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An aircraft departs at 02:43 LMT from an airport located on the 160°E meridian and after a 3-hour flight reaches at a destination airport located on the 170°W meridian. What will be the Local Mean Time on landing at the destination aerodrome?
  • A

    07:43

  • B
    05:43
  • C
    16:43
  • D
    19:03

At the Equator arc, and therefore longitude, can be directly related to distance. Arc, and therefore longitude, can also be related to time. As the mean Sun appears to travel 360º in 24 hours, we can get the following Arc-to-Time conversions:

  • 360º = 24 hours
  • 15º = 1 hour
  • 1º = 4 minutes
  • 1' = 4 seconds

For this question, the Arc-to-Time conversion is based on the Change of Longitude between the two airports.

The Change of Longitude between the two airports is: 160°E + 170°W = 330°. (''Different Hemispheres-Add').

So, the Change of Longitude 330° corresponds to: 330º / 15º = 22 hr.

Thus, when taking-off from the departure airport, the LMT at destination will be: 02:43 LMT - 22 hr = 04:43 LMT of the previous day (The Earth rotates Eastwards).

Since, the flight lasts for 3 hours, the LMT on landing will be: 04:43 LMT + 3 hr = 07:43 LMT.

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