The leading-edge droop flap is a device on the leading edge of aircraft wings designed to improve airflow at high pitch angles (high angle of attack). The droop flap is similar to the

leading-edge slat Slats are aerodynamic surfaces on the leading edge of the wing of a fixed-wing aircraft which, when deployed, allow the wing to operate at a higher angle of attack. A higher coefficient of lift is produced as a result of angle of attack and speed, ...

and the Krueger flap, but with the difference that the entire leading edge section rotates downwards, whereas the slat and Krueger flap are panels which move away from the wing leading edge when it is deployed.Norris & Wagner (2005), pp.67-68

Location

A leading-edge droop flap comprises the rounded front part of a wing, in movable form. The

Airbus A380 The Airbus A380 is a large wide-body airliner that was developed and produced by Airbus. It is the world's largest passenger airliner and only full-length double-deck jet airliner. Airbus studies started in 1988, and the project was annou ...

has droop flaps between the fuselage and each inboard engine, at the leading edge of the thickest part of each wing. Early variants of the

Hawker Siddeley Trident The Hawker Siddeley HS-121 Trident (originally the de Havilland DH.121 and briefly the Airco DH.121) is a British airliner produced by Hawker Siddeley. In 1957, de Havilland proposed its DH.121 trijet design to a British European Airways (BEA ...

had two droop flaps on the outboard of each wing and a Krueger flap on the section closest to the fuselage.''Flight International'' 29 June 1972, p.933
retrieved 7 March 2014

Use and effect

Droop flaps function with other high-lift devices on an aircraft to increase the

camber Camber may refer to a variety of curvatures and angles: * Camber angle, the angle made by the wheels of a vehicle * Camber beam, an upward curvature of a joist to compensate for load deflection due in buildings * Camber thrust in bike technology * ...

of the wing and reduce the stalling speed. On the Airbus A380, the first stage of lift device selection deploys the droop flaps (called ''droop noses'' by Airbus) and leading-edge slats located further out on the wing; with the main flaps starting to extend when the second stage is selected. The variable sections on the A380 may be drooped to a position 22 or 25 degrees lower than their stowed position.Norris & Wagner (2005), p.155 Another function of droop flaps on the A380 is to change the stall characteristics of the wing. The A380's designers found that the airflow between the engines was separating from the wing surface prior to the airflow between the engine and the fuselage, an undesirable characteristic. Adding droop between the engine and the fuselage fixed the problem; whereas using a leading-edge slat would not have done so because of the gap (or slot) created between a slat and the wing when a slat is deployed.Norris & Wagner (2005), p.67

Aircraft with droop flaps

Airbus A350 The Airbus A350 is a long-range, wide-body twin-engine jet airliner developed and produced by Airbus. The first A350 design proposed by Airbus in 2004, in response to the Boeing 787 Dreamliner, would have been a development of the A330 ...

Dassault Falcon 20 The Dassault Falcon 20 is a French business jet developed and manufactured by Dassault Aviation. The first business jet developed by the firm, it became the first of a family of business jets to be produced under the same name; of these, both t ...

Mikoyan-Gurevich MiG-23 The Mikoyan-Gurevich MiG-23 (russian: Микоян и Гуревич МиГ-23; NATO reporting name: Flogger) is a variable-geometry fighter aircraft, designed by the Mikoyan-Gurevich design bureau in the Soviet Union. It is a third-generati ...

Northrop F-5 The Northrop F-5 is a family of supersonic light fighter aircraft initially designed as a privately funded project in the late 1950s by Northrop Corporation. There are two main models, the original F-5A and F-5B Freedom Fighter variants and t ...

References

Notes

Bibliography