On Sunday, October 4, 2015 at 10:57:33 PM UTC-6, Sean Fidler wrote:
I had an interesting conversation with a pal about auto-tow glider launching method recently. It seems academic really.

When cost is considered, auto-towing has to be far more affordable than even winching. Maybe $1.50 per tow, max? In aviation, the cost is always critical. Especially in gliding club environments. Aerotows are $30-50 per tow. Winches are extremely expensive to purchase, to maintain, and insure and require skilled operators.

Auto-tow procedure seems fairly simple. 1) Steady strong acceleration until the glider comes airborne, then 2) add 5mph and 3) hold that speed until you hear differently from the pilot. Of course, 4) stop at the end of the runway :-).

Why is auto-towing not a mainstream method of getting gliders airborne?

I saw auto-towing happen regularly at Hobbs this year (my first visit). It was quite graceful and almost exotic. To be honest, it looks even more fun than winching.

I am very interested in learning what you know, your thoughts and your opinions.

Sean
7T

Sean, I've done a lot of both auto tows and winch launches. The low cost of auto tow is illusionary because people tend to ignore the costs associated with the tow car. Auto towing is really, really hard on a car. Modern gliders need 60 - 65 knots to safely rotate into the climb phase so the tow car is doing full throttle 0 - 75 mph on every tow followed by maximum effort braking to stop. It's basically drag racing so maintenance and tire replacement become a huge cost. Auto tow operations typically use a noob's car - until the owner figures out the wear and tear his vehicle is subject to..

As other poster pointed out, it also takes a LOT of room. To get decent height you need a long rope which takes up a large chunk of runway before anything gets rolling. Then, you need the acceleration distance for the car before the glider can start the climb. Finally, the tow must end so as to leave enough distance for the tow car to stop before running off the end of the runway.

If unlimited space is available as on Mojave dry lakes, then auto tow sorta makes sense but with any runway less than 5500 feet long, winches will get you higher and cost you less money doing it.