My copter was crashed yesterday because of all engines were stopped without any reason. According to the log files the apm receives invalid altitude value from GPS and it looks like it can be an explanation for my accident, but I'm not sure it's a good reason to switch all engines off and fall to the ground. I'll explain everything step by step:
1. I armed my copter and take off in stabilize mode
2. Made several loops in Loiter mode and switch it to RTL mode
3. After arriving I switch it to Alt hold mode
4. After I switched it to stabilize mode and tried increase altitude
5. After reaching ~100 meters all engines were stopped at the same time and it began to fall
6. after about 1.5 or 2 seconds of my attempts to do something all engines were started again
7. I tried to restore its orientation, but it was impossible and it fell on its back
Any Idea what could be a reason of such behavior (last log is attached)?
Had exactly the same with one of the 3.1.2rc's. Luckily this was only hovering 1-2 feet on soft grass, so only one cracked prop. Suspecting the firmware I went back to what was on before (3.1rc7). I hovered very close to the ground and found the APM randomly rebooting. This is I guess what you saw with the APM coming back to live after 1.5-2 seconds. After I disconnected my gimbal (on the same 3s battery) the problem went away. So my conclusion was a bad intermittent power connection to the gimbal that caused the power module/APM to reset. I replaced the power connector to the gimbal hoping this was the root cause. Since then I flew 4 batteries without any issues. Your post makes me nervous.
Thank you for your reply! You know, I also suspecting my 6-pos connector between 3DR Power Module and APM board, but I'm not sure. Now I replace it with a new one and also flew about 6 batteries without any accidents...
same thing happened to me.. after a crash and a rebuild. Been scratching my head for a week and a half on this.. it arms, at 45-50% (the quads' lift off throttle) it lifts off for a couple of inches and then all the motors shut down at the same time. It happens everytime. FINALLY, a few minutes ago, I decided to calibrate the compass and accelerometer. Son of a gun.. it worked!
Moral lesson.. after each crash, calibrate!