The automatic VTOL takeoff took too long and was abandoned

What ArduPilot says:

• Failed to complete takeoff within time limit

In AUTO a VTOL takeoff did not reach its height in the time allowed, and the aircraft switched to QLAND. The limit is the expected climb time multiplied by Q_TKOFF_FAIL_SCL (0, the default, means no limit), and never less than 5 s. The expected time is worked out from the takeoff height, Q_PILOT_SPD_UP (2.5 m/s by default) and Q_PILOT_ACCEL_Z; the clock starts at arming.

What to do, most likely first

1. The lift motors cannot climb at the speed asked: the aircraft is too heavy, the battery is weak, or a motor or propeller is not giving its thrust.

   CheckIn the log: lift-motor throttle near maximum and a climb rate well under the target.

   FixFind the lost thrust before another takeoff: the weight, the battery's state and its voltage under load, each motor and propeller.

2. Q_WP_SPEED_UP is lower than Q_PILOT_SPD_UP: the takeoff climbs at Q_WP_SPEED_UP (in cm/s), but the time limit is worked out from Q_PILOT_SPD_UP (in m/s).

   CheckCompare the two values: 250 in the first is the same speed as 2.5 in the second.

   FixMake them the same speed, or set Q_TKOFF_FAIL_SCL above the ratio between them.

3. A low takeoff height plus a delay before the motors spin up (Q_OPTIONS bit 11 waits 2 s after arming) uses up the 5 s minimum.

   FixTake off to a greater height, or raise Q_TKOFF_FAIL_SCL so that the limit covers the delay.

Parameters to look at