There's an excellent discussion at http://www.faa-aircraft-certification.com/compass-swing-requirements.html

The quoted regs say (to my surprise) that the calibration has to be done in level flight, and the calibration card has to state whether the calibration applies with radios on or off (seems like a very dated reg!)

I used a compass rose per Garmin 1000 installation manual to calibrate my magnetometer.  EXPERIENCE NOTE!  Rebar in concrete was enough to defeat the calibration process, the Garmin sent up a red flag and nothing worked until I went to a compass rose on asphalt.

I got my wet compass to within 2 degrees and I'm an illegal scum running around with no calibration card.  Hasn't killed me yet though.

Charley
Legacy 280 hr

On Aug 15, 2013, at 5:34 PM, Greenbacks, UnLtd. wrote:

If you could adjust out all compass error, are you still required to have a correction card posted in the cockpit next to the compass?
Also, is a compass rose of any practical benefit for checking the compass, given given the accuracy of on board GPS units?

Angier Ames
N4ZQ
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