Hi Bill

I respect your views but there are some differences in the way we see things he

Firstly please note that I am not advocating underpowered winches. I do however
maintain that power is not the most important safety issue in winch launching,
and that - for our fleet where the highest wingloading is relatively modest, and
the heaviest glider is a Blanik L13 - a winch with 220Hp is adequate. (maybe 250
would be better)

Bill Daniels wrote:
We have had several people writing that they have launched heavy glider X
with a low powered winch. I have done it and so have many others, but this
is still not a good idea. There are serious dangers involved.

Too low power is dangerous, and we agree entirely that more power is desirable.
Interestingly the most recent National Safety meeting addressed winch launching
as the primary theme.

There were 25 Safety Officers and at least ten Chief Flying Instructors as well
as the SSSA Exco present. One thing that became apparent was that there is no
optimal power winch. In particular - when launching old designs that are light,
high wing with the hook at a considerable vertical displacement from the wing,
there have been numerous dangerous launches where the initial acceleration
exceeds the control authority on the glider. The example given was launching a
Ka8 with the stick hard against the forward stop for most of the launch.

Too much acceleration is as dangerous as too little.

The best way to look at it is to consider power demand and supply. The
winch engine should be able to supply all the power the glider demands. If
the glider demands more power that is available by pulling up hard, the
airspeed will decay quickly. If the pilot knows this is going to happen, he
can manage it by controlling the pitch attitude carefully. If he doesn't
expect it, the airspeed will decay so quickly that a very dangerous
situation will develop.

Agreed, and all of our pilots have to learn to control their demands on the
winch before going solo. In this respect it would be safer and better to have
more power for perhaps 30% of our fleet. Conversely, any piulot who relies on
the generous power reserve of the winch to compensate for pulling back too hard
is dangerous. I am all for the speed decay to warn the pilot. That way, when the
winch falters, he will compensate automatically because he will be used to
monitoring and controlling airspeed carefully.

The attempt to launch gliders with a low powered winch gets into who is in
control of the launch. I think it goes without saying that who controls the
launch should not be in doubt. The majority view is clearly that the winch
driver should be in charge.

Here I differ, the pilot is always in control of his / her destiny. Our process
is that the launch marshal controlls the launch process, and the winch driver
and pilot must work together. A skilled winch driver is in control at all times
within the parameters dictated by physics. If we have a pilot who over rotates
and "bends the pole" a number of things will happen.
With the exception of the Blanik with its flaps deployed the winch driver will
be able to keep the glider above stall speed with full throttle.
The winch driver is still in control and may decide that the probability of a
maximum tension cable break is dangerously high and elect to reduce power until
the pilot takes the pressure off the cable. (even if it results in a low release)
If the pilot is being ham fisted the cable will probably break resulting in a
dangerous recovery and the possibility of landing damage. This probability is
directly proportional to the instantaneous force on the cable, here a powerful
winch is a distinct liability.
In any event an overzealous pilot is going to get a lecture from the CFI...


With a low powered winch, the winch driver is in charge early in the launch
but as the glider steepens the climb, the power demand exceeds supply and
speed control shifts to the glider pilot who now must control airspeed with
pitch since the winch is at full throttle. As the glider rises still
further and power demands lessen, airspeed control shifts back to the winch
driver who must reduce power to prevent over speeding the glider. There
are lots of ways this scenario can go badly wrong.

The other area where a low powered winch can cause problems is in the
initial acceleration. The German Aero Club specifies the maximum distance
that a glider can use to reach flying speed to determine the minimum winch
power. Specifically, under all conceivable wind, density altitude and
weight conditions, a glider must reach Vr (rotation speed) in 40 meters or
less - there is no minimum specified. This is a very intelligent
specification. The concern driving this spec is that should a glider's wing
drop to the ground before reaching flying speed, the resulting ground loop
will be very ugly and quite possibly fatal for the glider pilot.

These concerns and the desire to get the highest launch possible, has driven
winch horsepower higher and higher in recent years. Shortening the
accelerate to Vr distance has a powerful effect on the launch height
achievable. Many powerful winches have shortened this to less than 20
meters.

IF we were launching twin Astirs, or K21s or other heavy two seater I would
concur that you would want more power. But bear in mind that the Blue weak link
is easily overcome by a 200-250Hp winch. If that is the heaviest weak link
specified you are wasting your time on more power.

Again I agree that more initial acceleration is desirable - I HATE slow
acceleration launches in my Cirrus because the chance of a wing drop is higher.
TO overcome this we use gearing on the winch that increases the effective torque
available.

To summarize, I am advocating generous power reserves to permit the winch
driver to maintain control of the launch and to insure the glider reaches
flying speed before a wing can drop.

Bill Daniels


Generous power reserves are desirable. I am just not convinced that the use of
very powerful winches imnproves safety. My experience is that an adequately
powerful winch that is tractable and predictable is safe, even if there are
compromises on height and initial acceleration. In our mixed vintage and glass
setting it would be challenging to have a super powerful winch.

My conclusion is that it is desirable to have generous power reserves and good
torque for fast acceleration of the heaviest aircraft on the fleet. It is also
imperative that the control be adequately calibrated so that power output can be
modulated easily for all of the gliders the winch could be expected to launch.

Bruce