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An aircraft is flying from Position A (53°N, 10°35’W) to Position B (53°N, 51°45'E). Its average ground speed is equal to 375 kt. The time difference to UTC is 1 hour for Position A and 4 hours for Position B. Assuming the aircraft arrives at Position B on August 5th, 15:00 ST, what is its time of departure from Position A?
  • A
    August 4th, 06:00 ST
  • B
    August 5th, 04:00 ST
  • C
    August 5th, 14:00 ST
  • D
    August 4th, 16:00 ST

To solve this, we’ll break it down step-by-step:

1. Determine the distance (departure) between A and B:

Both positions are at 53°N, along a parallel (constant latitude).

Longitude difference:
From 10°35’W to 51°45’E = 10°35' + 51°45' = 62°20' = 62.33°

At 53°N, 1° of longitude ≈ 60 × cos(latitude)
So:
1° ≈ 60 × cos(53°) ≈ 36.11 NM

Thus, total distance (departure) = 62.33 × 36.11 ≈ 2250 NM

2. Calculate time en route:

Groundspeed = 375 kt

Time = Distance / Speed = 2250 / 375 = 6 hours

3. Convert arrival time to UTC:

Arrival at Position B (UTC+4) = August 5th, 15:00 ST

So in UTC: 15:00 - 4:00 = 11:00 UTC

4. Subtract flight time to find departure in UTC:

Departure UTC = 11:00 - 6:00 = 05:00 UTC

5. Convert to Position A local time (UTC-1):

Longitude east, UTC is least
Longitude west, UTC is best

05:00 UTC - 1:00 = 04:00 ST on August 5th

Your Notes (not visible to others)



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