Another quadcopter crash today. I was just hovering in my garden and it randomly flew into a fence. All four (carbon fiber reinforced) propellers broken, two motor mounts bent and a leg snapped.
Looking at the telemetry logs (which I happen to have as I had my laptop connected at the time) it seems the GPS suddenly reported the position wrong by a couple of hundred metres and the geofencing feature kicked in and it tried to return to launch. More investigation needed though.
I think I might change the fail safe to just auto-land, rather than RTL.
I may also do a complete rebuild and see if I can take the opportunity to make my quadcopter lighter and bit more agile.
Actually, the GPS didn’t suddenly report a wrong position – and in fact, arducopter has protection against that exact kind of GPS glitch (it ignores sudden impossible increases in GPS position).
What actually happened is the GPS position slowly drifted away from where it really was, avoiding the arducopter glitch detection, until it went outside my configured geofence distance. At that point, it went into failsafe mode and tried to fly where it thought home was (RTL – return to land).
So, I’ve changed the failsafe mode from RTL to just “land” for now and am investigating the GPS problem (though I was at the bottom of my garden which has poor GPS reception).