I recently had my compass swung and made my first flight this weekend since the work was done. It appears to be reading accurately on the ground with all radios, lights, electronics powered up. I flew from Grand Prairie to San Angelo (west southwesterly) and it appeared to be reasonably accurate in flight. On the return trip later the same day the compass indicated about 30-35 degrees all the way home. That should have been 74 degrees minus a few for the northerly winds...say 65 degrees for discussion. Any idea what's happening here? I’m assuming some sort of magnetized airframe maybe, but why would it not show up on the ground and not show up in flight for a few hours.
My airplane has original panel configuration, KX-155s, Garmin 327 xpndr, Garmin 796...nothing new or unusual. IPad mini with a cooling deck plugged into cigar lighter. The only electrical work I have done in the last year is to put in a 406 ELT, put in a tail beacon ADS-B, put in LED nav/strobes, wire up the pitot heat, put in an electric step motor. Nav lights stay on all the time since it powers the ADS-B.
Thanks for any insight.