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Given:

Course A to B: 088° T
Distance: 1250 NM
Mean TAS: 330 kt
Mean W/V: 340°/60 kt

The time from A to the PET between A and B is

  • A
    1 hour 54 minutes
  • B
    1 hour 43 minutes
  • C
    2 hours 02 minutes
  • D
    1 hour 39 minutes

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

1. Set wind direction to 340º under the "TRUE HEADING" index at the top.
2. Set the center point on the True Airspeed (TAS) of 330 kt.
3. Mark the wind velocity 60 kt down from the centre point.
4. Initially, set the True Track under the "TRUE HEADING" index.

  • GS home: 268º
5. Note that this heading would result in 11ºL drift and a track of 257º.
6. Reduce the heading value under the index until the heading minus the drift gives a track of 268º. This occurs at a heading of 279º with 10ºL drift.
7. The groundspeed for this track is approximately 310 kt.
  • GS out: 088º

5. Note that this heading would result in 10ºR drift and a track of 098º.
6. Reduce the heading value under the index until the heading plus the drift gives a track of 088º. This occurs at a heading of 078º with 10ºR drift.
7. The groundspeed for this track is approximately 345 kt.


We can now apply the formulas:
Distance to PET = (GS home x Distance) / (GS out + GS home)
Distance to PET = (310 x 1250) / (345 + 310)
Distance to PET = 591.6 NM

Time to PET = Distance to PET / GS out
Time to PET = 591.6 NM / 345 kt = 1 h 43 min

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