Refer to figures.

Convert CAS into TAS (CRP5 method):

(1) In the "Airspeed" window, align 41 000 ft with ISA OAT = -56.5ºC;
(2) On the inner arc, look for CAS 237 kt and read a result of approximately 480 kt TAS;
(3) Using the "COMP. CORR." window apply the compressibility correction: Move the disc approx. (480 / 100) - 3 = 1.8 to the left. Repeat step (2) and find the result of approx. 460 kt TAS.

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Calculate the Ground Speed:

Ground Speed = TAS - Headwind
Ground Speed = TAS + Tailwind
Ground Speed = 460 kt + 25 kt = 485 kt

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Determine True headind and True Track:

To get True heading/track from magnetic => add easterly variation or subtract a westerly variation.

• In this case:
  True Heading/Track = Magnetic Heading/Track - Westerly variation

  True Heading = 130º - 40º = 090º
  True Track = 122º - 40º = 082º

There is an 8º difference between the track and the heading, which means that there's a 8 degrees drift. Track is lower than heading, meaning it's a left drift (8ºL).

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Determine W/V (CRP5 method):

1. Set True Heading (090ºT) under "True Index"
2. Place centre dot over TAS (460 kts)
3. Mark the point where drift (8ºL) and GS (485 kt) meet.
4. Rotate the wind computer until mark is below TAS.
5. Check wind direction under "True Index" (197º)
6. Count down from TAS to obtain wind speed (460 - 390 = 70 kt)

=> W/V = 197º/70 kt