Flyingmac;
Thanks for the link to the NTSB report of the Cirrus-Pawnee mid air. The Schweizer sailplane/glider that was being towed by the Pawnee was fortunate to have not been "collected" by the wreckage of the mid-air collision. The glider pilot stated that he noticed the Cirrus approaching and fearing that it would impactl the towline, he reached for the release just as the Pawnee and Cirrus collided. The glider pilot reported flying through a "ball of fire" immediately after the collision, but the glider was reportedly undamaged. In my limited experience and from what I've read, most aero tow ropes used in the U.S. are 200 ft. long, and at the reported climb speed of 70 mph, approximately two seconds would elapse while traversing from one end (glider end) of the tow rope to the other end (tow plane end). Had the ballistic chute triggered at impact (causing the ball of fire) it is quite possible (maybe even likely) that the glider would have hit the shroud lines of the ballistic parachute. With all that said, I don't think that the ball of fire was caused by the rocket of the ballistic parachute system, but by the collision itself. I think that it is more likely that the ballistic parachute was triggered some time after the collision and resulting ball of fire.
Just my opinion.
Regards,
Grog