I had to do emergency landing last time (on my 3rd flight), lost power totally. I tried to find the problem, I got huge help from my colleague who remembered a similar issue from the past. It was a cable connection that failed.
The symptoms were quite alarming, the ESC booted up normally, I could even steer the plane. But for any power input the propeller just stuttered. When it happened and I was in the air I did not notice the stuttering since air passing by rotates the propeller even at no power. Just upon the very last moment when I wanted to adjust my gliding angle became it appearent. Quite scary it was.
I checked first if the problem persists. It did persist. Then I replaced my 25A ESC to my helicopter ESC that is 40A. Same problem. This helped to rule out quite a lot of items. The only one remaining was the electric motor. This gave me a bit of headache. I just glued it back to its place since it became loose.
Maybe I broke the connection there, where it is in the fuselage? Hope not. I started to peel away isolation from the contacts that are easy to access. The first one was okay, the second one actually was so broke that when I removed the isolation the connector just falled away. The cable just broke.
I decided to resolder all 3 of them. This item was not done by me, the connectors were on from the factory. Maybe they used some wrong parameters upon soldering, I don’t know. Anyhow during last time when I disconnected the motor and glued it back the cable broke and only that stiff black isolation held it together. At low power there was some current flow there, but after 2 flights and higher current draw the electrical connection got severed and the motor just quit on me. That explains the steering also, since it happens on a different circuit it was unaffected.
Now it is fixed, I tested the motor on the balcony. There was much rejoicing on part of my wife who tried to watch TV
I put some decals on the plane, now it is easier to see it in the air. I shall test this next time when I fly.
Sir Crash a Lot