I’ve just completed a build & attempted test flight of a 3DR quadcopter kit, with Pixhawk controller & GPS, and Futaba S-Bus R\C receiver.
The machine appears correctly set-up and arms properly etc
I’ve been flying model Helis for about 20 years, so my basic control skills are reasonably good.
After a gentle run-up of the motors it will take-off into a low hover and then sit fairly stable for around 30-60 seconds. Pitch and yaw control seems OK at first, but then after a random (<60 seconds) a single motor slows-down suddenly causing a near flip\crash. I’m not sure if there’s also a sudden power increase in the “opposite” motor.
Experimentation has shown that its usually either the front left, or right rear motor that fluctuates, and if the machine is “tethered” the failing motor speeds up again after a very short interval.
I’ve faffed around with checking logs etc, but there doesn’t seem to be any obvious cause (vibration, seems OK, for example) and the GPS\compass\ attitude all seems OK until the suden near-fliop.
In a word: “Help!”