INFORMATION:
Compass swinging was a rather time-consuming task. with a fitter sitting in the cockpit and the aircraft in flight-ready configuration, the engine was started and then the platform aligned so that the aircraft faced the 0 degree (north) heading. Then the fitter would check if the aircraft magnetic compass was in alignment with the magnetic north. If not, he would adjust the compensator screws with a non-magnetic screwdriver until the compass read 0 degrees. Then the procedure would be repeated for the 90-degree (east), 180 (south) and 270-degree (west) headings.