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A ground feature was observed on a relative bearing of 315° and 3 min later on a relative bearing of 270°. The W/V is calm; aircraft GS 180 kts. What is the minimum distance between the aircraft and the ground feature?
  • A
    9 NM
  • B
    12 NM
  • C
    6 NM
  • D
    3 NM

Distance1 flown in 3 minutes = 180 x 3 / 60 = 9 NM
Relative bearing at first position: 315˚
thereafter angle in the triangle at airplane location at old position = 45˚

Relative bearing after three minutes : 270˚
Thereafter angle in the triangle at airplane location after three minutes = 90˚

Difference in bearings = 45˚
Thereafter angle in the triangle at NDB location = 45˚

As we have triangle with 2 angles of 45˚ so we have isosceles triangle.
Thereafter distance flown in 3 minutes (9 NM) equal distance from airplane new location to NDB = 9 NM

Correct Answer: 9 NM

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