Airspeed control during ground launch?

"ucsdcpc" wrote in message
...
Speed control is OPPOSITE to that during aerotow and gliding

I'm sure if I asked this of one of our instructors the answer would be
"you don't" You control the attitude, the winch driver controls the speed.
Lowering the nose is the signal to the driver that you are too slow,
wagging the rudder the signal for too fast. If the winch driver doesn't
or cannot respond you abandon the launch.


And your instructor would be wrong in most cases. Pilots who think they are
controlling attitude are at risk of stalling while on the cable. We are in
a transition period in winch launch where old ideas are giving way to the
new. New gliders launched by new winches operate by somewhat different
rules.

In the modern view, the winch driver controls POWER and the pilot controls
AIRSPEED. The relationship is the same as in airplanes where throttle
controls power and pitch controls airspeed. As the glider leaves the ground
on a winch launch. the pilot smoothly pitches up to hit a target climb
airspeed. In an airplane, this would be Vy. In the typical glider, it
will be between 55 and 65 knots depending somewhat on headwind. It's
helpful to think of the winch driver as your flight engineer with his hands
on the power levers.

A modern trainer such as a ASK-21 would need a very powerful winch indeed
for its pilot to be unable to control airspeed. In most cases, the entire
launch will be flown with neutral elevator leaving considerable up elevator
to control airspeed.

An important exception is with gliders which have hooks too far forward
and/or have too little up elevator authority - for example, most Schweizers.
When flying these gliders the pilot will reach full up elevator before the
airspeed can be controlled. Since the pilot cannot control airspeed, the
winch driver has to. A further complication is that these gliders, which
require the winch driver to control airspeed, will not reach more than 1/2
to 2/3's the height of the modern 2-seater with a properly positioned CG
hook.

This exception case also introduces complications in the event of a cable
break. With the elevator positioned at full up, the glider will pitch up
strongly at the cable break - sometimes beyond the point where a safe
recovery can be made. In any event, a very quick and positive action will
be required of the pilot. This contrasts with gliders like the ASK-21 which
will continue on the same trajectory giving the pilot additional seconds to
handle the cable break.

Bill Daniels