Delta wing

HAL Tejas has a tailless delta wing configuration

MiG-21 had a tailed delta wing configuration (it had a conventional tail)

The delta wing Avro Vulcan bomber

For the race car, see DeltaWing.

The delta wing is a wing planform in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta (Δ).

History

Delta-shaped stabilizers

Between 1529 and 1556 Conrad Haas wrote a book in which he described rocket technology, involving the combination of fireworks and weapons technologies. This manuscript was re-discovered in 1961, in the Sibiu public records (Sibiu public records Varia II 374). His work dealt with the theory of motion of multi-stage rockets, different fuel mixtures using liquid fuel, and also introduced delta-shaped stabilizers.[1]

As the manuscript was discovered only in 1961 until recently the conception of such stabilizers and their name had been suggested in the 17th century by the Polish-Lithuanian military engineer Kazimierz Siemienowicz.^[1][2][3]

Delta wing

The first practical uses of delta wing came in the form of so called "tailless delta", i.e. without the horizontal tailplane. In fact the designs were at the same time also the first flying wings. It could be argued if 1924 Cheranovsky designs, having one-of-a-kind parabolic planform,^[4] fit the category of delta wings. Nevertheless, a triangular wing was pioneered especially by Alexander Lippisch in Germany. He was first to fly tailless delta aircraft in 1931,^[5][6] followed by four improved designs. None of these was easy in handling at slow speeds, and none saw widespread service.^[7][8] During the war Lippisch studied a number of ramjet powered (sometimes coal-fueled) delta-wing interceptor aircraft, one progressing as far as a glider prototype.^[9]

After the war, Lippisch was taken to the United States of America, where he worked at the Convair company in California. Some high-ranking Convair engineers became quite interested in his interceptor designs, and they started work on a larger test version known as the Convair XF-92. The prototype—although never put into production—was extensively flight-tested, and its design generated a lot of interest of various airplane manufacturers in several countries. Soon many aircraft designs, particularly interceptors, would be designed around the delta wing. The tail-less delta became a favored design for high-speed use, and was used almost to the exclusion of other designs by Convair and by Dassault Aviation in France. Convair's F-102 was the first fighter with a tailless delta wing in service with any air force anywhere in the world.

Meanwhile, the British also developed aircraft based on the data from Lippisch, notably the Avro Vulcan strategic bomber and the Gloster Javelin fighter. The Javelin incorporated a tailplane in order to rectify some of the perceived weaknesses of the pure delta, to improve low-speed handling and high-speed manoeuvrability and to allow a greater center of gravity range.^[10]

The tailed delta configuration was again adopted by the TsAGI (Central Aero and Hydrodynamic Institute, Moscow), to take advantage of both high angle-of-attack flying capability and high speeds. It was used in the MiG-21 (Fishbed) and Sukhoi Su-9/Su-11/15 fighters, built by the tens of thousands in several different communist countries.

More recently, Saab AB used a close-coupled canard foreplane^[11] in front of the main wing of the Viggen fighter. The close coupling actively modifies the airflow over the wing, most notably during flight at high angles of attack. In contrast to the classic tail-mounted elevators, the canards add to the total lift, enabling the execution of extreme maneuvers, improving low-speed handling and lowering the landing speed. The design was copied in other aircraft, such as the Eurofighter Typhoon.

Properties

The primary advantage of the delta wing is that, with a large enough angle of rearward sweep, the wing’s leading edge will not contact the shock wave boundary formed at the nose of the fuselage as the speed of the aircraft approaches and exceeds transonic to supersonic speed. The rearward sweep angle vastly lowers the airspeed normal to the leading edge of the wing, thereby allowing the aircraft to fly at high subsonic, transonic, or supersonic speed, while the over wing speed of the lifting air is kept to less than the speed of sound. The delta plan form gives the largest total wing area (generating useful lift) for the wing shape, with very low wing per-unit loading, permitting high maneuverability in the airframe. As the delta's platform carries across the entire aircraft, it can be built much more strongly than a swept wing, where the spar meets the fuselage far in front of the center of gravity. Generally a delta will be stronger than a similar swept wing, as well as having much more internal volume for fuel and other storage.

Another advantage is that as the angle of attack increases, the leading edge of the wing generates a vortex which energizes the flow, giving the delta a very high stall angle. A normal wing built for high speed use is typically dangerous at low speeds, but in this regime the delta changes over to a mode of lift based on the vortex it generates. The disadvantages, especially marked in the older tailless delta designs, are a loss of total available lift caused by turning up the wing trailing edge or the control surfaces (as required to achieve a sufficient stability) and the high induced drag of this low-aspect ratio type of wing. This causes delta-winged aircraft to 'bleed off' energy very rapidly in turns, a disadvantage in aerial maneuver combat and dogfighting. It also causes a reduction in lift at takeoff and landing until the correct angle of attack is achieved, this means that the rear undercarriage must be more strongly built than with a conventional wing.

Additional advantages of the delta wing are simplicity of manufacture, strength, and substantial interior volume for fuel or other equipment. Because the delta wing is simple, it can be made very robust (even if it is quite thin), and it is easy and relatively inexpensive to build - a substantial factor in the success of the MiG-21 and Mirage aircraft.

A canard-delta suffers from a smaller shift in the center of lift with increasing mach number than a wing and tail configuration, but requires a stronger wing in order to provide control inputs that a canard is less effective than a tail at providing.^[12]

When used with a T-tail as in the Gloster Javelin the large delta wing could give rise to a "deep stall"; at high angles of attack the wing blanked airflow over the tail and left the aircraft uncontrollable.^[13]

Delta-wing variations

Pure delta-wings fell out of favour somewhat due to their undesirable characteristics, notably flow separation at high angles of attack (swept wings have similar problems), and high drag at low altitudes. This limited them primarily to high-speed, high-altitude interceptor roles.

Many modern fighter aircraft, such as the JAS 39 Gripen, the Eurofighter Typhoon and the Dassault Rafale use a combination of canards and a delta wing.

Tailed delta - adds a conventional tailplane (with horizontal tail surfaces), to improve handling. Popular on Soviet types such as the Mikoyan-Gurevich MiG-21. Cropped delta - tip is cut off. This helps avoid tip drag at high angles of attack. Used for example in F-16.

In another variant known variously as compound delta, double delta or cranked arrow, the inner part of the wing has a very high sweepback, while the outer part has less sweepback, to create the high-lift vortex in a more controlled fashion, reduce the drag and thereby allow for landing the delta at acceptably slow speed. This design can be seen on the Saab Draken fighter, the prototype F-16XL "Cranked Arrow" and in the High Speed Civil Transport study. The ogee delta (or ogival delta) used on the Anglo-French Concorde Mach 2 airliner is similar, but with a smooth 'ogee' curve joining the two parts rather than an angle.

Tailless delta

Tailed delta

Cropped delta

Compound delta

Cranked arrow

Ogival delta

As the performance of jet engines grew, fighters with other planforms could perform as well as deltas, and do so while maneuvering much harder and at a wider range of altitudes. Today a remnant of the compound delta can be found on most fighter aircraft, in the form of leading edge extensions. These are effectively very small delta wings placed so they remain parallel to the airflow in cruising flight, but start to generate a vortex at high angles of attack. The vortex is then captured on the top of the wing to provide additional lift, thereby combining the delta's high-alpha performance with a conventional highly efficient wing planform.

Aircraft examples

Production examples

• Avro Vulcan - strategic bomber
• Buran Space Shuttle
• Chengdu J-7 - a Chinese development of MiG-21
• Chengdu J-10
• Concorde
• Convair B-58 Hustler
• Convair F-102 Delta Dagger
• Convair F-106 Delta Dart
• Dassault Mirage III
• Dassault Mirage IV
• Dassault Mirage 2000
• Dassault Rafale
• Eurofighter Typhoon
• Gloster Javelin - subsonic fighter
• HAL Tejas
• Lockheed SR-71 Blackbird
• McDonnell Douglas A-4 Skyhawk - a "tailed" delta wing aircraft
• Mikoyan-Gurevich MiG-21 "Fishbed" - a "tailed" delta wing fighter
• Saab 35 Draken
• Saab 37 Viggen
• Saab JAS 39 Gripen
• Shenyang J-8
• Space Shuttle Orbiter
• Sukhoi Su-9 "Fishpot"
• Sukhoi Su-11 "Fishpot"
• Sukhoi Su-15 "Flagon" - early models
• Tupolev Tu-144

Research or prototype-only examples

• Avro 707 (1949)
• Avro Canada CF-105 Arrow
• Boeing X-32
• Boulton Paul P.111 (1949) - research to investigate tailess deltas
• Boulton Paul P.120 (1952) - developed from P.111
• Chengdu J-9
• Chengdu J-20
• Convair F2Y Sea Dart - unique seaplane fighter
• Convair XF-92
• Convair XFY - one of the few propeller-driven delta wing aircraft
• Dyke Delta - another of the few propeller-driven double delta wing aircraft
• Fairey Delta 1 (1951) - transonic delta research
• Fairey Delta 2 (1954) - 1st aircraft to break 1,000 mph, rebuilt as BAC 211 for high speed delta research for Concorde
• HAL Tejas
• Handley Page HP.115 - low-speed delta research for Concorde
• Myasishchev M-50
• North American XB-70 Valkyrie
• Short SC.1 - first British VTOL aircraft
• Sukhoi T-4 / 100 Sotka

Notes

1. ^ Uranos.org.pl
2. ^ New Rocket Guide, NASA
3. ^ Bolesław Orłowski, Technology and Culture, Vol. 14, No. 3 (Jul., 1973), pp. 461-473, JSTOR
4. ^ Alexandre Savine. "Boris Ivanovich Cheranovskij". http://www.ctrl-c.liu.se/misc/ram/cheranovsky.html. Retrieved 12 February 2011. 
5. ^ Ford, Roger (2000). Germany's secret weapons in World War II (1. publ. ed.). Osceola, WI: MBI Publ.. p. 36. ISBN 0760308470. http://books.google.com/books?id=lU8xBhe9ntsC&lpg=PA36&dq=Lippisch&pg=PA36#v=onepage&q=Lippisch&f=false. 
6. ^ "New Triangle Plane Is Tailless", December 1931, Popular Science article and photo of Delta I at bottom of page 65
7. ^ Madelung, Ernst Heinrich Hirschel, Horst Prem, Gero (2004). Aeronautical research in Germany : from Lilienthal until today ([American ed.]. ed.). Berlin: Springer. ISBN 354040645X. http://books.google.com/books?id=OoFcHOLpCskC&lpg=PA168&dq=Lippisch%20Horten&pg=PA168#v=onepage&q=Lippisch%20Horten&f=false. 
8. ^ Wohlfahrt, Karl Nickel ; Michael (1990) (in German). Schwanzlose flugzeuge : ihre auslegung und ihre eigenschaften. Basel: Birkhauser Verlag. pp. 577–578. ISBN 376432502X. http://books.google.com/books?id=33fBLs7FhQ8C&lpg=PA577&dq=Lippisch%20Horten&pg=PA577#v=onepage&q=Lippisch%20Horten&f=false. Retrieved 13 February 2011. "[Lippisch Delta I and Horten H I] Both these aircraft shown, how not to do it." 
9. ^ Lippisch Prototype Test Footage at youtube
10. ^ Partridge, J.; Number 179 - The Gloster Javelin 1-6, Profile Publications, 1967
11. ^ Green, W. and Swanborough, G.; The complete book of fighters, Salamander, 1994
12. ^ Probert, B. "Aspects of Wing Design for Transonic and Supersonic Combat."
13. ^ Javelin thunder-and-lightnings.co.uk

References

• S. S. Sritharan and A. R. Seebass (1984). "A Finite Area Method for Nonlinear Supersonic Conical Flows". AIAA Journal 22: 226–233. Bibcode 1984AIAAJ..22..226S. doi:10.2514/3.8372. 
• S. S. Sritharan (1985). "Delta Wings with Shock-Free Cross Flow". Quarterly of Applied Mathematics XLIII: 275–286. 
• Jingling Guan and S. S. Sritharan (2008). "A Problem of Hyperbolic-Elliptic Type Conservation Laws on Manifolds that Arises in Delta-Wing Aerodynamics". International Journal of Contemporary Mathematical Sciences 3: 721–737. 
• Uwacadweb.uwyo.edu

External links

• Analysis of air flow over delta wings