Winch Launch - Fatal

At 04:19 10 December 2016,
wrote:
On Friday, December 9, 2016 at 8:45:05 AM UTC-7, Don
Johnstone wrote:
At 08:24 09 December 2016, Pete Smith wrote:
No, the position changes subtly.

On my cirrus and N2 it is at the lower left of the stick box
quadrant,=
=20
o
the=20
N3 in question and later gliders it is in the upper left.

Please read the accident report and its conclusions.

The accident described in the report was not so much of an
issue=20
when Earlier ASW,17, 18,19,20 were designed and built. Same
applied=20
to SH.
The accident is directly related to more powerful winches. The
same=20
situation would develop with less powerful winches but it took
much=20
much longer. There was more of a ground run to recognise the
wing=20
on the ground and the acceleration was much less which meant
that=20
when it went wrong it went wrong much slower with more time
to=20
react. Not so with a modern powerful winch, when the problem
occurs=20
it goes wrong very quickly, probably too quickly for any chance
for a=20
meaningful reaction. What is described has always happened
from time=20
to time, the only difference is that it did not start killing people
unti=
l
=20
the winches got powerful.

Muddled thinking, Don.

Not muddled, incomplete. The problem is far too complex to
describe in a short post.

All winches have throttles so they produce no more power than
the winch
ope=
rator chooses. If the winch seems too powerful, you're problem is
with
the=
winch operator, not the winch.

In part, yes however the difference is in what is possible. A less
powerful winch is incapable of the rapid acceleration. People make
mistakes, with a less powerful winch the operator cannot make the
mistake of applying too much power. A powerful winch has very
little to do with the cause, it has everything to do with the outcome.

Did "powerful" winches cause a wing drop and subsequent
ground loop?
Highl=
y unlikely. The problem is far more likely to be with pilot training
and
g=
eneral winch operations.

No, see above, the more powerful winch effects the outcome.

Wings go down on winch launch for three main reasons. =20

One, excessively slow acceleration allows a wing drop before the
pilot
gain=
s aileron control - same as with aero tow. The difference is with a
CG
hoo=
k an ensuing ground loop is going to be more violent. It's much
safer to
g=
et the glider up to aileron control airspeed in the minimum time.

Two, with a fast accelerating winch, should the pilot begin the
ground
roll=
with aileron input, they will take effect suddenly forcing a wing
tip to
t=
he ground before the pilot can react - consciously centering the
stick
befo=
re the launch starts is critical. Avoiding over-controlling ailerons
is
eq=
ually important.

Three, wing "runners" sometimes mishandle the situation. If they
are
accus=
tomed to aero tow, they will be surprised how quickly the tip must
be
relea=
sed.

Post hoc, ergo propter hoc. It seems widely believed that the "wing
drop" is a cause when it is far more likely it is a symptom. To take
your points individually. It used to be popular for pilots to apply
aileron and rudder, prior to moving on a winch launch to anticipate
wing drop in a crosswind, and people got away with this on slower
accelerating winches. Hopefully we have trained this out, certainly
something I am very pedantic about. All the controls, especially the
rudder should be central. The latest advice to wing runners is if
there is any significant force required for them to keep the wings
level the launch should be stopped and the pilot appraised. I would
go further and say if there is any significant force required, with
the ailerons central, then the launch should not take place at all.
Excessively slow acceleration does not cause wing drop, wing drop
is caused by aerodynamic forces. The slower acceleration does
reduce the effectiveness of the control making recovery more
difficult. The wing drop is still a symptom of a developing problem,
not a cause.

I have never said that a powerful winch is the cause of the problem,
it isn't. The same problem occurred from time to time on less
powerful winches but over a much longer period of time and less
energy was available to be put into the glider. The increased power
effects the outcome with the increase of available energy and
therefore the larger divergence and reduced time period over which
the incident takes place. If a control is inappropriately applied the
effect is much greater with the higher speed.

The problem has always been there, it is just that before powerful
winches it did not tend to kill people.

On Fri, 09 Dec 2016 20:19:18 -0800, Bill.Daniels wrote:

Three, wing "runners" sometimes mishandle the situation. If they are
accustomed to aero tow, they will be surprised how quickly the tip must
be released.

Two additional points (which you may already do):

-train the wing runner to hold the tip from behind (NEVER with
fingers round the leading edge).

This makes it much less likely that the
wing runner can deflect the glider before letting go.

-teach wing runners to BALANCE the glider on its wheel, raising or
lowering the tip a bit to counter the forces generated by a cross-wind.
Done right, you need little more than a finger and thumb on either side
of the TE to keep the wing balanced despite gusts.

If the wing runner is forcing the wing level against a cross wind, then
a wing-drop is almost guaranteed when the tip is released.



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

On Tuesday, December 6, 2016 at 9:15:05 AM UTC-5, Jock Proudfoot wrote:


My early flying was nearly all launched by winch; the winches
in the 60s were pretty anaemic.
Nevertheless, the standard practice was to take up cable slack
till it was pretty straight, so the initial acceleration was
directed along the glider axis. this would remove the roll couple as described in the report.
More recently, experience at Bristol GC and the Mynd was like
a superbungee launch and I admit to some concern about the elevator
power to cope with the pitchup.

It would seem that initial acceleration should be moderated.

The PTT problem is unknown to me, but I presume it must mean
passenger temper tantrum.

JMF

I must agree with Don Johnstone,
todays winches are very powerful.
Does this result in higher launches or just much more rapid ones?

On Fri, 09 Dec 2016 18:21:35 -0800, Scott Williams wrote:

I must agree with Don Johnstone,
todays winches are very powerful.

IME the control systems in the winch are the most important factor
provided that the winch has enough power to avoid running it flat out for
most of the launch.


Does this result in higher launches or just much more rapid ones?

I learned on a Supacat (240hp diesel V-8), straight drive, driver's
judgement and hand on the throttle were all that controlled the winch.
Now we have a Skylaunch (380hp LPG converted V-8), automatic gearbox,
analog launch controller which the driver can override. The Supacat used
steel cable while the Skylaunch has always used HD poly rope. I've
regularly flown my Libelle and club gliders (K21, Puchacz, Junior) off
both winches. Initial acceleration rates are similar and so are release
heights, but by and large the Skylaunch gives more consistent launches.

Oddly enough, Supacat launches were faster, typically just below Vwinch,
while the Skylaunch launches are about 5 kts slower, which feels a lot
nicer.


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

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

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.