Already in air error

[maciejgaleja]

Sometimes, Ardupilot reports that MAV is in air, even though it is on ground. In this state, most of commands is rejected.

• What is the reason of this behaviour?
• Perhaps it only occurs in simulator
• Can our code do anything about it?

[wojctrz]

I made a little bit of research, using SITL simulator, and this is what i found so far:

• The problem occurs only in VTOL (QuadPlane) mode, when arming and trying to takeoff in mode other than GUIDED
• In a conventional quadcopter, some modes (like land) are unarmable - arm command is rejected by MAV. In VTOL frame, modes like QLAND are armable (system don't throw any errors), but trying to takeoff after such an arming ends in failure - the command is rejected with "Already flying - no takeoff" message
• The issue is probably caused by some bug in SITL, but some verification test with real model in the future would be appreciated

Currently, the simplest solution to this issue is just checking the mode before the arming (and changing it, if it is needed)