Heavy quad, 12S power, PH2.1, AC3.5.3.
In every flight i have strange behavior after landing, copter not disarming and periodically pulsing motors. I can disarm it only using emergency stop. Log shows rapidly changing states from "Land complete" to "Not landed".
I can't look at the logs at work. But I an suggest three things.
First, this is almost always caused by bad vibration, so have a look at the VIBE logs. http://ardupilot.org/copter/docs/common-measuring-vibration.html
PILOT_THR_BHVshould be 4 or 6. If you have this set for anything else, it won't disarm on landing detection, and will instead wait for the disarm timer.
GND_EFFECT_COMPshould be enabled.
Vibrations are quite high inflight, but not critical. At the landing phase VibeZ is below 3.
Thanks, i have missed this parameter, will try set 4 next time. But i never touched it before and never had any problems.
Setting parameter PILOT_THR_BHV to 4 solves the problem, thank you!