F-15 Eagle landing with the speed brake up

In aeronautics, air brakes or speed brakes are a type of

flight control surface Aircraft flight control surfaces are aerodynamic devices allowing a pilot to adjust and control the aircraft's flight attitude. Development of an effective set of flight control surfaces was a critical advance in the development of aircraft. Ea ...

used on an

aircraft 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 by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engine ...

to increase the drag on the aircraft. Air brakes differ from spoilers in that air brakes are designed to increase drag while making little change to

lift Lift or LIFT may refer to: Physical devices * Elevator, or lift, a device used for raising and lowering people or goods ** Paternoster lift, a type of lift using a continuous chain of cars which do not stop ** Patient lift, or Hoyer lift, mobil ...

, whereas spoilers reduce the

lift-to-drag ratio In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the lift generated by an aerodynamic body such as an aerofoil or aircraft, divided by the aerodynamic drag caused by moving through air. It describes the aerodynamic efficiency under gi ...

and require a higher angle of attack to maintain lift, resulting in a higher

stall speed In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', p. 486. Aviation Supplies & Academics, 1997. This occurs when t ...

Introduction

An air brake is a part of an aircraft. When extended into the airstream, it causes an increase in the drag on the aircraft. When not in use, it conforms to the local streamlined profile of the aircraft in order to help minimise the drag.

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. In 1936,

Hans Jacobs Hans Jacobs (30 April 1907 in Hamburg - 24 October 1994) was a German sailplane designer and pioneer. He had been taught sailplane design by Alexander Lippisch, designer of many gliders during the 1920s and the 1930s. As the head of the ''Deut ...

, who headed Nazi Germany's ''

Deutsche Forschungsanstalt für Segelflug The ''Deutsche Forschungsanstalt für Segelflug'' (), or DFS , was formed in 1933 to centralise all gliding activity in Germany, under the directorship of Professor Walter Georgii. It was formed by the nationalisation of the Rhön-Rossitten G ...

'' (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. 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 written in 1942 discusses the need for air 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 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 Parasitic drag, also known as profile drag, is a type of aerodynamic drag that acts on any object when the object is moving through a fluid. Parasitic drag is a combination of form drag and skin friction drag. It affects all objects regardless of ...

created by the spoilers directly assists the braking effect.

Reverse 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 ...

is also used to help slow the aircraft after landing. Klm

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 The Arado Ar 234 ''Blitz'' (English: lightning) is a jet-powered bomber designed and produced by the German aircraft manufacturer Arado. It was the world's first operational turbojet-powered bomber, seeing service during the latter half of the ...

Boeing B-47 The Boeing B-47 Stratojet (Boeing company designation Model 450) is a retired American long- range, six-engined, turbojet-powered strategic bomber designed to fly at high subsonic speed and at high altitude to avoid enemy interceptor aircraft ...

) or after landing (

English Electric Lightning The English Electric Lightning is a British fighter aircraft that served as an interceptor during the 1960s, the 1970s and into the late 1980s. It was capable of a top speed of above Mach 2. The Lightning was designed, developed, and manufa ...

). Split-tailcone air brakes have been used on the Blackburn Buccaneer naval strike aircraft designed in the 1950s and

Fokker F28 Fellowship The Fokker F28 Fellowship is a twin-engined, short-range jet airliner designed and built by Dutch aircraft manufacturer Fokker. Following the Fokker F27 Friendship, an early and commercially successful turboprop-powered regional airliner, Fokk ...

and

British Aerospace 146 The British Aerospace 146 (also BAe 146) is a short-haul and regional airliner that was manufactured in the United Kingdom by British Aerospace, later part of BAE Systems. Production ran from 1983 until 2001. Manufacture by Avro Internati ...

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 The McDonnell Douglas F/A-18 Hornet is an all-weather, twin-engine, supersonic, carrier-capable, multirole combat aircraft, designed as both a fighter and attack aircraft (hence the F/A designation). Designed by McDonnell Douglas (now part ...

and other fighters have an air brake located just behind the cockpit.

Split control surfaces

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 The Northrop F-89 Scorpion was an American all-weather, twin-engined interceptor aircraft built during the 1950s, the first jet-powered aircraft designed for that role from the outset to enter service. Though its straight wings limited its per ...

and has since been used by Northrop on several aircraft, including the

B-2 Spirit The Northrop (later Northrop Grumman) B-2 Spirit, also known as the Stealth Bomber, is an American heavy strategic bomber, featuring low-observable stealth technology designed to penetrate dense anti-aircraft defenses. A subsonic flying ...

. The

Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program ...

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

References

External links