Definition and creation
Lift is generated by the creation of a pressure differential over the wing surface. The lowest pressure occurs over the upper wing surface and the highest pressure under the wing. This pressure differential triggers the roll up of the airflow aft of the wing resulting in swirling air masses trailing downstream of the wing tips. After the roll up is completed, the wake consists of two counter-rotating cylindrical vortices. This starts the wake vortex.
Wake vortices spread laterally away from the aircraft and descend approximately 500 to 900 feet at distances of up to five miles behind it. These vortices tend to descend at approximately 300 to 500 feet per minute during the first 30 seconds
Effect when flying behind wake turbulence
Depending on the location of the trailing aircraft relative to the wake vortices, it is most common to be rolled in both directions.
If the aircraft is flown between the vortices, high roll rates can coincide with very high sink rates in excess of 1000 feet per minute. Depending on the altitude, the outcome could be tragic.
Aircraft with smaller wingspans generate more intense wake vortices than aircraft with equivalent weights and longer wingspans. The Boeing 757, for example, has a relatively short wing and large power plant for the weight of the aircraft. The wake turbulence that is produced by the 757 is equivalent to that of a much heavier aircraft.
Wake turbulence avoidance procedure
- Landing traffic will land beyond the touchdown point of the preceding aircraft. (A)
- Landing traffic will land prior to the departing aircraft’s rotation point. (B)
- Departing aircraft will lift off (if possible) prior to preceding aircraft’s rotation point. (C)
- Departing aircraft will lift off past the preceding aircraft’s touchdown point. (D)
Wake turbulence categories of aircraft
- L = Light = maximum take-off mass < 7000 kilograms (15,000 lb)
- M = Medium = 7000 kilograms < maximum take-off mass < 136,000 kilograms
- H = Heavy = maximum take-off mass >136000 kilograms (300,000 lb)
- J = Super = specific category for Airbus A380 (Jumbo)
- ICAO Documentation 4444 - Air Traffic Management - 16th Edition 2016 - Chapter 4.9
- VID 150259 - Creation
- VID 150259 - Wiki integration
DATE OF SUBMISSION
- 00:24, 14 May 2021
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