The take-off was given up: the plane never reached 4 m/s

What ArduPilot says:

• Takeoff timeout: N.N m/s speed < 4m/s

TKOFF_TIMEOUT is set. After the motor was released for an automatic take-off, the plane has to reach a GPS ground speed of 4 m/s within that many seconds. It did not, so Plane disarmed; in AUTO the mission was also put back to its start. The number in the message is the speed it had.

What to do, most likely first

1. The plane could not move: held back, nose in the grass, a wheel blocked.

   FixClear the way and arm again.

2. The motor did not start or gave too little thrust.

   CheckIn the log, the throttle output rose after “Triggered AUTO” and the speed stayed near zero.

   FixFind it on the bench before the next attempt: battery, ESC wiring, propeller direction, and TKOFF_THR_MAX or THR_MAX not set too low.

3. TKOFF_TIMEOUT is shorter than a heavy plane needs to get rolling.

   FixGive it a few seconds more than the plane takes to reach 4 m/s on your runway.

Parameters to look at