Shirley if you want to degauss a whole airframe then you must remove all instrumentation that uses any sort of magnetic sensor or driver - and in particular the compass - otherwise you'll demagnetise the lot. Radio speakers and headsets 'may' survive but varios, moving coil meters and similar will likely be irrevocably stuffed. I'm in the process of scheming a giant set of helmholtz coils to degauss a K13 [classic steel tube glider] fuselage to get rid of gross compass errors, although for one of the club fleet this was more easily achieved by moving the radio speaker from it's mount next to the compass
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Jim