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MATHEMATICS FOR AIR CREW TRAINEES     45

[[image - drawing showing how to graphically determine drift angle and ground speed]]
FIGURE 55.

(d) Air speed heading vector+wind vector=ground speed track vector (Va+Vw=Vg).
(e) The angle between the ground speed track vector and the north line determines the course or track. The length of the ground speed track vector, according to the scale used, determines the ground speed.
(f) The drift angle is the angle between the air speed heading vector and the ground speed track vector. Since this is a case of left drift, the drift angle of 14° is subtracted from the heading of 56° to obtain the course 42°.
b. Exercises.-(1) On a secret maneuver, the pilot has been ordered to fly on a heading of 90° until further orders. Air speed of the airplane is 180 mph. After 1 hour of flight, motor trouble develops and a landing must be made. He is told over his radio that wind has been 40 mph from 135°. What has been his track and ground speed?
(2) The pilot observes an enemy scouting party. To avoid being seen, he changes his heading (as point "A") and flies on a heading of 315° with air speed 150 mph. If wind is 30 mph from 45°, what will be his new course and ground speed? C=304°, GS=153 Answer.
(3) Because of an error in plotting his course, a pilot finds himself over unfamiliar territory. His air speed has been 160 mph, his

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