Swing-wing
Encyclopedia
Wing
A wing is an appendage with a surface that produces lift for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid...
that may be swept back and then returned to its original position during flight. It allows the aircraft's planform
Planform
In aviation, a planform is the shape and layout of a fixed-wing aircraft's fuselage and wing. Of all the myriad planforms used, they can typically be grouped into those used for low-speed flight, found on general aviation aircraft, and those used for high-speed flight, found on many military...
to be modified in flight, and is therefore an example of a variable-geometry aircraft.
Typically, a swept wing
Swept wing
A swept wing is a wing planform favored for high subsonic jet speeds first investigated by Germany during the Second World War. Since the introduction of the MiG-15 and North American F-86 which demonstrated a decisive superiority over the slower first generation of straight-wing jet fighters...
is more suitable for high speeds, while an unswept wing is suitable for lower speeds, allowing the aircraft to carry more fuel and/or payload, as well as improving field performance. A variable-sweep wing allows a pilot to select the correct wing configuration for the plane's intended speed. The variable-sweep wing is most useful for those aircraft that are expected to function at both low and high speed, and for this reason it has been used primarily in military aircraft
Military aircraft
A military aircraft is any fixed-wing or rotary-wing aircraft that is operated by a legal or insurrectionary armed service of any type. Military aircraft can be either combat or non-combat:...
.
A number of successful and experimental designs were introduced from the 1940s into the 1970s, however, the recent advances in flight control technology and structural materials have allowed designers to closely tailor the aero-dynamics and structure of aircraft, removing the need for variable geometry to achieve the required performance.
History
The 1931 Westland-Hill PterodactylWestland-Hill Pterodactyl
The Westland-Hill Pterodactyl series of experimental tailess or flying wing aircraft designs were developed starting in the 1920s. They are named after the genus Pterodactylus, a well-known type of Pterosaur commonly known as the pterodactyl....
IV was a tailless
Tailless aircraft
A tailless aircraft traditionally has all its horizontal control surfaces on its main wing surface. It has no horizontal stabilizer - either tailplane or canard foreplane . A 'tailless' type usually still has a vertical stabilising fin and control surface...
design whose lightly swept wings could vary their sweep through a small angle during flight. This allowed longitudinal trim in the absence of a separate horizontal stabiliser.
Later, experimental aircraft were built to study the effects of a simple swept wing. The first of these was the Messerschmitt Me P.1101
Messerschmitt Me P.1101
|-See also:-References:NotesBibliography* Myrha, David. Messerschmitt P.1101- X Planes of the Third Reich Series. Atglen, PA: Schiffer Military History, 1999. ISBN 0-7643-0908-0....
whose sweep angle could be changed on the ground. World War II in Europe ended
End of World War II in Europe
The final battles of the European Theatre of World War II as well as the German surrender to the Western Allies and the Soviet Union took place in late April and early May 1945.-Timeline of surrenders and deaths:...
before the P.1101 could be completed.
Soon afterwards, the P.1101 was taken to the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
for study at Bell Aircraft
Bell Aircraft
The Bell Aircraft Corporation was an aircraft manufacturer of the United States, a builder of several types of fighter aircraft for World War II but most famous for the Bell X-1, the first supersonic aircraft, and for the development and production of many important civilian and military helicopters...
, but because of missing documentation and structural damage, Bell decided against completing it. Instead, a close copy was constructed which featured wings that could adjust sweep angle in flight. One problem discovered while testing the Bell X-5
Bell X-5
-See also:-Bibliography:* Hallion, Richard P. On The Frontier: Flight Research At Dryden 1946-1981 . Washington, DC: National Aeronautics and Space Administration, 1984 . ISBN 1-58834-134-8....
was that as the wing pivoted rearward, the lift vector also moved to the rear, pushing the nose down. A system to compensate for this basic effect had to be added for any such design to be viable.
Immediately after the war Barnes Wallis
Barnes Wallis
Sir Barnes Neville Wallis, CBE FRS, RDI, FRAeS , was an English scientist, engineer and inventor. He is best known for inventing the bouncing bomb used by the RAF in Operation Chastise to attack the dams of the Ruhr Valley during World War II...
had started work on variable geometry to maximise the economy of supersonic flight. Initial work was on the military "Wild Goose" project, then he went onto the "Vickers Swallow", intended to achieve a return flight from Europe to Australia in 10 hours. It had a blended wing
Blended wing body
Blended Wing Body aircraft have a flattened and airfoil shaped body, which produces most of the lift, the wings contributing the balance. The body form is composed of distinct and separate wing structures, though the wings are smoothly blended into the body...
tailless design and he successfully tested several models including a six foot scale model
Scale model
A scale model is a physical model, a representation or copy of an object that is larger or smaller than the actual size of the object, which seeks to maintain the relative proportions of the physical size of the original object. Very often the scale model is used as a guide to making the object in...
at speeds of up to Mach 2 in the 1950s but government backing was withdrawn. Wallis and his team presented their work to the Americans seeking a grant to continue their studies but none was forthcoming. In 1949, aeronautical engineer L. E. Baynes
L. E. Baynes
Leslie Everett Baynes, AFRAeS was an English aeronautical engineer.-Early life:Born at Barnes, Surrey, on 23 March 1902 the son of James and Florence Baynes. Baynes was educated at Gresham's School, Norfolk, leaving school at the age of sixteen to join an aircraft company...
patented a design for a supersonic variable-sweep wing fighter, but the design was not built.
A variable-sweep wing was tried on the Grumman F10F Jaguar in 1952. The XF10F never entered service; it possessed extremely poor flying characteristics and rather vicious spin tendencies. The idea was again revived in the early 1960s as a way to reconcile ever-growing aircraft weights (and thus wing loading
Wing loading
In aerodynamics, wing loading is the loaded weight of the aircraft divided by the area of the wing. The faster an aircraft flies, the more lift is produced by each unit area of wing, so a smaller wing can carry the same weight in level flight, operating at a higher wing loading. Correspondingly,...
) with the need to provide reasonable takeoff
Takeoff
Takeoff is the phase of flight in which an aerospace vehicle goes from the ground to flying in the air.For horizontal takeoff aircraft this usually involves starting with a transition from moving along the ground on a runway. For balloons, helicopters and some specialized fixed-wing aircraft , no...
and landing
Landing
thumb|A [[Mute Swan]] alighting. Note the ruffled feathers on top of the wings indicate that the swan is flying at the [[Stall |stall]]ing speed...
performance. The United States adopted this configuration for the TFX (Tactical Fighter Experimental) program, which emerged as the General Dynamics F-111
General Dynamics F-111
The General Dynamics F-111 "Aardvark" was a medium-range interdictor and tactical strike aircraft that also filled the roles of strategic bomber, reconnaissance, and electronic warfare in its various versions. Developed in the 1960s by General Dynamics, it first entered service in 1967 with the...
, the first production variable-sweep wing aircraft.
Similar requirements in the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
also led TsAGI
TsAGI
TsAGI is a transliteration of the Russian abbreviation for Центра́льный аэрогидродинами́ческий институ́т or "Tsentralniy Aerogidrodinamicheskiy Institut", the Central Aerohydrodynamic Institute....
, the Soviet aerodynamics bureau, to explore the possibilities of variable geometry. TsAGI evolved two distinct planform
Planform
In aviation, a planform is the shape and layout of a fixed-wing aircraft's fuselage and wing. Of all the myriad planforms used, they can typically be grouped into those used for low-speed flight, found on general aviation aircraft, and those used for high-speed flight, found on many military...
s, differing mainly in the distance (expressed as a percentage of total wingspan
Wingspan
The wingspan of an airplane or a bird, is the distance from one wingtip to the other wingtip. For example, the Boeing 777 has a wingspan of about ; and a Wandering Albatross caught in 1965 had a wingspan of , the official record for a living bird.The term wingspan, more technically extent, is...
) between the wing pivots. A wider spacing not only reduced the negative aerodynamic effects of changing wing sweep, but also provided a larger fixed wing section which could be used for landing gear
Landing Gear
Landing Gear is Devin the Dude's fifth studio album. It was released on October 7, 2008. It was his first studio album since signing with the label Razor & Tie. It features a high-profile guest appearance from Snoop Dogg. As of October 30, 2008, the album has sold 18,906 copies.-Track...
or stores pylons. This could, in fact, be adapted to more-or-less existing airframes, which the Soviets soon did, with the Sukhoi Su-17
Sukhoi Su-17
The Sukhoi Su-17 is a Soviet attack aircraft developed from the Sukhoi Su-7 fighter-bomber. It enjoyed a long career in Soviet, later Russian, service and was widely exported to communist and Middle Eastern air forces, under names Su-20 and Su-22.-Development:Seeking to improve low-speed and...
(based on the earlier swept wing
Swept wing
A swept wing is a wing planform favored for high subsonic jet speeds first investigated by Germany during the Second World War. Since the introduction of the MiG-15 and North American F-86 which demonstrated a decisive superiority over the slower first generation of straight-wing jet fighters...
Sukhoi Su-7
Sukhoi Su-7
The Sukhoi Su-7 was a swept wing, supersonic fighter aircraft developed by the Soviet Union in 1955. Originally, it was designed as tactical, low-level dogfighter, but was not successful in this role. On the other hand, soon-introduced Su-7B series became the main Soviet fighter-bomber and...
). The limitation of the wide spacing, however, was that it reduced the benefits of variable geometry as much as it reduced their technical difficulties. For the new, "clean-sheet" Soviet designs, TsAGI devised a more narrowly spaced arrangement similar to that of the F-111. This design was used (albeit at different scales) for the MiG-23 fighter and the Sukhoi Su-24
Sukhoi Su-24
The Sukhoi Su-24 is a supersonic, all-weather attack aircraft developed in the Soviet Union. This variable-sweep wing, twin-engined two-seater carried the USSR's first integrated digital navigation/attack system...
interdictor, which flew in prototype forms at the end of the 1960s, entering service in the early 1970s.
AFVG
|-References:NotesCitationsBibliography* Bowman, Martin W. SEPECAT Jaguar. Barnsley, South Yorkshire, UK: Pen and Sword Books, 2007. ISBN 1-84415-545-5....
). When French commitment was curtailed the British sought a second partner in the F-104 Consortium of European nations. This in turn led to the European consortium that adopted variable geometry for the Multi-Role Combat Aircraft (MRCA) project that emerged as the Panavia Tornado
Panavia Tornado
The Panavia Tornado is a family of twin-engine, variable-sweep wing combat aircraft, which was jointly developed and manufactured by the United Kingdom, West Germany and Italy...
. This was an interdictor and stand-off interceptor similar in function to the F-111, albeit on a smaller scale. Meanwhile, the U.S. Navy introduced the Grumman F-14 Tomcat to replace the canceled F-111B fleet interceptor with a fighter more nimble than the F-4 Phantom. Unlike the F-111, its variable-sweep wings were programmed automatically by speed and could be swept under G loading. In air combat, the wings could be swept forward for tight "bat" turns and back for dash speeds. Rockwell
Rockwell International
Rockwell International was a major American manufacturing conglomerate in the latter half of the 20th century, involved in aircraft, the space industry, both defense-oriented and commercial electronics, automotive and truck components, printing presses, valves and meters, and industrial automation....
, meanwhile, adopted variable geometry for the Advanced Manned Strategic Bomber (AMSA) program that produced the B-1 Lancer
B-1 Lancer
The Rockwell B-1 LancerThe name "Lancer" is only applied to the B-1B version, after the program was revived. is a four-engine variable-sweep wing strategic bomber used by the United States Air Force...
bomber, intended to provide an optimum combination of high-speed cruising efficiency and fast, supersonic
Supersonic
Supersonic speed is a rate of travel of an object that exceeds the speed of sound . For objects traveling in dry air of a temperature of 20 °C this speed is approximately 343 m/s, 1,125 ft/s, 768 mph or 1,235 km/h. Speeds greater than five times the speed of sound are often...
penetration speeds at extremely low level. The last variable-sweep wing military aircraft to date was the Soviet Tupolev Tu-160
Tupolev Tu-160
The Tupolev Tu-160 is a supersonic, variable-sweep wing heavy strategic bomber designed by the Tupolev Design Bureau in the Soviet Union. Although several civil and military transport aircraft are larger in overall dimensions, the Tu-160 is currently the world's largest combat aircraft, largest...
"Blackjack", which first flew in 1980.
A variable-sweep wing was also selected as the winning design used by Boeing
Boeing
The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...
's entry in the FAA
Federal Aviation Administration
The Federal Aviation Administration is the national aviation authority of the United States. An agency of the United States Department of Transportation, it has authority to regulate and oversee all aspects of civil aviation in the U.S...
's study for a supersonic transport
Supersonic transport
A supersonic transport is a civilian supersonic aircraft designed to transport passengers at speeds greater than the speed of sound. The only SSTs to see regular service to date have been Concorde and the Tupolev Tu-144. The last passenger flight of the Tu-144 was in June 1978 with its last ever...
, the 2707
Boeing 2707
The Boeing 2707 was developed as the first American supersonic transport . After winning a competition for a government-funded contract to build an American SST, Boeing began development at its facilities in Seattle, Washington...
. However it evolved through several configurations during the design stage, finally adding a canard, and it eventually became clear that the design would be so heavy that it would be lacking sufficient payload for the fuel needed. The design was later abandoned in favor of a more conventional tailed delta wing
Delta wing
The delta wing is a wing planform in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta .-Delta-shaped stabilizers:...
.
While variable-sweep provides many advantages, particularly in takeoff distance, load-carrying ability, and the fast, low-level penetration role, the configuration imposes a considerable penalty in weight and complexity. The advent of relaxed stability
Relaxed stability
In aviation, relaxed stability is the tendency of an aircraft to change its attitude and angle of bank of its own accord. An aircraft with relaxed stability will oscillate in simple harmonic motion around a particular attitude at an increasing amplitude....
flight control systems in the 1970s negated many of the disadvantages of a fixed platform. No new variable-sweep wing aircraft have been built since the Tu-160, though it has been noted that the F-14's replacement - the F/A-18E
F/A-18E/F Super Hornet
The Boeing F/A-18E/F Super Hornet is a twin-engine carrier-based multirole fighter aircraft. The F/A-18E single-seat variant and F/A-18F tandem-seat variant are larger and more advanced derivatives of the F/A-18C and D Hornet. The Super Hornet has an internal 20 mm gun and can carry air-to-air...
- has a reduced payload/range capability largely because of its small fixed wings.
Experimental
- Westland-Hill PterodactylWestland-Hill PterodactylThe Westland-Hill Pterodactyl series of experimental tailess or flying wing aircraft designs were developed starting in the 1920s. They are named after the genus Pterodactylus, a well-known type of Pterosaur commonly known as the pterodactyl....
IV - Bell X-5Bell X-5-See also:-Bibliography:* Hallion, Richard P. On The Frontier: Flight Research At Dryden 1946-1981 . Washington, DC: National Aeronautics and Space Administration, 1984 . ISBN 1-58834-134-8....
- Dassault Mirage GDassault Mirage G|-See also:-Bibliography:* Green, William. The Observer's Book of Aircraft. London. Frederick Warne & Co. Ltd., 1968.* Green, William. The Observer's Book of Aircraft. London. Frederick Warne & Co. Ltd., 1972. ISBN 0-7232-1507-3-External links:*...
- Messerschmitt Me P.1101Messerschmitt Me P.1101|-See also:-References:NotesBibliography* Myrha, David. Messerschmitt P.1101- X Planes of the Third Reich Series. Atglen, PA: Schiffer Military History, 1999. ISBN 0-7643-0908-0....
- Grumman XF10F-1 JaguarXF10F Jaguar|-See also:-References:NotesBibliography* DeMeis, Richard. "No Room to Swing a Cat." Wings, Volume 6, No. 4, August 1976.* Jones, Lloyd S. US Naval Fighters 1922 to 1980s. Fallbrook, CA: Aero Publishers, 1977. ISBN 978-0816892549....
Production
- General Dynamics F-111 Aardvark
- Grumman F-14 Tomcat
- Mikoyan-Gurevich MiG-23Mikoyan-Gurevich MiG-23The Mikoyan-Gurevich MiG-23 is a variable-geometry fighter aircraft, designed by the Mikoyan-Gurevich design bureau in the Soviet Union. It is considered to belong to the Soviet third generation jet fighter category, along with similarly aged Soviet fighters such as the MiG-25 "Foxbat"...
- Mikoyan-Gurevich MiG-27
- Panavia TornadoPanavia TornadoThe Panavia Tornado is a family of twin-engine, variable-sweep wing combat aircraft, which was jointly developed and manufactured by the United Kingdom, West Germany and Italy...
- Rockwell B-1 Lancer
- Sukhoi Su-17Sukhoi Su-17The Sukhoi Su-17 is a Soviet attack aircraft developed from the Sukhoi Su-7 fighter-bomber. It enjoyed a long career in Soviet, later Russian, service and was widely exported to communist and Middle Eastern air forces, under names Su-20 and Su-22.-Development:Seeking to improve low-speed and...
- Sukhoi Su-24Sukhoi Su-24The Sukhoi Su-24 is a supersonic, all-weather attack aircraft developed in the Soviet Union. This variable-sweep wing, twin-engined two-seater carried the USSR's first integrated digital navigation/attack system...
- Tupolev Tu-22MTupolev Tu-22MThe Tupolev Tu-22M is a supersonic, swing-wing, long-range strategic and maritime strike bomber developed by the Soviet Union. Significant numbers remain in service with the Russian Air Force....
- Tupolev Tu-160Tupolev Tu-160The Tupolev Tu-160 is a supersonic, variable-sweep wing heavy strategic bomber designed by the Tupolev Design Bureau in the Soviet Union. Although several civil and military transport aircraft are larger in overall dimensions, the Tu-160 is currently the world's largest combat aircraft, largest...
See also
- Adaptive Compliant WingAdaptive Compliant WingThe Adaptive Compliant Wing is a wing design developed by FlexSys, Inc., which is flexible so that aspects of its shape can be changed in flight....
- Oblique WingOblique wingAn oblique wing is a variable geometry wing concept. On an aircraft so equipped, the wing is designed to rotate on center pivot, so that one tip is swept forward while the opposite tip is swept aft...
- Variable-incidence wingVariable-incidence wingA variable-incidence wing has an adjustable angle of incidence in order to reduce landing and take-off distances. It was patented in France on May 20, 1912 by Bulgarian inventor George Boginoff....
- Variable camber wingVariable camber wingVariable camber wing is a design of aircraft wing by Vincent Burnelli that changes the camber of the airfoil , and varies the area and camber of the wing .A mechanism moves and rotates the leading and trailing edge to gain camber and wing area....