I was testing a new vibration damper for the camera gimbal of my little 6" prop "fun flyer". This little beast has been so much fun to fly because it behaves pretty much as you would expect - always. It is also extremely fast.
It would climb out of sight in about 12 seconds. I figure that is about 500-600 feet, giving it a climb rate of over 2500' / minute.
It would also go "sideways" faster than anything I have ever seen fly. The park that I normally go to is simply not big enough to gauge its true speed, since it will traverse the park in a few seconds. With a different quad, I once had a greyhound (dog) race me across that same park. They were 'even'. But that quad wasn't nearly as fast as little one. The craft has a KK2 controller. KK2's are easy to set up, easy to fly, and - since they don't have a lot of extra features like GPS, autonomous flight, or even a magnetometer, generally more reliable.
Controllers like APMs will go NUTS if they loose the signal from the compass, or if you accidentally mount the compass upside down, so it reads North and South correctly, but East and West backwards. I have done this. The craft would fly perfectly if you flew directly North or directly South. But if you tried to fly more than a few degrees off the N-S axis, it would veer one way or the other..
Back to my story - I was testing the gimbal vibration damper on my street. I did't want to take the time to drive to the nearby park for my test. After all, I only wanted to see whether or not there was "Jello" in the video that came from the camera. I ran up the street and down the street, then I took it up fairly high - probably about 200'. It was hovering at a steady altitude, then I started bringing it down. Not real fast, but not real slow, either. All of the sudden, it flipped over and started falling. I hit full throttle, thinking that it would have a better chance of catching itself if the props had some RPM. I heard the motors wind up - then it flipped again! This happened about 3 times
And then it hit!
Hard pavement. Sad. Big mess. 4 Broken props. 3 broken motors. Broken frame. Sad. Broken gimbal .1 broken gimbal motor (of 2).Broken SJCAM HD camera. Bent (and therefore useless) battery. Cracked case on the radio receiver. Sad. It would have been in better shape if a car had run over it. Maybe 2 or 3 cars. I was really sad! The only other thing that could have created more damage is if the wiring had shorted and the whole quad burned up in a fireball fueled by lithium.
So, I salvaged one motor, one gimbal motor and the main wiring harness - and the controller (amazingly, the only damage was 12 bent connector pins (which I fixed with a needle-nosed pliers). And I resoldered two tiny wires and used a bit of epoxy and fixed the SJCAM camera. I used more of that same epoxy to fix the radio receiver case.
The rest of the metal and plastic went in the trash.
I ordered a new frame ($8.99 from HK's US west warehouse) and a new gimbal and one gimbal motor. Fortunately, I had 3 new (or slightly used) "main" motors that I can use to rebuild the craft.
I should have a complete replacement running by next weekend.
And I STILL don't know what happened.