Winch Yaw/roll incidents - releasing

I have started a new thread on this because it is an important subject.
I have read the article at
https://dl.dropboxusercontent.com/u/...celeration.pdf

The first thing to understand is that the wing drop is a symptom of a
problem that has already occurred, it is not the primary cause of the
problem. The problem, or rather the serious consequences, were almost
unknown prior to the introduction of powerful winches with rapid
acceleration. With less powerful winches wing drop did occur but this did
not result in the airborne cartwheel which occurs off a powerful winch. The
lack of acceleration gave the pilot plenty of time to react and release.
The assertion that the accidents are caused by slow acceleration is
incorrect, in fact the opposite is true.

For many years I flew with the Air Cadet organisation and accidents of this
type are almost unknown, certainly there has never been one where there has
been death or injury. I suggest the reason for this is the strict limits
put on the operation and the manpower available to move gliders around at
the launch point. Air Cadet Gliding Squadrons employ staff cadets who do
most of this work. I suggest the basic reason why there are fewer
incidents, and the Air Cadet movement does as many winch launches in a year
as the BGA clubs, is for the following reasons.
1. The Air Cadets operate to strict weather minima especially crosswind
limits.
2. Gliders are always taken to cables, cables are never taken to aircraft.
3. If you are pulling out 6 cables at a time you have to keep them very
straight. the MVG winch has 6 drums.
4. Of all the winches I have flown the MVG winch has the smoothest and most
rapid acceleration, typically in a 15knot wind the glider (Grob103) would
be airborne in it's own length.

This operation reduces the factors which can contribute to yaw. The only
incident I witnessed was caused by the pilot starting the launch with
rudder applied anticipating yaw from a crosswind. The wing obligingly
dropped as a result of the yaw produced. The glider was released before the
wing struck the ground.
With early low powered Eagle winches the procedure was to adopt a gentle
climb to a safe height before entering the full climb. The procedure
changed following the introduction of the MVG winch which had a very large
diesel engine (8 litres if my memory serves) driving through a true torque
converter so that if the gentle climb scenario was carried out or over done
the speed increased very rapidly. The recommended procedure was to enter
the the full climb provided that the glider was above the minimum speed and
accelerating. This was the procedure I used in the 10 years I flew off the
MVG winch. It was never ever suggested that the elevator should be anywhere
other than at neutral prior to the launch.
From what I have read in accident/incident reports the accidents have all
occurred very rapidly and the acceleration is part of the problem in that
it exacerbates the yaw/roll condition.
One of the symptoms is wing drop. In most cases aileron is applied to try
and level the wings, in the case of the accidents this is invariably
unsuccessful. During a winch launch we are approaching the stall from the
"Other" direction, we are accelerating through the stalled condition.If we
think about what we tell people not to do with a glider which has a high
angle of attack with yaw/roll and pitch present, aka spinning this might be
a clue. Well tell them to keep the ailerons neutral, we tell them NOT to
try and pick up the wing with aileron.
Because the ground is so close once the yaw/roll has started the glider is
irrecoverable and the only option is to release to lessen the impact, not
to prevent it, it is already too late for that, but to try and prevent the
glider from becoming airborne. Given the rapid acceleration of modern
winches the time allowed to pull the release is very very short and that is
the reason why my hand is always on the release ready to pull it if at any
time there is roll over which I have no control. I cannot stress the
importance of holding that release, it can be a lifesaver.
My feeling is that the primary culprit in these cases is yaw, I am
convinced that the roll is a symptom of this yaw.

Don, I can't imagine roll or yaw happening if the glider is pointed at the winch and the wings balanced while the pilot holds neutral ailerons. My experience says by far the most likely cause of wing drops is the pilot unintentionally holding deflected ailerons. I've been known to grab a roll of wing tape to put a vertical white stripe down the center of the panel for a transition pilot - "THATS neutral aileron, put the stick there."

High acceleration puts a very large download on the tail wheel it so it strongly resists yaw as long as it's in contact with the runway - and it should remain there through lift-off. However, I absolutely agree that rudder input must be used sparingly and brought back amidships as the glider lifts off.

Note the term "balanced" is not the same as "level". It means wing is tilted so the glider has no tendency to fall to the right or left. If this is done, and the ailerons are neutral, the glider just goes straight and true.




On Sunday, October 13, 2013 7:15:26 PM UTC-6, Don Johnstone wrote:
I have started a new thread on this because it is an important subject.

I have read the article at

https://dl.dropboxusercontent.com/u/...celeration.pdf



The first thing to understand is that the wing drop is a symptom of a

problem that has already occurred, it is not the primary cause of the

problem. The problem, or rather the serious consequences, were almost

unknown prior to the introduction of powerful winches with rapid

acceleration. With less powerful winches wing drop did occur but this did

not result in the airborne cartwheel which occurs off a powerful winch. The

lack of acceleration gave the pilot plenty of time to react and release.

The assertion that the accidents are caused by slow acceleration is

incorrect, in fact the opposite is true.



For many years I flew with the Air Cadet organisation and accidents of this

type are almost unknown, certainly there has never been one where there has

been death or injury. I suggest the reason for this is the strict limits

put on the operation and the manpower available to move gliders around at

the launch point. Air Cadet Gliding Squadrons employ staff cadets who do

most of this work. I suggest the basic reason why there are fewer

incidents, and the Air Cadet movement does as many winch launches in a year

as the BGA clubs, is for the following reasons.

1. The Air Cadets operate to strict weather minima especially crosswind

limits.

2. Gliders are always taken to cables, cables are never taken to aircraft..

3. If you are pulling out 6 cables at a time you have to keep them very

straight. the MVG winch has 6 drums.

4. Of all the winches I have flown the MVG winch has the smoothest and most

rapid acceleration, typically in a 15knot wind the glider (Grob103) would

be airborne in it's own length.



This operation reduces the factors which can contribute to yaw. The only

incident I witnessed was caused by the pilot starting the launch with

rudder applied anticipating yaw from a crosswind. The wing obligingly

dropped as a result of the yaw produced. The glider was released before the

wing struck the ground.

With early low powered Eagle winches the procedure was to adopt a gentle

climb to a safe height before entering the full climb. The procedure

changed following the introduction of the MVG winch which had a very large

diesel engine (8 litres if my memory serves) driving through a true torque

converter so that if the gentle climb scenario was carried out or over done

the speed increased very rapidly. The recommended procedure was to enter

the the full climb provided that the glider was above the minimum speed and

accelerating. This was the procedure I used in the 10 years I flew off the

MVG winch. It was never ever suggested that the elevator should be anywhere

other than at neutral prior to the launch.

From what I have read in accident/incident reports the accidents have all

occurred very rapidly and the acceleration is part of the problem in that

it exacerbates the yaw/roll condition.

One of the symptoms is wing drop. In most cases aileron is applied to try

and level the wings, in the case of the accidents this is invariably

unsuccessful. During a winch launch we are approaching the stall from the

"Other" direction, we are accelerating through the stalled condition.If we

think about what we tell people not to do with a glider which has a high

angle of attack with yaw/roll and pitch present, aka spinning this might be

a clue. Well tell them to keep the ailerons neutral, we tell them NOT to

try and pick up the wing with aileron.

Because the ground is so close once the yaw/roll has started the glider is

irrecoverable and the only option is to release to lessen the impact, not

to prevent it, it is already too late for that, but to try and prevent the

glider from becoming airborne. Given the rapid acceleration of modern

winches the time allowed to pull the release is very very short and that is

the reason why my hand is always on the release ready to pull it if at any

time there is roll over which I have no control. I cannot stress the

importance of holding that release, it can be a lifesaver.

My feeling is that the primary culprit in these cases is yaw, I am

convinced that the roll is a symptom of this yaw.

The few wing drops I have personally witnessed in my long
gliding career have always occurred in gusty crosswind
conditions. None of these led to accidents. Either the pilot pulled
off or managed to get the wing back up by the use of opposite
aileron and rudder. One of the problems with this scenario is
that 9 out of 10 times you will probably get away with it, but the
10th time you won't. This is one were the pilots did get away
with it.

http://flightbox.net/galleries/wingdrop/wingdrop_1.htm

N,B, the instructor in this incident tried to pull off, but at his first
attempt his gloved hand slipped round the release knob. His
second attempt was successful, but the glider had already lifted
off by then. Pulling off under full load may require a much
harder pull than normal.

Derek Copeland


At 01:15 14 October 2013, Don Johnstone wrote:
I have started a new thread on this because it is an important
subject.
I have read the article at
https://dl.dropboxusercontent.com/u/...Acceleration.p
df

The first thing to understand is that the wing drop is a
symptom of a
problem that has already occurred, it is not the primary cause
of the
problem. The problem, or rather the serious consequences,
were almost
unknown prior to the introduction of powerful winches with
rapid
acceleration. With less powerful winches wing drop did occur
but this did
not result in the airborne cartwheel which occurs off a powerful
winch. The
lack of acceleration gave the pilot plenty of time to react and
release.
The assertion that the accidents are caused by slow
acceleration is
incorrect, in fact the opposite is true.

For many years I flew with the Air Cadet organisation and
accidents of this
type are almost unknown, certainly there has never been one
where there has
been death or injury. I suggest the reason for this is the strict
limits
put on the operation and the manpower available to move
gliders around at
the launch point. Air Cadet Gliding Squadrons employ staff
cadets who do
most of this work. I suggest the basic reason why there are
fewer
incidents, and the Air Cadet movement does as many winch
launches in a year
as the BGA clubs, is for the following reasons.
1. The Air Cadets operate to strict weather minima especially
crosswind
limits.
2. Gliders are always taken to cables, cables are never taken
to aircraft.
3. If you are pulling out 6 cables at a time you have to keep
them very
straight. the MVG winch has 6 drums.
4. Of all the winches I have flown the MVG winch has the
smoothest and most
rapid acceleration, typically in a 15knot wind the glider
(Grob103) would
be airborne in it's own length.

This operation reduces the factors which can contribute to yaw.
The only
incident I witnessed was caused by the pilot starting the launch
with
rudder applied anticipating yaw from a crosswind. The wing
obligingly
dropped as a result of the yaw produced. The glider was
released before the
wing struck the ground.
With early low powered Eagle winches the procedure was to
adopt a gentle
climb to a safe height before entering the full climb. The
procedure
changed following the introduction of the MVG winch which had
a very large
diesel engine (8 litres if my memory serves) driving through a
true torque
converter so that if the gentle climb scenario was carried out
or over done
the speed increased very rapidly. The recommended
procedure was to enter
the the full climb provided that the glider was above the
minimum speed and
accelerating. This was the procedure I used in the 10 years I
flew off the
MVG winch. It was never ever suggested that the elevator
should be anywhere
other than at neutral prior to the launch.
From what I have read in accident/incident reports the
accidents have all
occurred very rapidly and the acceleration is part of the
problem in that
it exacerbates the yaw/roll condition.
One of the symptoms is wing drop. In most cases aileron is
applied to try
and level the wings, in the case of the accidents this is
invariably
unsuccessful. During a winch launch we are approaching the
stall from the
"Other" direction, we are accelerating through the stalled
condition.If we
think about what we tell people not to do with a glider which
has a high
angle of attack with yaw/roll and pitch present, aka spinning
this might be
a clue. Well tell them to keep the ailerons neutral, we tell them
NOT to
try and pick up the wing with aileron.
Because the ground is so close once the yaw/roll has started
the glider is
irrecoverable and the only option is to release to lessen the
impact, not
to prevent it, it is already too late for that, but to try and
prevent the
glider from becoming airborne. Given the rapid acceleration of
modern
winches the time allowed to pull the release is very very short
and that is
the reason why my hand is always on the release ready to pull
it if at any
time there is roll over which I have no control. I cannot stress
the
importance of holding that release, it can be a lifesaver.
My feeling is that the primary culprit in these cases is yaw, I
am
convinced that the roll is a symptom of this yaw.