Winching - Reverse Auto Tow

"W.J. \(Bill\) Dean \(U.K.\)." wrote in message ...
The initial acceleration for a car or reverse pulley launch is no worse than
for an aerotow; it is flown in the same way. There is of course no tug
slipstream to contend with.

A car launch starts like an aerotow, and turns into a winch launch when you
are airborne.

W.J. (Bill) Dean (U.K.).
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"Chris Nicholas" wrote in
message ...

Initial acceleration is certainly much slower with autotow (whether
pulley or direct) than with winching. At both North Weald and Aston Down
there was more than one runway, so most launches were broadly into-wind.
Such cross wind as there was could be handled. The initial ground run
was a phase of flight in its own right - the pilot had to learn to
balance on the wheel and taxi straight until flying speed was achieved.
Wingdrop was not normally a problem, but training people to taxi was a
feature. The same considerations apply when landing, in any case, so
they got two lots of taxi training in one flight.

On tarmac or concrete the F250 trucks had adequate power and grip. F100's
were not bad, but we didn't have such heavy gliders in those days.
Aston Down tried a variety of tow vehicles over the years, including
some home-built diesel dragsters, but I believe they ended up with
factory-built trucks, as we did, and as Lasham (using straight autotow
at one time) also did. I worked for Ford then, and helped to get some
advantageous prices for imported US-built vehicles for two if not all
three clubs IIRC - Ford used gliders at North Weald as background for
some advertisements, and did us a favour in return.

My club used LPG rather than petrol/gasoline, which made it a comparable
fuel cost to diesel winching, per launch/cable-retrieve. Total
depreciation/financing cost was probably about comparable, but needed
less cash flow up front. Trucks were cheaper capital cost than new
winches, though not as durable - ours lasted for about 50,000 launches
each and were not fully worn out - we recycled one old powertrain into a
winch when we had to adopt that method for our Ridgewell site.

The key features for us at North Weald were that on hard runways we had
to use piano wire (single strand steel cable), not stranded, to avoid
too much wear and cable cost, and pulley/autotow lends itself to that
better, with pulley giving also the benefit of fast launch rate when
well organised. We did about 9,000 launches a year, and added
considerably to our cash flow, when we had optimised the system.

Chris N.



It was the Dublin Gliding Club which used reverse pulley launching in
Ireland up to the early 1970s.

I flew there, from Baldonnel airfield. The pulley was about 3feet in
diameter and very simple with hardly any fairing. It was mounted on
the back of a large Chrysler car which had a tow-beam coming out of
the front with a heavy metal spike at right angles that was embedded
in the ground to anchor it. The mount for the pulley allowed it to
rotate to any angle to follow the line of the cable. The cable was
single strand piano wire. The concrete runways would have worn out
stranded cable too quickly.

The tow car, a large American automatic transmission car, had a
standard cable release mechanism welded to a lever which compressed a
small plastic football filled with water connected to a clear plastic
tube leading in to the top of the dashboard. The water rose in the
tube as the tension in the cable increased. Marks indicated the right
pressure for single seaters and two seaters (we flew K7, K13, K8, K6
mainly). The launch driver technique was very simple. Accelerate
rapidly to the correct tension once the glider was established in
climb. Slow down or speed up to keep the tension on the mark. I don't
remember ever having to signal too slow or too fast from the glider.

When the wind was strong, it was possible to reverse down the runway,
paying out the cable, as the glider kited upwards. My highest launch
was 4500 feet using this approach.

Cable breaks took rather a long time to disentangle as the cable
sprang back and tied itself in knots. Good heavy gloves were useful.
Splices were carried out by two people standing opposite each other
and winding the free ends back over the wire by hand.

The end came when the Army Air Corps installed VASI instrument landing
lights at the ends of the runways. The runway lights had been
expensive to replace if hit by flying rings, but the VASI lights were
£20,000 each and would have meant bankruptcy.

The Dublin Gliding Club still launches by (straight) car tow from
beaches in County Kerry each year on their wave safaris, using parafil
cable.

Frank Dobbs
Ulster Gliding Club, Northern Ireland