Yesterday, I dodged not one, but two bullets while flying my F550 hexacopter.
The first close call happened as I was flying near
Vimperk. I flew to about 100 m AGL to gain a view of the town. After short while filming I decided to return. And guess what, I couldn't find my starting place no matter what I tried. Video link got quite spotty and I thought I am above myself, but in fact I was behind some trees and not very close. I tried to recognize the terrain (meadows with groves) but I couldn't no matter how hard I tried. Eventually, I decided that it's better to land at unknown place than to fall while searching fruitlessly. Fortunately, the craft did not lose the control link (that would trigger RTH which I don't think would work as I suspect that GPS fix was lost). After about 15-30 minutes I found the copter intact in the middle of a meadow. Video from the camera eventually showed, that the landing was fairly smooth, if bit fast.
The second close call happened on different place, where I decided to finish off the same battery from the previous flight. It was showing 14.75 V (4S battery) or so, so I thought I can eke out a minute or two. Bad decision. After I reached my target some 300 m away I noticed that my main voltage is 9 V! Before I could do anything, the copter started to descend rapidly. Fortunately, I was just a few metres above the ground, but even then the impact was more violent then in my previous screw up. The landing gear legs snapped on one side, but apparently gimbal did not hit the ground. So it seems nothing but the landing gear broke. Of course, now I need to order new one, before I fly again.
Lessons learned:
- on unfamiliar location don't just fly away, but look back and find some orientation landmarks that will help you find your way back
- make sure you're receiving GPS coordinates in telemetry; make sure your transmitter is displaying all pertinent navigational data: AGL height, ground range, distance!
- have alarm for low voltage that triggers at about 13 V
Edit: Video of the above is
available.