Hmmm! Watched a similar at Valley 'performed' by a Gnat stude, No 3 in a formation take-off.The slipper tanks ruptured and the fuel spill ignited and followed the aircraft along the runway, about 20 yards astern. The first vehicle in the queue to cross the runway at the departure end was an AvGas bowser, whose driver reckoned he stripped every gear in the box trying to get one to move away from the approaching fire-ball!!the aircraft eventually came to rest, on the peri-track, a short distance behind the vehicle queue and 'Bloggs' was out and legging it in short order! The 22 det standby Whirly rushed over seeing the possibility of 'trade', only to make a VERY rapid lateral exit as the pneumatic seat blew upwards. No idea if 'Bloggs' continued beyond the 'nil coffee, nil biscuits' interview, but it served as a useful visual aid for our S&R studes re approaching burning Gnats!!