View source for Fairey Delta 2

{{Short description|1950s British supersonic research aircraft}}
{{Use dmy dates|date=September 2019}}
{{Use British English|date=December 2016}}
{{Infobox aircraft
 |name = Fairey Delta 2
 |image = File:FD2.png
 |image_border= yes
 |caption = World speed record holder WG774
 |type = high-speed research aircraft
 |national_origin=United Kingdom
 |manufacturer = [[Fairey Aviation Company]]
 |first_flight = 6 October 1954
 |introduction = Experimental
 |retired = 1966 (''WG777''), 1973 (''WG774'')
 |status = On public display
 |primary_user = [[Royal Aircraft Establishment]] 
 |more_users = <!--up to three more. please separate with <br/>.-->
 |produced = <!--years in production, e.g. 1970-1999, if still in active use but no longer built-->
 |number_built = 2
 |unit cost = 
 |variants =
}}

The '''Fairey Delta 2''' or '''FD2''' (internal designation '''Type V''' within Fairey) is a British supersonic [[research aircraft]] that was produced by the [[Fairey Aviation Company]] in response to a [[List of Air Ministry specifications|specification]] from the [[Ministry of Supply]] for a specialised aircraft for conducting investigations into flight and control at [[transonic]] and [[supersonic]] speeds. Features included a [[delta wing]] and a [[Droop nose (aeronautics)|drooped nose]]. On 6 October 1954, the Delta 2 made its [[maiden flight]], flown by Fairey test pilot [[Peter Twiss]]; two aircraft would be produced. The Delta 2 was the final aircraft to be produced by Fairey as an independent manufacturer.<ref name = "WG777 ind his"/>

The Fairey Delta 2 was the first jet aircraft to exceed {{convert|1000|mph|km/h}} in level flight.<ref>[http://www.flightglobal.com/pdfarchive/view/1956/1956%20-%200315.html?tracked=1 ''Flight Magazine''] 23 March 1956</ref> On 10 March 1956, it set a new [[Flight airspeed record|world speed record]] of {{convert|1132|mph|km/h|abbr=on}}, exceeding the previous official record by {{convert|310|mph|km/h|abbr=on}}.{{refn|group=note|name=first|Far exceeded both the official 1955 record of {{convert|822.1|mph|km/h|abbr=on}} by the "C" variant of a [[North American F-100 Super Sabre]] and the secret 1947 record (by {{convert|241|mph|km/h|abbr=on}}) of {{convert|891|mph|km/h|abbr=on}} by the [[Bell X-1]].}} The Delta 2 held the absolute World Air Speed Record for over a year. It continued to be used for flight testing, and was allocated to the [[Royal Aircraft Establishment]] (RAE) in 1958.

A testbed aircraft was required to verify design calculations and wind tunnel results for the [[Concorde]] "[[Delta wing#ogee delta|ogee delta]]" wing design so one of the aircraft was extensively rebuilt as the '''BAC 221'''. On 1 May 1964, the modified aircraft performed its first flight. The FD2 was also used as the basis for Fairey's submissions to the Ministry for advanced [[Interceptor aircraft|all-weather interceptor]] designs, culminating in the proposed '''Fairey Delta 3''' to meet the [[Operational Requirement F.155|F.155 specification]]; however, the FD3 never got past the drawing-board stage.

==Development==
===Background===
During the late 1940s, [[Fairey Aviation]], a British aircraft manufacturer, had become interested in [[delta wing]] technology and proceeded to submit multiple submissions based on the delta wing concept to the [[Ministry of Supply]].<ref name = "wood 73">Wood 1975, p. 73.</ref> The Ministry, being interested in these proposals, issued orders for models to test the envisioned delta wing, the first of which being built in 1947; testing was performed by the [[Royal Aircraft Establishment]] (RAE). The program was succeeded multiple times, including an investigation into potential [[VTOL]] operations, leading to further flight tests of the delta wing models to be conducted in [[Cardigan Bay]], [[Wales]] and [[Woomera, Australia]].<ref>Wood 1975, pp. 73–74.</ref> In 1947, [[List of Air Ministry specifications|Air Ministry Specification E.10/47]] was issued for a full-scale piloted delta wing aircraft, resulting in the [[Fairey Delta 1]], which conducted its maiden flight at [[MoD Boscombe Down|RAF Boscombe Down]] on 12 March 1951.<ref name = "wood 74">Wood 1975, p. 74.</ref>

Meanwhile, throughout the early and mid 1950s, the [[Royal Air Force]] (RAF) had developed an intense desire to advance the performance of their aircraft; in particular, the service sought new fighter aircraft that would be capable of routinely flying at very high speeds and high altitudes as a long-term replacement for its existing inventory of roughly 700 [[first-generation jet fighter]]s.<ref name = "wood 71">Wood 1975, p. 71.</ref> At the time, there was a perception that Britain was trailing behind in supersonic aircraft design, and there was pressure to correct this.<ref name = "rafmus over">[http://www.rafmuseum.org.uk/research/collections/fairey-fd2/ "Fairey FD2."] ''Royal Air Force Museum'', Retrieved: 13 December 2016.</ref><ref name = "wood 75"/> Events such as the [[Korean War]] and rapid advances in the fields of [[supersonic]] aerodynamics, structures and aero engines by the British aircraft industry had the effect of increasing demand and the potential capabilities of new fighters. In addition to developing improved versions of existing and emerging fighters such as the [[Hawker Hunter]] and [[Gloster Javelin]], there was an appetite for even more promising entirely new aircraft.<ref>Wood 1975, pp. 71–72.</ref>

Following on from the Delta 1, the Ministry of Supply requested that Fairey conduct a further model programme for the purpose of [[transonic]] investigations.<ref name = "wood 74"/> However, Fairey did not find this proposal attractive, believing that a piloted aircraft would be mandatory if the project was to produce any worthwhile data. Fairey commenced work on a highly [[swept wing|swept]] twin-engine aircraft; however, the Ministry lacked enthusiasm for the twin-engine configuration, largely due to an existing rival project underway to produce a twin-engine supersonic aircraft – this would become the [[English Electric Lightning]].<ref name = "wood 75">Wood 1975, p. 75.</ref> In February 1949, it was suggested that Fairey examine the prospects for a single-engine transonic aircraft as an alternative; by the end of the year, the company had produced their new project, out of which the Fairey Delta 2 (FD2) would directly originate. Accordingly, the Ministry issued Air Ministry Specification ER.103 for the project, ordering that a pair of prototype aircraft be produced.<ref name = "wood 75"/>

[[File:Fairey FD2 XG774 Farnborough 08.09.56 edited-2.jpg|thumb|right|The first Delta 2 ''WG774'' in its original design format landing at [[Farnborough Airport|Farnborough]] in 1956 during that year's [[Farnborough Air Show|SBAC Show]] using its 'droop snoot', described by its inventor as a sectional fuselage<ref>https://patents.google.com/patent/US2736523A/en, "Sectional fuselage for aircraft"</ref>]]
At the time, Fairey was mostly known for producing naval aircraft, such as the [[Fairey Swordfish]] [[biplane]] and the [[Fairey Firefly]] [[monoplane]]; the design team lacked experience with high speed projects.<ref name = "wood 75"/> As a remedy to this, in October 1951, Sir [[Robert Lickley]] of [[Hawker Aircraft]] was promptly recruited as Fairey's new Chief Engineer and became a major force behind the programme. Data that had been obtained from the earlier model work also proved to have been highly valuable to the Fairy Delta 2 programme.<ref name = "wood 75 76">Wood 1975, pp. 75–76.</ref> Early development work on the FD2 would be hindered by two major factors, a lack of available information on wing and intake design, and the declaring of [[Fairey Gannet]] as a 'super-priority' by the British government, which had necessitated delays.<ref name = "wood 75"/>

In September 1952, technical drawings of the Fairey Delta 2 were issued and the development proper commenced.<ref name = "wood 75"/> From the project's beginning, Fairey designed the parameters of the FD2 to intentionally exceed that which was necessary only to achieving [[Mach number|Mach 1]]. In addition to seeking very high performance, the design adopted a general configuration and structure that would be readily adapted to future military requirements, so that it could potentially become a fighter aircraft.<ref name = "wood 75"/> In total, a pair of flight-capable aircraft were produced: [[United Kingdom military aircraft serials|Serial numbers]] ''WG774'' and ''WG777''.<ref name = "WG777 ind his"/> ''WG777'', the second to be manufactured, was very similar to ''WG774'' except the underwing [[Flap (aeronautics)|flap]] system was not incorporated. There were also a few differences in terms of equipment and instrumentation. In addition to the two flying aircraft, a single static test airframe was also completed.<ref name = "WG777 ind his">[http://www.rafmuseum.org.uk/documents/collections/85-A-10-Fairey-FD-2-WG777.pdf "Individual History: Fairey FD-2 Delta WG777/7986M."] ''Royal Air Force Museum'', Retrieved: 13 December 2016.</ref>

===Flight testing===
On 6 October 1954, ''WG774'', the first FD2 to be completed, conducted its [[maiden flight]], flown by Fairey test pilot [[Peter Twiss]].<ref name = "rafmus over"/> According to aviation author Derek Wood, the Delta 2 "proved to be an exceptional aeroplane from the outset".<ref name = "wood 76"/> On 17 November 1954, ''WG774'' suffered an engine [[flameout]] on its 14th flight when internal pressure build-up collapsed the fuselage collector tank, closing off the fuel supply to the engine, while heading away from the airfield at 30,000&nbsp;ft (9,100&nbsp;m), 30&nbsp;mi (50&nbsp;km) after taking off from RAF Boscombe Down.<ref name = "wood 76"/> Twiss managed to glide to a [[Deadstick landing|dead-stick landing]] at high speed on the airfield. Only the nose gear had deployed, and the aircraft sustained damage that put it out of action for eight months.<ref name = "wood 76 77">Wood 1975, pp. 76–77.</ref> Twiss, who was shaken up by the experience but otherwise uninjured, received the [[Queen's Commendation for Valuable Service in the Air]].<ref>Taylor 1984, pp. 430–431.</ref> One result of the crash was a temporary halt on the test programme, which did not resume until August 1955.<ref>Jackson 1986, p. 104.</ref>

During early flight tests, repeated supersonic test runs over southern Britain were conducted; as a result of these flights, a number of claims for damages against the [[supersonic boom]]s were received.<ref name="twiss">Twiss, 2000.</ref> Tests of the Delta 2's low-level supersonic flight capability were disrupted due to the perceived heightened risk posed by supersonic booms being produced during lower altitude flight; as such, the Ministry of Supply refused to allow this testing to be performed over the UK.<ref name = "wood 85"/> Despite this refusal, Fairey was able to base the Delta 2 temporarily in [[France]] and later in [[Norway]] so that the tests could be performed. The French government required the tests to be insured against damage claims; this demand had proved unacceptable with two British insurance companies quoting a premium of about £1,000 per flight; however, a French company insured them for £40. No claims were ever received in either France or Norway.<ref name="twiss" /><ref name = "wood 85 86"/>

[[File:Fairey Delta 2.jpg|thumb|right|WG774 with the original polished-metal finish. It later received yellow stripes, followed by a purple and yellow scheme, before conversion to the BAC 221]]
On 15 February 1956, ''WG777'', the second Delta 2, performed its maiden flight from RAF Boscombe Down; piloted by Twiss, the aircraft reached transonic speeds during this first flight.<ref name = "WG777 ind his"/> Following the final contractor check flight on 14 April 1956, ''WG777'' was formally accepted, upon which it was assigned to the RAE's high-speed research programme, conducting measurement, stability and handling research. In September 1956, both aircraft performed flight displays at the [[Farnborough Airshow]] in [[Hampshire]].<ref name = "WG777 ind his"/> The Delta 2 was typically used to conduct a multitude of tests including aerodynamics characteristics, handling, and stability performance.<ref name = "WG777 ind his"/>

Testing of the Delta 2 was carried out in France for some time, in part due to Fairey's good relations with [[Dassault Aviation]] of France and the [[French Air Force]].<ref name = "wood 85"/> In October and November 1956, a total of 47 low-level supersonic test flights were conducted from [[Cazaux Air Base]], [[Bordeaux]], France; a detachment of Dassault engineers observed these trials, learning a great deal about delta wing aircraft from the FD2. Dassault had flown the MD.550 Mystère-Delta design in June 1955, which Wood notes "bore a striking resemblance to the layout of the FD.2". The MD.550 design would proceed to be manufactured as the successful [[Dassault Mirage III]] fighter, which first flew two days after the return of the FD.2 from the tests in France.<ref name = "wood 85 86">Wood 1975, pp. 85–86.</ref> Wood credits the Delta 2 as having served to confirm Dassault's theories and supporting the Mirage III program.<ref name = "wood 86">Wood 1975, p. 86.</ref>

Once the manufacturer's testing was completed, both aircraft were formally handed over to the RAE. In addition to providing the institution with useful information on the characteristics of the 60°-swept delta wing, from 1958 onwards, the FD2 aircraft participated in various research projects and flying trials, including an investigation into the performance of ejector-type propulsive [[nozzle]]s.<ref name="flight 133"/> The substantial rebuilding of the aircraft to participate in further research was first mooted in that same year as well.<ref name="flight 133"/> In its original configuration, the Delta 2 performed flight tests, interspersed with periods of storage, up until mid-1966.<ref name = "WG777 ind his"/>

===Breaking the world airspeed record===
During August 1955, the Delta 2 flew at supersonic speed without using its [[afterburner|reheat]] since the testing schedule did not yet require its use at that time.<ref name="twiss" /> According to Wood, many members of the development team recognised that the FD2 possessed huge speed potential, beyond any other British-built aircraft in existence of that time.<ref name = "wood 77">Wood 1975, p. 77.</ref> During early flight testing, Twiss came to realise that the Delta 2 would be capable of speeds above {{convert|1,000|mph|km/h}} and proposed that it be flown on with the aim of breaking the current air speed record, which had then been held since 1955 by a [[North American F-100 Super Sabre]].<ref name = "50 years flight">[https://www.flightglobal.com/news/articles/50-years-ago-16-mar-1956-205374/ "50 years ago: 16 Mar 1956."] ''Flight International'', 10 March 2006.</ref> However, Fairey found the Ministry of Supply unsupportive, having adopted the prevailing belief being that manned military aircraft would soon be replaced by [[guided missiles]]. Fairey had great difficulty in obtaining permission for the attempt. Twiss stated that the situation was "curiously inverted" from expectations, having expected that government agencies would have been enthusiastically pressing for a record-breaking flight as a means to bolster national prestige.<ref name = "wood 77 78">Wood 1975, pp. 77–78.</ref>

According to Wood, Fairey was confronted by a combination of scepticism and apathy from [[Her Majesty's Civil Service]], to the extent that it appeared that the government were opposing the endeavor.<ref name = "wood 78">Wood 1975, p. 78.</ref> The Ministry of Supply sought to avoid any association with a speed record bid while [[Rolls-Royce Limited|Rolls-Royce]], the FD2's engine manufacturer, also dismissed the attempt, claiming that the air intakes were unsuitable for speeds around Mach 1.5, and that the Avon engine would disintegrate at such speeds, despite an absence of any practical data to support this assertion. In spite of this opposition, Fairey sought to continue, and were given permission to proceed.<ref name = "wood 78"/> The Ministry provided no financial support, having opted instead to loan the aircraft itself to Fairey and to charge the firm for its use of RAE assets. Fairey also had to finance its own insurance.<ref name = "wood 78 79">Wood 1975, pp. 78–79.</ref> Regardless, Fairey chose to continue with the record attempt.<ref name = "wood 79"/>

[[File:Fairey Delta 2 WG774 in flight c1956.jpg|thumb|left|The first Fairey Delta 2 (s/n WG774) in flight, circa 1956]]
In order to reduce the risk of another competitor beating them to it, preparations had to be carried out in a short space of time and in great secrecy.<ref name = "wood 79"/> The development and deployment of equipment suitable for the accurate measurement of flight at such speeds was a challenge in itself. For this purpose, a variety of ground measurement cameras were set up at [[Chichester]] and at [[HM Prison Ford|RNAS Ford]], various ground markers were installed at specified locations, and [[radar]] tracking from RNAS Ford and [[RAF Sopley]]; flights by [[Gloster Meteor]]s and [[de Havilland Venom]]s for calibration purposes were also conducted by the RAF.<ref name = "wood 79"/> Operational demands on both the pilot and ground crews were severe and many runs were attempted but failed to qualify on one technicality or another. On the final day available, the first run also failed; the second and last run that day became the only chance left before the attempt would end.

On 10 March 1956, the Fairey Delta 2 broke the [[Flight airspeed record|World Air Speed Record]], raising it to 1,132&nbsp;mph (1,811&nbsp;km/h) or Mach 1.73.<ref name = "rafmus over"/> This achievement exceeded the prior recorded airspeed record by 310&nbsp;mph, or 37 per cent; never before had the record ever been raised by such a margin.<ref name = "50 years flight"/><ref name = "wood 79">Wood 1975, p. 79.</ref> The achievement had also made the Fairey Delta 2 the first jet aircraft to exceed 1,000&nbsp;mph (1,600&nbsp;km/h) in level flight.

News of the new airspeed record quickly spread and had a prompt impact upon the international aeronautics industry, typical reactions being shock and near-disbelief.<ref name = "wood 79"/> According to Wood, consequences included in-depth studies of the FD2 airframe by the United States and the major reshaping of military aircraft programs in France. Fairey itself was elated with the achievement, viewing it as a practical endorsement of their design, and fuelled the firm's ambitions to establish a family of supersonic fighters on its basis.<ref name = "wood 79"/> The record stood until 12 December 1957, when it was beaten by a [[McDonnell F-101 Voodoo|McDonnell JF-101A Voodoo]] of the United States Air Force.<ref name="twiss" /><ref>Taylor, 1984, pp. 431–433.</ref>

===Proposed derivatives===
{{See also|Operational Requirement F.155}}
Fairey produced a number of proposals which would have involved the further development of the Delta 2. The first of these was another experimental aircraft, designated as the ''ER.103/B'', which would have paired the wings of the FD2 with a revised fuselage, which had a greater span and length.<ref name = "wood 79"/> The ER.103/B was to have been powered by either a [[de Havilland Gyron]] or [[Rolls-Royce RB.106|Rolls-Royce RB.122]] and would have accommodated underwing fuel tanks for extended endurance. A combat fighter model, the ''ER.103/C'', was also proposed, upon which the wings would have been scaled up by 50 per cent, with no radical aerodynamic alterations made. Combat equipment would have been provisioned, including a [[Ferranti]]-built [[aircraft interception radar#AI.23|aircraft interception radar 1495]] and [[de Havilland Firestreak]] [[air-to-air missile]]s.<ref name = "wood 79 82">Wood 1975, pp. 79, 82.</ref> Fairey claimed that the ER.103/C would be capable of attaining Mach 2.26 at an altitude of {{convert|55,000|ft|m}}.<ref name = "wood 82"/>

{{Quote box|align=right|width=19%|quote="If it were not for the clumsy way in which you tackle things in Britain, you could have made the [[Dassault Mirage III|Mirage]] yourself."|source=<small>[[Marcel Dassault]], founder of [[Dassault Aviation]]<ref name = "wood 86 87">Wood 1975, pp. 86–87.</ref></small>}}
According to Fairey's projections, the ER.103/B could have been ready to fly within eighteen months of having received an order, while the ER.103/C could reach the same readiness within 30 months.<ref name = "wood 82">Wood 1975, p. 82.</ref> In particular, Fairey pursued [[Operational Requirement F.155]], which called for a two-seat fighter equipped with radar and missiles with suitable performance to achieve an altitude of {{convert|60,000|ft|m}} and Mach 2 within six minutes of taking off; while the company thought that their design would be fully capable of meeting the specified requirements, it was believed that the complete weapon system would not be fully developed until 1962. Thus, Fairey proposed that a simpler interim aircraft, if selected, could be available by 1960 or potentially earlier.<ref name = "wood 82 83">Wood 1975, pp. 82–83.</ref>

In addition to the Gyron engine of earlier proposals, the proposed fighter was to be equipped with a pair of [[de Havilland Spectre]] [[rocket engine]]s that were mounted in fairings on the rear fuselage.<ref name = "wood 83">Wood 1975, p. 83.</ref> The [[high-test peroxide]] (HTP) fuel for the rocket engines was stored in tanks held in underwing [[aircraft fairing|fairing]]s and within the wing's [[leading edge]], separate from the turbojet engine's fuel storage. It featured a two-man crew, a pilot and radar operator/navigation, seated in a side-by-side configuration.<ref name = "wood 83"/> The fuselage was [[area rule]]d while large rectangular [[intake ramp|variable air intake]]s were adopted. As specified, the fighter was tentatively armed with wingtip-mounted [[Red Top (missile)|de Havilland Red Top]] air-to-air missiles.<ref name = "wood 83"/> Further design revisions saw the single Gyron engine being replaced by a pair of RB.122 engines instead and the adoption of the [[Red Dean]] missile,  alongside refinements such as intake improvements and increased internal fuel capacity. Fairey stated that the aircraft was suited to [[Interceptor aircraft|interceptor]] duties at various altitudes, [[Attack aircraft|strike]] and [[aerial reconnaissance]] missions were also mooted.<ref name = "wood 83"/>

On 1 April 1957, Fairey were informed by officials within the Ministry of Supply that their proposals were the favourite to meet Operational Requirement F.155.<ref name = "wood 85">Wood 1975, p. 85.</ref> However, on 4 April 1957, [[Duncan Sandys]], the [[Secretary of State for Defence|Minister of Defence]], announced the effective termination of nearly all fighter aircraft development for the RAF, instantly removing the F.155 requirement.<ref name = "wood 85"/>

A final attempt was made to progress a Delta 2 derivative into production came during the late 1950s for the new [[German Air Force]] of [[West Germany]].<ref name = "wood 87 88">Wood 1975, pp. 87–88.</ref> Running against a competing American bid with the [[Lockheed F-104 Starfighter|Lockheed F-104G Starfighter]], Fairey joined forces with Rolls-Royce and Dassault in a collaborative effort to produce a delta wing aircraft capable of reaching Mach 2 to meet the German demand for fighter aircraft. The proposal would have seen Dassault produce the wings, Fairey manufacture the fuselage, and Rolls-Royce provide the engine, which was intended to be a [[Rolls-Royce Spey]] engine with reheat; Belgium also played a role in the programme.<ref name = "wood 88">Wood 1975, p. 88.</ref> However, the American lobby proved to be too strong, in part due to the subsequently uncovered [[Lockheed bribery scandals]] that had influenced German decision makers, and the F-104G was selected instead. This was the end for the FD2 as a fighter concept; the concept never saw any use as a production aircraft; Wood summarised the state of affairs as "the harvest was left to France to gather".<ref name = "wood 86 88">Wood 1975, pp. 86, 88.</ref>

===BAC 221===
The [[Concorde]] design used a then-new type of delta wing that was being developed at the RAE known as the [[ogee]] or ogival delta design. This design aimed to improve both supersonic wave drag with high leading-edge sweep and low thickness/chord ratio at the root,<ref>A Case Study By Aerospatiale And British Aerospace On The Concorde By Jean Rich and Clive S.Leyman,AIAA Professional Study Series,p.3-4</ref> and low-speed lift through flow separation at the leading edge which creates a rolled up vortex on top of the wing. The added suction under the vortex increases lift<ref>https://reports.aerade.cranfield.ac.uk/handle/1826.2/3017?show=full, para 6.2.1 'Lift'</ref> by an amount known as vortex lift. The wing root chord should be as long as possible, and highly swept where it meets the forward fuselage. Continued studies of this basic concept led to the ogee layout and it eventually became apparent that a series of full-scale flight tests would be necessary for its validation.<ref name="flight 133">''Flight'' 1964, p. 133.</ref>

[[File:BAC221.JPG|thumb|left|BAC 221 at the [[Fleet Air Arm Museum]]. The forward wing extension and curved leading edge can be seen]]
Low-speed testing of the concept was already being provided by the [[Handley Page HP.115]]. Although high-speed performance appeared to be predictable, a dedicated testbed aircraft was desired, especially for drag measurements. As early as 1958, the RAE and Fairey began discussions about converting one of the Delta 2 prototypes to support the ogee wing.<ref name="flight 133"/><ref>Jarrett 2002, p. 179.</ref> Fairey proposed stretching the fuselage a further three feet to better match the long planform, with the wing extending out onto the drooping nose. However, calculations showed that this extension was not great enough to counter the forward moving [[center of pressure (fluid mechanics)|centre of pressure]] (CoP) that resulted from the extended planform, and there were also concerns that the over-wing engine intakes would swallow the vortex above the wing.<ref name="flight 133"/>

During 1960, further development activity was disrupted by the purchase of Fairey by [[Westland Aircraft]], who assigned further work on the conversion project to [[Hunting Aircraft]].<ref name="flight 133"/> Accordingly, in July 1960, the programme moved to Bristol and was now a part of the larger [[British Aircraft Corporation]] (BAC). Bristol suggested two ways forward, a minimal conversion with a sub-optimal wing but no other major changes, or a "maximal" conversion with a larger six foot extension to the fuselage and a much taller [[landing gear]] more typical of the type expected on the Concorde. Both would also be equipped with a new [[Elliott Brothers (computer company)|Elliott Brothers]] stabilization system, and have the engine intakes moved under the wing. The minimal conversion was considered to be more of a 'compromise', being less slender and lacking the additional fuel capacity that the maximal option provided for.<ref name="flight 133 134">''Flight'' 1964, pp. 133–134.</ref>

In early September 1960, it was agreed that the "maximal" conversion would proceed; on 5 September of that year,  ''WG774'' was flown to Bristol's Filton facility.<ref name="flight 134"/> Following a period of detailed design work, the re-manufacturing process commenced in April 1961. Considerable cost-cutting measures and management strategies, such as [[Program evaluation and review technique|PERT]], were adopted by BAC in order to not overrun on the fixed-price contract it had been issued for the work; some engineers were allegedly frustrated by this as apparent means of further improvement were dismissed.<ref name="flight 134"/> On 7 July 1961, the newly christened ''BAC 221'' was completed.<ref name="flight 134">''Flight'' 1964, p. 134.</ref>
Various problems were encountered during the conversion. The newly lengthened landing gear required more [[hydraulics|hydraulic]] fluid, which required a larger reservoir to hold it, a higher capacity pump to move it quickly enough through the system, and so on through the hydraulic system.<ref name="flight 134"/> Moving the intakes below the wing meant they were no longer in-line with the compressor face so the ducting to the engine was curved upwards giving a noticeable bulge on the wing upper surface. No attempt was made to fit variable intakes.<ref name="flight 135"/> At high throttle settings, considerable suction into the inlets was generated; in the event of a sudden down-throttle motion by the pilot would result in air "spilling" out of the intakes, which was a concern because it could flow above the wing and disrupt the vortex. Small lips were added to the intakes to help prevent this, but this proved to cause intake buzzing. Changes to the ducts, assisted by Rolls-Royce, addressed this issue.<ref name="flight 135">''Flight'' 1964, p. 135.</ref>

One major advantage of the new design was its larger fuel capacity, which has been a major problem for the original FD2.<ref name="flight 135 137">''Flight'' 1964, pp. 135, 137.</ref> The Delta 2 had often run low on fuel while still accelerating, thereby never reaching its full performance. The modifications for the 221 meant it was not capable of the same levels of performance; however, speeds of Mach 1.6 were attained during its test flights. In total, the BAC 221 featured a new wing, engine inlet configuration, a Rolls-Royce Avon RA.28, modified vertical stabilizer and a lengthened undercarriage to mimic Concorde's attitude on the ground. It first flew on 1 May 1964.<ref name="Janes 65 p130">Taylor 1965, p. 130.</ref><ref name="flight 134"/> The sole 221 was used for varied flight testing from 1964 until 1973, after which it was placed on public display.<ref name = "faamus"/>

==Design==
[[File:Fary Delta II (27686869390).jpg|thumb|Head-on view of an FD2 on static display, June 2016]]
The Fairey Delta 2 has a mid-wing [[Tailless aircraft|tailless]] delta monoplane. It was powered by a single [[Rolls-Royce Avon|Rolls-Royce Avon RA.14R]] [[turbojet]] engine with [[reheat]].<ref name = "rafmus over"/><ref name="flight 136">''Flight'' 1964, p. 136.</ref> The engine was fed by [[Components of jet engines#Air intakes|air intakes]] which were blended into the wing roots and featured an [[eyelid]]-type nozzle.<ref name = "wood 75"/> Located just forward of the nozzle were [[petal]]-type [[Air brake (aeronautics)|air brake]]s.<ref name = "wood 75"/>

The Delta 2 has a [[cylinder|cylindrical]] cross-section [[fuselage]], which closely fitted the Avon engine, and smoothly flowed into a long [[Tapering (mathematics)|taper]]ed nose.<ref name = "wood 75"/> A long nose would normally have obscured the pilot's forward vision during landing, take-off and movement on the ground; so, to provide adequate visibility a [[Droop nose (aeronautics)|drooped nose]] was fitted; the nose section, including the cockpit, could be drooped 10° using a hydraulically actuated mechanism, in a similar manner to that which was used later on Concorde.<ref name = "rafmus over"/><ref name = "wood 76">Wood 1975, p. 76.</ref>

The Delta 2 has a relatively small cockpit for the pilot which left little room for the installation of additional equipment.<ref name="flight 134"/> The Delta was the first British aircraft to fly using all-powered controls. These controls, designed and produced by Fairey, were fully duplicated.<ref name = "wood 73">Wood 1975, p. 73.</ref><ref name = "wood 75 76"/> The flight control system was hydraulically operated and possessed no mechanical backup. Fairey had recently developed a new high-pressure hydraulic system and this was used in the design. The hydraulics provided no feedback or "feel" to the pilot's controls, so another system providing artificial feel was necessary.<ref name="twiss" />

The wing features a 60° sweep of the leading edge and was very thin, at only 4% [[thickness ratio|thickness-chord ratio]], making the Delta 2's wing one of the thinnest known at that time.<ref name = "wood 75"/> The internal space housed both the main undercarriage and a total of four fuel tanks without any bulges or fairings in the wing, while four [[spar (aeronautics)|spar]]s provided for significant structural strength. The sizable horn-balanced [[aileron]]s and inboard [[elevator]]s gave the Delta 2 a high level of manoeuvrability.<ref name = "wood 75"/>

==Aircraft on display==
[[File:Fairey Delta 2 at RAF Museum Cosford - geograph.org.uk - 1013863.jpg|thumb|''WG777'' preserved in the [[Royal Air Force Museum Cosford|Royal Air Force Museum]] at [[RAF Cosford]]]]
* ''WG774'', in BAC 221 form, is now on display alongside the British Concorde prototype at the [[Fleet Air Arm Museum]] at [[RNAS Yeovilton (HMS Heron)|Yeovilton]].<ref name = "faamus">[http://www.fleetairarm.com/exhibit/british-aircraft-corporation-221/4-6-47.aspx "British Aircraft Corporation 221."] {{Webarchive|url=https://web.archive.org/web/20170113165213/http://www.fleetairarm.com/exhibit/british-aircraft-corporation-221/4-6-47.aspx |date=13 January 2017 }} ''Royal Navy Fleet Air Arm Museum'', Retrieved: 13 December 2016.</ref>
* ''WG777'', is preserved at the [[Royal Air Force Museum Cosford|Royal Air Force Museum]] at [[RAF Cosford]].<ref name = "rafmus over"/>

==Operators==
;{{UK}}
*[[Royal Aircraft Establishment]]

==Specifications (Fairey Delta 2)==
[[File:Fairy Delta 23 (10023615886).jpg|thumb|Close-up rear view of the Delta 2]]
[[File:BAC 221, Fleet Air Arm Museum, RNAS Yeovilton. (11674250044).jpg|thumb|upright|Forward view of the Delta 2. Note the drooped nose]]
{{aircraft specs
|ref=''The Illustrated Encyclopedia of Aircraft''<ref name="Orbis1695">Orbis 1985, p. 1695.</ref>
|prime units?=<!-- eng for US/UK aircraft, met for all others -->imp

|crew=1
|capacity=
|length m=15.74
|length ft=51
|length in=7.5
|span m=8.18
|span ft=26
|span in=10
|height m=3.35
|height ft=11
|height in=0
|wing area sqm=33.44
|wing area sqft=360
|empty weight kg=4990
|empty weight lb=11,000
|gross weight kg=6298
|gross weight lb=13,884

|eng1 number=1
|eng1 name=[[Rolls-Royce Avon|Rolls-Royce Avon RA.14R]] with only one reheat setting, later replaced with an RA.28 as used for speed record<ref>
Rolls-Royce Aero Engines, Bill Gunston 1989,{{ISBN|1 85260 037 3}}, p.137</ref>
|eng1 kn=<!-- jet/rocket engines -->44.59
|eng1 lbf=<!-- jet/rocket engines -->10,000

|max speed kmh=2092
|max speed mph=1300
|range km=1336
|range miles=830
}}

==See also==
* [[Flight airspeed record]]
* [[Peter Twiss]]
* [[Aerospatiale-BAC Concorde]]
{{aircontent|
|related=
* [[Fairey Delta 1]]
|similar aircraft=
* [[Dassault Mirage]]
* [[English Electric Lightning|English Electric P1A]]
* [[Bristol 188]]
* [[Avro 707|Avro 707C]]
* Mikoyan-Gurevich MiG-21I Analog
|lists=
* [[List of experimental aircraft]]
}}

==References==

===Citations===
{{Reflist|2}}

===Notes===
{{reflist|group=note}}

===Bibliography===
* Buttler, Tony. "Fairey's Famous Research Deltas, Part Two - Type 221". ''Air Enthusiast'', No. 94, July–August 2001, pp.&nbsp;2–6. {{ISSN|0143-5450}}
*Buttler, Tony and Jean-Louis Delezenne. ''X-Planes of Europe: Secret Research Aircraft from the Golden Age 1946-1974''. Manchester, UK: Hikoki Publications, 2012. {{ISBN|978-1-902-10921-3}}
* [http://www.flightglobal.com/pdfarchive/view/1964/1964%20-%202112.html "BAC.211: Slender-delta Research Aircraft."] ''Flight International'', 23 July 1964, pp.&nbsp;133–138.
* Jackson, Robert. "Combat Aircraft Prototypes since 1945." Arco/Prentice Hall Press, New York, 1986. Library of Congress card number 85-18725. {{ISBN|0-671-61953-5}}.
* [[Philip Jarrett |Jarrett, Philip]]. ''Faster, Further, Higher: Leading-edge Aviation Technology Since 1945.'' Putnam, 2002. {{ISBN|0-851-77876-3}}.
* [[John W. R. Taylor|Taylor, John W. R.]] ''Jane's All The World's Aircraft 1965–66''. London: Sampsom Low, Marston, 1965.
* "The [[Illustrated Encyclopedia of Aircraft]] (Part Work 1982–1985)." Orbis Publishing, 1985.
* Taylor, H. A. ''Fairey Aircraft since 1915''. London: Putnam, 1974. {{ISBN|0-370-00065-X}}.
* Twiss, Peter. ''Faster than the Sun''. London: Grub Street, 2000. {{ISBN|1-902304-43-8}}.
* Winchester, Jim. ''Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft''. Rochester, Kent, UK: Grange Books, 2005. {{ISBN|1-84013-809-2}}.
* Wood, Derek. ''Project Cancelled''. Macdonald and Jane's Publishers, 1975. {{ISBN|0-356-08109-5}}.

==External links==
{{Commons category|Fairey Delta 2}}
* [http://naca.central.cranfield.ac.uk/reports/arc/rm/3738.pdf "Analysis of Flight and Tunnel Tests on the Fairey Delta 2 Research Aircraft." ''Her Majesty's Stationery Office''.] {{Webarchive|url=https://web.archive.org/web/20070714130023/http://naca.central.cranfield.ac.uk/reports/arc/rm/3738.pdf |date=14 July 2007 }}
* [https://www.flightglobal.com/FlightPDFArchive/1957/1957%20-%200233.PDF "The Fairey Delta 2." ''Flight International''.]
* [https://www.youtube.com/watch?v=ShrlmUk6Q0U Britain’s Missed Mirage? - The Fairey Delta 2]

{{British Aircraft Corporation aircraft}}
{{Fairey aircraft}}
{{Bristol aircraft}}
{{British military aircraft since World War II}}
{{Authority control}}

[[Category:Fairey aircraft|Delta 2]]
[[Category:1950s British experimental aircraft]]
[[Category:Tailless delta-wing aircraft]]
[[Category:Aircraft first flown in 1954]]
[[Category:Single-engined jet aircraft]]
[[Category:Aircraft with retractable tricycle landing gear]]