The aircraft did not reach flying speed in the time allowed

What ArduPilot says:

• Transition failed, exceeded time limit

A transition (from hovering to flying on the wing) waits on the lift motors until the airspeed is above AIRSPEED_MIN. That wait has lasted longer than Q_TRANS_FAIL seconds (0, the default, means no limit). What follows is set by Q_TRANS_FAIL_ACT: 0 switches to QLAND (the default), 1 to QRTL, -1 only warns and keeps waiting. A tiltrotor with Q_OPTIONS bit 19 set and a ground speed above half of AIRSPEED_MIN finishes the transition instead.

What to do, most likely first

1. The forward motor gives too little thrust, or none.

   CheckIn the log, look at the forward throttle output during the wait and at the ground speed: full throttle with no gain in speed is a motor, propeller or battery problem; no throttle is a set-up problem (the output's SERVOn_FUNCTION must be 70).

   FixOn the bench, props off, check that the forward motor follows the throttle in MANUAL and turns the right way; then that its propeller is not mounted backwards and that THR_MAX is not holding it back.

2. The airspeed sensor reads too low, so the target is never seen as reached.

   CheckCompare airspeed with ground speed in the log.

   FixRepair the tubing and calibrate the sensor.

3. Assistance never stops: the wait ends only when the airspeed is above AIRSPEED_MIN and no assistance is active.

   CheckLook for “QAssist: Force enabled” (the QAssist switch held high), a Q_ASSIST_SPEED above AIRSPEED_MIN, or a transition flown below Q_ASSIST_ALT.

   FixPut the QAssist switch in the middle, set Q_ASSIST_SPEED below AIRSPEED_MIN, and transition above Q_ASSIST_ALT.

4. Q_TRANS_FAIL is shorter than this aircraft needs on an ordinary day.

   CheckIn earlier logs, measure the time from “Transition started” to “Transition airspeed reached”.

   FixSet Q_TRANS_FAIL to about twice that time.

Q_OPTIONS bit 19 has an effect on tiltrotors only, whatever its description says: on any other QuadPlane the outcome is always Q_TRANS_FAIL_ACT.

Parameters to look at