Editing Swept wing (section)

===German developments===
[[Image:Adolf Busemann at Langley.jpg|thumb|left|[[Adolf Busemann]] proposed the use of swept-wings to reduce drag at high speed, at the [[Volta Conference]] in 1935.]]

The idea of using swept wings to reduce high-speed drag was developed in Germany in the 1930s. At a [[Volta Conference]] meeting in 1935 in Italy, [[Adolf Busemann]] suggested the use of swept wings for [[supersonic]] 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]] in 1924, although not in the context of high-speed flight).<ref name="history">Anderson, John D. Jr. ''A History of Aerodynamics''. New York: McGraw Hill, 1997, p. 424.</ref> [[Albert Betz]] immediately suggested the same effect would be equally useful in the transonic.<ref>[http://www.ascho.wpafb.af.mil/encounter/Chap1-28.htm "Comment by Hans von Ohain during public talks with Frank Whittle, p. 28."] {{webarchive|url=https://web.archive.org/web/20071209170510/http://www.ascho.wpafb.af.mil/encounter/Chap1-28.htm |date=9 December 2007 }} ''ascho.wpafb.af.mil.'' Retrieved: 1 August 2011.</ref> After the presentation the host of the meeting, [[Gaetano Crocco|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 1950s fighter design, with swept wings and tail surfaces, although he also sketched a swept propeller powering it.<ref name="history" />

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 {{convert|400|km/h|0|abbr=on}}.The presentation was largely of academic interest, and soon forgotten. Even notable attendees including [[Theodore von Kármán]] and [[Eastman Jacobs]] did not recall the presentation 10 years later when it was re-introduced to them.<ref name="history423-424">Anderson 1997, pp. 423–424.</ref>

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.<ref name=GerDev /> Two wings, one with no sweep, and one with 45 degrees of sweep were tested at [[Mach number]]s of 0.7 and 0.9 in the 11 x 13&nbsp;cm wind tunnel.  The results of these tests confirmed the drag reduction offered by swept wings at transonic speeds.<ref name=GerDev />  The results of the tests were communicated to [[Albert Betz]] who then passed them on to [[Willy Messerschmitt]] 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.<ref name=GerDev />

With the introduction of [[jet engine|jets]] in the later half of the [[Second World War]], the swept wing became increasingly applicable to optimally satisfying aerodynamic needs. The German jet-powered [[Messerschmitt Me 262]] and rocket-powered [[Messerschmitt Me 163]] suffered from [[compressibility]] effects that made both aircraft very difficult to control at high speeds. In addition, the speeds put them into the [[wave drag]] 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]]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.<ref>Hermann Pohlmann; ''Chronik Eines Flugzeugwerkes 1932–1945'', 2nd Impression, Motorbuch, 1982, pp. 190-193.</ref> The [[Focke-Wulf Ta 183]] was another swept wing fighter design, but was also not produced before the war's end.<ref name="Myhra p. 4">Myhra 1999, p. 4.</ref> In the post-war era, [[Kurt Tank]] developed the Ta 183 into the [[IAe Pulqui II]], but this proved unsuccessful.<ref name="IPMS">Waligorski, Martin. [http://www.ipmsstockholm.org/magazine/2002/06/stuff_eng_profile_pulqui.htm "Pulqui: Argentina's Jet Adventure."] ''Camouflage & Markings'': ''IPMS Stockholm'', 22 September 2006. Retrieved: 27 April 2010.</ref>

A prototype test aircraft, the [[Messerschmitt Me P.1101]], was built to research the tradeoffs of the design and develop general rules about what angle of sweep to use.<ref name=Christopher>Christopher 2013, pp. 157–160.</ref> When it was 80% complete, the P.1101 was captured by US forces and returned to the [[United States]], where two additional copies with US-built engines carried on the research as the [[Bell X-5]].<ref>Winchester 2005, p. 37.</ref> 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.<ref name="ley194811">{{Cite magazine |last=Ley |first=Willy |date=November 1948 |title=The 'Brickwall' in the Sky |url=https://archive.org/stream/Astounding_v42n03_1948-11_cape1736#page/n77/mode/2up |magazine=Astounding Science Fiction |pages=78–99}}</ref>