On Friday, 11 December 2015 00:23:42 UTC, wrote:

I witness a LAK 17b FES 21 meter termination of the tow at tree top,about 25 meters high. No place to land.

The pilot turn the motor on flew away found a thermal and came back 5 hours
later.

Any other glider would have been destroyed.

I wonder what the point was of doing that. By the time you have queued for an aerotow, and paid anything for it, you have lost all the benefit of having a self launcher. So why on earth accept even the admittedly very small risk of a problem with the FES, instead of holding onto the aerotow up to a height for a comfortable landing back on the airfield if the FES does not perform?