Hawker Sea Hawk
The Hawker Sea Hawk is a British single-seat jet fighter of the Fleet Air Arm, the air branch of the Royal Navy, built by Hawker Aircraft and its sister company, Armstrong Whitworth Aircraft. Although its design originated from earlier Hawker piston-engined fighters, the Sea Hawk became the company's first jet aircraft. Following acceptance in the RN, the Sea Hawk proved to be a sturdy workhorse. A considerable number were produced for the export market and were operated from aircraft carriers in Dutch and Indian service; the last operational Sea Hawks, operated by the Indian Navy, were retired in 1983. Towards the end of the Second World War, Hawker's design team had become interested in developing a fighter aircraft that took advantage of the newly developed jet propulsion technology. Prior to this, Hawker had been committed until late 1944 to the production and further development of its piston-powered aircraft, such as the Hurricane and Typhoon, to meet the wartime demands for these aircraft.
On 1 September 1944, the first prototype of the company's latest fighter aircraft, the Hawker Fury/Sea Fury, conducted its maiden flight. The design team studied the potential adaption of the aircraft, having opted to use the Rolls-Royce Griffon-powered Fury prototype as the starting point; the team started with the deletion of the piston engine, with its replacement, a single Rolls-Royce Nene turbojet engine, being fitted in a mid-fuselage position, along with lateral air intakes and a tailpipe which emerged beneath the tailplane. The prospective modifications included "stretching" the fuselage and moving the cockpit to the extreme front of the fuselage in a re-contoured nose. Use of the Rolls-Royce Derwent engine had been studied but discarded as lacking power for an aircraft of this size. In November 1944 the P.1035 design was submitted for evaluation by the Air Ministry. In December 1944 Hawker refined the proposed design substantially; the jet exhaust was moved from beneath the tail and re-designed as two short split-lateral bifurcated exhausts, embedded in the trailing edge of the wing root, which needed a corresponding thickening of the wing root.
The shorter unusual bifurcated jet pipe reduced pressure losses in the jet pipe and had the additional advantage of freeing up space in the rear fuselage for fuel tanks, which gave the aircraft a longer range than many other early jets. The absence of fuel tanks meant a thinner wing could be adopted without the penalty of reduced range; the fuselage fuel tanks, being fore and aft of the engine provided for a stable centre of gravity during flight. The tail plane was raised to clear the jet exhausts; the Sea Hawk featured a nose wheel undercarriage arrangement, the first for a Hawker-built aircraft. The aircraft was built to accommodate four 20mm Hispano-Suiza Mk. V cannons; the redesign had led to a new name for the project, P.1040. The Air Ministry issued its encouragement for Hawker's development of the project but according to aviation author Francis K. Mason, the Air Ministry and the Admiralty had viewed the project with only academic interest. Official interest had cooled by the expression of doubts voiced by Rolls-Royce Limited on the viability of the bifurcated jet pipes that the design used.
Like the piston-powered Fury it had been derived from, Hawker remained keen to promote the P.1040 to the Royal Air Force and to the Navy. The P.1040 was intended to be an interceptor though a top speed of only 600 mph was forecast. Shortly following the end of the war, the RAF decided to cancel several large orders for Hawker's piston-powered aircraft and to announce that the service would be taking no further interest in the P.1040 proposals. Hawker elected to refine the P.1040 design as a private venture, albeit being prepared with a view for service with British military customers in mind. In October 1945, Sydney Camm, Hawker's chief designer, being satisfied with the results generated from engineering mock-ups and wind tunnel testing, authorised a production order for a prototype by the company's experimental department. In light of the diminished RAF interest in the project due to the aircraft offering insufficient advances over the jet fighters that were in service, such as the Gloster Meteor and de Havilland Vampire, in January 1946, a naval version of the P.1040 was offered by Hawker to the Admiralty as a fleet support fighter, as the P.1046.
The Admiralty was not enthusiastic, in part due the development of the jet-powered Supermarine Attacker aircraft. The service was intrigued by the long-range of the P.1040 and the promise of increased power from the Nene engine. In May 1946, the Naval Staff authorised the manufacture of three prototypes and a further test specimen, one of these being the original prototype internally ordered by Hawker, in accordance with Naval Specification N.7/46. Hawker found their development focus for the type being divided between the naval P.1046 and the general-purpose P.1040, still hoped to be viable as an RAF fighter. The P.1040 would lead to the eventual development of the land-based swept wing Hawker Hunter fighter. Swept wing versions were built and experience gained with these were instrumental in developing the design of the Hunter. On 2 September 1947, the P.1040 prototype, VP401, sometimes referred to as the Hawker N.7/46 after the relat
RAF Martlesham Heath
Royal Air Force Station Martlesham Heath or more RAF Martlesham Heath is a former Royal Air Force station located 1.5 miles south west of Woodbridge, England. It was active between 1917 and 1963, played an important role in the development of Airborne Interception radar. Martlesham Heath was first used as a Royal Flying Corps airfield during World War I. In 1917 it became home to the Aeroplane Experimental Unit, RFC which moved from Upavon with the site named as the Aeroplane Experimental Station which became the Aeroplane and Armament Experimental Establishment in 1924; the A&AEE carried the evaluation and testing of many of the aircraft types and much of the armament and other equipment that would be used during World War II. No. 22 Squadron RAF and No. 15 Squadron RAF were present during the 1920s. No. 64 arrived in the 1930s. The A&AEE moved to RAF Boscombe Down on 9 September 1939 at the outbreak of World War II and Martlesham became the most northerly station of No. 11 Group RAF, Fighter Command.
Squadrons of Bristol Blenheim bombers, Hawker Hurricanes, Supermarine Spitfires and Hawker Typhoons operated from this airfield, among the many pilots based there were such famous men as Robert Stanford Tuck, Squadron Leader Douglas Bader, there as Commanding Officer of 242 Squadron. Ian Smith, the post-war Rhodesian prime minister, was at Martlesham for a time. During the Battle of Britain, Anti-Aircraft defence for the area was the responsibility of the Harwich Gun Defence Area, manned by 99th Heavy Anti-Aircraft Regiment, Royal Artillery; the GDA's main focus was on the Port of Harwich, in July 1940 there were daily attacks on shipping off the East Coast, but 302 Heavy AA Battery had a detachment stationed at Martlesham. The Luftwaffe began its offensive against RAF Fighter Command airfields in August. On 15 August the experimental Fighter-bomber unit Erprobungsgruppe 210 attacked RAF Martlesham Heath and a neighbouring signal station; the Hurricanes of No. 17 Squadron stationed at Martlesham were some 20 miles out to sea looking for the raid among the many traces being plotted by the radar stations.
The raiders slipped through and spent five minutes over the target and Strafing, while the HAA gun detachment got off five rounds of Shrapnel shell, all they had to use against low-level attack. The raiders got away without loss, despite being engaged by the Harwich AA guns while withdrawing; the equivalent of seven Fighter Command squadrons had been ordered to intercept, but only a few reached Martlesham as the attackers were leaving. The damage to the airfield took a full day to repair. On 27 October 1940 another daylight raid was made on Martlesham by about 40 Messerschmitt Bf 109 fighter-bombers, which were engaged by the HAA guns on their way in and out. 99th HAA Regiment claimed that the raiders were disrupted by the fire, the bomb damage was slight. No. 71 Squadron a squadron formed of American volunteers operated from the station in the middle and end of 1941. In 1943, Martlesham Heath became one of a group of grass-surfaced airfields earmarked for use by fighters of the United States Army Air Forces Eighth Air Force.
The airfield was assigned USAAF designation Station 369. The airfield was opened in May 1943 and was first used by the United States Army Air Forces Eighth Air Force 356th Fighter Group, arriving from RAF Goxhill on 5 October 1943; the group was under the command of the 67th Fighter Wing of the VIII Fighter Command. Aircraft of the 356th were identified by a magenta/blue diamond pattern around their cowling; the group consisted of the following squadrons: 359th Fighter Squadron 360th Fighter Squadron 361st Fighter Squadron The 356th FG served in combat from October 1943, participating in operations that prepared for the invasion of the Continent, supporting the landings in Normandy and the subsequent Allied drive across France and Germany. The group flew Republic P-47 Thunderbolts until they were replaced by North American P-51 Mustangs in November 1944. From October 1943 until January 1944, they operated as escort for Boeing B-17 Flying Fortress/Consolidated B-24 Liberator bombers that attacked such objectives as industrial areas, missile sites and communications.
Fighters from the 356th engaged in bombing and strafing missions after 3 January 1944, with its targets including U-boat installations, shipyards, hangars, marshalling yards, trucks, oil facilities, flak towers, radar stations. Bombed and strafed in the Arnhem area on 17, 18, 23 September 1944 to neutralize enemy gun emplacements, received a Distinguished Unit Citation for this contribution to the airborne attack on the Netherlands; the group flew its last combat mission, escorting B-17's dropping propaganda leaflets, on 7 May 1945. It returned to Camp Kilmer New Jersey and was inactivated on 10 November 1945. With the departure of the USAAF, the airfield reverted to the RAF. In the immediate post-war years, Fighter Command squadrons were in residence at Martlesham but the proximity to Ipswich and the physical limitations on lengthening the runways restricted jet operation. In an effort to improve the station the main runway was extended in 1955. Early in 1946, the Bomb Ballistics and Blind Landing Unit moved in which, in 1950, was rechristened the Armament and Instrument Experimental Unit remaining at Martlesham until disbanding in 1957.
An RAF Police flight had occupied the station from 1951–1953. The following year, the A&IEU was disbanded and the station was retained in reserve status during which time an Air Sea Rescue helicopter unit was in residence. In 1958, another Reserve F
The Blackburn B. T.1 Beagle was a British single-engine, two-seat biplane bomber/torpedo aircraft from 1928. Designed to Air Ministry specifications which led to no contracts for any manufacturer, only one Beagle was built; the B. T. in the Beagle's designation stood for bomber and torpedo, the first aircraft that Blackburn had built for both roles. Its design was started to Air Ministry specification 24/25 for a high-altitude bomber, but was modified to meet specification 23/25 for a day bomber and torpedo aircraft; the Beagle was a single-bay biplane with staggered and swept wings. The fabric-covered wings, which did not fold as the aircraft was not intended for carrier service, had spruce spars and ribs with metal bracing. Four ailerons were fitted; the fuselage followed standard Blackburn practice with a steel tube centre section and wooden construction aft, though the final section was again of tube steel. Fin area was small and the rudder large, with a horn balance merging into the fin but reduced, leaving a prominent step similar to that of the Blackburn Nautilus.
The braced tailplane had greater elevator than stabiliser area, the former having prominent horn balances. The undercarriage was of the split type required by the torpedo dropping role, but a carrier mechanism between the legs could hold a 185 imp gal fuel tank for reconnaissance work. Cockpits were open with the pilot in front, armed with a forward-firing.303 in Vickers machine gun mounted on the port side. The gunner's cockpit was close to the pilot's for communication, he had a Scarff ring-mounted.303 in Lewis Gun, but to fulfil his role as torpedo or bomb aimer, he moved into a prone position in a station below the pilot's cockpit. This had a bombsight, used via an opening with a sliding door in the bottom of the fuselage and had bomb fusing and release controls plus altitude and airspeed gauges and a hand-operated rudder control for yaw corrections on target; the Beagle was powered by a 460 hp Bristol Jupiter VIIIF radial engine mounted in a smooth and rather pointed nosecone, leaving the tops of the nine cylinders exposed.
After the competitive trials it was re-engined with a supercharged 590 hp Jupiter XF, though the extra power seems not to have led to significant performance improvement. This installation had a more pointed cowling, with more cylinder heads exposed for better cooling; the Beagle flew first at Brough Aerodrome on 18 February 1928 piloted by W. S. Bulman; the rudder modification mentioned above was made. Trials took place at RAF Martlesham Heath in July 1929, where the Beagle was ranged against the Gloster Goring, the Handley Page Hare, the Hawker Harrier and the Westland Witch. None of these aircraft met the performance requirements, but as it had received favourable handling reports, the Beagle, along with the Vickers Vildebeest and Hare, was chosen for further testing, it was re-engined and returned to Martlesham in March 1931. By this time, the Vildebeest had been chosen to meet the RAFs requirements for a torpedo bomber; the Beagle remained operational until October 1933. Data from Jackson 1968, p. 249General characteristics Crew: two Length: 33 ft 1 in Wingspan: 45 ft 6 in Height: 11 ft 9 in Wing area: 570 ft2 Empty weight: 3,495 lb Gross weight: 6,120 lb Powerplant: 1 × 9-cylinder radial Bristol Jupiter VIIIF, 460 hp Performance Maximum speed: at 5,000 ft 140 mph Cruise speed: 115 mph Endurance: 3 hours 30 min Service ceiling: service 16,000 ft Rate of climb: at 5,000 ft 740 ft/min Armament 1 × fixed forward-firing 0.303 in Vickers machine gun 1 × ring-mounted 0.303 in Lewis gun in rear cockpit Jackson, A.
J.. Blackburn Aircraft since 1909. London: Putnam Publishing. ISBN 0-370-00053-6. Mason, Francis K.. The British Bomber since 1914. London: Putnam. ISBN 0-85177-861-5. Contemporary picture in Flight magazine
The Hawker Horsley was a British single-engined biplane bomber of the 1920s. It was the last all-wooden aircraft built by Hawker Aircraft, served as a medium day bomber and torpedo bomber with Britain's Royal Air Force between 1926 and 1935, as well as the navies of Greece and Denmark; the Horsley was designed to meet Air Ministry Specification 26/23 for a day bomber powered by a single Rolls-Royce Condor engine. While the specification called for any production aircraft to be of metal construction, Hawker proposed to build the prototype of wooden construction switching to a metal structure during production; this was acceptable to the Air Ministry, an order for a single prototype was placed. The first prototype was flown in March 1925, powered by a 650 hp engine, was delivered to the Aeroplane and Armament Experimental Establishment at Martlesham Heath on 4 May 1925. Meanwhile, the Air Ministry revised its requirements, producing Specification 23/25 which increased the required payload from one to two 551 lb bombs.
At the same time, it issued Specification 24/25 for a torpedo bomber, required to carry a 2,150 lb ) torpedo. The Horsley's ability to cope with the increased loads required to meet these new specifications led to the design being favoured by the RAF, with an initial order of forty aircraft, consisting of ten wooden Mk Is and 30 Mk IIs of mixed metal and wood construction, being placed; the Horsley was a large single-engined two-bay biplane. It had a crew of two, comprising a pilot and a gunner/bomb-aimer/radio operator, who had a.303 in Lewis gun mounted in a Scarff ring in the rear cockpit and a prone position for bomb aiming. The rear cockpit was fitted with dual controls; the payload included one 1,500 lb bomb or a torpedo weighing 2,800 lb. The structure was all wood, but before production was complete an all-metal structure was introduced, made in what became the famous Hawker system of metal construction; the three methods of construction were designated: Horsley Mk I for the all-wooden aircraft, Horsley Mk II for the mixed material, Horsley III for the all-metal aircraft.
Some aircraft were fitted with floats. Two aircraft, known as the Hawker Dantorp and powered by Leopard II engines were sold to the Danish Government, they had a different fuselage, accommodating a third crew member. The Danes purchased a licence to build a further ten aircraft at the Danish Naval Workshops, but these were not built owing to a shortage of funds. Production aircraft were powered by the Condor IIIA, but the Horsley was much used as a flying testbed for other engines, including the Napier Lion, Rolls-Royce Buzzard, Rolls-Royce Eagle, the Armstrong Siddeley Leopard radial engine, the Junkers Jumo diesel engine and early versions of the Rolls-Royce Merlin; the first aircraft were delivered to No 100 Squadron of the Royal Air Force in September 1927, with two more squadrons, No. 15 and No. 11 Squadrons receiving Horsleys by the end of the year, replacing the Fairey Fawn. The Horsleys proved superior to the Fawn, carrying up to three times the bomb load over greater ranges and at higher speeds, while being agile for their size, were popular with their pilots.
In October 1928, No. 36 Squadron formed at Donibristle, Scotland as a torpedo-bomber squadron. It was transferred to Singapore in 1930, helping to suppress a rebellion in Burma as well as maintaining its torpedo bombing skills. 100 Squadron converted to the torpedo bombing role in 1930 to fill the gap in home-based defences. The Horsley was chosen to attempt a non-stop flight to India, with a specially modified aircraft, carrying much more fuel and taking off at a weight of over 14,000 lb took off from RAF Cranwell on 20 May 1927, flown by Flight Lieutenants Roderick Carr and L. E. M Gillman, it ran out of fuel en route, ditching in the Persian Gulf near Bandar Abbas, Iran. Despite this it had covered a distance of 3,420 mi, sufficient to set a new world distance record, but was beaten in turn within a few hours by Charles Lindbergh, whose solo Atlantic flight between New York and Paris in the Spirit of St. Louis covered 3,590 mi ); the Horsleys remained in service in the day-bombing role until 1934, with 504 Squadron's Horsleys being replaced by Westland Wallaces in March 1934.
No 36 Squadron at Singapore retained the Horsely in the Torpedo bomber role until July 1935. The last Horsley, a Merlin-powered testbed flew its final flight at RAE Farnborough on 7 March 1938. A total of 124 Horsleys were built, including six aircraft for the Hellenic Naval Air Service and the two Dantorps built for Denmark. DenmarkMarinens Flyvevæsen GreeceHellenic Air Force Hellenic Naval Air Service United KingdomRoyal Air Force No. 11 Squadron RAF No. 15 Squadron RAF No. 25 Squadron RAF No. 33 Squadron RAF No. 36 Squadron RAF No. 100 Squadron RAF No. 504 Squadron RAF No. 1 Flying Training School RAF Royal Air Force College Cranwell Anti-Aircraft Cooperation Flight Data from Hawker Aircraft since 1919 General characteristics Crew: 2, pilot and bomb-aimer/gunner Length: 38 ft 10 in Wingspan: 56 ft 5 3⁄4 in Height: 13 ft 8 in Wing area: 693 sq ft Empty weight: 4,760 lb Gross weight: 7,800 lb Fuel capacity: 230 imp gal Powerplant: 1 × Rolls Royce Condor IIIA water-cooled V12 engine, 665 hp Propellers: 2-bladed Watts wooden propeller, 14 ft 6 in diameterPerformance Maximum speed: 125 mph at 6,000 ft Range: 900 mi (782 nmi.
The Bristol Jupiter was a British nine-cylinder single-row piston radial engine built by the Bristol Aeroplane Company. Designed late in World War I and known as the Cosmos Jupiter, a lengthy series of upgrades and developments turned it into one of the finest engines of its era; the Jupiter was used on many aircraft designs during the 1920s and 1930s. Thousands of Jupiters of all versions were produced, both abroad under licence. A turbo-supercharged version of the Jupiter known as the Orion suffered development problems and only a small number were produced; the "Orion" name was re-used by Bristol for an unrelated turboprop engine. The Jupiter was designed during World War I by Roy Fedden of Brazil Straker and Cosmos Engineering; the first Jupiter was completed by Brazil Straker in 1918 and featured three carburettors, each one feeding three of the engine's nine cylinders via a spiral deflector housed inside the induction chamber. During the rapid downscaling of military spending after the war, Cosmos Engineering became bankrupt in 1920, was purchased by the Bristol Aeroplane Company on the strengths of the Jupiter design and the encouragement of the Air Ministry.
The engine matured into one of the most reliable on the market. It was the first air-cooled engine to pass the Air Ministry full-throttle test, the first to be equipped with automatic boost control, the first to be fitted to airliners; the Jupiter was standard in design, but featured four valves per cylinder, uncommon at the time. The cylinders were machined from steel forgings, the cast cylinder heads were replaced with aluminium alloy following studies by the Royal Aircraft Establishment. In 1927, a change was made to move to a forged head design due to the rejection rate of the castings; the Jupiter VII introduced a mechanically-driven supercharger to the design, the Jupiter VIII was the first to be fitted with reduction gears. In 1925, Fedden started designing a replacement for the Jupiter. Using a shorter stroke to increase the revolutions per minute, including a supercharger for added power, resulted in the Bristol Mercury of 1927. Applying the same techniques to the original Jupiter-sized engine in 1927 resulted in the Bristol Pegasus.
Neither engine would replace the Jupiter for a few years. In 1926 a Jupiter-engined Bristol Bloodhound with the registration G-EBGG completed an endurance flight of 25,074 miles, during which the Jupiter ran for a total of 225 hours and 54 minutes without part failure or replacement; the Jupiter saw widespread use in licensed versions, with fourteen countries producing the engine. In France, Gnome-Rhone produced a version known as the Gnome-Rhône 9 Jupiter, used in several local civilian designs, as well as achieving some export success. Siemens-Halske took out a licence in Germany and produced several versions of increasing power resulting in the Bramo 323 Fafnir, which saw use in German wartime aircraft. In Japan, the Jupiter was license-built from 1924 by Nakajima, forming the basis of its own subsequent radial aero-engine design, the Nakajima Ha-1 Kotobuki, it was produced in Poland as the PZL Bristol Jupiter, in Italy as the Alfa Romeo 126-RC35, in Czechoslovakia by Walter Engines. The most produced version was in the Soviet Union, where its Shvetsov M-22 version powered the initial Type 4 version of the Polikarpov I-16.
Type 4 Polikarpovs can be identified by their lack of exhaust stubs, rounded NACA cowling and lack of cowling shutters, features which were introduced on the Shvetsov M-25 powered Type 5 and variants. Production started in 1918 and ceased in 1930; the Jupiter was produced in many variants, one of, the Bristol Orion of 1926. Metallurgy problems with this turbo-supercharged engine caused the project to be abandoned after only nine engines had been built. Brazil Straker Jupiter I 400 hp. Cosmos Jupiter II 400 hp. Bristol Jupiter II 400 hp. Bristol Jupiter III 400 hp. Bristol Jupiter IV 430 hp. Bristol Jupiter V 480 hp. Bristol Jupiter VI 520 hp. Bristol Jupiter VIA 440 hp. Bristol Jupiter VIFH 440 hp. Bristol Jupiter VIFL 440 hp. Bristol Jupiter VIFM 440 hp. Bristol Jupiter VIFS 400 hp. Bristol Jupiter VII 375 hp. Bristol Jupiter VIIF 480 hp. Bristol Jupiter VIIFP 480 hp. Bristol Jupiter VIII 440 hp. Bristol Jupiter VIIIF 460 hp. Bristol Jupiter VIIIFP 460 hp. Bristol Jupiter IX 480 hp. Bristol Jupiter IXF 550 hp.
Hawker Siddeley Harrier
The Hawker Siddeley Harrier, developed in the 1960s, is the first of the Harrier Jump Jet series of aircraft. It was the first operational close-support and reconnaissance fighter aircraft with vertical/short takeoff and landing capabilities and the only successful V/STOL design of the many that arose in that era; the Harrier was developed directly from the Hawker Siddeley Kestrel prototype aircraft, following the cancellation of a more advanced supersonic aircraft, the Hawker Siddeley P.1154. The British Royal Air Force ordered the Harrier GR.1 and GR.3 variants in the late 1960s. It was exported to the United States as the AV-8A, for use by the US Marine Corps, in the 1970s. During the Harrier's service the RAF positioned the bulk of the aircraft in West Germany to defend against a potential invasion of Western Europe by the Warsaw Pact forces; the USMC used their Harriers for close air support, operating from amphibious assault ships, and, if needed, forward operating bases. Harrier squadrons saw several deployments overseas.
The Harrier's ability to operate with minimal ground facilities and short runways allowed it to be used at locations unavailable to other fixed-wing aircraft. The Harrier received criticism for having a high accident rate and for a time-consuming maintenance process. In the 1970s the British Aerospace Sea Harrier was developed from the Harrier for use by the Royal Navy on Invincible-class aircraft carriers; the Sea Harrier and the Harrier fought in the 1982 Falklands War, in which the aircraft proved to be crucial and versatile. The RN Sea Harriers provided fixed-wing air defence while the RAF Harriers focused on ground-attack missions in support of the advancing British land force; the Harrier was extensively redesigned as the AV-8B Harrier II and British Aerospace Harrier II by the team of McDonnell Douglas and British Aerospace. The innovative Harrier family and its Rolls-Royce Pegasus engines with thrust vectoring nozzles have generated long-term interest in V/STOL aircraft; the Harrier's design was derived from the 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. 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 underway for the British military. Hawker sought to move on to a new project and became interested in Vertical Take Off/Landing aircraft, which did not need runways. According to Air Chief Marshal 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. Design work on the P.1127 was formally started in 1957 by Sir Sydney Camm, Ralph Hooper of Hawker Aircraft, Stanley Hooker of the Bristol Engine Company. The close cooperation between Hawker, the airframe company, Bristol, the engine company, was viewed by project 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.
Rather than using rotors or a direct jet thrust, the P.1127 had an innovative vectored thrust turbofan engine, the Pegasus. The Pegasus I was rated at 9,000 pounds of thrust and first ran in September 1959. A contract for two development prototypes was signed in June 1960 and the first flight followed in October 1960. Of the six prototypes built, three crashed, including one during an air display at the 1963 Paris Air Show. In 1961 the United Kingdom, United States and West Germany jointly agreed to purchase nine aircraft developed from the P.1127, for the evaluation of the performance and potential of V/STOL aircraft. These aircraft were built by Hawker Siddeley and were designated Kestrel FGA.1 by the UK. The Kestrel was an evaluation aircraft and to save money the Pegasus 5 engine was not developed as intended, only having 15,000 pounds of thrust instead of the projected 18,200 pounds; the Tripartite Evaluation Squadron numbered ten pilots. The Kestrel's first flight took place on 7 March 1964.
A total of 960 sorties had been made during the trials, including 1,366 takeoffs and landings, by the end of evaluations in November 1965. One aircraft was destroyed in an accident and six others were transferred to the United States, assigned the US designation XV-6A Kestrel, underwent further testing; the two remaining British-based Kestrels were assigned to further trials and experimentation at RAE Bedford with one being modified to use the uprated Pegasus 6 engine. At the time of the development of the P.1127 Hawker and Bristol had undertaken considerable development work on a supersonic version, the Hawker Siddeley P.1154, to meet a North Atlantic Treaty Organisation requirement issued for such an aircraft. The design used a single Bristol Siddeley BS100 engine with four swivelling nozzles, in a fashion similar to the P.1127, required the use of plenum chamber burning to achieve supersonic speeds. The P.1154 won the competition to meet the requirement against strong competition from other aircraft manufacturers such as Dassault Aviation's Mirage IIIV.
The French government withdrew. The Royal Air Force and the Royal Navy planned to develop and introduce the supersonic P.1154 independently of the cancelled NATO requirement. This ambition was complicated by the c