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Given the following information, calculate the wind velocity:

HDG: 074°T
TAS: 230 kt
Track: 066°T
GS: 242 kt

• A
180°T /35 kt
• B
180°T /40 kt
• C
185°T /35 kt
• D
180°T /30 kt

Refer to figure.
Finding unknown wind:
Four variables must be known: Track, Heading, TAS and GS.

Follow the steps detailed below in order to find unknown wind:
(1) Place the heading (074º) under the true index.
(2) Place the centre of the rotating disk on the value representing the true airspeed (230 kt).
(3) Determine the drift:

• Drift or drift angle, is the angular difference between the track of the aircraft and its heading. Keep in mind, to determine the drift the reference is heading to track.
In this case, Heading is 074º and the Track is 066º, therefore we have 8º left drift.

(4) Place a mark (in this case, the end of the line) at the intersection of the arc representing your GS (242 kt) and the drift (8ºL).
(5) Rotate the disk (azimuth) until the mark is located on the centreline below TAS.
(6) Read wind speed (difference between the centre and mark on the centreline) and direction (under the true index): 180º/35 kt

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• Austro Control