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 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. [1]
A leading-edge droop flap comprises the rounded front part of a wing, in movable form. The Airbus A380 has droop flaps between the fuselage and each inboard engine, at the leading edge of the thickest part of each wing. [1] [2] Early variants of the Hawker Siddeley Trident had two droop flaps on the outboard of each wing and a Krueger flap on the section closest to the fuselage. [3]
Droop flaps function with other high-lift devices on an aircraft to increase the camber 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. [2] Another function of droop flaps on the A380 is to change the stall characteristics of the wing. [4] 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. [4]
The Airbus A300 is a wide-body airliner developed and manufactured by Airbus. In September 1967, aircraft manufacturers in the United Kingdom, France, and West Germany signed a memorandum of understanding to develop a large airliner. West Germany and France reached an agreement on 29 May 1969 after the British withdrew from the project on 10 April 1969. European collaborative aerospace manufacturer Airbus Industrie was formally created on 18 December 1970 to develop and produce it. The prototype first flew on 28 October 1972.
A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expressed as its lift-to-drag ratio. The lift a wing generates at a given speed and angle of attack can be one to two orders of magnitude greater than the total drag on the wing. A high lift-to-drag ratio requires a significantly smaller thrust to propel the wings through the air at sufficient lift.
A tailplane, also known as a horizontal stabiliser, is a small lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters and gyroplanes. Not all fixed-wing aircraft have tailplanes. Canards, tailless and flying wing aircraft have no separate tailplane, while in V-tail aircraft the vertical stabiliser, rudder, and the tail-plane and elevator are combined to form two diagonal surfaces in a V layout.
In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases. This occurs when the critical angle of attack of the foil is exceeded. The critical angle of attack is typically about 15°, but it may vary significantly depending on the fluid, foil, and Reynolds number.
A leading-edge extension (LEX) is a small extension to an aircraft wing surface, forward of the leading edge. The primary reason for adding an extension is to improve the airflow at high angles of attack and low airspeeds, to improve handling and delay the stall. A dog tooth can also improve airflow and reduce drag at higher speeds.
A vortex generator (VG) is an aerodynamic device, consisting of a small vane usually attached to a lifting surface or a rotor blade of a wind turbine. VGs may also be attached to some part of an aerodynamic vehicle such as an aircraft fuselage or a car. When the airfoil or the body is in motion relative to the air, the VG creates a vortex, which, by removing some part of the slow-moving boundary layer in contact with the airfoil surface, delays local flow separation and aerodynamic stalling, thereby improving the effectiveness of wings and control surfaces, such as flaps, elevators, ailerons, and rudders.
A jet airliner or jetliner is an airliner powered by jet engines. Airliners usually have two or four jet engines; three-engined designs were popular in the 1970s but are less common today. Airliners are commonly classified as either the large wide-body aircraft, medium narrow-body aircraft and smaller regional jet.
British European Airways Flight 548 was a scheduled passenger flight from London Heathrow to Brussels that crashed near Staines, Middlesex, England, soon after take-off on 18 June 1972, killing all 118 people on board. The accident became known as the Staines air disaster. As of 2021, it remains the deadliest air accident in the United Kingdom and was the deadliest air accident involving a Hawker Siddeley Trident. Two passengers initially survived the impact but soon after died from their injuries.
In aircraft design and aerospace engineering, a high-lift device is a component or mechanism on an aircraft's wing that increases the amount of lift produced by the wing. The device may be a fixed component, or a movable mechanism which is deployed when required. Common movable high-lift devices include wing flaps and slats. Fixed devices include leading-edge slots, leading edge root extensions, and boundary layer control systems.
A flap is a high-lift device used to reduce the stalling speed of an aircraft wing at a given weight. Flaps are usually mounted on the wing trailing edges of a fixed-wing aircraft. Flaps are used to reduce the take-off distance and the landing distance. Flaps also cause an increase in drag so they are retracted when not needed.
Lufthansa Flight 540 was a scheduled commercial flight for Lufthansa, serving the Frankfurt–Nairobi–Johannesburg route.
A leading-edge slot is a fixed aerodynamic feature of the wing of some aircraft to reduce the stall speed and promote good low-speed handling qualities. A leading-edge slot is a spanwise gap in each wing, allowing air to flow from below the wing to its upper surface. In this manner they allow flight at higher angles of attack and thus reduce the stall speed.
A supercritical airfoil is an airfoil designed primarily to delay the onset of wave drag in the transonic speed range.
The Hunting H.126 was an experimental aircraft designed and built by British aviation company Hunting Aircraft.
The Hawker Siddeley HS-121 Trident is a British airliner produced by Hawker Siddeley. In 1957, de Havilland proposed its DH.121 trijet design to a British European Airways (BEA) request. By 1960, de Havilland had been acquired by Hawker Siddeley. The Trident's maiden flight happened on 9 January 1962, and it was introduced on 1 April 1964, two months after its main competitor, the Boeing 727. By the end of the programme in 1978, 117 Tridents had been produced, and the Trident was withdrawn from service in 1995.
A circulation control wing (CCW) is a form of high-lift device for use on the main wing of an aircraft to increase the maximum lift coefficient. CCW technology has been in the research and development phase for over sixty years. Blown flaps were an early example of CCW.
The wing configuration of a fixed-wing aircraft is its arrangement of lifting and related surfaces.
Slats are aerodynamic surfaces on the leading edge of the wings of 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, so by deploying slats an aircraft can fly at slower speeds, or take off and land in shorter distances. They are usually used while landing or performing maneuvers which take the aircraft close to a stall, but are usually retracted in normal flight to minimize drag. They decrease stall speed.
Krueger flaps, or Krüger flaps, are lift enhancement devices that may be fitted to the leading edge of an aircraft wing. Unlike slats or droop flaps, the main wing upper surface and its nose is not changed. Instead, a portion of the lower wing is rotated out in front of the main wing leading edge. Several modern aircraft use this design between the fuselage and closest engine, where the wing is thickest. Outboard of the engine, slats are used on the leading edge. The Boeing 727 also used a mix of inboard Krueger flaps and outboard slats, although it had no engine between them. Most early jet airliners, such as the Boeing 707 and Boeing 747, used Krueger flaps only.
The leading edge of an airfoil surface such as a wing is its foremost edge and is therefore the part which first meets the oncoming air.