![]() The angular difference between true north and magnetic north at any point on the earth is called variation. The magnetic poles are not in the same places as the true poles however, currently they are close, enabling us to use magnets to navigate around the world. This results in a magnetic North Pole and a magnetic South Pole.įigure 1 The earth has geographical and magnetic north and south poles The earth has a geographical (true) North Pole and a geographical (true) South Pole.Ī magnetic field exists around the earth, produced by the equivalent of a very large bar magnet within the earth (see Figure 1). To turn accurately onto, and maintain, compass headings, compensating for known errors in the magnetic compass. A basic understanding of the causes of compass errors is all that is required. The cause of compass errors is not as important as how to compensate for those errors in flight. If, for any reason, the DI becomes unusable, the pilot will need to be able to turn onto and maintain a compass heading. The magnetic compass displays several errors in its use, most of which the DI eliminates. In using the magnetic compass for navigation purposes there are more considerations than just the turning errors. To be of any value it must be manually aligned with the magnetic compass on a regular basis. The direction indicator ( DI) or directional gyro ( DG) is simply gyro-stabilised and can be set to any heading. It's the only instrument in most light aeroplanes that indicates the correct heading. The magnetic compass is the primary navigation aid for most light aeroplanes. ![]()
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