Wake Turbulence
Wake Turbulence
Wake turbulence is generated by a pressure exchange between the lower and upper surface of the wing. This pressure exchange causes counter-rotating vortices trailing from the outer wing tips. The larger the aeroplane the larger those vortices will be. The wake of a large aeroplane may generate large control inputs on an aeroplane flying in the area behind it. Those control inputs may exceed the roll control capability of the following aeroplane. The pilot must be aware of the location of the vortex flow generated by a preceding aeroplane and adjust his flight path accordingly. Tests with large/heavy aeroplanes have shown that the vortex flow field, in a plane cutting through the wake at any point downstream, covers an area about twice the wing span in width and one wing span in depth. The vortices from the two tips remain spaced and will drift with the wind.
The vortices will sink with a rate of descent of around 500 fpm. There is a tendency that the vortices will level off about 1.000 ft below the flight path of the vortex-generating aeroplane.
Vortex strength diminishes with time and distance behind the aeroplane. Vortex generation will begin on rotation when the nose wheel lifts off the ground and ends, when the nose wheel touches down on landing. In conditions with very weak or calm winds, the remaining vortices from a landing aeroplane may persist up to 5 minutes or even longer. All this has prompted national authorities and ICAO to establish minimum separation criteria.
Take-off and Landing
Turbulence encountered during approach or take-off may be due to wake turbulence. Aeroplane turbulence categorisation and wake turbulence separation minima are defined by ICAO Doc. 4444 as follows:
Wake turbulence separation minima gave below to define a minimum separation time behind Heavy aeroplane to cope with wake turbulence:
*Intersection take-off: Departure from an intermediate part of the same runway or an intermediate part of a parallel runway less than 760m (2500ft) apart.
Radar Separation on Approach
Wake turbulence separation minima given below define a minimum separation distance on approach behind Heavy or Medium aeroplane to cope with wake turbulence:
Wake turbulence may be encountered in cruise, where aeroplane flying in the same direction and are vertically separated by 1.000 ft only (e.g. North Atlantic OTS). In this case, if considered necessary, the pilot may offset from the cleared track by up to a maximum of 2 NM in order to alleviate the effects of wake turbulence. ATC should be advised of this contingency action. The aeroplane should be returned to cleared track as soon as the situation allows.
Wake turbulence is generated by a pressure exchange between the lower and upper surface of the wing. This pressure exchange causes counter-rotating vortices trailing from the outer wing tips. The larger the aeroplane the larger those vortices will be. The wake of a large aeroplane may generate large control inputs on an aeroplane flying in the area behind it. Those control inputs may exceed the roll control capability of the following aeroplane. The pilot must be aware of the location of the vortex flow generated by a preceding aeroplane and adjust his flight path accordingly. Tests with large/heavy aeroplanes have shown that the vortex flow field, in a plane cutting through the wake at any point downstream, covers an area about twice the wing span in width and one wing span in depth. The vortices from the two tips remain spaced and will drift with the wind.
The vortices will sink with a rate of descent of around 500 fpm. There is a tendency that the vortices will level off about 1.000 ft below the flight path of the vortex-generating aeroplane.
Vortex strength diminishes with time and distance behind the aeroplane. Vortex generation will begin on rotation when the nose wheel lifts off the ground and ends, when the nose wheel touches down on landing. In conditions with very weak or calm winds, the remaining vortices from a landing aeroplane may persist up to 5 minutes or even longer. All this has prompted national authorities and ICAO to establish minimum separation criteria.
Take-off and Landing
Turbulence encountered during approach or take-off may be due to wake turbulence. Aeroplane turbulence categorisation and wake turbulence separation minima are defined by ICAO Doc. 4444 as follows:
- (L) Light: MTOW less than 7000kg;
- (M) Medium: 7000kg < MTOW < 136000kg;
- (H) Heavy: MTOW 136000kg or more;
- (J) Super: A380-800.
Wake turbulence separation minima gave below to define a minimum separation time behind Heavy aeroplane to cope with wake turbulence:
- On Approach: 2 minutes;
- On Line-up: 2 minutes (3 minutes if at intersection take-off).
- On Approach: 3 minutes;
- On Line-up: 3 minutes (4 minutes if at intersection take-off*).
*Intersection take-off: Departure from an intermediate part of the same runway or an intermediate part of a parallel runway less than 760m (2500ft) apart.
Radar Separation on Approach
Wake turbulence separation minima given below define a minimum separation distance on approach behind Heavy or Medium aeroplane to cope with wake turbulence:
- Behind Super: 7 NM;
- Behind Heavy: 5 NM;
- Behind Medium: 3 NM.
Wake turbulence may be encountered in cruise, where aeroplane flying in the same direction and are vertically separated by 1.000 ft only (e.g. North Atlantic OTS). In this case, if considered necessary, the pilot may offset from the cleared track by up to a maximum of 2 NM in order to alleviate the effects of wake turbulence. ATC should be advised of this contingency action. The aeroplane should be returned to cleared track as soon as the situation allows.
Wake Turbulence
Reviewed by Aviation Lesson
on
5:13 PM
Rating:
Reviewed by Aviation Lesson
on
5:13 PM
Rating:
No comments: