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As the INS position of the departure aerodrome, coordinates 35°32.7'N 139°46.3'W are input instead of 35°32.7'N 139°46.3'E. What will be the longitude value shown on the INS when the aircraft subsequently passes point 52°N 180°W?
  • A
    099°32,6'E
  • B
    080°27,4'E
  • C
    080°27,4'W
  • D
    099°32,6'W

Refer to figure.

Actual Position: 139º46,3'E
However, a different position is inserted in the IRS: 139º46,3'W
The aircraft will fly towards 180ºE/W, which equals a Longitude Change = 180º - 139º46,3º = 40º13'42''

  • The IRS position will experience the same longitude change, but from the initial position entered in the IRS:
    Therefore, the new IRS position is: 139º46,3'W - 40º13'40'' = 99º32'40''W

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