Compass Disk Compensating Disk

During the Second World War all major German airports were provided with a compensating disk to be able to calibrate the compass on the aircraft. This compared the compass in the aircraft with the direction of the compass ring of the compensating disk.
The aircraft was placed on the compensating disk, then the aircraft was pointed north and the compass was adjusted. Other checks were then carried out on the compass on the aircraft.

There are different compensating discs. One is located at Gilze-Rijen Air Base and has since become a protected monument for military cultural heritage. There was also one present at Deelen airport.

The construction consisted of a concrete construction (without reinforcing steel) with a completely wooden rotating construction. The ball bearings were made of glass. Metal was not used to not disturb the compass.

The aircraft was placed on this in flight position, with the engines running, after which the compass on board could be calibrated in as real a flight conditions as possible.

Later, newer types were built that could be made simpler, but worked in the same way. These compensating discs are still present in the Netherlands on an air base Twenthe and Deelen airbase at Schaarsbergen.

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Source

• Text: Alex Ossel
• Photos: Maarten Scholtens