Toward the end of the video you can see the crash. The plane is trying to follow a runway beam but winds up oscillating back and forth and eventually tip stalls. The only thing that saved me from ending up on the roof of the barn was accidentally flipping on the autopilot for 1/4 of a second as I was in a panic flipping every switch.
My beamfollow is what I suspect caused the crash. It works like this:
1) The "beam" is created and basically defines a path to follow. It is assigned a bearing.
2) I get the distance from the aircraft to the beam. 30m out the bearing command is perpendicular to the beam. As the aircraft gets nearer and nearer, the bearing command converges to the actual beam bearing
3) The aircraft follows the beam bearing by feeding the bearing error into the bank command (The aircraft simply banks toward the bearing)
If the aircraft is going decently fast, there aren't any issues. But something oscillates when I go slow, and especially when I just hover in the wind making no progress as in this video.
So the two bugs are:
1) Beamfollow oscillations induced by low airspeed
2) Altitude was lost making all the turns, making recovery impossible.
3) Probably flying 30 feet above the treetops in gusty winds made for all sorts of funky air currents.
I've learned 2 things from all this:
1) Don't ignore strange behavior. It WILL happen near the ground one day.
2) FAILSAFE MODES! Plane should recognize dangerously low altitudes or oscillations and enter a wings level climb and alert the user.
The damage? Stripped aileron servo gears, Cracked left aileron, busted pitot tube, chipped prop, and a few cracks on the fuse. She'll fly again in a few weeks!
