|The DH108 Swallow|
A tailless aircraft (often tail-less) has no other horizontal surface besides its main wing. All its aerodynamic control and stabilisation functions in pitch and roll are incorporated into the main wing. A 'tailless' type usually still has a vertical stabilising fin (vertical stabilizer) and control surface (rudder). However, NASA has recently adopted the 'tailless' description for the novel X-36 research aircraft which has a canard foreplane but no vertical fin.
- 1 Flying wings
- 2 Aerodynamics
- 3 History
- 4 List of tailless aircraft
- 5 See also
- 6 References
- 7 External links
A flying wing is a tailless design which also lacks a distinct fuselage, having the pilot, engines, etc. located directly in or on the wing.
A conventional fixed-wing aircraft has a horizontal stabiliser surface separate from its main wing. This extra surface causes additional drag requiring 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 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 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 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 to 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 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; 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 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 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 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 B-2 Spirit flying wing is an example.
Many early designs failed to provide effective pitch control to compensate for the missing stabiliser. Some examples, such as Dunne's, 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 shown to be undeserved.
The solution usually adopted is to provide large elevator and/or elevon surfaces on the wing trailing edge. 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 manoeuvres than its conventional equivalent. The problem is less where sweepback is sharp and the distance between trailing edge and aerodynamic centre larger, as with the delta wing. 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.
- See also History of the flying wing
- J. W. Dunne
Although originally conceived as a monoplane design, most of Dunne's designs were required by his superior officer Col. Capper to be biplanes, typically featuring a fuselage nacelle between the planes with rear-mounted 'pusher' propeller and twin rudders between each pair of wing tips. Control surfaces on the trailing edge of each wing tip acted together as combined ailerons, elevators and rudders. His D.6 monoplane of 1910 was a pusher type high-wing monoplane which featured turned-down wingtips with pronounced wash-out.
In his book An Experiment with Time Dunne claims that one of these was the first aeroplane ever to achieve natural stability in flight. Certainly, Dunne designed the first practical tailless aeroplanes. The British Army eventually rejected Dunne's design for a bomber because its high stability meant that it lacked the required manoeuvrability.
Dunne gave some help initially to Geoffrey T. R. Hill who produced the Pterodactyl series of tailless aircraft from 1920s onwards which were specifically designed to reduce the likelihood of stalling and spinning.
Inter-war and WWII
- Lippisch deltas
The German designer Alexander Lippisch produced the first tailless delta 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.
- Messerschmitt Me 163 Komet
During the Second World War, Lippisch worked for the German designer Willy Messerschmitt on the first tailless aircraft to go into production, 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. Its rocket propulsion system was highly unsafe, especially the early versions, due to the hypergolic nature of the fuel and oxidizer combination used for its powerplant. Landing was hazardous not only because the Komet had no main wheel units following its normal rocket-powered "sharp start" take off, jettisoning its twin-wheeled "dolly" during the takeoff run, but because sparks from the metal landing skid often flew up and ignited fuel vapours escaping from the propulsion system. More pilots were killed in takeoff and landing incidents than in combat.
- de Havilland DH 108 Swallow
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 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.
Similar to the D.H. 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 D.H.108, but both X-4 examples built survived their flight test programs without serious incidents through some 80 total research flights from 1950-1953, only reaching top speeds of 640 mph (1,035 km/h).
- Dassault Mirage
The French Mirage series of supersonic jet fighters were an example of 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.
- Convair F2Y Sea Dart
- Supersonic airliners
The Anglo-French Concorde Supersonic transport and its Soviet counterpart the Tupolev Tu-144 were tailless supersonic jet airliners, with gracefully curved ogival delta wings. The grace and beauty of these aircraft in flight were often remarked upon.
- Lockheed SR-71 Blackbird
The American Lockheed SR-71 Blackbird reconnaissance aircraft was the fastest jet powered aircraft at the time it was retired, achieving speeds above Mach 3.
List of tailless aircraft
Military jets and rockets
- Avro CF-105 Arrow
- Avro Vulcan
- Convair F-102 Delta Dagger
- Convair F-106 Delta Dart
- Convair B-58 Hustler
- Dassault Mirage series
- Douglas F4D Skyray
- HAL Tejas
- Lockheed Blackbird series
- Messerschmitt Me 163 Komet
- Saab 35 Draken
- Vought F7U Cutlass
Research and experimental types
- Avro 707 - research for Avro Vulcan, 1/3 scale of Vulcan
- Boulton Paul P.111 - delta wing research
- Convair F2Y Sea Dart
- de Havilland DH.108 Swallow
- Dunne types
- Fairey Delta 2 - high speed delta design
- General Dynamics F-16XL - delta wing research fighter/bomber
- Handley Page HP.75 Manx
- Handley Page HP.115 - low speed handling of delta wing
- Kalinin K-12 of 1936 
- Lippisch delta types
- Northrop X-4 Bantam
- Short SB.1 (glider) and Short SB.4 Sherpa - tested aero-isoclinic wing
- University of Pretoria Exulans: glider with Stromburg wing
- Westland-Hill Pterodactyl series
- X-44 MANTA
Commercial and general aviation
- Concorde - SST
- DINFIA IA 38 - transport prototype
- Fauvel AV.36 and others by Charles Fauvel 
- Granger Archaeopteryx
- Tupolev Tu-144 - SST
Modern hang gliders and ultralights
- Aériane Swift: tailless foot-launched glider
- Kollman Composites Raptor
- John K. Moody/Larry Mauro Easy Riser
- Poulsen, C.M. "Tailless trials, Tribute to a British Pioneer: The Dunne Biplanes and Monoplane.", "p. 557.", "p. 558." Flight, 27 May 1943, pp, 556–558.
- Tailless Aircraft - discussion of design and stability.