On Sunday, October 26, 2014 8:59:46 AM UTC-4, son_of_flubber wrote:
The case of the towplane being on the ground and aborting takeoff when the glider is flying in ground effect is problematic.

If the runway has poor straight ahead landing options (I mean poor options for landing after a 100 AGL engine failure), then aborting takeoff before the towplane leaves the ground, even for an unconfirmed engine/pilot problem, is understandable. But the glider having much less drag is fated to fly past the tow plane (if it avoids collision).

Is it possible for the glider to turn fast enough to avoid colliding with the towplane? What happens when a glider touches a wingtip to the ground at 40 knots?

At what velocity does the glider have enough energy to fly over top of the towplane? Or is that impossible?

Any experiences/thoughts?

I don't understand why you call low level tow plane engine failure "problematic". I've seen two actual low level engine failures in ten years of glider flying (to be specific, the glider was flying and the tow plane was not). Tow planes lead a rough life and engine failures do happen, a lot more than we'd like.

Your comment "the glider is fated to fly past the tow plane" is exactly why (1) you need to prepare for this and (2) you need to see this situation for real. Yes, you can turn to avoid the tow plane if (and only if) you recognize that you must do so soon enough. If you touch a wingtip at 40 kt you will be in for Mr. Toad's wild ride - hopefully you and the glider will not need major repairs. I wouldn't even think about trying to fly over the tow plane - but then the runways I fly from have lots of good grass on their sides.

Again, the point I was trying to make is that a low level tow plane engine failure does happen and that experiencing one (albeit simulated) was a completely different affair from what I had imagined from reading about them. You have to be alert, and you must react quickly.

-John, Q3