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Old 29th Jun 2012, 14:24
  #100 (permalink)  
keith williams
Join Date: Jan 2011
Location: England
Posts: 643
To solve this type of problem using the CRP5:

a. No heading is specified so select one at random, 000 degrees for example.

b. Set the high-speed slide with the centre dot at 240 kts.

c. The question specifies a +45 wind component. This means a 45 kt tailwind component. This means that the ground speed is 240 TAS + 45 kts = 285 kts.

d. The question also specifies 150 left drift. So draw a cross where the 15 degrees left drift line crosses the 285 kt arc.

e. With 15 degrees left drift the track is 345 degrees. So the reverse track is 165 degrees.

f. Rotate window to align 165 degrees with true heading index.

g. The cross now indicates 19 degrees right drift. Align the 165 degrees track with 19 degrees right drift. The cross now indicates 15 degrees right drift. Align 165 degrees with 15 degrees right drift. The cross now indicates 16 degrees right drift. Align 165 degrees with 16 degrees right drift. Both the cross now indicates Move and the outer scale now indicate 16 degrees right drift, so the drift is balanced.

h. The cross is now on an arc 65 kts below the centre dot. The wind component was a headwind during the outward leg so it must be a tailwind during the return leg This means that the wind component is -65 kts.

There are quicker ways of doing the job (I saw one once here in PPRuNe but I can't remember what it was), but the above is the method described in the CRP 5 instruction sheet.

Last edited by keith williams; 29th Jun 2012 at 14:28.
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