normal 1G and the down-force on the tailwheel will keep the glider rolling straight.

At 23:16 13 December 2016,
wrote:

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
muc=
h better in this case to align the glider pointing slightly to the left
of
=
the winch, and giving left rudder at the start.
=20
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
consequen=
ce - you're not trying to fly formation on a winch.
=20
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
conditio=
n 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!
;=
-)
=20
Uli
=20
Uli and Bill D beat me to it: that's exactly my experience. The
offset
ho=
ok myth is just that, an old wifes tale, to be used for bedtime
stories to
=
scare your children.
Herb

Actually, just to be obstinate, there is a scenario where an offset
hook
wi=
ll induce a swing to the side. That's under ridiculously low
acceleration
=
where the glider swings a bit each time the tailwheel bounces.
Increase
th=
e acceleration to a normal 1G and the down-force on the tailwheel
will
keep=
the glider rolling straight.

In the days of yore, when gliders had compromise hooks and
winches had less power, but were still capable of getting a glider in
the air in it's own length, given the right circumstances, the
problem did not occur. With introduction of the incorrectly named
CoG hook the problem of rapid pitch up appeared. The pitch up was
alarming but in the main recovery was made with only a slight stain
to ones shreddies. The yaw, pitch, roll events also occurred but that
happened slowly compared to today, due to the power of the winch
being less. With wooden gliders the wing tips tended to be higher
and sufficient bank to touch the ground was more obvious, it
happened from time to time but again was scary but seldom fatal.
With the introduction of low wing glass gliders and powerful
winches that changed. We have observed the result but failed to
really identify the cause. Wing drop is a symptom certainly but
maybe not the cause, and the same applies to the yaw and rapid
pitch up. I believe that there is no single cause, it is a coming
together of several factors, and an offset hook may be one. It would
appear that larger wing span increases the chances of it happening,
as does a significant crosswind component. Like spinning in, the
only person who could tell us what really happened is not able to.
Gliders drag wings along the ground and get away with it, gliders
rear up and are recovered. Gliders are yawed by a cable out of line
and climb away, there is no single factor that you can point to and
say, if this happens then that will happen.
What is clear is that the current practice of having the hand on the
release ready to pull it is not working, by the time the problem is
recognised it is too late, because of the "normal" acceleration rate of
modern winches. I am still drawn towards yaw being the root
cause, why sometimes this develops into something more serious is
the puzzle. If anyone has an answer please share it, however crazy,
in pulling it to bits we might just stumble on the solution.

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.