Editing Hawker Siddeley Harrier (section)

===Origins===
{{Main|Hawker Siddeley P.1127}}
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The Harrier's design was derived from the [[Hawker Siddeley P.1127|Hawker P.1127]]. Prior to developing the P.1127, [[Hawker Aircraft]] had been working on a replacement for the [[Hawker Hunter]], the [[Hawker P.1121]].<ref>Davies and Thornborough 1997, pp.&nbsp;12–13.</ref> The P.1121 was cancelled after the release of the British Government's [[1957 Defence White Paper]], which advocated a policy shift away from manned aircraft and towards missiles. This policy resulted in the termination of the majority of aircraft development projects then underway for the British military.<ref name= Jefford_11>Jefford 2006, p.&nbsp;11.</ref> Hawker sought to quickly move on to a new project and became interested in Vertical Take Off/Landing (VTOL) aircraft, which did not need runways.{{refn|The development of a V/STOL jet was not Hawker's primary objective as it had put in a joint bid with [[Avro]] to meet the GOR.339 Requirement (which resulted in the [[BAC TSR-2]] development programme), but had been unsuccessful. The inability to obtain work on conventional aircraft in a hostile political climate was perhaps the greatest motivation for Hawker to proceed with the development of the Harrier.<ref name= Jefford_25>Jefford 2005, pp.&nbsp;11–12, 25.</ref>|group=N}} According to Air Chief Marshal [[Patrick Hine|Sir Patrick Hine]] this interest may have been stimulated by the presence of Air Staff Requirement 345, which sought a V/STOL ground attack fighter for the Royal Air Force.<ref name= "Jefford_11–12">Jefford 2006, pp.&nbsp;11–12.</ref>

Design work on the P.1127 was formally started in 1957 by Sir [[Sydney Camm]], [[Ralph Hooper]] of Hawker Aircraft, and [[Stanley Hooker]] of the [[Bristol Engine Company]].<ref name= Jefford_26-27>Jefford 2006, pp.&nbsp;26–27.</ref> The close cooperation between Hawker, the airframe company, and Bristol, the engine company, was viewed by project engineer [[Gordon Lewis (engineer)|Gordon Lewis]] as one of the key factors that allowed the development of the Harrier to continue in spite of technical obstacles and political setbacks.<ref name= Jefford_23>Jefford 2006, p. 23.</ref> Rather than using rotors or a direct jet thrust, the P.1127 had an innovative [[thrust vectoring|vectored thrust]] [[turbofan engine]], the [[Rolls-Royce Pegasus|Pegasus]]. The Pegasus I was rated at {{convert|9000|lb(f)|kN|sigfig=2}} of thrust and first ran in September 1959.<ref name= Jefford_24>Jefford 2006, p. 24.</ref> A contract for two development prototypes was signed in June 1960 and the first flight followed in October 1960.<ref name= Jefford_24/> Of the six prototypes built, three crashed, including one during an air display at the 1963 [[Paris Air Show]].<ref name="Mason 91 p413-6">Mason 1991, pp. 413–416.</ref>