Aeronautical Information Manual

AIM

4/20/23

FIG 7

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Vortex Movement Near Ground

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with Cross Winds

3K Wind

0 (3K - 3K)

(3K + 3K)

Pilots should be alert at all times for possible wake vortex encounters when conducting approach and

landing operations. The pilot is ultimately responsible for maintaining an appropriate interval, and should

consider all available information in positioning the aircraft in the terminal area, to avoid the wake turbulence

created by a preceding aircraft. Test data shows that vortices can rise with the air mass in which they are

embedded. The effects of wind shear can cause vortex flow field “tilting.” In addition, ambient thermal lifting

and orographic effects (rising terrain or tree lines) can cause a vortex flow field to rise and possibly bounce.

A crosswind will decrease the lateral movement of the upwind vortex and increase the movement of the

downwind vortex. Thus, a light wind with a cross

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runway component of 1 to 5 knots could result in the upwind

vortex remaining in the touchdown zone for a period of time and hasten the drift of the downwind vortex toward

another runway. (See FIG 7

6.) Similarly, a tailwind condition can move the vortices of the preceding aircraft

forward into the touchdown zone. THE LIGHT QUARTERING TAILWIND REQUIRES MAXIMUM

CAUTION. Pilots should be alert to large aircraft upwind from their approach and takeoff flight paths. (See

7.)

Wake Turbulence

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