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55-472: 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, all but the first were produced by Westland Aircraft Ltd after Hill joined them. Captain G.T.R. Hill developed the Pterodactyl series in an attempt to develop

110-410: A bell-shaped lift distribution which minimises induced drag for the aircraft weight. He applied this distribution in the "Prandtl-D" series of designs. By the end of 2017, he had flown three such research models. Elevon Elevons or tailerons are aircraft control surfaces that combine the functions of the elevator (used for pitch control) and the aileron (used for roll control), hence

165-504: A fuselage nacelle between the planes with rear-mounted pusher propeller and fixed endplate fins between each pair of wing tips. After his Army work had ended, in 1910 the D.5 biplane was witnessed in stable flight by Orville Wright and Griffith Brewer , who submitted an official report to the Royal Aeronautical Society to that effect. It thus became the first aeroplane ever to achieve natural stability in flight, as well as

220-464: A horizontal attitude and so counteract any aerodynamic instability, as in the paraglider . However, in practice this is seldom sufficient to provide stability on its own, and typically is augmented by the aerodynamic techniques described. A classic example is the Rogallo wing hang glider, which uses the same sweepback, washout and conical surface as Dunne. Stability can also be provided artificially. There

275-498: A large flying wing operated by the United States Air Force as a strategic stealth bomber , also used elevons in its control system. Northrop had opted to control the aircraft via a combination of split brake- rudders and differential thrust after assessing various different means of exercising directional control with minimal infringement on the aircraft's radar profile. Four pairs of control surfaces are positioned along

330-446: A more powerful engine, especially at high speeds. If longitudinal (pitch) stability and control can be achieved by some other method (see below), the stabiliser can be removed and the drag reduced. A tailless aeroplane has no separate horizontal stabilizer. Because of this the aerodynamic center of an ordinary wing would lie ahead of the aircraft's center of gravity, creating instability in pitch . Some other method must be used to move

385-409: A safer aircraft: many pilots lost their lives when their aircraft stalled, went into a spin and flew into the ground, and Hill wanted to develop a design which was resistant to stalling and spinning. The pioneer J. W. Dunne had previously developed stable aircraft in the form of tailless swept wings and Hill took Dunne's ideas as his starting point. Helped by his wife, he constructed a prototype which

440-440: A series of tailless aircraft intended to be inherently stable and unstallable. Inspired by his studies of seagulls in flight, they were characterised by swept wings with a conical upper surface. The cone was arranged so that the wing twisted progressively outwards towards the tips creating negative incidence, and hence negative lift, in the outboard sections, creating overall stability in both pitch and yaw. A single control surface on

495-411: A tail fin to keep it straight. Movement of the ailerons creates an adverse yaw pulling it out of the turn, which also has to be compensated by the rudder . While a swept wing is stable in straight flight, it still experiences adverse yaw during a turn. One solution is to give the wing sufficient twist for the outer section to angle downwards and give negative lift. This reverses the adverse yaw action of

550-480: A wing surface can change shape in flight to deflect air flow. The X-53 Active Aeroelastic Wing is a NASA effort. The Adaptive Compliant Wing is a military and commercial effort. In fluidics , forces in vehicles occur via circulation control, in which larger more complex mechanical parts are replaced by smaller simpler fluidic systems (slots which emit air flows) where larger forces in fluids are diverted by smaller jets or flows of fluid intermittently, to change

605-402: Is a trade-off between stability and maneuverability. A high level of maneuverability requires a low level of stability. Some modern hi-tech combat aircraft are aerodynamically unstable in pitch and rely on fly-by-wire computer control to provide stability. The Northrop Grumman B-2 Spirit flying wing is an example. Many early designs failed to provide effective pitch control to compensate for

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660-562: Is controlled as though the pilot still has separate aileron and elevator surfaces at their disposal, controlled by the yoke or stick. The inputs of the two controls are mixed either mechanically or electronically to provide the appropriate position for each elevon. One of the first operational aircraft to utilise elevons was the Avro Vulcan , a strategic bomber operated by the Royal Air Force 's V-force . The original production variant of

715-432: Is done progressively along the span of the outer section, it is called tip washout . Dunne achieved it by giving the wing upper surface a conical curvature. In level flight the aircraft should be trimmed so that the tips do not contribute any lift: they may even need to provide a small downthrust. This reduces the overall efficiency of the wing, but for many designs – especially for high speeds – this

770-617: Is known to have influenced later designers such as John K. Northrop (father of the Northrop Grumman B-2 Spirit stealth bomber). After WWI, pilot Geoffrey T. R. Hill also sought a stable, unstallable design. Dunne gave some help initially and Hill went on to produce the Pterodactyl series of tailless aircraft from the 1920s onwards. Hill also began to develop the theory of the intrinsically stable aerofoil and incorporated it into his designs. German theorists further developed

825-459: Is larger so enlarged surfaces are not required. The Dassault Mirage tailless delta series and its derivatives were among the most widely used combat jets. However even in the Mirage, pitch control at the high angles of attack experienced during takeoff and landing could be problematic and some later derivatives featured additional canard surfaces. A conventional aeroplane is unstable in yaw and needs

880-530: Is outweighed by the reductions in drag, weight and cost over a conventional stabiliser. The long wing span also reduces manoeuvrability, and for this reason Dunne's design was rejected by the British Army. An alternative is the use of low or null pitching moment airfoils , seen for example in the Horten series of sailplanes and fighters. These use an unusual wing aerofoil section with reflex or reverse camber on

935-430: Is to provide large elevator and/or elevon surfaces on the wing trailing edge. Unless the wing is highly swept, these must generate large control forces, as their distance from the aerodynamic center is small and the moments less. Thus a tailless type may experience higher drag during pitching manoeuvres than its conventional equivalent. In a highly swept delta wing the distance between trailing edge and aerodynamic centre

990-789: The DINFIA . Similar to the DH.108, the twin-jet powered 1948-vintage Northrop X-4 was one of the series of postwar X-planes experimental aircraft developed in the United States after World War II to fly in research programs exploring the challenges of high-speed transonic flight and beyond. It had aerodynamic problems similar to those of the DH.108, but both X-4 examples built survived their flight test programs without serious incidents through some 80 total research flights from 1950 to 1953, only reaching top speeds of 640 mph (1,035 km/h). The French Mirage series of supersonic jet fighters were an example of

1045-508: The Me 163 Komet . It was the only rocket-powered interceptor ever to be placed in front-line service, and was the fastest aircraft to reach operational service during the war. In the 1930s, Walter and Reimar Horten started to build simple tailless gliders, the first of which flew in 1933. The Hortens designed the world's first jet-powered flying wing , the Horten Ho 229 In parallel with Lippisch, in

1100-481: The Tupolev Tu-144 , were tailless supersonic jet airliners, with ogival delta wings. The grace and beauty of these aircraft in flight were often remarked upon. The American Lockheed SR-71 Blackbird strategic reconnaissance aircraft is the fastest jet powered aircraft, achieving speeds above Mach 3. The NASA Preliminary Research Aerodynamic Design To Lower Drag (PRANDTL-D) wing has been developed by Al Bowers at

1155-636: The IB. The Pterodactyl 1A of 1926 is held by the Science Museum London. Aircraft of comparable role, configuration, and era Tailless aircraft Theoretical advantages of the tailless configuration include low parasitic drag as on the Horten H.IV soaring glider and good stealth characteristics as on the Northrop B-2 Spirit bomber. Disadvantages include a potential sensitivity to trim . Tailless aircraft have been flown since

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1210-509: The Mk. IA flying in 1928. The Mks II and III failed to gain Ministry acceptance. The next model to be built was a three-seat cabin monoplane to Ministry Specification 16/29, in which the all-moving tips were replaced by conventional ailerons. An unusual feature was the use of variable wing sweep to provide longitudinal trim. Designated the Mk. IV, it first flew in 1931. The final Westland-built variant,

1265-428: The Mk. V, flew the next year, in 1932. Built to Ministry specification F.3/32, it was a two-seat fighter powered by a 600 h.p. Rolls-Royce Goshawk engine and differing noticeably from the previous versions in having a sesquiplane lower wing and tractor propeller. The lower wing was unswept and of short span, and braced to the upper wing. The forward propeller position, together with the tailless wing configuration, gave

1320-532: The NASA Armstrong Flight Research Center . Bowers was inspired by the work of Ludwig Prandtl and, like Dunne, by watching bird flight. As with the Dunne design, it has a wing twist sufficient to set the wing tips at a negative angle and create the same positive roll-yaw coupling. Bowers developed a quantitative analysis of the lifting characteristics, leading to his more general discovery of

1375-418: The Pterodactyl I, was built to Air Ministry Specification 23/26. It took the form of a braced shoulder-wing monoplane with fully moving wingtips and a single pusher propeller. If both tips were moved in the same way they functioned as elevators , in opposite ways then as ailerons . It was designated the Mk. IA or IB according to which engine was fitted. It and subsequent models flew initially from RAF Andover ,

1430-452: The Pterodactyl programme was cancelled before any order for the Mk, VI had been received. At the time of cancellation, wind tunnel models of a Mk. VII four-engined reconnaissance seaplane had been tested, and a proposal for a Mk. VIII transatlantic airliner was being worked on. After World War II, Hill helped develop the similar NRC tailless glider in Canada. Returning to England, he developed

1485-529: The US, Jack Northrop was developing his own ideas on tailless designs. The N-1M flew in 1941 and a succession of tailless types followed, some of them true flying wings. In the 1940s, the British aircraft designer John Carver Meadows Frost developed the tailless jet-powered research aircraft called the de Havilland DH.108 Swallow , built using the forward fuselage of the de Havilland Vampire jet fighter. One of these

1540-488: The Vulcan, designated as the B.1 , did not have any elevons present; instead, it used an arrangement of four inboard elevators and four outboard ailerons along its delta wing for flight control. The Vulcan received elevons on its extensively redesigned second variant, the B.2' ; all of the elevators and ailerons were deleted in favour of eight elevons. When flown at slow speeds, the elevons operated in close conjunction with

1595-489: The aero-isoclinic wing and helped Short Brothers develop the Short SB.1 and SB.4 tailless swept-wing test aircraft. Hill's Pterodactyl designs were all intended to handle safely without any definite stall point, allowing reliable recovery without loss of altitude even by inexperienced pilots. The characteristic wing was of moderately tapered and swept planform, with reverse taper at the root to improve pilot vision. The wing

1650-409: The aerodynamic center backward and make the aircraft stable . There are two main ways for the designer to achieve this, the first being developed by the pioneer aviator J. W. Dunne . Sweeping the wing leading edge back, either as a swept wing or delta wing , and reducing the angle of incidence of the outer wing section allows the outer wing to act like a conventional tailplane stabiliser. If this

1705-475: The ailerons, helping the plane into the turn and eliminating the need for a vertical rudder or differential-drag spoilers. The bell-shaped lift distribution this produces has also been shown to minimise the induced drag for a given weight (compared to the elliptical distribution, which minimises it for a given span). Between 1905 and 1913, the British Army Officer and aeronaut J. W. Dunne developed

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1760-624: The aircraft's complex quadruplex computer-controlled fly-by-wire flight control system in order to counteract the inherent instability of the flying wing configuration. Several technology research and development efforts exist to integrate the functions of aircraft flight control systems such as ailerons, elevators, elevons and flaps into wings to perform the aerodynamic purpose with the advantages of less: mass, cost, drag, inertia (for faster, stronger control response), complexity (mechanically simpler, fewer moving parts or surfaces, less maintenance), and radar cross section for stealth . However,

1815-645: The aircraft's six electrically-actuated three-position airbrakes . Another early aircraft to use elevons was the Convair F-102 Delta Dagger , an interceptor operated by the United States Air Force . A few years after the F-102's introduction, Convair built the B-58 Hustler , an early supersonic bomber, which was also equipped with elevons. Perhaps the most iconic aircraft fitted with elevons

1870-456: The center of gravity must also be moved forward of the usual position. Due to the Bernoulli effect , reflex camber tends to create a small downthrust, so the angle of attack of the wing is increased to compensate. This in turn creates additional drag. This method allows a wider choice of wing planform than sweepback and washout, and designs have included straight and even circular (Arup) wings. But

1925-448: The drag inherent in a high angle of attack is generally regarded as making the design inefficient, and only a few production types, such as the Fauvel and Marske Aircraft series of sailplanes, have used it. A simpler approach is to overcome the instability by locating the main weight of the aircraft a significant distance below the wing, so that gravity will tend to maintain the aircraft in

1980-523: The first practical tailless aeroplane. The later D.8 was license-built and sold commercially by W. Starling Burgess in America as the Burgess-Dunne. He also returned to his monoplane. The D.6 of 1911 was a pusher type high-wing monoplane which also featured pronounced anhedral or droop to the wing tips. The control surfaces now also acted as rudders. Many of Dunne's ideas on stability remain valid, and he

2035-501: The main drawback is that when the elevons move up in unison to raise the pitch of the aircraft, generating additional lift, they reduce the camber, or downward curvature of the wing. Camber is desirable when generating high levels of lift, and so elevons reduce the maximum lift and efficiency of a wing. These may be used in many unmanned aerial vehicles (UAVs) and sixth generation fighter aircraft . Two promising approaches are flexible wings, and fluidics. In flexible wings, much or all of

2090-427: The main wing. A tailless type may still have a conventional vertical tail fin ( vertical stabilizer ) and rudder . A flying wing is a tailless design which also lacks a distinct fuselage , having the pilot, engines, etc. located wholly or partially in the wing. A conventional fixed-wing aircraft has a horizontal stabiliser surface separate from its main wing. This extra surface causes additional drag requiring

2145-438: The missing stabiliser. Some examples were stable but their height could only be controlled using engine power. Others could pitch up or down sharply and uncontrollably if they were not carefully handled. These gave tailless designs a reputation for instability. It was not until the later success of the tailless delta configuration in the jet age that this reputation was widely accepted to be undeserved. The solution usually adopted

2200-469: The name. They are frequently used on tailless aircraft such as flying wings . An elevon that is not part of the main wing, but instead is a separate tail surface, is a stabilator (but stabilators are also used for pitch control only, with no roll function, as on the Piper Cherokee series of aircraft). Elevons are installed on each side of the aircraft at the trailing edge of the wing. When moved in

2255-622: The pioneer days; the first stable aeroplane to fly was the tailless Dunne D.5 , in 1910. The most successful tailless configuration has been the tailless delta , especially for combat aircraft, though the Concorde airliner is also a delta configuration. NASA has used the 'tailless' description for the novel X-36 research aircraft which has a canard foreplane but no vertical fin. A tailless aircraft has no other horizontal surface besides its main wing. The aerodynamic control and stabilisation functions in both pitch and roll are incorporated into

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2310-483: The rear gun turret an outstanding field of fire. Despite its performance and flyability in other respects rivalling its conventional competitor the Hawker Hart it was not accepted for production. Associated with the Mk. V was a complementary Mk. VI design for a pusher variant with front-mounted gun turret, and the intention was to fly a mixed squadron with front-firing machines leading and rear-firing machines behind, but

2365-446: The rear or all of the wing. With reflex camber the flatter side of the wing is on top, and the strongly curved side is on the bottom, so the front section presents a high angle of attack while the back section is more horizontal and contributes no lift, so acting like a tailplane or the washed-out tips of a swept wing. Reflex camber can be simulated by fitting large elevators to a conventional airfoil and trimming them noticeably upwards;

2420-407: The same direction (up or down) they will cause a pitching force (nose up or nose down) to be applied to the airframe. When moved differentially, (one up, one down) they will cause a rolling force to be applied. These forces may be applied simultaneously by appropriate positioning of the elevons e.g. one wing's elevons completely down and the other wing's elevons partly down. An aircraft with elevons

2475-680: The tailless delta configuration, and became one of the most widely produced of all Western jet aircraft. By contrast the Soviet Union's equivalent widely produced delta-winged fighter, the Mikoyan-Gurevich MiG-21 , does have a tail stabiliser. In the 1950s, the Convair F2Y Sea Dart prototype became the only seaplane to exceed the speed of sound. Convair built several other successful tailless delta types. The Anglo-French Concorde Supersonic transport , and its Soviet counterpart,

2530-581: The theory of the stable aerofoil. The designer Alexander Lippisch produced his first tailless design, the Delta I, in 1931. He went on to build a series of ever-more sophisticated designs, and at the end of the Second World War was taken to America to continue his work . During the Second World War , Lippisch worked for the German designer Willy Messerschmitt on the first tailless aircraft to go into production,

2585-481: The trailing edge of each wing tip acted as combined aileron and elevator. Dunne had an advanced qualitative appreciation of the aerodynamic principles involved, even understanding how negative lift at the wing tips, combined with steep downward-angled anhedral, enhanced directional stability. Although originally conceived as a monoplane , Dunne's initial designs for the Army were required to be biplanes , typically featuring

2640-546: The trailing edge of the wing's; while most surfaces are used throughout the aircraft's flight envelope, the inner elevons are normally only ever applied while being flown at slow speeds, such as on approach to landing. To avoid potential contact damage during takeoff and to provide a nose-down pitching attitude, all of the elevons remain drooped during takeoff until a high enough airspeed has been attained. The B-2's flight surfaces are automatically adjusted and repositioned without pilot input to do so, these changes being commanded by

2695-556: The vehicle's controlled descent back to Earth. There were a total of four elevons affixed to the trailing edges of its delta wing. While flown outside of atmospheric flight, the Shuttle's attitude control was instead provided by the Reaction Control System (RCS), which consisted of 44 compact liquid-fueled rocket thrusters controlled via a sophisticated fly-by-wire flight control system . The Northrop Grumman B-2 Spirit ,

2750-446: The wing trailing edge. Yaw stability was generally achieved by vertical fins, and control by vertical rudders, but the exact arrangement varied between types and even during the flight testing of individual machines. The Mk. I differed in having horizontal "electroscope rudders" on the trailing edge, inboard of the movable wingtips, which acted to provide differential drag. The IA had no vertical surfaces but small fixed fins were added to

2805-520: Was " washed out ", having a slight twist which reduced the angle of incidence progressively towards the tips, providing a near-stationary overall centre of pressure and ensuring that the aircraft was stable in pitch. Thus, no horizontal stabiliser was needed and the craft was tailless, allowing the fuselage to be relatively short. Early examples used a patented system in which the wingtips pivoted to act as slab elevons providing control in pitch and roll, while later types had more conventional elevons in

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2860-456: Was flown as a glider in 1924. The design gained official interest and in 1925 it was fitted with a 35 h.p. Bristol Cherub engine and taken to Farnborough. It was later demonstrated to the Secretary of State for Air, Sir Samuel Hoare . All subsequent examples were funded under Air Ministry contract and built by Westland Aircraft , who took on Hill for this purpose. The first Westland-built type,

2915-482: Was possibly one of the first aircraft ever to break the sound barrier – it did so during a shallow dive, and the sonic boom was heard by several witnesses. All three built were lost in fatal crashes. The DINFIA IA 38 was a 1960s Argentine four-engine experimental tailless transport aircraft , designed under the direction of Reimar Horten and based on the German Horten H.VIII project and built by

2970-514: Was the Aérospatiale / BAC Concorde , a British–French supersonic passenger airliner . In addition to the requirement to maintain precise directional control while flying at supersonic speeds, designers were also confronted by the need to appropriately address the substantial forces that were applied to the aircraft during banks and turns, which caused twisting and distortions of the aircraft's structure. The solution applied for both of these issues

3025-456: Was via management of the elevons; specifically, as the aircraft speed varied, the active ratio between the inboard and outboard elevons was adjusted considerably. Only the innermost elevons, which are attached to the stiffest area of the wings, would be active while Concorde was flown at high speeds. The Space Shuttle Orbiter was furnished with elevons, although these were only operable during atmospheric flight, which would be encountered during

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