Air brake (aeronautics)

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Air brakes on the rear fuselage of a Eurowings BAe 146-300 Eurowings bae146-300 d-aewb arp.jpg
Air brakes on the rear fuselage of a Eurowings BAe 146-300
Convair F-106 Delta Dart air brake deployed CONVAIR F-106A DELTA DART Air Brake.jpg
Convair F-106 Delta Dart air brake deployed
A U.S. Air Force F-16 Fighting Falcon showing its split speed brakes inboard of the stabilators or "tailerons" 416th FLTS F-16 at Red Flag 12-2.jpg
A U.S. Air Force F-16 Fighting Falcon showing its split speed brakes inboard of the stabilators or "tailerons"
An F-15 landing with its large dorsal air brake panel deployed F-15 Eagle landing with the speed brake up.jpg
An F-15 landing with its large dorsal air brake panel deployed
Extended DFS type air brakes on a Slingsby Capstan Airbrakes on Capstan.jpg
Extended DFS type air brakes on a Slingsby Capstan

In aeronautics, air brakes or speed brakes are a type of flight control surface used on an aircraft to increase the drag on the aircraft. [1] When extended into the airstream, air brakes cause an increase in the drag on the aircraft. When not in use, they conform to the local streamlined profile of the aircraft in order to help minimize drag. [2]

Contents

Air brakes differ from spoilers in that air brakes are designed to increase drag while making little change to lift, whereas spoilers reduce the lift-to-drag ratio and require a higher angle of attack to maintain lift, resulting in a higher stall speed. [3]

History

In the early decades of powered flight, air brakes were flaps mounted on the wings. They were manually controlled by a lever in the cockpit, and mechanical linkages to the air brake.

An early type of air brake, developed in 1931, was fitted to the aircraft wing support struts. [4]

In 1936, Hans Jacobs, who headed Nazi Germany's Deutsche Forschungsanstalt für Segelflug (DFS) glider research organization before World War II, developed blade-style self-operating dive brakes, on the upper and lower surface of each wing, for gliders. [5] Most early gliders were equipped with spoilers on the wings in order to adjust their angle of descent during approach to landing. More modern gliders use air brakes which may spoil lift as well as increase drag, dependent on where they are positioned.

A British report [6] written in 1942 discusses the need for dive brakes to enable dive bombers, torpedo bombers and fighter aircraft to meet their respective combat performance requirements and, more generally, glide-path control. It discusses different types of air brakes and their requirements, in particular that they should have no appreciable effect on lift or trim and how this may be achieved with split trailing edge flaps on the wings, for example. There was also a requirement to vent the brake surfaces using numerous perforations or slots to reduce airframe buffeting.

A US report [7] written in 1949 describes numerous air brake configurations, and their performance, on wings and fuselage for propeller and jet aircraft.

Air brake configurations

Often, characteristics of both spoilers and air brakes are desirable and are combined - most modern airliner jets feature combined spoiler and air brake controls. On landing, the deployment of these spoilers ("lift dumpers") causes a significant reduction in wing lift, so the weight of the aircraft is transferred from the wings to the undercarriage. The increased weight increases the available friction force for braking. In addition, the form drag created by the spoilers directly assists the braking effect. Reverse thrust is also used to help slow the aircraft after landing. [8]

A Fokker 70 of KLM landing with speed brakes deployed. Klm.fokker70.airbrakes.arp.750pix.jpg
A Fokker 70 of KLM landing with speed brakes deployed.

Virtually all jet-powered aircraft have an air brake or, in the case of most airliners, lift spoilers that also act as air brakes. Propeller-driven aircraft benefit from the natural braking effect of the propeller when engine power is reduced to idle, but jet engines have no similar braking effect, so jet-powered aircraft must use air brakes to control speed and descent angle during landing approach. Many early jets used parachutes as air brakes on approach (Arado Ar 234, Boeing B-47) or after landing (English Electric Lightning).

Split-tailcone air brakes have been used on the Blackburn Buccaneer naval strike aircraft designed in the 1950s and Fokker F28 Fellowship and British Aerospace 146 airliners. The Buccaneer air brake, when opened, reduced the length of the aircraft in the confined space on an aircraft carrier.

The F-15 Eagle, Sukhoi Su-27, F-18 Hornet and other fighters have an air brake located just behind the cockpit.

Split control surfaces

Space Shuttle Discovery on landing, showing its rudder deployed in speed brake mode STS-116 landing port behind.jpg
Space Shuttle Discovery on landing, showing its rudder deployed in speed brake mode

The deceleron is an aileron that functions normally in flight but can split in half such that the top half goes up as the bottom half goes down to brake. This technique was first used on the F-89 Scorpion and has since been used by Northrop on several aircraft, including the B-2 Spirit.

The Space Shuttle used a similar system. The vertically-split rudder opened in "clamshell" fashion on landing to act as a speed brake. [9]

See also

Related Research Articles

<span class="mw-page-title-main">Aircraft</span> Vehicle or machine that is able to fly by gaining support from the air

An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or the dynamic lift of an airfoil, or, in a few cases, direct downward thrust from its engines. Common examples of aircraft include airplanes, helicopters, airships, gliders, paramotors, and hot air balloons.

<span class="mw-page-title-main">Wing</span> Appendage used for flight

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.

<span class="mw-page-title-main">Fixed-wing aircraft</span> Heavier-than-air aircraft with fixed wings generating aerodynamic lift

A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane, which is capable of flight using wings that generate lift caused by the aircraft's forward airspeed and the shape of the wings. Fixed-wing aircraft are distinct from rotary-wing aircraft, and ornithopters. The wings of a fixed-wing aircraft are not necessarily rigid; kites, hang gliders, variable-sweep wing aircraft and airplanes that use wing morphing are all examples of fixed-wing aircraft.

<span class="mw-page-title-main">Stall (fluid dynamics)</span> Abrupt reduction in lift due to flow separation

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.

<span class="mw-page-title-main">Flight</span> Process by which an object moves, through an atmosphere or beyond it

Flight or flying is the process by which an object moves through a space without contacting any planetary surface, either within an atmosphere or through the vacuum of outer space. This can be achieved by generating aerodynamic lift associated with gliding or propulsive thrust, aerostatically using buoyancy, or by ballistic movement.

<span class="mw-page-title-main">Flying wing</span> Tailless fixed-wing aircraft that has no definite fuselage

A flying wing is a tailless fixed-wing aircraft that has no definite fuselage, with its crew, payload, fuel, and equipment housed inside the main wing structure. A flying wing may have various small protuberances such as pods, nacelles, blisters, booms, or vertical stabilizers.

<span class="mw-page-title-main">Landing</span> Transition from being in flight to being on a surface

Landing is the last part of a flight, where a flying animal, aircraft, or spacecraft returns to the ground. When the flying object returns to water, the process is called alighting, although it is commonly called "landing", "touchdown" or "splashdown" as well. A normal aircraft flight would include several parts of flight including taxi, takeoff, climb, cruise, descent and landing.

<span class="mw-page-title-main">Wingtip device</span> Aircraft component fixed to the end of the wings to improve performance

Wingtip devices are intended to improve the efficiency of fixed-wing aircraft by reducing drag. Although there are several types of wing tip devices which function in different manners, their intended effect is always to reduce an aircraft's drag. Wingtip devices can also improve aircraft handling characteristics and enhance safety for following aircraft. Such devices increase the effective aspect ratio of a wing without greatly increasing the wingspan. Extending the span would lower lift-induced drag, but would increase parasitic drag and would require boosting the strength and weight of the wing. At some point, there is no net benefit from further increased span. There may also be operational considerations that limit the allowable wingspan.

<span class="mw-page-title-main">Flight control surfaces</span> Surface that allows a pilot to adjust and control an aircrafts flight attitude

Aircraft flight control surfaces are aerodynamic devices allowing a pilot to adjust and control the aircraft's flight attitude.

<span class="mw-page-title-main">Ducted fan</span> Air moving arrangement

In aeronautics, a ducted fan is a thrust-generating mechanical fan or propeller mounted within a cylindrical duct or shroud. Other terms include ducted propeller or shrouded propeller. When used in vertical takeoff and landing (VTOL) applications it is also known as a shrouded rotor.

<span class="mw-page-title-main">Thrust reversal</span> Temporary diversion of an aircraft engines thrust

Thrust reversal, also called reverse thrust, is the temporary diversion of an aircraft engine's thrust for it to act against the forward travel of the aircraft, providing deceleration. Thrust reverser systems are featured on many jet aircraft to help slow down just after touch-down, reducing wear on the brakes and enabling shorter landing distances. Such devices affect the aircraft significantly and are considered important for safe operations by airlines. There have been accidents involving thrust reversal systems, including fatal ones.

<span class="mw-page-title-main">Spoiler (aeronautics)</span> Device for reducing lift and increasing drag on aircraft wings

In aeronautics, a spoiler is a device which intentionally reduces the lift component of an airfoil in a controlled way. Most often, spoilers are plates on the top surface of a wing that can be extended upward into the airflow to spoil the streamline flow. By so doing, the spoiler creates a controlled stall over the portion of the wing behind it, greatly reducing the lift of that wing section. Spoilers differ from airbrakes in that airbrakes are designed to increase drag without disrupting the lift distribution across the wing span, while spoilers disrupt the lift distribution as well as increasing drag.

<span class="mw-page-title-main">Flap (aeronautics)</span> Anti-stalling high-lift device on aircraft

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.

<span class="mw-page-title-main">Conventional landing gear</span> Aircraft undercarriage

Conventional landing gear, or tailwheel-type landing gear, is an aircraft undercarriage consisting of two main wheels forward of the center of gravity and a small wheel or skid to support the tail. The term taildragger is also used, although John Brandon of Recreational Aircraft Australia argues it should apply only to those aircraft with a tailskid rather than a wheel.

<span class="mw-page-title-main">Airplane</span> Powered, flying vehicle with wings

An airplane or aeroplane, informally plane, is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, propeller, or rocket engine. Airplanes come in a variety of sizes, shapes, and wing configurations. The broad spectrum of uses for airplanes includes recreation, transportation of goods and people, military, and research. Worldwide, commercial aviation transports more than four billion passengers annually on airliners and transports more than 200 billion tonne-kilometers of cargo annually, which is less than 1% of the world's cargo movement. Most airplanes are flown by a pilot on board the aircraft, but some are designed to be remotely or computer-controlled such as drones.

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<span class="mw-page-title-main">Propeller (aeronautics)</span> Aircraft propulsion component

In aeronautics, an aircraft propeller, also called an airscrew, converts rotary motion from an engine or other power source into a swirling slipstream which pushes the propeller forwards or backwards. It comprises a rotating power-driven hub, to which are attached several radial airfoil-section blades such that the whole assembly rotates about a longitudinal axis. The blade pitch may be fixed, manually variable to a few set positions, or of the automatically variable "constant-speed" type.

<span class="mw-page-title-main">Tailless aircraft</span> Aircraft whose only horizontal aerodynamic surface is its main wing

In aeronautics, a tailless aircraft is an aircraft with no other horizontal aerodynamic surface besides its main wing. It may still have a fuselage, vertical tail fin, and/or vertical rudder.

<span class="mw-page-title-main">Glider (sailplane)</span> Type of aircraft used in the sport of gliding

A glider or sailplane is a type of glider aircraft used in the leisure activity and sport of gliding. This unpowered aircraft can use naturally occurring currents of rising air in the atmosphere to gain altitude. Sailplanes are aerodynamically streamlined and so can fly a significant distance forward for a small decrease in altitude.

The drag curve or drag polar is the relationship between the drag on an aircraft and other variables, such as lift, the coefficient of lift, angle-of-attack or speed. It may be described by an equation or displayed as a graph. Drag may be expressed as actual drag or the coefficient of drag.

References

  1. Wragg, David W. (1973). A Dictionary of Aviation (first ed.). Osprey. p. 13. ISBN   9780850451634.
  2. Aircraft Design, Kundu 2010, ISBN   978 0 521 88516 4, p.283
  3. "Speed brake". Britannica. Retrieved 28 December 2019.
  4. "Air Brakes for Planes Greatly Reduce the Landing Speed". Popular Science . Vol. 122, no. 1. January 1933. p. 18.
  5. Reitsch, Hanna (April 1997) [1955]. The Sky My Kingdom: Memoirs of the Famous German WWII Test-Pilot (Greenhill Military Paperback). Stackpole Books. p. 108. ISBN   9781853672620.
  6. Davies, H.; Kirk, F. N. (June 1942). "A Résumé of Aerodynamic Data on Air Brakes" (PDF) (Technical Report). Ministry of Supply.
  7. Stephenson, Jack D. (September 1949). "The Effects of Aerodynamic Brakes Upon the Speed Characteristics of Airplanes" (PDF) (Technical Note). NACA.
  8. "Spoilers And Speedbrakes - SKYbrary Aviation Safety". www.skybrary.aero. Retrieved 2019-12-28.
  9. "Extract from NSTS Shuttle Reference Manual (1988): Space Shuttle Coordinate System – Vertical Tail". NASA. Archived from the original on 7 December 2021. Retrieved 25 October 2012.

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