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When is wake turbulence risk the highest?
  • A
    When a heavy aircraft has just performed a take-off at a closely situated parallel runway with a light crosswind.
  • B
    If just before landing a much lighter aircraft has landed at the same runway with heavy crosswind.
  • C
    When a preceding aircraft has briefly applied reverse-thrust just prior to take-off.
  • D
    Following a preceding aircraft at high speed.

Refer to figure.


Whenever an airplane generates lift, air spills over the wing tips from the high pressure areas below the wings to the low pressure areas above them. This flow causes rapidly rotating whirlpools of air called wingtip vortices. An aircraft generates vortices from the moment it rotates on take-off to touchdown.

The intensity depends on aircraft weight, speed and configuration. The greatest wake turbulence danger is produced by large, heavy airplanes operating at low speeds, high angles of attack and in a clean configuration.

Although wake turbulence settles, it persists in the air for several minutes, depending on wind conditions. In light winds of 3 to 7 knots, the vortices can stay in the touchdown area, sink into your take-off or landing path, or drift over a parallel runway

=> Light crosswinds may cause the vortices to drift. A 3 to 5 knot crosswind will tend to keep the upwind vortex in the runway area and may cause the downwind vortex to drift toward another runway.

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