PreArm error blank

We're trying to arm our plane with ONLY the PreArm check for INS turned on (16, bitmask 4). However, the Pixhawk fails to arm and returns the error:

"APM: PreArm: "


"Got MAVLink msg: COMMAND_ACK {command : 400, result : 4}" When running on MavProxy

Where there is no error following PreArm. 

Pixhawk is running 3.5.2.

We calibrated the Accelerometer

We have the compass disabled (b/c our launch system is slightly magnetic) with:

        Mag_Enable: 0

        Compass_Use: 0

Gyro's look fine (the graphs are ok)

And the Roll/Pitch look fine too. 

Any ideas on what to check? We'd rather not fly with an INS that's not passing checks. 

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  • 100KM

    We had the same issue yesterday, when we started implementing pre arm checks. It went away after doing another 3d accelerometer calibration, but I'm not sure that was the issue. Hope someone can shed light on this.

    • Yup - still have this issue with the newest release no matter if we do accel or mag calibration. Happens no matter if GPS is plugged in or not. 

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