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Given the following information, what time deviation will be encountered on the leg?

Reference leg time on the flight plan: 17 minutes
Leg track: 090°
Leg distance: 100 NM
TAS: 345 kt
Wind: 065°/50 kt

  • A
    A delay of 3 minutes.
  • B
    A delay of 1 minute.
  • C
    An advance of 2 minutes.
  • D
    No delay.

Refer to figure.
Solving from Heading (HDG) & Ground Speed (GS), knowing WV, TAS and required track.

  1. Set wind direction to 065º under the "TRUE HEADING" index at the top.
  2. Set the center point on the True Airspeed (TAS) of 345 kt.
  3. Mark the wind velocity 50 kt down from the centre point.
  4. Initially, set the True Track to 090º under the "TRUE HEADING" index.
  5. Note that this heading would result in 4ºR drift and a track of 094º.
  6. Reduce the heading value under the index until the heading plus the drift gives a track of 090º. This occurs at a heading of 086º with 3ºR drift.
  7. The groundspeed for this track is approximately 300 kt.
Actual Ground Speed has been calculate above - 300 kt. We can now calculate our actual Flight Time:
  • Actual Flight Time = Distance / Ground Speed = 100 NM / 300 kt = 20 min
Time Deviation will be the difference between the planned flight time and the actual flight time:
  • 20 min - 17 min = 3 min delay

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