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AC compass swung : latitude only ?

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  • AC compass swung : latitude only ?

    Good afternoon,

    In navigation section, it is mentionned that and Aircraft's compass must be swung after a change of theatre of operations which leads to a large change of magnetic latitude.
    I fail to understand why the compass should not be swung after a large change of magnetic longitude.
    Since, as I understood, the angle between isogonic lines and meridians can vary a lot depending on location.

    If anyone would be kind enough to enlight me...

    Many thanks !

  • #2
    Hello Matj,

    I'm a student so don't trust me 100%,
    Compass swing tries to reduce and measure the gap between Magnetic and Compass heading, the so-called Deviation.
    Deviation depends on magnetic latitude (changes in dip angle), heading, aircraft equipment etc...

    Isogonic and agonic lines are a matter of Variation, that is the difference between True and Magnetic.


    • #3
      I see, so the change of dip angle, which occurs with a change of latitude, is the key point here.
      Thanks a lot !