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A swept wing is a
wing 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 expres ...
that angles either backward or occasionally
forward Forward is a relative direction, the opposite of backward. Forward may also refer to: People * Forward (surname) Sports * Forward (association football) * Forward (basketball), including: ** Point forward ** Power forward (basketball) ** Sm ...
from its root rather than in a straight sideways direction. Swept wings have been flown since the pioneer days of aviation. Wing sweep at high speeds was first investigated in Germany as early as 1935 by Albert Betz and
Adolph Busemann Adolf Busemann (20 April 1901 – 3 November 1986) was a German aerospace engineer and influential Nazi-era pioneer in aerodynamics, specialising in supersonic airflows. He introduced the concept of swept wings and, after emigrating in 1947 to t ...
, finding application just before the end of the
Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
. It has the effect of delaying the shock waves and accompanying
aerodynamic drag In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding fl ...
rise caused by fluid
compressibility In thermodynamics and fluid mechanics, the compressibility (also known as the coefficient of compressibility or, if the temperature is held constant, the isothermal compressibility) is a measure of the instantaneous relative volume change of a f ...
near the
speed of sound The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. At , the speed of sound in air is about , or one kilometre in or one mile in . It depends strongly on temperature as w ...
, improving performance. Swept wings are therefore almost always used on
jet aircraft A jet aircraft (or simply jet) is an aircraft (nearly always a fixed-wing aircraft) propelled by jet engines. Whereas the engines in propeller-powered aircraft generally achieve their maximum efficiency at much lower speeds and altitudes, je ...
designed to fly at these speeds. The term "swept wing" is normally used to mean "swept back", but variants include forward sweep, variable sweep wings and
oblique wing An oblique wing (also called a slewed 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. By changing its swee ...
s in which one side sweeps forward and the other back. The
delta wing A delta wing is a wing shaped in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta (Δ). Although long studied, it did not find significant applications until the Jet Age, when it proved suitabl ...
is also aerodynamically a form of swept wing.


Reasons for sweep

There are three main reasons for sweeping a wing: 1. to arrange the center of gravity of the aircraft and the aerodynamic center of the wing to coincide more closely for longitudinal balance, e.g.
Messerschmitt Me 163 Komet The Messerschmitt Me 163 Komet is a rocket-powered interceptor aircraft primarily designed and produced by the German aircraft manufacturer Messerschmitt. It is the only operational rocket-powered fighter aircraft in history as well as ...
and
Messerschmitt Me 262 The Messerschmitt Me 262, nicknamed ''Schwalbe'' (German: "Swallow") in fighter versions, or ''Sturmvogel'' (German: "Storm Bird") in fighter-bomber versions, is a fighter aircraft and fighter-bomber that was designed and produced by the Germa ...
. Although not a swept wing the wing panels on the Douglas DC-1 outboard of the nacelles also had slight sweepback for similar reasons.Design For Air Combat,Ray Whitford 1987,,p.42 2. to provide longitudinal stability for tailless aircraft, e.g.
Messerschmitt Me 163 Komet The Messerschmitt Me 163 Komet is a rocket-powered interceptor aircraft primarily designed and produced by the German aircraft manufacturer Messerschmitt. It is the only operational rocket-powered fighter aircraft in history as well as ...
. 3. most commonly to increase Mach-number capability by delaying to a higher speed the effects of
compressibility In thermodynamics and fluid mechanics, the compressibility (also known as the coefficient of compressibility or, if the temperature is held constant, the isothermal compressibility) is a measure of the instantaneous relative volume change of a f ...
(abrupt changes in the density of the airflow), e.g. combat aircraft, airliners and business jets. Other reasons include: 1. enabling a wing carry-through box position to achieve a desired cabin size, e.g.
HFB 320 Hansa Jet The HFB 320 Hansa Jet is a twin-engine, ten-seat business jet that was designed and produced by German aircraft manufacturer Hamburger Flugzeugbau between 1964 and 1973. The most recognisable and unconventional feature of the aircraft is its for ...
. 2. providing static aeroelastic relief which reduces bending moments under high g-loadings and may allow a lighter wing structure.


Structural design

For a wing of given span, sweeping it increases the length of the spars running along it from root to tip. This tends to increase weight and reduce stiffness. If the fore-aft chord of the wing also remains the same, the distance between leading and trailing edges reduces, reducing its ability to resist twisting (torsion) forces. A swept wing of given span and chord must therefore be strengthened and will be heavier than the equivalent unswept wing. A swept wing typically angles backward from its root rather than forwards. Because wings are made as light as possible, they tend to flex under load. This
aeroelasticity Aeroelasticity is the branch of physics and engineering studying the interactions between the inertial, elastic, and aerodynamic forces occurring while an elastic body is exposed to a fluid flow. The study of aeroelasticity may be broadly classif ...
under aerodynamic load causes the tips to bend upwards in normal flight. Backwards sweep causes the tips to reduce their angle of attack as they bend, reducing their lift and limiting the effect. Forward sweep causes the tips to increase their angle of attack as they bend. This increases their lift causing further bending and hence yet more lift in a cycle which can cause a runaway structural failure. For this reason forward sweep is rare and the wing must be unusually rigid. There are two sweep angles of importance, one at the leading edge for supersonic aircraft and the other 25% of the way back from the leading edge for subsonic and transonic aircraft. Leading edge sweep is important because the leading edge has to be behind the mach cone to reduce wave drag. The quarter chord (25%) line is used because subsonic lift due to angle of attack acts there and, up until the introduction of supercritical sections, the crest was usually close to the quarter chord. Typical sweep angles vary from 0 for a straight-wing aircraft, to 45 degrees or more for fighters and other high-speed designs.


Aerodynamic design


Subsonic and transonic flight

Shock waves can form on some parts of an aircraft moving at less than the speed of sound. Low-pressure regions around an aircraft cause the flow to accelerate, and at transonic speeds this local acceleration can exceed Mach 1. Localized supersonic flow must return to the freestream conditions around the rest of the aircraft, and as the flow enters an adverse pressure gradient in the aft section of the wing, a discontinuity emerges in the form of a shock wave as the air is forced to rapidly slow and return to ambient pressure. At the point where the density drops, the local speed of sound correspondingly drops and a shock wave can form. This is why in conventional wings, shock waves form first ''after'' the maximum Thickness/Chord and why all airliners designed for cruising in the transonic range (above M0.8) have supercritical wings that are flatter on top, resulting in minimized angular change of flow to upper surface air. The angular change to the air that is normally part of lift generation is decreased and this lift reduction is compensated for by deeper curved lower surfaces accompanied by a reflex curve at the trailing edge. This results in a much weaker shock wave towards the rear of the upper wing surface and a corresponding ''increase'' in critical mach number. Shock waves require energy to form. This energy is taken out of the aircraft, which has to supply extra
thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that syst ...
to make up for this energy loss. Thus the shocks are seen as a form of drag. Since the shocks form when the local air velocity reaches supersonic speeds, there is a certain "
critical mach In aerodynamics, the critical Mach number (Mcr or M*) of an aircraft is the lowest Mach number at which the airflow over some point of the aircraft reaches the speed of sound, but does not exceed it.Clancy, L.J. ''Aerodynamics'', Section 11.6 At t ...
" speed where sonic flow first appears on the wing. There is a following point called the
drag divergence mach number The drag-divergence Mach number (not to be confused with critical Mach number) is the Mach number at which the aerodynamic drag on an airfoil or airframe begins to increase rapidly as the Mach number continues to increase. This increase can caus ...
where the effect of the drag from the shocks becomes noticeable. This is normally when the shocks start generating over the wing, which on most aircraft is the largest continually curved surface, and therefore the largest contributor to this effect. Sweeping the wing has the effect of reducing the curvature of the body as seen from the airflow, by the cosine of the angle of sweep. For instance, a wing with a 45 degree sweep will see a reduction in effective curvature to about 70% of its straight-wing value. This has the effect of increasing the critical Mach by 30%. When applied to large areas of the aircraft, like the wings and
empennage The empennage ( or ), also known as the tail or tail assembly, is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an arrow.Crane, Dale: ''Dictionary of Aeronautical Terms, third e ...
, this allows the aircraft to reach speeds closer to Mach 1. One limiting factor in swept wing design is the so-called "middle effect". If a swept wing is continuous - an oblique swept wing - the pressure isobars will be swept at a continuous angle from tip to tip. However, if the left and right halves are swept back equally, as is common practice, the pressure isobars on the left wing in theory will meet the pressure isobars of the right wing on the centerline at a large angle. As the isobars cannot meet in such a fashion, they will tend to curve on each side as they near the centerline, so that the isobars cross the centerline at right angles to the centerline. This causes an "unsweeping" of the isobars in the wing root region. To combat this unsweeping, German aerodynamicist
Dietrich Küchemann Dietrich Küchemann CBE FRS FRAeS (11 September 1911 – 23 February 1976) was a German aerodynamicist who made several important contributions to the advancement of high-speed flight. He spent most of his career in the UK, where he is ...
proposed and had tested a local indentation of the fuselage above and below the wing root. This proved to not be very effective.Meier, Hans-Ulrich, editor ''German Development of the Swept Wing 1935–1945'', AIAA Library of Flight, 2010. Originally published in German as ''Die deutsche Luftahrt Die Pfeilflügelentwicklung in Deutschland bis 1945'', Bernard & Graefe Verlag, 2006. During the development of the
Douglas DC-8 The Douglas DC-8 (sometimes McDonnell Douglas DC-8) is a long-range narrow-body airliner built by the American Douglas Aircraft Company. After losing the May 1954 US Air Force tanker competition to the Boeing KC-135, Douglas announced in July ...
airliner, uncambered airfoils were used in the wing root area to combat the unsweeping.


Supersonic flight

Swept wings on supersonic aircraft usually lie within the cone-shaped shock wave produced at the nose of the aircraft so will "see" subsonic airflow and work as a subsonic wing. The angle needed to lie behind the cone increases with increasing speed, at Mach 1.3 the angle is about 45 degrees, at Mach 2.0 it is 60 degrees. The angle of the
Mach cone In fluid dynamics, a Mach wave is a pressure wave traveling with the speed of sound caused by a slight change of pressure added to a compressible flow. These weak waves can combine in supersonic flow to become a shock wave if sufficient Mach wa ...
formed off the body of the aircraft will be at about sinμ = 1/M (μ is the sweep angle of the Mach cone)


Disadvantages

When a swept wing travels at high speed, the airflow has little time to react and simply flows over the wing almost straight from front to back. At lower speeds the air ''does'' have time to react, and is pushed spanwise by the angled leading edge, towards the wing tip. At the wing root, by the fuselage, this has little noticeable effect, but as one moves towards the wingtip the airflow is pushed spanwise not only by the leading edge, but the spanwise moving air beside it. At the tip the airflow is moving along the wing instead of over it, a problem known as ''spanwise flow''. The lift from a wing is generated by the airflow over it from front to rear. With increasing span-wise flow the boundary layers on the surface of the wing have longer to travel, and so are thicker and more susceptible to transition to turbulence or flow separation, also the effective aspect ratio of the wing is less and so air "leaks" around the wing tips reducing their effectiveness. The spanwise flow on swept wings produces airflow that moves the stagnation point on the leading edge of any individual wing segment further beneath the leading edge, increasing effective
angle of attack In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is m ...
of wing segments relative to its neighbouring forward segment. The result is that wing segments farther towards the rear operate at increasingly higher angles of attack promoting early stall of those segments. This promotes tip stall on back-swept wings, as the tips are most rearward, while delaying tip stall for forward-swept wings, where the tips are forward. With both forward and back-swept wings, the rear of the wing will stall first creating a nose-up moment on the aircraft. If not corrected by the pilot the plane will pitch up, leading to more of the wing stalling and more pitch up in a divergent manner. This uncontrollable instability came to be known as the ''
Sabre dance "Sabre Dance", ''Suserov par''; russian: Танец с саблями, ''Tanets s sablyami'' is a Movement (music), movement in the final act of Aram Khachaturian's ballet ''Gayane (ballet), Gayane'' (1942), where the Ballet dancer, dancers dis ...
'' in reference to the number of North American F-100 Super Sabres that crashed on landing as a result. Reducing pitch-up to an acceptable level has been done in different ways such as the addition of a fin known as a ''
wing fence Wing fences, also known as boundary layer fences and potential fences are fixed aerodynamic devices attached to aircraft wings. Often seen on swept-wing aircraft, wing fences are flat plates fixed to the upper surfaces parallel to the wing ch ...
'' on the upper surface of the wing to redirect the flow to a streamwise direction. The
MiG-15 The Mikoyan-Gurevich MiG-15 (russian: Микоя́н и Гуре́вич МиГ-15; USAF/DoD designation: Type 14; NATO reporting name: Fagot) is a jet fighter aircraft developed by Mikoyan-Gurevich for the Soviet Union. The MiG-15 was one of ...
was one example of an aircraft fitted with wing fences.Gunston 1995, p. 188. Another closely related design was the addition of a dogtooth notch to the leading edge, used on the
Avro Arrow The Avro Canada CF-105 Arrow was a delta-winged interceptor aircraft designed and built by Avro Canada. The CF-105 held the promise of Mach 2 speeds at altitudes exceeding and was intended to serve as the Royal Canadian Air Force's (RCAF) p ...
interceptor. Other designs took a more radical approach, including the
Republic XF-91 Thunderceptor The Republic XF-91 Thunderceptor (originally designated XP-91) is a mixed-propulsion prototype interceptor aircraft, developed by Republic Aviation. The aircraft would use a jet engine for most flight, and a cluster of four small rocket engines ...
's wing that grew wider towards the tip to provide more lift at the tip. The
Handley Page Victor The Handley Page Victor is a British jet-powered strategic bomber developed and produced by Handley Page during the Cold War. It was the third and final '' V bomber'' to be operated by the Royal Air Force (RAF), the other two being the Avro ...
was equipped with a
crescent wing The crescent wing is a fixed-wing aircraft configuration in which a swept wing has a greater sweep angle on the inboard section than the outboard, giving the wing a crescent shape. The planform attempts to reduce several unpleasant side-effects o ...
, with three values of sweep, about 48 degrees near the wing root where the wing was thickest, a 38 degree transition length and 27 degrees for the remainder to the tip. Modern solutions to the problem no longer require "custom" designs such as these. The addition of
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, ...
s and large compound flaps to the wings has largely resolved the issue.High-Lift Aerodynamics, by A. M. O. Smith, McDonnell Douglas Corporation, Long Beach, June 1975
Perkins, Courtland; Hage, Robert (1949). ''Airplane performance, stability and control'', Chapter 2, John Wiley and Sons. . On fighter designs, the addition of leading-edge extensions, which are typically included to achieve a high level of maneuverability, also serve to add lift during landing and reduce the problem. In addition to pitch-up there are other complications inherent in a swept-wing configuration. For any given length of wing, the actual span from tip-to-tip is shorter than the same wing that is not swept. There is a strong correlation between low-speed drag and aspect ratio, the span compared to chord, so a swept wing always has more drag at lower speeds. In addition, there is extra torque applied by the wing to the fuselage which has to be allowed for when establishing the transfer of wing-box loads to the fuselage. This results from the significant part of the wing lift which lies behind the attachment length where the wing meets the fuselage.


Sweep theory

Sweep theory is an
aeronautical engineering Aerospace engineering is the primary field of engineering concerned with the development of aircraft and spacecraft. It has two major and overlapping branches: Aeronautics, aeronautical engineering and Astronautics, astronautical engineering. A ...
description of the behavior of airflow over a
wing 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 expres ...
when the wing's leading edge encounters the airflow at an oblique angle. The development of sweep theory resulted in the swept wing design used by most modern jet aircraft, as this design performs more effectively at transonic and
supersonic Supersonic speed is the speed of an object that exceeds the speed of sound ( Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...
speeds. In its advanced form, sweep theory led to the experimental
oblique wing An oblique wing (also called a slewed 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. By changing its swee ...
concept.
Adolf Busemann Adolf Busemann (20 April 1901 – 3 November 1986) was a German aerospace engineer and influential Nazi-era pioneer in aerodynamics, specialising in supersonic airflows. He introduced the concept of swept wings and, after emigrating in 1947 to t ...
introduced the concept of the swept wing and presented this in 1935 at the 5. Volta-Congress in Rome. Sweep theory in general was a subject of development and investigation throughout the 1930s and 1940s, but the breakthrough mathematical definition of sweep theory is generally credited to
NACA The National Advisory Committee for Aeronautics (NACA) was a United States federal agency founded on March 3, 1915, to undertake, promote, and institutionalize aeronautical research. On October 1, 1958, the agency was dissolved and its assets ...
's Robert T. Jones in 1945. Sweep theory builds on other wing lift theories. Lifting line theory describes lift generated by a straight wing (a wing in which the leading edge is perpendicular to the airflow). Weissinger theory describes the distribution of lift for a swept wing, but does not have the capability to include chordwise pressure distribution. There are other methods that do describe chordwise distributions, but they have other limitations. Jones' sweep theory provides a simple, comprehensive analysis of swept wing performance. An explanation of how the swept wing works was offered by Robert T. Jones: "Assume a wing is a cylinder of uniform airfoil cross-section, chord and thickness and is placed in an airstream at an angle of yaw – i.e., it is swept back. Now, even if the local speed of the air on the upper surface of the wing becomes supersonic, a shock wave cannot form there because it would have to be a sweptback shock – swept at the same angle as the wing – i.e., it would be an oblique shock. Such an oblique shock cannot form until the velocity component normal to it becomes supersonic." To visualize the basic concept of simple sweep theory, consider a straight, non-swept wing of infinite length, which meets the airflow at a perpendicular angle. The resulting air pressure distribution is equivalent to the length of the wing's chord (the distance from the leading edge to the trailing edge). If we were to begin to slide the wing sideways ( spanwise), the sideways motion of the wing relative to the air would be added to the previously perpendicular airflow, resulting in an airflow over the wing at an angle to the leading edge. This angle results in airflow traveling a greater distance from leading edge to trailing edge, and thus the air pressure is distributed over a greater distance (and consequently lessened at any particular point on the surface). This scenario is identical to the airflow experienced by a swept wing as it travels through the air. The airflow over a swept wing encounters the wing at an angle. That angle can be broken down into two vectors, one perpendicular to the wing, and one parallel to the wing. The flow parallel to the wing has no effect on it, and since the perpendicular vector is shorter (meaning slower) than the actual airflow, it consequently exerts less pressure on the wing. In other words, the wing experiences airflow that is slower - and at lower pressures - than the actual speed of the aircraft. One of the factors that must be taken into account when designing a high-speed wing is
compressibility In thermodynamics and fluid mechanics, the compressibility (also known as the coefficient of compressibility or, if the temperature is held constant, the isothermal compressibility) is a measure of the instantaneous relative volume change of a f ...
, which is the effect that acts upon a wing as it approaches and passes through the
speed of sound The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. At , the speed of sound in air is about , or one kilometre in or one mile in . It depends strongly on temperature as w ...
. The significant negative effects of compressibility made it a prime issue with aeronautical engineers. Sweep theory helps mitigate the effects of compressibility in transonic and supersonic aircraft because of the reduced pressures. This allows the mach number of an aircraft to be higher than that actually experienced by the wing. There is also a negative aspect to sweep theory. The lift produced by a wing is directly related to the speed of the air over the wing. Since the airflow speed experienced by a swept wing is lower than what the actual aircraft speed is, this becomes a problem during slow-flight phases, such as takeoff and landing. There have been various ways of addressing the problem, including the
variable-incidence wing A variable-incidence wing has an adjustable angle of incidence relative to its fuselage. This allows the wing to operate at a high angle of attack for take-off and landing while allowing the fuselage to remain close to horizontal. The pivot mech ...
design on the
Vought F-8 Crusader The Vought F-8 Crusader (originally F8U) is a single-engine, supersonic, carrier-based air superiority jet aircraft built by Vought for the United States Navy and United States Marine Corps (replacing the Vought F7U Cutlass), and for the Fren ...
,Bjorkman, Eileen. Gunfighters. Air & Space, November 2015. p. 62. and swing wings on aircraft such as the
F-14 The Grumman F-14 Tomcat is an American carrier-capable supersonic, twin-engine, two-seat, twin-tail, variable-sweep wing fighter aircraft. The Tomcat was developed for the United States Navy's Naval Fighter Experimental (VFX) program after the ...
,
F-111 The General Dynamics F-111 Aardvark is a retired supersonic, medium-range, multirole combat aircraft. Production variants of the F-111 had roles that included ground attack (e.g. interdiction), strategic bombing (including nuclear weapons ca ...
, and the
Panavia Tornado The Panavia Tornado is a family of twin-engine, variable-sweep wing multirole combat aircraft, jointly developed and manufactured by Italy, the United Kingdom and West Germany. There are three primary Tornado variants: the Tornado IDS (inter ...
.Woolridge, Capt. E.T., ed. ''Into the Jet Age: Conflict and Change in Naval Aviation 1945–1975, an Oral History''. Annapolis, Maryland: Naval Institute Press, 1995. .Spick, Green and Swanborough 2001, p. 33.


Variant designs

The term "swept wing" is normally used to mean "swept back", but other swept variants include forward sweep, variable sweep wings and
oblique wing An oblique wing (also called a slewed 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. By changing its swee ...
s in which one side sweeps forward and the other back. The
delta wing A delta wing is a wing shaped in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta (Δ). Although long studied, it did not find significant applications until the Jet Age, when it proved suitabl ...
also incorporates the same advantages as part of its layout.


Forward sweep

Sweeping a wing forward has approximately the same effect as rearward in terms of drag reduction, but has other advantages in terms of low-speed handling where tip stall problems simply go away. In this case the low-speed air flows towards the fuselage, which acts as a very large wing fence. Additionally, wings are generally larger at the root anyway, which allows them to have better low-speed lift. However, this arrangement also has serious stability problems. The rearmost section of the wing will stall first causing a pitch-up moment pushing the aircraft further into stall similar to a swept back wing design. Thus swept-forward wings are unstable in a fashion similar to the low-speed problems of a conventional swept wing. However unlike swept back wings, the tips on a forward swept design will stall last, maintaining roll control. Forward-swept wings can also experience dangerous flexing effects compared to aft-swept wings that can negate the tip stall advantage if the wing is not sufficiently stiff. In aft-swept designs, when the airplane maneuvers at high load factor the wing loading and geometry twists the wing in such a way as to create washout (tip twists leading edge down). This reduces the angle of attack at the tip, thus reducing the bending moment on the wing, as well as somewhat reducing the chance of tip stall. However, the same effect on forward-swept wings produces a wash-in effect that increases the angle of attack promoting tip stall. Small amounts of sweep do not cause serious problems, and had been used on a variety of aircraft to move the spar into a convenient location, as on the
Junkers Ju 287 The Junkers Ju 287 was an aerodynamic testbed built in Nazi Germany to develop the technology required for a multi-engine jet bomber. It was powered by four Junkers Jumo 004 engines, featured a novel forward-swept wing, and apart from the wing ...
or
HFB 320 Hansa Jet The HFB 320 Hansa Jet is a twin-engine, ten-seat business jet that was designed and produced by German aircraft manufacturer Hamburger Flugzeugbau between 1964 and 1973. The most recognisable and unconventional feature of the aircraft is its for ...
.Bedell, Peter A
"Quick Look: Hansa Jet: The ‘German LearJet’ was forward thinking, yet doomed."
''aopa.org'', 1 February 2017.
However, larger sweep suitable for high-speed aircraft, like fighters, was generally impossible until the introduction of fly by wire systems that could react quickly enough to damp out these instabilities. The
Grumman X-29 The Grumman X-29 was an American experimental aircraft that tested a forward-swept wing, canard control surfaces, and other novel aircraft technologies. The X-29 was developed by Grumman, and the two built were flown by NASA and the United St ...
was an experimental technology demonstration project designed to test the forward swept wing for enhanced maneuverability during the 1980s. The Sukhoi Su-47 ''Berkut'' is another notable demonstrator aircraft implementing this technology to achieve high levels of agility.Jackson 2000, pp. 457–458. To date, no highly swept-forward design has entered production.


History


Early history

The first successful aeroplanes adhered to the basic design of rectangular wings at right angles to the body of the machine, but there were experimentalists who explored other geometries to achieve better aerodynamic results. The swept wing geometry appeared before
World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
, and was conceived as a means of permitting the design of safe and stable aeroplanes. The best of these designs imposed "self-damping" inherent stability upon a tailless swept wing. These inspired several flying wing gliders and some powered aircraft during the interwar years. The first to achieve stability was British designer J. W. Dunne who was obsessed with achieving inherent stability in flight. He successfully employed swept wings in his tailless aircraft (which, crucially, used washout) as a means of creating positive longitudinal static stability. For a low-speed aircraft, swept wings may be used to resolve problems with the
center of gravity In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force ma ...
, to move the wing spar into a more convenient location, or to improve the sideways view from the pilot's position. By 1905, Dunne had already built a model glider with swept wings and by 1913 he had constructed successful powered variants that were able to cross the
English Channel The English Channel, "The Sleeve"; nrf, la Maunche, "The Sleeve" (Cotentinais) or ( Jèrriais), (Guernésiais), "The Channel"; br, Mor Breizh, "Sea of Brittany"; cy, Môr Udd, "Lord's Sea"; kw, Mor Bretannek, "British Sea"; nl, Het Kana ...
. The Dunne D.5 was exceptionally aerodynamically stable for the time, and the D.8 was sold to the
Royal Flying Corps "Through Adversity to the Stars" , colors = , colours_label = , march = , mascot = , anniversaries = , decorations ...
; it was also manufactured under licence by Starling Burgess to the
United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
amongst other customers. Dunne's work ceased with the onset of war in 1914, but afterwards the idea was taken up by
G. T. R. Hill Geoffrey Terence Roland Hill, (1895 – 26 December 1955) was a British aviator and aeronautical engineer. Early life Geoffrey Terence Roland Hill was born in 1895, the son of Michael J. M. Hill, Professor of Mathematics at the University Colleg ...
in England who designed a series of gliders and aircraft to Dunne's guidelines, notably the
Westland-Hill Pterodactyl Pterodactyl was the name given to a series of experimental tailless aircraft designs developed by G. T. R. Hill in the 1920s and early 1930s. Named after the genus Pterodactylus, a well-known type of Pterosaur commonly known as the pterodactyl, a ...
series. However, Dunne's theories met with little acceptance amongst the leading aircraft designers and aviation companies at the time.


German developments

The idea of using swept wings to reduce high-speed drag was developed in Germany in the 1930s. At a
Volta Conference The Volta Conference was the name given to each of the international conferences held in Italy by the Royal Academy of Science in Rome, and funded by the Alessandro Volta Foundation. In the interwar period, they covered a number of topics in sci ...
meeting in 1935 in Italy, Dr.
Adolf Busemann Adolf Busemann (20 April 1901 – 3 November 1986) was a German aerospace engineer and influential Nazi-era pioneer in aerodynamics, specialising in supersonic airflows. He introduced the concept of swept wings and, after emigrating in 1947 to t ...
suggested the use of swept wings for
supersonic Supersonic speed is the speed of an object that exceeds the speed of sound ( Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...
flight. He noted that the airspeed over the wing was dominated by the normal component of the airflow, not the freestream velocity, so by setting the wing at an angle the forward velocity at which the shock waves would form would be higher (the same had been noted by
Max Munk Max Michael Munk (October 22, 1890 – June 3, 1986) was a German aerospace engineer who worked for the National Advisory Committee for Aeronautics (NACA) in the 1920s and made contributions to the design of airfoils. Education and early career M ...
in 1924, although not in the context of high-speed flight).Anderson, John D. Jr. ''A History of Aerodynamics''. New York: McGraw Hill, 1997, p. 424. Albert Betz immediately suggested the same effect would be equally useful in the transonic. After the presentation the host of the meeting, Arturo Crocco, jokingly sketched "Busemann's airplane of the future" on the back of a menu while they all dined. Crocco's sketch showed a classic 1950's fighter design, with swept wings and tail surfaces, although he also sketched a swept propeller powering it. At the time, however, there was no way to power an aircraft to these sorts of speeds, and even the fastest aircraft of the era were only approaching .The presentation was largely of academic interest, and soon forgotten. Even notable attendees including
Theodore von Kármán Theodore von Kármán ( hu, ( szőllőskislaki) Kármán Tódor ; born Tivadar Mihály Kármán; 11 May 18816 May 1963) was a Hungarian-American mathematician, aerospace engineer, and physicist who was active primarily in the fields of aeronaut ...
and
Eastman Jacobs Eastman Jacobs (1902–1987) was a leading aerodynamicist who worked for NACA's Langley Memorial Aeronautical Laboratory (renamed NASA Langley Research Center in 1958) from the 1920s to the 1940s. He was responsible for advancing many fields ...
did not recall the presentation 10 years later when it was re-introduced to them.Anderson 1997, pp. 423–424. Hubert Ludwieg of the High-Speed Aerodynamics Branch at the AVA Göttingen in 1939 conducted the first wind tunnel tests to investigate Busemann's theory. Two wings, one with no sweep, and one with 45 degrees of sweep were tested at Mach numbers of 0.7 and 0.9 in the 11 x 13 cm wind tunnel. The results of these tests confirmed the drag reduction offered by swept wings at transonic speeds. The results of the tests were communicated to Albert Betz who then passed them on to
Willy Messerschmitt Wilhelm Emil "Willy" Messerschmitt (; 26 June 1898 – 15 September 1978) was a German aircraft designer and manufacturer. In 1934, in collaboration with Walter Rethel, he designed the Messerschmitt Bf 109, which became the most important ...
in December 1939. The tests were expanded in 1940 to include wings with 15, 30 and -45 degrees of sweep and Mach numbers as high as 1.21. With the introduction of jets in the later half of the
Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
, the swept wing became increasingly applicable to optimally satisfying aerodynamic needs. The German jet-powered
Messerschmitt Me 262 The Messerschmitt Me 262, nicknamed ''Schwalbe'' (German: "Swallow") in fighter versions, or ''Sturmvogel'' (German: "Storm Bird") in fighter-bomber versions, is a fighter aircraft and fighter-bomber that was designed and produced by the Germa ...
and rocket-powered
Messerschmitt Me 163 The Messerschmitt Me 163 Komet is a rocket-powered interceptor aircraft primarily designed and produced by the German aircraft manufacturer Messerschmitt. It is the only operational rocket-powered fighter aircraft in history as well as ...
suffered from
compressibility In thermodynamics and fluid mechanics, the compressibility (also known as the coefficient of compressibility or, if the temperature is held constant, the isothermal compressibility) is a measure of the instantaneous relative volume change of a f ...
effects that made both aircraft very difficult to control at high speeds. In addition, the speeds put them into the
wave drag In physics, mathematics, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Waves can be periodic, in which case those quantities oscillate repeatedly about an equilibrium (r ...
regime, and anything that could reduce this drag would increase the performance of their aircraft, notably the notoriously short flight times measured in minutes. This resulted in a crash program to introduce new swept wing designs, both for fighters as well as
bomber A bomber is a military combat aircraft designed to attack ground and naval targets by dropping air-to-ground weaponry (such as bombs), launching aerial torpedo, torpedoes, or deploying air-launched cruise missiles. The first use of bombs dropped ...
s. The Blohm & Voss P 215 was designed to take full advantage of the swept wing's aerodynamic properties; however, an order for three prototypes was received only weeks before the war ended and no examples were ever built. The
Focke-Wulf Ta 183 The Focke-Wulf Ta 183 ''Huckebein'' was a design for a jet-powered fighter aircraft intended as the successor to the Messerschmitt Me 262 and other day fighters in Luftwaffe service during World War II. It had been developed only to the exten ...
was another swept wing fighter design, but was also not produced before the war's end.Myhra 1999, p. 4. In the post-war era,
Kurt Tank Kurt Waldemar Tank (24 February 1898 – 5 June 1983) was a German aeronautical engineer and test pilot who led the design department at Focke-Wulf from 1931 to 1945. He was responsible for the creation of several important Luftwaffe aircraft o ...
developed the Ta 183 into the IAe Pulqui II, but this proved unsuccessful.Waligorski, Martin
"Pulqui: Argentina's Jet Adventure."
''Camouflage & Markings'': ''IPMS Stockholm'', 22 September 2006. Retrieved: 27 April 2010.
A prototype test aircraft, the
Messerschmitt Me P.1101 The Messerschmitt P.1101 was a single-seat, single- jet fighter project of World War II, developed as part of the 15 July 1944 Emergency Fighter Program which sought a second generation of jet fighters for the Third Reich. A prominent feature ...
, was built to research the tradeoffs of the design and develop general rules about what angle of sweep to use.Christopher 2013, pp. 157–160. When it was 80% complete, the P.1101 was captured by US forces and returned to the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
, where two additional copies with US-built engines carried on the research as the
Bell X-5 The Bell X-5 was the first aircraft capable of changing the sweep of its wings in flight. It was inspired by the untested wartime P.1101 design of the German Messerschmitt company. In contrast with the German design, which could only have its ...
. Germany's wartime experience with the swept wings and its high value for supersonic flight stood in strong contrast to the prevailing views of Allied experts of the era, who commonly espoused their belief in the impossibility of manned vehicles travelling at such speeds.


Postwar advancements

During the immediate post-war era, several nations were conducting research into high speed aircraft. In the United Kingdom, work commenced during 1943 on the
Miles M.52 The Miles M.52 was a turbojet-powered supersonic research aircraft project designed in the United Kingdom in the mid-1940s. In October 1943, Miles Aircraft was issued with a contract to produce the aircraft in accordance with Air Ministry Sp ...
, a high-speed experimental aircraft equipped with a straight wing that was developed in conjunction with
Frank Whittle Air Commodore Sir Frank Whittle, (1 June 1907 – 8 August 1996) was an English engineer, inventor and Royal Air Force (RAF) air officer. He is credited with inventing the turbojet engine. A patent was submitted by Maxime Guillaume in 1921 for ...
's
Power Jets Power Jets was a British company set up by Frank Whittle for the purpose of designing and manufacturing jet engines. The company was nationalised in 1944, and evolved into the National Gas Turbine Establishment. History Founded on 27 Januar ...
company, the
Royal Aircraft Establishment The Royal Aircraft Establishment (RAE) was a British research establishment, known by several different names during its history, that eventually came under the aegis of the Ministry of Defence (United Kingdom), UK Ministry of Defence (MoD), bef ...
(RAE) in Farnborough, and the National Physical Laboratory.Wood 1975, p. 29. The M.52 was envisioned to be capable of achieving in level flight, thus enabling the aircraft to potentially be the first to exceed the speed of sound in the world. In February 1946, the programme was abruptly discontinued for unclear reasons.Wood 1975, pp. 34–35. It has since been widely recognised that the cancellation of the M.52 was a major setback in British progress in the field of supersonic design. Another, more successful, programme was the US's
Bell X-1 The Bell X-1 (Bell Model 44) is a rocket engine–powered aircraft, designated originally as the XS-1, and was a joint National Advisory Committee for Aeronautics– U.S. Army Air Forces–U.S. Air Force supersonic research project built by Be ...
, which also was equipped with a straight wing. According to Miles Chief Aerodynamicist Dennis Bancroft, the
Bell Aircraft The Bell Aircraft Corporation was an American aircraft manufacturer, 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 ...
company was given access to the drawings and research on the M.52.Wood 1975, p. 36. On 14 October 1947, the Bell X-1 performed the first manned
supersonic Supersonic speed is the speed of an object that exceeds the speed of sound ( Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...
flight, piloted by
Captain Captain is a title, an appellative for the commanding officer of a military unit; the supreme leader of a navy ship, merchant ship, aeroplane, spacecraft, or other vessel; or the commander of a port, fire or police department, election precinct, e ...
Charles "Chuck" Yeager, having been
drop launch A drop test is a method of testing the in-flight characteristics of prototype or experimental aircraft and spacecraft by raising the test vehicle to a specific altitude and then releasing it. Test flights involving powered aircraft, particularly ...
ed from the bomb bay of a Boeing B-29 Superfortress and attained a record-breaking speed of Mach 1.06 (). The news of a successful straight-wing supersonic aircraft surprised many aeronautical experts on both sides of the Atlantic, as it was increasingly believed that a swept-wing design not only highly beneficial but also necessary to break the sound barrier. During the final years of the Second World War, aircraft designer Sir
Geoffrey de Havilland Captain Sir Geoffrey de Havilland, (27 July 1882 – 21 May 1965) was an English aviation pioneer and aerospace engineer. The aircraft company he founded produced the Mosquito, which has been considered the most versatile warplane ever built,D ...
commenced development on the
de Havilland Comet The de Havilland DH.106 Comet was the world's first commercial jet airliner. Developed and manufactured by de Havilland in the United Kingdom, the Comet 1 prototype first flew in 1949. It featured an aerodynamically clean design with four ...
, which would become the world's first jet airliner. An early design consideration was whether to apply the new swept-wing configuration. Thus, an experimental aircraft to explore the technology, the
de Havilland DH 108 The de Havilland DH 108 "Swallow" was a British experimental aircraft designed by John Carver Meadows Frost in October 1945. The DH 108 featured a tailless, swept wing with a single vertical stabilizer, similar to the layout of the wartime ...
, was developed by the firm in 1944, headed by project engineer John Carver Meadows Frost with a team of 8–10 draughtsmen and engineers. The DH 108 primarily consisted of the pairing of the front fuselage of the
de Havilland Vampire The de Havilland Vampire is a British jet fighter which was developed and manufactured by the de Havilland, de Havilland Aircraft Company. It was the second jet fighter to be operated by the Royal Air Force, RAF, after the Gloster Meteor, and ...
to a swept wing and small vertical tail; it was the first British swept wing jet, unofficially known as the "Swallow". It first flew on 15 May 1946, a mere eight months after the project's go-ahead. Company test pilot and son of the builder,
Geoffrey de Havilland Jr Geoffrey Raoul de Havilland Jr., OBE (18 February 1910 – 27 September 1946) was a British test pilot. He was the son of Geoffrey de Havilland, the English aviation pioneer and aircraft designer. Early life Geoffrey Raoul de Havilland was b ...
., flew the first of three aircraft and found it extremely fast – fast enough to try for a world speed record. On 12 April 1948, a D.H.108 did set a world's speed record at 973.65 km/h (605 mph), it subsequently became the first jet aircraft to exceed the speed of sound. Around this same timeframe, the
Air Ministry The Air Ministry was a department of the Government of the United Kingdom with the responsibility of managing the affairs of the Royal Air Force, that existed from 1918 to 1964. It was under the political authority of the Secretary of State ...
introduced a program of experimental aircraft to examine the effects of swept wings, as well as the
delta wing A delta wing is a wing shaped in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta (Δ). Although long studied, it did not find significant applications until the Jet Age, when it proved suitabl ...
configuration. Furthermore, the
Royal Air Force The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) and ...
(RAF) identified a pair of proposed fighter aircraft equipped with swept wings from Hawker Aircraft and
Supermarine Supermarine was a British aircraft manufacturer that is most famous for producing the Spitfire fighter plane during World War II as well as a range of seaplanes and flying boats, and a series of jet-powered fighter aircraft after World War II ...
, the
Hawker Hunter The Hawker Hunter is a transonic British jet-powered fighter aircraft that was developed by Hawker Aircraft for the Royal Air Force (RAF) during the late 1940s and early 1950s. It was designed to take advantage of the newly developed Rolls-R ...
and Supermarine Swift respectively, and successfully pressed for orders to be placed 'off the drawing board' in 1950.Wood 1975, pp. 43–46. On 7 September 1953, the sole Hunter Mk 3 (the modified first prototype, ''WB 188'') flown by
Neville Duke Neville Frederick Duke, (11 January 1922 – 7 April 2007) was a British test pilot and fighter ace of the Second World War. He was credited with the destruction of 27 enemy aircraft. After the war, Duke was acknowledged as one of the world's fo ...
broke the world
air speed record An air speed record is the highest airspeed attained by an aircraft of a particular class. The rules for all official aviation records are defined by Fédération Aéronautique Internationale (FAI), which also ratifies any claims. Speed records ...
for jet-powered aircraft, attaining a speed of 727.63 mph (1,171.01 km/h) over
Littlehampton Littlehampton is a town, seaside resort, and pleasure harbour, and the most populous civil parish in the Arun District of West Sussex, England. It lies on the English Channel on the eastern bank of the mouth of the River Arun. It is south sout ...
,
West Sussex West Sussex is a county in South East England on the English Channel coast. The ceremonial county comprises the shire districts of Adur, Arun, Chichester, Horsham, and Mid Sussex, and the boroughs of Crawley and Worthing. Covering an ar ...
. This world record stood for less than three weeks before being broken on 25 September 1953 by the Hunter's early rival, the Supermarine Swift, being flown by Michael Lithgow. In February 1945,
NACA The National Advisory Committee for Aeronautics (NACA) was a United States federal agency founded on March 3, 1915, to undertake, promote, and institutionalize aeronautical research. On October 1, 1958, the agency was dissolved and its assets ...
engineer Robert T. Jones started looking at highly swept
delta wing A delta wing is a wing shaped in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta (Δ). Although long studied, it did not find significant applications until the Jet Age, when it proved suitabl ...
s and V shapes, and discovered the same effects as Busemann. He finished a detailed report on the concept in April, but found his work was heavily criticised by other members of NACA Langley, notably Theodore Theodorsen, who referred to it as "hocus-pocus" and demanded some "real mathematics". However, Jones had already secured some time for free-flight models under the direction of
Robert Gilruth Robert Rowe Gilruth (October 8, 1913 – August 17, 2000) was an American aerospace engineer and an aviation/space pioneer who was the first director of NASA's Manned Spacecraft Center, later renamed the Lyndon B. Johnson Space Center. He worked ...
, whose reports were presented at the end of May and showed a fourfold decrease in drag at high speeds. All of this was compiled into a report published on June 21, 1945, which was sent out to the industry three weeks later. Ironically, by this point Busemann's work had already been passed around. In May 1945, the American
Operation Paperclip Operation Paperclip was a secret United States intelligence program in which more than 1,600 German scientists, engineers, and technicians were taken from the former Nazi Germany to the U.S. for government employment after the end of World War ...
reached
Braunschweig Braunschweig () or Brunswick ( , from Low German ''Brunswiek'' , Braunschweig dialect: ''Bronswiek'') is a city in Lower Saxony, Germany, north of the Harz Mountains at the farthest navigable point of the river Oker, which connects it to the Nor ...
, where US personnel discovered a number of swept wing models and a mass of technical data from the wind tunnels. One member of the US team was
George S. Schairer George S. Schairer (May 19, 1913 – October 28, 2004) was an aerodynamicst at Consolidated Aircraft and Boeing whose design innovations became standard on virtually all types of military and passenger jet planes. Early life George Swift Schaire ...
, who was at that time working at the Boeing company. He immediately forwarded a letter to Ben Cohn at Boeing, communicating the value of the swept wing concept.Gunston and Gilchrist 1993, pp. 39–40. He also told Cohn to distribute the letter to other companies as well, although only Boeing and North American made immediate use of it. Boeing was in the midst of designing the
B-47 Stratojet 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. ...
, and the initial Model 424 was a straight-wing design similar to the B-45, B-46 and B-48 it competed with. Analysis by Boeing engineer Vic Ganzer suggested an optimum sweepback angle of about 35 degrees. By September 1945, the Braunschweig data had been worked into the design, which re-emerged as the Model 448, a larger six-engine design with more robust wings swept at 35 degrees. Another re-work moved the engines into strut-mounted pods under the wings due to concerns of the uncontained failure of an internal engine could potentially destroy the aircraft via either fire or vibration.Gunston and Gilchrist 1993, p. 40. The resulting B-47 was hailed as the fastest of its class in the world during the late 1940s,Fraser November 1949, p. 139. and trounced the straight-winged competition. Boeing's jet-transport formula of swept wings and pylon-mounted engines has since been universally adopted. In fighters,
North American Aviation North American Aviation (NAA) was a major American aerospace manufacturer that designed and built several notable aircraft and spacecraft. Its products included: the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the F ...
was in the midst of working on a straight-wing jet-powered naval fighter, then known as the FJ-1; it was later submitted to the United States Air Force as the XP-86. Larry Green, who could read German, studied the Busemann reports and convinced management to allow a redesign starting in August 1945.Lednicer, David
"The Incomplete Guide to Airfoil Usage."
''ae.illinois.edu,'' 15 October 2010. Retrieved: 19 July 2011.
The performance of the F-86A allowed it set the first of several official world speed records, attaining on 15 September 1948, flown by Major Richard L. Johnson. With the appearance of the MiG-15, the F-86 was rushed into combat, while straight-wing jets like the
Lockheed P-80 Shooting Star The Lockheed P-80 Shooting Star was the first jet fighter used operationally by the United States Army Air Forces (USAAF) during World War II. Designed and built by Lockheed in 1943 and delivered just 143 days from the start of design, prod ...
and
Republic F-84 Thunderjet The Republic F-84 Thunderjet was an American turbojet fighter-bomber aircraft. Originating as a 1944 United States Army Air Forces (USAAF) proposal for a "day fighter", the F-84 first flew in 1946. Although it entered service in 1947, the Thun ...
were quickly relegated to ground attack missions. Some, such as the F-84 and
Grumman F-9 Cougar The Grumman F9F/F-9 Cougar is a carrier-based fighter aircraft for the United States Navy and United States Marine Corps. Based on Grumman's earlier F9F Panther, the Cougar replaced the Panther's straight wing with a more modern swept wing. Th ...
, were later redesigned with swept wings from straight-winged aircraft.Knaack 1978, p. 42.Kinzey 1983, p. 4. Later planes, such as the
North American F-100 Super Sabre The North American F-100 Super Sabre is an American supersonic jet fighter aircraft that served with the United States Air Force (USAF) from 1954 to 1971 and with the Air National Guard (ANG) until 1979. The first of the Century Series of ...
, would be designed with swept wings from the start, though additional innovations such as the afterburner, area-rule and new control surfaces would be necessary to master supersonic flight. The
Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...
was also quick to investigate the advantages of swept wings on high speed aircraft, when their "captured aviation technology" counterparts to the western Allies spread out across the defeated Third Reich.
Artem Mikoyan Artem (Artyom) Ivanovich Mikoyan (russian: Артём Ива́нович Микоя́н; hy, Արտյոմ (Անուշավան) Հովհաննեսի Միկոյան, translit=''Artyom (Anushavan) Hovhannesi Mikoyan''; – 9 December 1970) was a ...
was asked by the Soviet government's
TsAGI The Central Aerohydrodynamic Institute (also (Zhukovsky) Central Institute of Aerodynamics, russian: Центра́льный аэрогидродинами́ческий институ́т, ЦАГИ, Tsentral'nyy Aerogidrodinamicheskiy Institut, ...
aviation research department to develop a test-bed aircraft to research the swept wing idea — the result was the late 1945-flown, unusual MiG-8 ''Utka'' pusher canard layout aircraft, with its rearwards-located wings being swept back for this type of research. The swept wing was applied to the
MiG-15 The Mikoyan-Gurevich MiG-15 (russian: Микоя́н и Гуре́вич МиГ-15; USAF/DoD designation: Type 14; NATO reporting name: Fagot) is a jet fighter aircraft developed by Mikoyan-Gurevich for the Soviet Union. The MiG-15 was one of ...
, an early jet-powered fighter, its maximum speed of outclassed the straight-winged American jets and piston-engined fighters initially deployed during the
Korean War , date = {{Ubl, 25 June 1950 – 27 July 1953 (''de facto'')({{Age in years, months, weeks and days, month1=6, day1=25, year1=1950, month2=7, day2=27, year2=1953), 25 June 1950 – present (''de jure'')({{Age in years, months, weeks a ...
. The MiG-15 is believed to have been one of the most produced jet aircraft; in excess of 13,000 would ultimately be manufactured. The MiG-15, which could not safely exceed Mach 0.92, served as the basis for the
MiG-17 The Mikoyan-Gurevich MiG-17 (russian: Микоян и Гуревич МиГ-17; NATO reporting name: Fresco) is a high-subsonic fighter aircraft produced in the Soviet Union from 1952 and was operated by air forces internationally. The MiG-17 w ...
, which was designed to be controllable at higher Mach numbers. Its wing sweep, 45° near the fuselage ( the same as the F-100 Super Sabre), changed to 42° for the outboard part of the wing.Crosby 2002, p. 212. A further derivative of the design, designated
MiG-19 The Mikoyan-Gurevich MiG-19 (russian: Микоян и Гуревич МиГ-19; NATO reporting name: Farmer) is a Soviet second generation, single-seat, twinjet fighter aircraft, the world's first mass-produced supersonic aircraft. It was the ...
, featured a relatively thin wing suited to supersonic flight that was designed at TsAGI, the Soviet
Central Aerohydrodynamic Institute The Central Aerohydrodynamic Institute (also (Zhukovsky) Central Institute of Aerodynamics, russian: Центра́льный аэрогидродинами́ческий институ́т, ЦАГИ, Tsentral'nyy Aerogidrodinamicheskiy Institut, ...
; swept back at an angle of 55 degrees, this wing featured a single
wing fence Wing fences, also known as boundary layer fences and potential fences are fixed aerodynamic devices attached to aircraft wings. Often seen on swept-wing aircraft, wing fences are flat plates fixed to the upper surfaces parallel to the wing ch ...
on each side.Gordon 1997, p. 124. A specialist high-altitude variant, the Mig-19SV, featured, amongst other changes, an adjustable flap to generate greater lift at higher altitudes, helping to increase the aircraft's ceiling from to .Belyakov and Marmain 1994, pp. 225–227.Gunston 1995, pp. 197–198. Germany's swept wing research was also obtained by the Swedish aircraft manufacturer
SAAB Saab or SAAB may refer to: Brands and enterprises * Saab Group, a Swedish aerospace and defence company, formerly known as SAAB, and later as Saab AB ** Datasaab, a former computer company, started as spin off from Saab AB * Saab Automobile, a fo ...
, with the help of ex-Messerschmitt engineers that had fled to
Switzerland ). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...
during late 1945.Erichs et al. 1988, p. 37.Dorr 2013, p. 237. At the time, SAAB saw the need to make aeronautical advances, particularly in the new field of jet propulsion.Widfeldt 1966, p. 3. The company incorporated both the jet engine and the swept wing to produce the
Saab 29 Tunnan The Saab 29 ''Tunnan'', colloquially ''Flygande tunnan'' or just ''Tunnan'' ( en, "The flying barrel", "The barrel"),. is a Swedish fighter that was designed and manufactured by Saab in the late 1940s. It was the second turbojet-powered comb ...
fighter; on 1 September 1948, the first prototype conducted its maiden flight, flown by the English test pilot S/L Robert A. 'Bob' Moore, DFC and bar,''Flight'' 1950, p. 558. Although not well known outside Sweden, the Tunnan was the first Western European fighter to be introduced with such a wing configuration.Boyne 2002, p. 547."1940s."
''Saab'', Retrieved: 27 March 2016.
In parallel, SAAB also developed another swept wing aircraft, the
Saab 32 Lansen The Saab 32 Lansen (English: Lance) is a two-seat, transonic military aircraft designed and manufactured by Saab AB from 1955 to 1960 for the Swedish Air Force (''Flygvapnet''). Three principal variants of the Lansen were built for attack (A 32A ...
, primarily to serve as Sweden's standard attack aircraft.''Saab'' 30 December 1960, p. 1017. Its wing, which had a 10 per cent laminar profile and a 35° sweep, featured triangular fences near the
wing root The wing root is the part of the wing on a fixed-wing aircraft or winged-spaceship that is closest to the fuselage The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, o ...
s in order to improve airflow when the aircraft was being flown at a high
angle of attack In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is m ...
. On 25 October 1953, a SAAB 32 Lansen attained a Mach number of at least 1.12 while in a shallow dive, exceeding the
sound barrier The sound barrier or sonic barrier is the large increase in aerodynamic drag and other undesirable effects experienced by an aircraft or other object when it approaches the speed of sound. When aircraft first approached the speed of sound, th ...
.Gunston and Gilchrist 1993, p. 135. The successes of aircraft such as the Hawker Hunter, the B-47, and F-86 showed the value of the swept wing research acquired from Germany. Eventually, almost all advanced design efforts for high speed aircraft would incorporate a wing with a swept leading edge, with either a swept wing or
delta wing A delta wing is a wing shaped in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta (Δ). Although long studied, it did not find significant applications until the Jet Age, when it proved suitabl ...
planform In technical drawing and computer graphics, a multiview projection is a technique of illustration by which a standardized series of orthographic two-dimensional pictures are constructed to represent the form of a three-dimensional object. Up to ...
. The Boeing B-52, designed in the 1950s, continues in service as a subsonic long-range heavy bomber. While the Soviets never matched the performance of the
Boeing B-52 Stratofortress The Boeing B-52 Stratofortress is an American long-range, subsonic, jet-powered strategic bomber. The B-52 was designed and built by Boeing, which has continued to provide support and upgrades. It has been operated by the United States Air ...
with a jet aircraft, the intercontinental range Tupolev Tu-95
turboprop A turboprop is a turbine engine that drives an aircraft propeller. A turboprop consists of an intake, reduction gearbox, compressor, combustor, turbine, and a propelling nozzle. Air enters the intake and is compressed by the compressor. ...
bomber with its near-jet class top speed of 920 km/h, combining swept wings with propeller propulsion, also remains in service today, being the fastest propeller-powered production aircraft. In Britain, two swept-wing bombers entered service, the Vickers Valiant (1955)Andrews and Morgan 1988, p. 439. and the
Handley Page Victor The Handley Page Victor is a British jet-powered strategic bomber developed and produced by Handley Page during the Cold War. It was the third and final '' V bomber'' to be operated by the Royal Air Force (RAF), the other two being the Avro ...
(1958).Barnes 1976, p. 503. By the early 1950s, nearly every new fighter had a swept wing. By the 1960s, most civilian jets also adopted swept wings. Most early transonic and supersonic designs such as the MiG-19 and F-100 used long, highly swept wings. Swept wings would reach Mach 2 on the BAC Lightning, and
Republic F-105 Thunderchief The Republic F-105 Thunderchief is an American supersonic fighter-bomber that served with the United States Air Force from 1958 to 1984. Capable of Mach 2, it conducted the majority of strike bombing missions during the early years of the Viet ...
, built to operate at low level and very high speed primarily for nuclear strike, but with a secondary air-to-air capability. By the late 1960s, the
McDonnell F-4 Phantom II The McDonnell Douglas F-4 Phantom II is an American tandem two-seat, twin-engine, all-weather, long-range supersonic jet interceptor and fighter-bomber originally developed by McDonnell Aircraft for the United States Navy.Swanborough and Bow ...
, was used in large numbers by air forces influenced by the United States. Variable geometry wings were employed on the American
F-111 The General Dynamics F-111 Aardvark is a retired supersonic, medium-range, multirole combat aircraft. Production variants of the F-111 had roles that included ground attack (e.g. interdiction), strategic bombing (including nuclear weapons ca ...
,
Grumman F-14 Tomcat The Grumman F-14 Tomcat is an American carrier-capable supersonic, twin-engine, two-seat, twin-tail, variable-sweep wing fighter aircraft. The Tomcat was developed for the United States Navy's Naval Fighter Experimental (VFX) program after the ...
and Soviet
Mikoyan MiG-27 The Mikoyan MiG-27 (russian: Микоян МиГ-27; NATO reporting name: Flogger-D/J) is a variable-sweep ground-attack aircraft, originally built by the Mikoyan-Gurevich design bureau in the Soviet Union and later licence-produced in Ind ...
, although the idea would be abandoned for the American SST design. After the 1970s, most newer generation fighters optimized for maneuvering air combat since the USAF F-15 and Soviet
Mikoyan MiG-29 The Mikoyan MiG-29 (russian: Микоян МиГ-29; NATO reporting name: Fulcrum) is a twin-engine fighter aircraft designed in the Soviet Union. Developed by the Mikoyan design bureau as an air superiority fighter during the 1970s, the MiG ...
have employed relatively short-span fixed wings with relatively large wing area.


See also

*
Delta wing A delta wing is a wing shaped in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta (Δ). Although long studied, it did not find significant applications until the Jet Age, when it proved suitabl ...
*
Theodore von Kármán Theodore von Kármán ( hu, ( szőllőskislaki) Kármán Tódor ; born Tivadar Mihály Kármán; 11 May 18816 May 1963) was a Hungarian-American mathematician, aerospace engineer, and physicist who was active primarily in the fields of aeronaut ...
, first to recognize the importance of the swept wingAerodynamics Selected topics in the light of their historical development. Dover publications, New York, 2004. *
Trapezoidal wing In aeronautics, a trapezoidal wing is a straight-edged and tapered wing planform. It may have any aspect ratio and may or may not be swept.G. Dimitriadis; ''Aircraft Design'Lecture 2: Aerodynamics Université de Liège. (retrieved 30 November ...
*
Wing configuration The wing configuration of a fixed-wing aircraft (including both glider (aircraft), gliders and powered aeroplanes) is its arrangement of lifting and related surfaces. Aircraft designs are often classified by their wing configuration. For examp ...


References


Citations


Bibliography

* Anderson, John D. Jr. ''A History of Aerodynamics''. New York: McGraw Hill, 1997. * Andrews, C.F. and Eric B. Morgan. ''Vickers Aircraft since 1908''. London: Putnam, 1988. . * Barnes, C.H. ''Handley Page Aircraft since 1907''. London: Putnam, 1976. . * Belyakov, R. A. and Marmain, J. ''MiG: Fifty Years of Secret Aircraft Design''. Shrewsbury, UK: Airlife Publishing, 1994. . * Blackman, Tony. ''Vulcan Test Pilot: My Experiences in the Cockpit of a Cold War Icon.'' London: Grub Street, 2007. . * Boyne, Walter J. ''Air Warfare: An International Encyclopedia, Volume 1.'' ABC-CLIO, 2002. . * Brookes, Andrew
''Victor Units of the Cold War''.
Osprey Publishing, 2011. . * Buttler, Tony. "Avro Type 698 Vulcan (Database)." ''Aeroplane,'' Vol. 35, No. 4, Issue No. 408, April 2007. * * Cook, William H. ''The Road to the 707: The Inside Story of Designing the 707.'' Bellevue, Washington: TYC Publishing, 1991. . * Crosby, Francis. ''Fighter Aircraft''. London: Lorenz Books, 2002. . * * Davies, R.E.G. and Philip J. Birtles. ''Comet: The World's First Jet Airliner.'' McLean, Virginia: Paladwr Press, 1999. . * Dorr, Robert F. ''Fighting Hitler's Jets: The Extraordinary Story of the American Airmen Who Beat the Luftwaffe and Defeated Nazi Germany.'' MBI Publishing Co, 2013. . * Erichs, Rolph et al. ''The Saab-Scania Story''. Stockholm: Streiffert & Co., 1988. . * Fraser, Jim
"I Fly The World's Fastest Bomber."
''Popular Science'', November 1949. Vol. 155, No. 5. pp. 139–142. . * Gordon, Yefim. "Mikoyan MiG-19 Variants". ''Wings of Fame'', Volume 9, 1997. pp. 116–149. . . * * Gunston, Bill. ''The Osprey Encyclopedia of Russian Aircraft: 1875–1995''. London: Osprey Aerospace, 1996. . * Gunston, Bill and Peter Gilchrist. ''Jet Bombers: From the Messerschmitt Me 262 to the Stealth B-2''. Osprey, 1993. . * Seidov, Igor and Stuart Britton. ''Red Devils over the Yalu: A Chronicle of Soviet Aerial Operations in the Korean War 1950–53.'' Helion and Company, 2014. . * * Kinzey, Bert. ''F9F Cougar in Detail & Scale''. Fallbrook, California: Aero Publishers, Inc., 1983. . * Knaack, Marcelle Size. ''Encyclopedia of US Air Force Aircraft and Missile Systems: Volume 1 Post-World War II Fighters 1945–1973''. Washington, DC: Office of Air Force History, 1978. . * * Mendenhall, Charles A. ''Delta Wings: Convair's High-Speed Planes of the Fifties and Sixties''. Motorbooks. 1983. * Myhra, David. ''Focke-Wulf Ta 183'' (X Planes of the Third Reich). Atglen, PA: Schiffer Publishing, 1999. . * Radinger, Willy and Walter Schick. ''Me 262: Entwicklung und Erprobung des ertsen einsatzfähigen Düsenjäger der Welt, Messerschmitt Stiftung'' (in German). Berlin: Avantic Verlag GmbH, 1996. .

''Flight International'', 4 May 1950. pp. 556–58.

''Flight International'', 30 December 1960. pp. 1017–20. * Spick, Mike and William Green, Gordon Swanborough. ''Illustrated Anatomy of the World's Fighters.'' Zenith Imprint, 2001. . * * Sweetman, Bill. ''Modern Fighting Aircraft: Volume 9: MiGs.'' New York: Arco Publishing, 1984. . * Wagner, Ray. ''The North American Sabre''. London: Macdonald, 1963. * * Whitcomb, Randall. ''Avro Aircraft and Cold War Aviation.'' St. Catharine's, Ontario: Vanwell, 2002. . * Winchester, Jim. "Bell X-5." ''Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft''. Kent, UK: Grange Books plc., 2005. . * Wood, Derek. ''Project Cancelled''. Indianapolis: The Bobbs-Merrill Company Inc., 1975. .


Further reading

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External links

{{Commons category, Wing sweep
''Swept Wings and Effective Dihedral''
Wing configurations Aircraft wing design German inventions of the Nazi period