ORIGINAL: Gordon Mc
ORIGINAL: paf
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.
Sounds like something's wrong with your engine.
I'll tell you what.... if I give you the choice of sticking your arm into a 34 inch prop running at full bore, and doing the same for a prop that's windmilling lightly 5 seconds after being shut down on an engine that apparently has little or no compression - which would you choose ?
Given that you assert point blank that PCM set for engine kill could not have made any difference to the outcome of this event, either you have documented proof that the fatalities were not in any way attributable to the prop, or you believe that being struck by such a prop at full power can't kill you -- which is it ?
Gordon
What I'm saying is that, both the plane with windmilling prop and the fast spinning prop on its own, have enough energy to kill you several times over. Just shutting the engine does not make the plane safe - just a bit safer. From the video, I'm not able to tell if the engine was set with PCM idle failsafe or not, but even with the engine shut, there wasn't enough time for the plane to slow down to a non-deadly airspeed. I doubt that both victims got a direct prop hit, suggesting to me it was purely the total mass/velocity of the thing that did major part of the damage.
The major advantage of killing/idling the engine with failsafe is that hopefully, in most scenarios, the plane will impact at lower speed than with an engine running. However the plane has enough energy to be deadly several times over even with the engine dead.
Another wakeup call for me is what seems to be a generally accepted "safe flying practices" by the pilot - flying parallel to the runway behind a seemingly reasonable deadline, yet it's no help and doesn't give anybody time to react. I doubt sounding a horn would have helped much here either.
A really tall fence separating the spectators from the flying activity is about the only preventive measure I can see helping here.
I don't have the answers, but increasing the overall reliabality of the control system we all use sure sounds like a good start.
P.