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Instructions to Swing a Compass

A compass uses the magnetism of the earth to determine direction, but nearby objects can throw off that magnetic reading. This is often a problem on aircraft, which need to use compasses but have a lot of metal parts and electronics. Before departing, you will need to "swing" your compass so that you can find out just how much deviation there is between your compass' reading and true north.

Instructions

- 1
  Align the aircraft so that it's pointing due north, either by using a calibrated mater compass or by positioning the aircraft on "compass rose" -- a large compass painted on the tarmac.
- 2
  Write down the difference between your compass reading and the correct reading. For example, if your compass displays a reading of 007°15', and you are pointed due north (which should cause the compass to read 000°00'), your compass is off by 007°15'.
- 3
  Point the plane due east and measure your compass' reading against the true course of 090°00'.
- 4
  Point the plane south (180°00') and west (270°00') as well, and keep rotating until you get a consistent difference between your compass and the true course. Write down this figure and use it for readings while in flight to correct your compass to the true course.

Aviation