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AIM 

6/17/21 

5. 

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. 

b. 

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

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

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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 
FIG 7

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7.) 

FIG 7

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Vortex Movement in Ground Effect 

 Tailwind 

Tail Wind

Tail Wind 

Touchdown Point

Light Quartering 

Tailwind 

Light Quartering 

Tailwind 

Touchdown Point 

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5.  Operations Problem Areas 

a. 

A wake turbulence encounter can range from 

negligible to catastrophic. The impact of the 
encounter depends on the weight, wingspan, size of 
the generating aircraft, distance from the generating 
aircraft, and point of vortex encounter. The 
probability of induced roll increases when the 
encountering aircraft’s heading is generally aligned 
with the flight path of the generating aircraft. 

b. 

AVOID THE AREA BELOW AND BEHIND 

THE WAKE GENERATING AIRCRAFT, ESPE-
CIALLY AT LOW ALTITUDE WHERE EVEN A 
MOMENTARY WAKE ENCOUNTER COULD BE 
CATASTROPHIC. 

NOTE

 

A common scenario for a wake encounter is in terminal 
airspace after accepting clearance for a visual approach 
behind landing traffic. Pilots must be cognizant of their 
position relative to the traffic and use all means of vertical 

Wake Turbulence 

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