| Ron Hunter 2007-05-31, 7:33 am |
| Marc Ramsey wrote:
> Robert Peffers. wrote:
>
> This may be partially true of ship compasses, but talking as a pilot and
> aircraft owner:
>
> 1. Aircraft are not de-gaussed.
> 2. Magnetic compasses are a still a primary navigation instrument
> required in most aircraft.
> 3. Courses, headings, wind directions, runways, etc., are in magnetic
> degrees by default.
> 4. The directional gyros in most (but not all) aircraft are periodically
> manually reset to the current reading of the magnetic compass, and
> normally point to magnetic north. Directional gyros are used as
> magnetic compasses are subject to large acceleration errors while turning.
> 5. Aircraft magnetic compasses contain adjustable compensation magnets
> which allow for removal of large errors due to masses of ferrous metal
> in the aircraft. There is always a correction card on the compass which
> the pilot uses to allow for any smaller errors that could not be removed
> with the compensation magnets. Aircraft compasses are calibrated by
> putting the aircraft on a compass rose painted on the tarmac, physically
> rotating the aircraft, and adjusting the compass accordingly.
>
> Marc
The same process is used when installing a good magnetic compass in a
car. There are other types of compasses which are not subject to such
environmental considerations, such as laser types that are set and then
maintain the direction by inertial measurements. Out of the price range
of most compass users, of course.
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