| Marc Ramsey 2007-05-30, 3:33 pm |
| Robert Peffers. wrote:
> Sorry to disillusion you but ships, aircraft compasses are only made
> possible due to the vehicles being degaussed, (demagnetised), and the
> vehicle's natural magnetism neutralised with magnets. Not only that but they
> use gyroscopes to assure the compass points to true North instead of the
> magnetic North than actually moves around a bit. They are also mounted on
> gimbals inside a binnacle.
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
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