Aeronautical Information Manual (AIM), page 525

Index   524 -- Page 525 -- 526

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.

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

(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.

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

7-3-9. Air Traffic Wake Turbulence

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.
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


(b) Two minutes or the appropriate radar
separation when takeoff will be behind a heavy

(c) Two minutes or the appropriate radar
separation when a small aircraft will takeoff behind
a B757.

Wake Turbulence 7-3-7

Page 525 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   524 -- Page 525 -- 526