7-4-6. Vortex Avoidance Procedures
a. Under certain conditions, airport traffic controllers apply procedures for separating IFR aircraft. If a pilot
accepts a clearance to visually follow a preceding aircraft, the pilot accepts responsibility for separation and wake
turbulence avoidance. The controllers will also provide to VFR aircraft, with whom they are in communication
and which in the tower"s opinion may be adversely affected by wake turbulence from a larger aircraft, the
position, altitude and direction of flight of larger aircraft followed by the phrase "CAUTION - WAKE
TURBULENCE." After issuing the caution for wake turbulence, the airport traffic controllers generally do not
provide additional information to the following aircraft unless the airport traffic controllers know the following
aircraft is overtaking the preceding aircraft. WHETHER OR NOT A WARNING OR INFORMATION HAS
BEEN GIVEN, HOWEVER, THE PILOT IS EXPECTED TO ADJUST AIRCRAFT OPERATIONS AND
FLIGHT PATH AS NECESSARY TO PRECLUDE SERIOUS WAKE ENCOUNTERS. When any doubt exists
about maintaining safe separation distances between aircraft during approaches, pilots should ask the control
tower for updates on separation distance and aircraft groundspeed.
b. The following vortex avoidance procedures are recommended for the various situations:
1. Landing behind a larger aircraft- same runway. Stay at or above the larger aircraft"s final approach
flight path-note its touchdown point-land beyond it.
2. Landing behind a larger aircraft- when parallel runway is closer than 2,500 feet. Consider possible
drift to your runway. Stay at or above the larger aircraft"s final approach flight path- note its touchdown point.
3. Landing behind a larger aircraft- crossing runway. Cross above the larger aircraft"s flight path.
4. Landing behind a departing larger aircraft- same runway. Note the larger aircraft"s rotation point-
land well prior to rotation point.
5. Landing behind a departing larger aircraft- crossing runway. Note the larger aircraft"s rotation
point- if past the intersection- continue the approach- land prior to the intersection. If larger aircraft rotates prior
to the intersection, avoid flight 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, particularly
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 conditions. 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.
7-4-7. 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 characteristics similar to wing tip
vortices produced by fixed wing aircraft. However, the vortex circulation is outward, upward, around, and away

7-4-6

Wake Turbulence