On Sunday, October 4, 2015 at 11:57:33 PM UTC-5, Sean Fidler wrote:
I had an interesting conversation with a pal about auto-tow glider launching method recently. It seems academic really.


Auto launching can be an economical, if laborious, way to get gliders in the air. My club used to do a lot of auto and winch launching. We did hundreds of auto launches and thousands of winch launches. For auto launch, we used the "pulley in the middle" system with the pulley on the to car, pulling from the middle of the rope. We used about 4000 feet of dacron line. 2:1 mechanical advantage of this system meant that the tow car never had to exceed 28 mph. With 10 mph headwind, our Ka-8 sometimes achieved launches of 2000' agl. We usually got 1400-1600' with the Ka-7 and ASK-21. The tow car was an old Ford Crown Vic that came from a junk yard. We had around 300-400 lbs of bricks in the trunk to keep the wheels from spinning in the later stages of a launch. I think it only ran on 5 cylinders, but it produced about the perfect amount of power for launching the 2 seaters. Put it in low gear and just push the accelerator smoothly to the floor. The glider would be airborne in about the same distance as a winch launch. The car would get to about 28 mph and by then the glider was beginning to pitch up. With the pedal all the way to the floor, a 2-seater glider in a steep climb would begin to slowly decelerate the car. This resulted in launches with very close to the perfect speed in the climb. We would be down below 25 mph with the glider at the top of the launch. Letting off the gas made for a very short stop.. The rope usually back released at that point. Made it easy peasy to launch two seaters. With the single place birds, we'd have to go a little easier on the throttle to keep speed below 30 at the car. Still, it was very easy to drive the launch as long as the pilot pitched up correctly.

Recovery of the rope was a bit fiddly and was the time consuming part of it all. We were at the end of the runway at the end of the launch, so we could not continue on to pull the rope down to the car. The rope just fell wherever. We had no chute on it anyway. We'd recover and straighten the line by putting it back on the pulley then having the anchor vehicle tow the other end of the rope to the launch point. We could do a launch every 10 minutes if we hustled. Usually it was more like 15 minutes per launch.

We always had two people in the car. A driver and an observer. The observers job was to keep an eye on the glider and relay info to the driver. The observer also had a very sharp machete with which to cut the rope should the glider be unable to release.

Our pulley system was just a truck wheel mounted on a steel arm that fit into an hitch receiver.