Landing detection problem, no disarming

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.

  • Parameter PILOT_THR_BHV should 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.

  • Parameter GND_EFFECT_COMP should be enabled.

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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.

Enabled, check.

Setting parameter PILOT_THR_BHV to 4 solves the problem, thank you!

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As i can see on the full paramater page PILOT_THR_BHV has settings 1 to 4 and not 5&6 included.
Also states that Sprung return radios should be set to 1. Could someone say what 5 and 6 are?
Because while virtual testing with 4 i found that motors shut down long before. My virtual test was to arm with no props, take off (while lifting the quad to 2m) and virtually land, while lowering height when lowering throttle and found that my props would shut down long before “landing”