ORIGINAL: Gordon Mc
ORIGINAL: paf
To me, the model seems to have went out of control approximately 5 seconds before impact. That's not enough time to bleed off enough kinetic energy to make it non-lethal, even with the engine at idle. However that's no excuse for anyone to not have a PCM failsafe go to idle.
5 seconds is more than enough time to stop a prop by having failsafe set to engine kill
From my experience (failed throttle servo, killing the engine using electronic kill switch in order to land), it takes around 15 seconds for a 32x10 CF prop to actually come to a stop during level flight.
20kg model at 80 mph (33 m/s) has 10890 J kinetic energy. Your average, relatively high-drag, giant scale model will slow down to approx. 55mph (23m/s) in 5 seconds, dropping the energy down to 5290 J.
A 32" prop has has moment of intertia approx. 0.025 kg/m^2, so spinning it at 5000 RPM gives you 3152 J kinetic energy.
A 9mm bullet right at the nozzle has approx. 500 J kinetic energy.
Either scenario is a losing proposition.
Although not intuitive, you're better off falling into a stationary 32" prop at 5000 RPMs rather than getting hit by 20kg glider at 55mph. Your worst nighmare (like the accident in question) is a spinning prop on a nose of a heavy airplane
P.