Aeronautical Information Manual (AIM), page 524

Index   523 -- Page 524 -- 525

below the larger aircraft's flight path. Abandon the
approach unless a landing is ensured well before
reaching the intersection.
6. Departing behind a larger aircraft. Note
the larger aircraft's rotation point and rotate prior to
the larger aircraft's rotation point. Continue climbing
above the larger aircraft's climb path until turning
clear of the larger aircraft's wake. Avoid subsequent
headings which will cross below and behind a larger
aircraft. Be alert for any critical takeoff situation
which could lead to a vortex encounter.

7. Intersection takeoffs- same runway. Be
alert to adjacent larger aircraft operations, particular-
ly upwind of your runway. If intersection takeoff
clearance is received, avoid subsequent heading
which will cross below a larger aircraft's path.

8. Departing or landing after a larger
aircraft executing a low approach, missed
approach, or touch-and-go landing. Because
vortices settle and move laterally near the ground, the
vortex hazard may exist along the runway and in your
flight path after a larger aircraft has executed a low
approach, missed approach, or a touch-and-go
landing, particular in light quartering wind condi-
tions. You should ensure that an interval of at least
2 minutes has elapsed before your takeoff or landing.

9. En route VFR (thousand-foot altitude plus
500 feet). Avoid flight below and behind a large
aircraft's path. If a larger aircraft is observed above on
the same track (meeting or overtaking) adjust your
position laterally, preferably upwind.

7-3-7. Helicopters
In a slow hover taxi or stationary hover near the
surface, helicopter main rotor(s) generate downwash
producing high velocity outwash vortices to a
distance approximately three times the diameter of
the rotor. When rotor downwash hits the surface, the
resulting outwash vortices have behavioral character-
istics similar to wing tip vortices produced by fixed
wing aircraft. However, the vortex circulation is
outward, upward, around, and away from the main
rotor(s) in all directions. Pilots of small aircraft
should avoid operating within three rotor diameters
of any helicopter in a slow hover taxi or stationary
hover. In forward flight, departing or landing
helicopters produce a pair of strong, high-speed
trailing vortices similar to wing tip vortices of larger

fixed wing aircraft. Pilots of small aircraft should use
caution when operating behind or crossing behind
landing and departing helicopters.
7-3-8. Pilot Responsibility

a. Government and industry groups are making
concerted efforts to minimize or eliminate the
hazards of trailing vortices. However, the flight
disciplines necessary to ensure vortex avoidance
during VFR operations must be exercised by the pilot.
Vortex visualization and avoidance procedures
should be exercised by the pilot using the same degree
of concern as in collision avoidance.
b. Wake turbulence may be encountered by
aircraft in flight as well as when operating on the
airport movement area.

Pilot/Controller Glossary Term- Wake Turbulence.

c. Pilots are reminded that in operations conducted
behind all aircraft, acceptance of instructions from
ATC in the following situations is an acknowledg-
ment that the pilot will ensure safe takeoff and
landing intervals and accepts the responsibility for
providing wake turbulence separation.
1. Traffic information.
2. Instructions to follow an aircraft; and

3. The acceptance of a visual approach
d. For operations conducted behind super or
heavy aircraft, ATC will specify the word "super" or
"heavy" as appropriate, when this information is
known. Pilots of super or heavy aircraft should
always use the word "super" or "heavy" in radio
e. Super, heavy, and large jet aircraft operators
should use the following procedures during an
approach to landing. These procedures establish a
dependable baseline from which pilots of in-trail,
lighter aircraft may reasonably expect to make
effective flight path adjustments to avoid serious
wake vortex turbulence.
1. Pilots of aircraft that produce strong wake
vortices should make every attempt to fly on the
established glidepath, not above it; or, if glidepath
guidance is not available, to fly as closely as possible
to a "3-1" glidepath, not above it.
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.

7-3-6 Wake Turbulence

Page 524 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   523 -- Page 524 -- 525