Aircraft extremely low aspect ratio

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Vought V-173

An aircraft with an extremely low aspect ratio has a structural design in which wings with a relatively small span and a relatively large area are used. The aspect ratio is defined as the ratio of the squared wingspan to the wing area.

definition

There is no generally applicable definition for "extremely low aspect ratio" in the literature. However, a value of = 3 for low aspect ratio, = 5 to 6 for medium aspect ratio (6 to 10 for “ordinary” aircraft) and > 20 for high aspect ratio is given. “Very low” values, on the other hand, are used for the transonic and supersonic ranges. Aircraft of general aviation have a stretch 6 to 8

Examples
Model span Wing area Elongation
Handley Page HP.115 00.6.10 m 00.39.95 m² 00.0.9
Chance Vought V-173 00.7.12 m 00.39.67 m² 00.1.3
Arup S 2 00.5.80 m 00.19.60 m² 00.1.7
Canova PC 100 00.5.90 m 00.17.80 m² 00.2.0
Dyke JD-2 Delta 00.6.87 m 00.16.00 m² 00.2.95
Conventional aircraft
Cessna 172 0.10.97 m 00.16.17 m² 00.7.4
Boeing 737 MAX 0.35.92 m 0.124.60 m² 0.10.4
Washer SF 25 C 0.15.30 m 00.18.20 m² 0.13.4

Influence on aerodynamic efficiency

At low stretch and low speed, the induced drag dominates the "lift behavior". In slow flight aircraft, the induced drag accounts for more than 50% of the total drag. The extension of a wing is therefore a decisive parameter for the aerodynamic efficiency of an aircraft in the subsonic range. With the same wing area, wings with the greater aspect ratio have a higher efficiency in terms of lift. That is why the greatest possible aspect ratio is generally aimed for in the construction of aircraft. In supersonic this is not true, can be omitted here to a high elongation. An example of this is the delta wing , the X-15 or the F-104 .

In addition to the induced drag, the parasitic drag also contributes to the overall efficiency of a wing . The latter grows proportionally to the wing area. Aircraft with a low aspect ratio therefore have a high level of parasitic resistance in addition to a large induced drag. However, despite these disadvantages, there are certainly reasons to design a subsonic aircraft in this way.

Dyke JD2 Delta

Usually the reason for such constructions is flying with a very high angle of attack (= lift coefficient .) Aviation pioneers realized very early that the classic rhombus-shaped or hexagonal children's kite has a very high angle of attack on the rope and still generates a lot of lift. Many of these attempts were aimed at creating a completely stall-proof aircraft or one that can still be flown at a very high angle of attack. The diamond-shaped gliders of the Italian Flaminio Piana Canova are said to have reached up to 35 ° before the stall occurred. The same applies to the Suchanow disco plan and the Wainfan family's Facettomobile. Most of these constructions have in common that they do not have a conventional flow around the supporting surface, but a vortex system above the wing generates the necessary lift.

Applications

Suchanov Diskoplan II in the Monino Museum

There were variants with a separate horizontal stabilizer, but the majority was designed without a tail . The Nemeth "Parasol" was a high-wing aircraft with a completely normal fuselage and a disc-shaped wing. Other applications for aircraft with extremely low aspect ratios such as William Horton's “Wingless” tended to be more in the direction of a flying car or a compact “people's plane”.

Still other designs were simply used to research the flow behavior of wings with extremely low aspect ratios, e.g. B. the Handley Page HP.115 . Last but not least, some attempts were aimed at finding out to what extent such aircraft are suitable as re-entry vehicles for space travel. The last stage of these considerations are the so-called lifting bodies .

Last but not least, the wish to have an absolutely unique flying device available for show purposes may have been the inspiration, as in the case of David Rowe. The Australian built a small circular plane called UFO (= Useless Flying Object) and is demonstrating it at flight days. Since 2015 it has a retractable landing gear, which reinforces the impression of a UFO .

For years, flying disks were popular in model aircraft construction, whereby the attached fin was often designed as a comic figure etc. Here they did not even bother to profile the "wing", but used a styrofoam plate with vertical edges that were reinforced with a surrounding wooden strip.

Graphic representations

Of the aircraft shown, only the Dyke JD2 was produced in larger numbers (~ 50). All the others remained unique.

  • Scroggs "The Last Laugh", USA 1930

  • Arup S2 , USA 1932

  • Arup S4, USA 1935

  • Hoffmann Younghusband Flying Pancake, USA 1934

  • Payen AP10a , France 1935

  • Fauvel AV10, France 1935

  • Canova PC 100, Italy 1934

  • Canova PC 500, 1935

  • Canova PC 140, Italy 1936

  • Moskalev SAM-9, USSR 1937

  • Johnson Uniplane, USA

  • Eshelman Flying Flounder, USA 1942

  • Chance Vought V-173 , USA 1942

  • Sack AS-6 , Germany 1944

  • Horton Swoopy, USA 1951

  • Horton "Wingless", USA 1952

  • Sukhanov Diskoplan 1, USSR 1958

  • Sukhanov Diskoplan 2, USSR 1960

  • Sukhanov Diskoplan 4, USSR 1965

  • Baker Delta Kitten, 1960

  • Dyke JD-2 Delta , USA 1964

  • Potier P40, 1968

  • Borchers Delta Stingray, USA 1979

  • Debreyer JCD2, France 1981

  • Hatfield Little Bird, USA 1986

  • Verhees Delta 2001

  • Rutan Space Ship One , USA 2006

  • Rowe UFO, Australia 2015

literature

  • Rudolf Storck among others: Flying Wings . The historical development of the world's tailless and flying wing aircraft. Bernard and Graefe, Bonn 2003, ISBN 3-7637-6242-6 .
  • Vincenzo Pedrielli, Francesco Camastra: Italian Vintage Sailplanes. EQIP Werbung & Verlag GmbH, Königswinter 2011, ISBN 978-3-9808838-9-4 , pp. 198f

Individual evidence

  1. ^ AC Kermode: Mechanics of Flight , Pearson, 12th edition 2012, pp. 97 and 100
  2. ^ David F. Anderson, Scott Eberhardt: Understanding Flight , McGraw Hill, 2nd edition 2010, p. 267

Web links