I have an APM 2.6 and loaded the 3.1.5 Firmware for my H-Quad on it.
Everything worked fine. Since yesterday. I wanted to start my Quad and first it made a backflip on the ground. I haven’t changed anything. I have flashed it again. Because I did not want to damage the quad I held it and gave a little bit throttle. For first it was stable but then it seemed that the pitch gyro was reversed. I tilt the quad forward and it tilts automatically more so that it flips. But it is just with that one. If I tilt it right it stabilze itself. In the missionplanner it gets shown correctly. I have made a reset of the APM and loaded the firmware again on it. I checked the wires. I can’t find a solution for the problem.
I would be interrested if somebody also has/had this problem and how they could fix it.
I don’t know what to do 
(sorry for my english, I’m Austrian)
Hi, from the sounds of it your radio control might have mixing enabled, or a channel is reversed. However you said that everything used to be working, did you fly correctly it before?
To check this you should connect your APM to your PC via mission planner and then go to the radio calibration screen, then if you move your throttle stock you should only see the throttle channel moving, similar with the other sticks, only one should move at a time. If this is the case you might of accidently changes the model on your radio. However if its just one channel that is causing the problem then you might have to reverse the channel on your RC radio. If you let me know what radio you are using I might be able to help you do this if you dont know.
I am using the spektrum dx8. The days before it flews really great but then it went crazy. I haven’t changed anything before. I have also checked the 3,3V regulator and it is ok.
Its kind of hard to guess what the problem could be but after reading your post again I see that when you pitch the quad by hand it does not seem to recover ratehr than when using your radio so it might not be a radio issue.
Some things you should check:
- Make sure your motors are connected correctly, but since you said that you have not changed anything this will also probably not be the case
- I suggest you check the APM orientation is set correctly
