The landing approach was cut short: the aircraft could not hold its speed

What ArduPilot says:

• VTOL pos1 low speed as=N.N at=N.N
• VTOL pos1 thrust loss as=N.N at=N.N

On the wing-borne part of a VTOL landing approach the aircraft got too slow, so ArduPilot switched early to position1, the stage where the lift motors carry it. as is the airspeed, at the threshold: AIRSPEED_MIN minus 2 m/s, or Q_ASSIST_SPEED if that is higher. “low speed”: the airspeed fell below the threshold. “thrust loss”: for 5 s the forward throttle was at THR_MAX while the aircraft sank faster than 0.2 m/s with its airspeed less than 4 m/s above the threshold. Only on QuadPlanes with a separate forward motor.

What to do, most likely first

1. The forward motor, its ESC or its propeller failed, or the battery can no longer feed it.

   CheckIn the log: forward throttle at maximum with falling airspeed, and the battery voltage at that time.

   FixInspect the forward drive after landing. The rest of the way is flown on the lift motors, which costs far more battery: do not extend the flight.

2. The airspeed sensor reads too low.

   CheckCompare airspeed with ground speed in the log.

   FixRepair the tubing and calibrate the sensor.

3. THR_MAX is set so low that full forward throttle cannot hold the approach speed.

   CheckRead THR_MAX, and in the log see whether the forward throttle sat at exactly that value.

   FixSet THR_MAX to what the motor and battery can safely give.

Parameters to look at