with lots of new snow, I decided to test recovery time needed to stop the fall if motors stopped during the flight.
I did it the way I see this accident to happend. - while in loiter, I took the throttle stick all the way down, for descend - then - switched to stabilize.
Motors stopped, I pushed the throttle up, - apparently 8 meters was not enought to stabilize, and it hit some bushes. The test was a success.
What to learn from this ? - it should be impossible to stop motors in flight ? -a minimum RPM should be maintained from the point of arming, to disarming ?
I do not think I would fly APM if you couldn't turn off the motors. I always want the ability to ditch if I so choose. I have ditched my Raptor 50 before when I lost my tail servo and had an un controlable pyro. It was heading towards stock animals and there was no time to auto. Its just a matter of safety. Perhaps you should have performed your test at 30m+, that would have given you a fair chance for recovery.
MK copters do that... stick all the way down... motors still spinning at very low rpms till disarm
yes, and low RPM spinning props poses no real danger, compared to the free-falling aircraft, anyway
Set #define CUT_MOTORS 1 in your apm_config.h file and your motors will always run at min_throttle when armed.
I accidentally shut off my motors in flights doing exactly what you described. I immediately showed the throttle up full and no harm was done (it was pretty high at the time).
Video of the flight (around 4:03 for motor shutoff):
yes, I allowed mine to roll/pitch beyond 90degree before. It got there really fast, probably due to wind/forward speed or uneven load.
Also - I've been flying is very strong sidewind ( gusts well over >15m/s) - and getting down (to land) in manual mode was dangerously close to motor-off position. (with such strong sidewind, very little throttle is needed.)