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.