The airspeed for lift-motor assistance has not been chosen

What ArduPilot says:

• PreArm: Q_ASSIST_SPEED is not set

Q_ASSIST_SPEED is 0, as it is on a new QuadPlane. It is the airspeed below which, in a fixed-wing mode, the lift motors start by themselves to hold the aircraft up before it stalls (“assistance”). At 0 or below, all assistance is off: Q_ASSIST_ALT and Q_ASSIST_ANGLE do nothing either. ArduPilot will not arm until you choose a value; tailsitters (aircraft that take off standing on their tail) are exempt.

What to do, most likely first

1. The parameter was never set on this aircraft.

   FixSet Q_ASSIST_SPEED below the slowest speed you fly on the wing: about 3 m/s under AIRSPEED_MIN with an airspeed sensor, 5 m/s under without one. Keep it below AIRSPEED_MIN, or the lift motors will keep cutting in during normal flight.

2. The parameters were reset, or loaded from a file that leaves Q_ASSIST_SPEED out.

   CheckOther settings back at their defaults as well point to a reset.

   FixLoad your saved parameter file again, or set the value as above.

-1 also passes this check: it keeps speed, altitude and angle assistance off except during a transition. Choose it only knowing that a stall in a fixed-wing mode will then not be caught by the lift motors.

Parameters to look at