Basics For Air Traffic Control - Wake Turbulence

Assuming similar aircraft, which aircraft would create a greater wake turbulence effect?

aircraft on approach to the airport

What is lift generated by?

The creation of pressure differential over the wing surface. lowest pressure above the wing. highest pressure is below the wing.

Wake Turbulence

Phenomena resulting from the passage of an aircraft through the atmosphere. The term includes vortices, thrust stream turbulence, jet blast, jet wash, propeller wash, and rotor wash both on the ground and in the air.

vortices

circular patterns of air created by the movement of an

airfoil through the air when generating lift.

The greatest vortex strength is generated when the aircraft is

heavy, clean, and slow

Strength of a vortex (rotational force) is governed by three factors:

-Weight of the generating aircraft

-Shape of the wing (wing configuration)

• This determines wing loading, or how many pounds per square foot the wing is required to support

-Speed of the generating aircraft.

Strength of three vortices will diminish with

time and distance

The slower the speed, the greater the ___

chance for the wake to take form. This is especially critical for aircraft on approach to an airport.

The greatest wake turbulence is associated with which aircraft configuration?

Heavy, clean, slow

which one of these has the greatest wake turbulence?

weight

Vortex Circulation

off the wingtip is counterclockwise right wing clockwise off left wing. both vortices will drift outward.

when are vortices generated?

The moment the aircraft generates lift.

Vortices sink at a rate of

approximately 300 to 500 feet per minute. normally level off 500 to 1,000 feet below the flight path.

Separation is based on

time and/or distance

When close to the ground and there is zero wind,

vortices from larger aircraft will move laterally.

What is/are the names given to the circular patterns created by wake turbulence?

wake vortex and wingtip vortices

when do vortices begin for a fixed wing aircraft?

At rotation or when lift begins

when observing an aircraft from behind, the circulation of vortices off the right wingtip is ___ and _____ off the left wingtip

counterclockwise, clockwise

Vortices from larger aircraft will sink approximately 300 to 500 feet per minute and level off approximately ___ feet below the flight path

500 to 1000

with no wind, vortices within 100 to 200 feet of the ground will move ___ knots laterally across the ground

2 to 3

Induced Roll

the mechanical force a wake vortex has on an aircraft

Vortex Roll

wingspan of the aircraft

counter control capability of the aircraft

Why would extra spacing be necessary when smaller aircraft are following larger aircraft at a terminal environment?

To avoid the aircraft wake turbulence vortices

counter control is most effective and roll is minimal when the wingspan and the ailerons extend beyond the

outer edges

Helicopter Downwash

In a slow hover taxi or stationary hover, a helicopter will generate a downwash from its main rotors, which produces a high speed outward vortex as it approaches the ground. the downward circulation is outward, upward, around, and away from main rotors in all directions

slow hover taxi or stationary hover

avoid operations within distance of 3 times rotor diameter

jet blast

Jet engine exhaust (thrust stream turbulence)

Controllers may use the following terms in lieu of the term "wake turbulence":

• Jet blast

• Prop wash

• Rotor wash

a hovering helicopter creates a downwash from its main rotors that can travel how far?

Three times the diameter of its rotors

When do helicopters generate wingtip vortices?

Must be in forward flight

Why is the controller not responsible for anticipating th existence or effects of wake turbulence?

Because it's unpredictable

Wake turbulence has the greatest impact on ATC in the areas of ___

Increased separation and traffic delays

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