Orientation question - FC and 3DR GPS/Compass


In setting up a plane, I am challenged with getting inconsistent compass errors, after doing the compass calibration.

Here is the setup;

Pixhawk facing forward(North) and rotated/rolled to the left, with all the DF13 plugs facing to the left(West) as the FC is mounted to the right side of the fuse. AHRS orientation selected is 20, ROLL270.

The 3DR GPS/compass M6 puck is mounted 20cm behind the FC, and to the right of the plane centerline, with the arrow on the puck facing forward. The compass orientation selected on 0.

Are the above orientation selections correct? Why am I getting “PreArm: Inconsistent Compasses” message when arming?

Any help or recommendations is greatly appreciated.


Neil, I have had problems with “Inconsistent Compasses” often, especially when my plane used a permanent magnet to secure the canopy. I often fly with all internal compasses disabled, in order to pass the prearm check. (Note: I have also removed the permanent magnets, and used tape/velcro instead) Does disabling your internal compass(es) also allow you to arm successfully?


Thanks for the info.

When you are disabling compasses, and I have seen other threads say compasses are not needed for plane, are you referring compass2, which I believe is internal to the pixhawk? The 3DR pucks have both GPS and compass, which is appearing as compass1 and external compass checkbox is checked.

It seems to be somewhat random, and I have not unchecked either compass to test. What would you suggest disabling/unchecking?


Yes, I uncheck “compass2” which I believe is the internal compass.

I leave both “Use Compass1” and “External Compass” checked in order to use the (external) GPS+Compass.

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Excellent! Thanks again for the info!