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AIM

10/12/17

7−3−7

Wake Turbulence

2. Pilots of aircraft that produce strong wake

vortices should fly as closely as possible to the

approach course centerline or to the extended

centerline of the runway of intended landing as

appropriate to conditions.

f. Pilots operating lighter aircraft on visual

approaches in−trail to aircraft producing strong wake

vortices should use the following procedures to assist

in avoiding wake turbulence. These procedures apply

only to those aircraft that are on visual approaches.

1. Pilots of lighter aircraft should fly on or

above the glidepath. Glidepath reference may be

furnished by an ILS, by a visual approach slope

system, by other ground−based approach slope

guidance systems, or by other means. In the absence

of visible glidepath guidance, pilots may very nearly

duplicate a 3−degree glideslope by adhering to the

“3 to 1” glidepath principle.

EXAMPLE−

Fly 3,000 feet at 10 miles from touchdown, 1,500 feet at

5 miles, 1,200 feet at 4 miles, and so on to touchdown.

2. If the pilot of the lighter following aircraft has

visual contact with the preceding heavier aircraft and

also with the runway, the pilot may further adjust for

possible wake vortex turbulence by the following

practices:

(a) Pick a point of landing no less than

1,000 feet from the arrival end of the runway.

(b) Establish a line−of−sight to that landing

point that is above and in front of the heavier

preceding aircraft.

(c) When possible, note the point of landing

of the heavier preceding aircraft and adjust point of

intended landing as necessary.

EXAMPLE−

A puff of smoke may appear at the 1,000−foot markings of

the runway, showing that touchdown was that point;

therefore, adjust point of intended landing to the

1,500−foot markings.

(d) Maintain the line−of−sight to the point of

intended landing above and ahead of the heavier

preceding aircraft; maintain it to touchdown.

(e) Land beyond the point of landing of the

preceding heavier aircraft.

3. During visual approaches pilots may ask ATC

for updates on separation and groundspeed with

respect to heavier preceding aircraft, especially when

there is any question of safe separation from wake

turbulence.

7−3−9. Air Traffic Wake Turbulence

Separations

a. Because of the possible effects of wake

turbulence, controllers are required to apply no less

than specified minimum separation to all IFR aircraft,

to all VFR aircraft receiving Class B or Class C

airspace services when operating behind super or

heavy aircraft, and to small aircraft operating behind

a B757.

1. Separation is applied to aircraft operating

directly behind a super or heavy at the same altitude

or less than 1,000 feet below, and to small aircraft

operating directly behind a B757 at the same altitude

or less than 500 feet below:

(a) Heavy behind super − 6 miles.
(b) Large behind super − 7 miles.
(c) Small behind super − 8 miles.
(d) Heavy behind heavy −4 miles.
(e) Small/large behind heavy − 5 miles.
(f) Small behind B757 − 4 miles.

2. Also, separation, measured at the time the

preceding aircraft is over the landing threshold, is

provided to small aircraft:

(a) Small landing behind heavy − 6 miles.
(b) Small landing behind large, non−B757

− 4 miles.

REFERENCE−

Pilot/Controller Glossary Term− Aircraft Classes.

3. Additionally, appropriate time or distance

intervals are provided to departing aircraft when the

departure will be from the same threshold, a parallel

runway separated by less than 2,500 feet with less

than 500 feet threshold stagger, or on a crossing

runway and projected flight paths will cross:

(a) Three minutes or the appropriate radar

separation when takeoff will be behind a super

aircraft;

(b) Two minutes or the appropriate radar

separation when takeoff will be behind a heavy

aircraft.

(c) Two minutes or the appropriate radar

separation when a small aircraft will takeoff behind

a B757.