I had what I thought was a strange crash today...
I was testing some new additions (fpv camera, 5.8 transmitter, jdioboard, LEDs) to my hexacopter when I performed an action I have done several times in the past: At a decent altitude while in stabilize mode cut the throttle to 0 then watch the copter pitch over and fall for a few feet then stab the throttle which normally results in the copter snapping back into shape. This has been a nice demonstration in the past for how awesome the APM is :-)
Today when I tried this (which was of course right after I said "Watch this" ;-) I heard a screaming motor (same as when after crashing a motor is still trying to turn when the prop is stuck) and my copter fell to the earth like a brick <sigh> I left the throttle up for a bit but tried to cut it back to 0 before it hit the ground (hard to say since it did happen quickly).
The damage does not appear to be that bad. The camera and GPS ejected but look OK as far as a visual inspection goes. Some cabling is hosed, 1 set of landing gear is toast, my CD spindle cover is shattered, and several supports for the stack are broken. My props were already pretty rough (been waiting to install new ones until it did not fly happily) so the one of those that snapped is no great loss. The motors all still seem fine except one which is full of dirt. The arms still look fine as does the APM <exhale> and other electronics. The battery still works but at least needs to be wrapped. Could have been worse...could have been better.
I am curious to know what made the motors scream...surely going from 0 RPM to full throttle while at an odd angle would not do it? I think part of the problem was the battery dropped down to 8V when I stabbed the throttle. My guess is this resulted in insufficient prop speed to do anything. The battery was fine beforehand and I had not received any alerts from Mission Planner yet. Previous testing shows I get over 10 minutes before the first alert from Mission Planner under normal conditions. The new gear added less than 10 ounces to the all-up weight (which was 4lbs 10.6oz FWIW).
If anyone sees anything notable in my logs please sing out!
Thanks :-)
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I am happy to report after a couple hours of work it is nigh ready to go aloft again :-) The motors were fine along with the GPS and other electronics (all reports in via telemetry and gives reasonable values). Now I need to sort out landing gear (which the 3DR ones were not on back order or I would already have spares ;-) and the little plastic stand-off things that support the stack. Does anyone know what the official name for those are? The little black plastic "posts" that have a threaded screw on one end and a threaded hole on the other...