AUTO will not arm: the mission is not at a VTOL takeoff

What ArduPilot says:

• not in VTOL takeoff

Q_OPTIONS bit 18 (ARMVTOL) is set: the aircraft may be armed only in a Q mode, or in AUTO while the mission's current item is a VTOL takeoff. It is in AUTO and the current item is something else, so it would not lift off on its lift motors. A NAV_TAKEOFF item counts as a VTOL takeoff unless Q_OPTIONS bit 1 (allow fixed-wing takeoff) is set.

What to do, most likely first

1. The mission does not begin with a takeoff item, or no mission is loaded.

   CheckOpen the mission: item 1 should be VTOL_TAKEOFF (or NAV_TAKEOFF).

   FixAdd a VTOL_TAKEOFF as the first item and write the mission to the aircraft again.

2. The mission is being resumed part-way: MIS_RESTART is 0 and the current item is left from the last flight.

   CheckThe ground station shows which mission item is current.

   FixMake the first item current (or restart the mission) before arming; MIS_RESTART 1 starts from the beginning every time AUTO is entered.

3. Q_OPTIONS bit 1 is set, so NAV_TAKEOFF means a fixed-wing takeoff.

   FixUse a VTOL_TAKEOFF item for a vertical takeoff, or arm in a Q mode.

A tailsitter with Q_TAILSIT_ENABLE 2 sets bit 18 by itself at every start. In the other modes the same rule reads “not Q mode”. The 4.6 parameter list describes bit 18 as “arm only in VTOL or AUTO modes”; the code has the takeoff condition in 4.6 too.

Parameters to look at

Where to do it:Mission Energy Check