2nd compass advisable, or extra trouble?

I now have three helis (2x TRex 500 and 1x TRex 550) flying with Ardupilot. One of the 500s has internal and external compass, and has had no issues to date. The other two only have an external GPS/compass, but have also had no issues.

But my experience of the latter two is limited – maybe 6 flights each – so I’m wondering if I should add another compass to them. I think I read somewhere that having a second compass can cause problems by deviating from the first one, so I’m wondering if overall reliability is improved with a second compass, or not.

A second compass is a form of redundancy, so there is that aspect.
You can even use the flight controllers internal compass if it is calibrated correctly. You can perform a flight with plenty of yaw and use MagFit to calculate updated compass settings and even the Mot/Bat settings.
If the internal compass is too badly affected by magnetic fields, you could certainly add another if you have the space.

There’s some info on MagFit in the docs, or just upload a .bin log and someone here might be able to check it and send the updated compass values.

Tradheli does not support motBat

Thanks Bill, I did not know that. That is probably a bit annoying :frowning:
Well external compass it is, and far away from battery and motor.

I would take anyone’s help in implementing it. I just don’t know enough about it.

I should have said, the first compass on my 2-compass setup is the FC’s internal compass. I’ve never had any problem calibrating it alongwith the external one. The FCs on my other two helis don’t have internal compasses, hence my question about the desirability of adding a second external one.

Sounds like, with the reliability track record of external compasses, there’s not much to be gained by adding a second one if things are working well at the moment. Is that the generally accepted view?

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