The gyros could not find their zero at power-on

What ArduPilot says:

• PreArm: Gyros not calibrated

At power-on each gyro measures its zero while the aircraft stands still: two half-second averages in a row must agree within 0.1°/s, and ArduPilot keeps trying for up to 30 s. For at least one gyro they never agreed. With that start-up calibration switched off (INS_GYR_CAL 0) the same message appears when the gyro found is not the one the saved calibration belongs to, or when a gyro whose ID is still saved in INS_GYR_ID, INS_GYR2_ID or INS_GYR3_ID is missing.

What to do, most likely first

1. The aircraft was moving in the first seconds after power-on: held in the hand, rocked by wind, on a boat or a running vehicle.

   CheckReboot with the aircraft on firm ground and do not touch it: the message is gone.

   FixPlug the battery in, then leave the aircraft alone until the start-up lights or tones have finished.

2. Gyro calibration at start-up is switched off, and the saved calibration does not match the gyros found: new firmware, parameters from another board, or an IMU that did not start.

   CheckINS_GYR_CAL is 0. Count the “IMU” lines in the start-up messages and compare with how many of INS_GYR_ID, INS_GYR2_ID and INS_GYR3_ID are not 0.

   FixSet INS_GYR_CAL to 1 and reboot standing still: the start-up calibration also stores the IDs of the gyros now present. On a platform that always moves, keep 0 and run the gyro calibration from the ground station once while it is still.

3. One gyro is noisy or faulty and never settles.

   CheckThe message returns at every boot although the aircraft stands perfectly still on firm ground.

   FixReplace the flight controller. A gyro that cannot find its zero on the bench will drift in the air.

Parameters to look at

Where to do it:Setup & Tuning Guide