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Old 29th Jul 2009, 22:17
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2close
 
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At that speed:

For heading:
Max Drift = 6 degrees of into wind correction per 10 knots of windspeed
Then for every 20 degrees off heading, subtract 1/4 of the correction, i.e. up to 20 degrees off the nose / tail = 1/4, 20 - 40 degrees = 1/2, 40 - 60 = 3/4, 60 + = ALL

For speed:
For every 20 degrees off heading or reciprocal, add or subtract 1/4 of the wind speed,
i.e. up to 20 degrees off the nose / tail = ALL, 20 - 40 degrees = 3/4, 40 - 60 = 1/2, 60 + = 1/4

(Some use 0-15, 15-30, 30-45, etc. but I find that the 20's work just as well with minimal difference and are easier for people to cope with the mental gymnastics)


In the above situation, I'd have corrected 7 degrees into wind and flown 83 degrees True with 2 - 3 knots on the TAS to give GS ~ 90 knots - a very convenient 1.5 NM per minute.

These are only rules of thumb but are very quick to do in your head on the fly and accurate enough for practical flying - a 2 degree correction error translates into only a 2 NM off-track error over 60 NM and can be easily monitored in flight.

During the CPL my instructor insisted on all pre-flight and in-flight calculations being done on Max Drift with no use of CRP. It certainly helped me and has helped my students since.
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