Background During the late 1950s,
Hawker Siddeley Aviation (HSA) was keen to develop a new generation of combat aircraft that would be capable of
supersonic speeds. Unfortunately, despite repeated attempts to revive the program, the in-development
Hawker P.1121 fighter would ultimately be left unfinished, principally due to a lack of a political support for development following the release of the
1957 Defence White Paper by
Minister of Defence Duncan Sandys. Recognising the need to promptly commence work on another development program, HSA's chief aircraft designer
Sir Sydney Camm, who had been in regular discussions with
Sir Stanley Hooker of
Bristol Aero Engines, decided that the company should investigate the prospects of developing and manufacturing a viable combat-capable
vertical take-off and landing (VTOL) fighter aircraft. Bristol Aero Engines and Hooker had already been working on a project to produce a suitable VTOL engine; this engine combined major elements of their
Olympus and
Orpheus jet engines to produce a
directable fan jet. The projected fan jet harnessed rotatable
cold jets which were positioned on either side of the
compressor along with rotatable 'hot' jets which was directed via a bifurcated tailpipe. With a suitable engine already being developed, Camm and his team at HSA proceeded to develop the company's first VTOL aircraft, designated as the
Hawker Siddeley P.1127. HSA was also interested in the prospects and feasibility of a more sophisticated development of the P.1127, knowing that a supersonic-capable VTOL aircraft would likely be more attractive to customers, there being a general perception at the time that supersonic aircraft held significantly more value than their subsonic counterparts. The P.1150 proposal broadly resembled its P.1127 predecessor despite major changes being made, including its revised fuselage, the adoption of a thinner wing, and an advanced version of the Pegasus engine.
NATO requirements In August 1961, NATO released an updated revision of its VTOL strike fighter requirement, NATO Basic Military Requirement 3 (
NBMR-3). Specifications called for a supersonic V/STOL strike fighter with a
combat radius of . Cruise speed was to be Mach 0.92, with a dash speed of Mach 1.5. In January 1962, HSA submitted the P.1154 design to NATO via the
Ministry of Aviation. NBMR.3 also attracted ten other contenders, among which was P.1154's principal competitor, the
Dassault Mirage IIIV. NATO lacked any central budget, relying on individual member nations to actually procure military equipment, and the NBMR-3 selection went unheeded by all of these nations. Thus, in 1965, the whole project was terminated. In February 1962, the Royal Navy's
Admiralty received the aircraft concept with great interest as the Royal Navy was in the process of seeking a new
interceptor aircraft for use on their
aircraft carriers at the time. The services sought different characteristics in their aircraft – the RAF desired a single-seat fighter with secondary intercept capability, while the
Fleet Air Arm (FAA) sought a two-seat interceptor capable of secondary low-level strike capability. Accordingly, HSA's submission involved the development of two distinct variants of the same P.1154 aircraft, each aimed towards a particular service and its stated requirements. When HSA submitted the design on 8 August, the Royal Navy criticised the proposal, which had a tandem undercarriage layout incompatible with
catapult operations; consequently, a
tricycle undercarriage design was investigated and accepted as practical. In December 1962, Bristol performed the first successful run of a PCB-equipped Pegasus 2 engine. In order to perform a vertical takeoff, the use of PCB was necessitated; however, this feature would have come at the cost of significant ground erosion during operations. However, as HSA carried out further work on the detailed design phase of the programme, it was becoming clear that opinions on the internal equipment for the aircraft varied substantially between the two services. Despite a stated Navy preference for a
swing-wing fighter, the services agreed that the aircraft would be completely common, with the exception of different radar systems. However, upon requests by various electronics manufacturers to the Ministry of Aviation to be issued with the requirements for the electronics fit, no response was ever issued; this lack of leadership proved disruptive to the overall programme. By October 1963, according to Wood, the situation had become critical and some officials were beginning to examine alternative options, such as conventional fighter aircraft in the form of the
McDonnell Douglas F-4 Phantom II. In November 1963, the
Sunday Telegraph publicly announced that the bi-service P.1154 had been aborted. Wood attributes Thorneycroft's ambition to reconcile the requirements of the two services into the one model and insistence on this vision as having "put the whole project in jeopardy". Around this point, the Royal Navy expressed their open preference for the F-4 Phantom II and soon Thorneycroft conceded that the service would get this aircraft instead, and that development of the P.1154 would continue to meet the RAF's requirement. On 26 February 1964, it was announced in the
House of Commons by the Conservative government that a development contract had been placed for the P.1154, equipped with the BS100 engine, as an RAF strike aircraft. At the same time, it was announced that the Naval requirement would instead be met by Spey-engined Phantoms. Wood stated that this decision was "the beginning of the end for the 1154 as the original operation requirement was for joint-service use". , instead of the P.1154 which was later cancelled.|alt=Starboard black-and-white view of jet aircraft in-flight. In the aftermath of the government announcement, HSA persisted with work on the P.1154. By September 1964, the first full-scale mock-up meeting had been conducted. On 30 October 1964, a milestone in the development programme was attained when the first run of a BS100 engine was performed; around the same time, HSA received favourable reports that the P.1154 was competitive with the performance of other aircraft, including the F-4 Phantom II. The P.1154 ultimately became a victim of the incoming
Labour government, led by
Harold Wilson. In November 1964, Wilson's government informed the Air Staff to prepare to cancel two of three specific ongoing development projects, these being the P.1154, the
BAC TSR-2 strike aircraft, and the
Hawker Siddeley HS.681 V/STOL transport aircraft; in order to save the TSR-2 programme, the RAF was satisfied to abandon the P.1154. On 2 February 1965, it was announced that the P.1154 had been terminated on the grounds of cost. At the time of cancellation, at least three prototypes had reached various stages of construction. Following the cancellation, the RAF adopted the F-4 Phantom II (as ordered by the RN) instead; however, the government also issued a contract for continued work on the original subsonic P.1127 (RAF), which led to the
Harrier; this name had originally been reserved for the P.1154 should it have entered service. In retrospect, aviation author Tony Buttler considered the cancellation of the aircraft to be justified, noting the time-consuming and expensive failures of attempts by other nations (such as Soviet/Russia's
Yak-41 and West Germany's
EWR VJ 101) at a supersonic VTOL aircraft. These aircraft all used a multiple engines configuration like the Mirage IIIV, and not the single vectored thrust turbofan of the likes of the BS.100 and Pegasus which went on to great success in the Harrier. Wood described the overall situation as: "From start to finish the P.1154 programme was a story of delay, ministerial interference and indecision... the P.1150 would now be the ideal aircraft for the new generation
through-deck cruisers" ==Specifications (P.1154 – RAF version)==