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Leading Edge Devices

This page give a detailed desciption on leading edge devices as well as a background history and an explanation on the different designs solutions and their implications on the aircraft performance.

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  • General understanding of effect of leading edge devices to the aircraft performance

Leading edge devices are located at the leading edge of the wing and can be deployed during different flight phases (take off, landing and cruise) in order to improve the aerodynamic performances of the the aircraft. More generally they are used during take off and landing to increase the lift and so be able to reduce the landing speed, or increase lift for take off. Also leading edge devices will create drag but the overall Lift to drag ratio is still an advantage. Following on this, the leading edge devices are retracted for cruise to decrease the drag and so have clean airfoil profile which is more efficient for cruise condition.

  • History of leading edge device

The leading edge devices were used on early aircraft to improve the performance of the aircraft. One of the pioneer of the leading edge device was Handley Page who first tried this on his aircraft. First of all he used a fixed leading edge slat which provided him with high lift coefficient but the associated drag was detrimental to maximum speed. Handley page then tried to have an automatic deployment of the leading edge slat using the aerodynamic forces at the leading edge (suction). As the aircraft take off and land the speed see for more information http://en.wikiversity.org/wiki/History-of-LE-devices


  • different concepts used for leading edge devices

Currently different type of devices are used on commercial and military aircraft, depending on the aircraft type and also on the overall aircraft geometry. One of the most common device is the slat track concept which is used on most of the modern passenger aircraft (Boeing 737 [[[w:B737]]] and Airbus A320 [[[w:A320]]]). Another device currently used on A380 [[[w:A380]]]is the droop nose mechanism.

The slat track mechanism is made of a track which deploy the leading edge slat, the slat once in the deployed position open a slot for the air to go through. The track is deployed and guided by rollers, both vertical and horizontal to garantuee the right deployment conpare to the wing. This is a simple and effective design.

The droop nose solution is basically increasing the wing camber while not extending by a huge amount the chord of the wing.This allows to gain lift , but does not provide a slot for the airflow to renergise over the wing when landing and so is less performant than the slat track option.

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