The aircraft has detected that it is on the ground

What ArduPilot says:

• Land complete
• Mission continue

Sent in the last part of a VTOL landing when the lift motors have been at their lowest output for 5 s and the height estimate has not moved by more than Q_LAND_ALTCHG (0.2 m by default) for 4 s. The aircraft then disarms. In AUTO with MIS_OPTIONS bit 2 (continue after land) it stays armed instead, prints “Mission continue” and goes on to the next mission item.

If the aircraft sits on the ground with its motors turning and this line does not come, the height estimate is still moving by more than Q_LAND_ALTCHG, often a barometer disturbed by the propeller wash. Shield the barometer first; only then raise Q_LAND_ALTCHG a little (0.6 at most).

Parameters to look at