Hawker Sea Hawk
The Hawker Sea Hawk is a British single-seat jet day fighter formerly 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 was the company's first jet aircraft.
Following acceptance in the RN, the Sea Hawk proved to be a reliable and sturdy workhorse. A considerable number were also 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.
Design and development
Origins
Towards the end of the Second World War, Hawker's design team had become increasingly 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, Tempest 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; it was this aircraft that would serve as the basis for Hawker's first jet-powered aircraft.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 also included "stretching" the fuselage and moving the cockpit to the extreme front of the fuselage in a re-contoured nose; this design received the internal designation P.1035. Use of the Rolls-Royce Derwent engine had been studied but quickly 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 air intakes were moved to the wing root leading edge, similar to the contemporary de Havilland Vampire. 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 wing fuel tanks also meant a thinner wing could be adopted without the penalty of reduced range; to ease manufacture, the elliptical wingform of the Fury was discarded in favour of a straight tapered wing design. The fuselage fuel tanks, being fore and aft of the engine, also provided for a stable centre of gravity during flight. The tail plane was raised to clear the jet exhausts. The Sea Hawk also 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 cannon.
The redesign had led to a new name for the project, P.1040. The Air Ministry quickly 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 initially viewed the project with only academic interest. Official interest had also 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, even 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, allegedly due to the aircraft offering insufficient advances over the jet fighters that were already 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 to the development of the jet-powered Supermarine Attacker aircraft. The service was however 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 quickly found their development focus for the type being divided between the naval P.1046 and the general-purpose P.1040, which was 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.
Prototypes
On 2 September 1947, the P.1040 prototype, VP401, sometimes referred to as the Hawker N.7/46 after the related naval specification, conducted its maiden flight from RAF Boscombe Down, piloted by Bill Humble. Three days later, VP401 flew to Farnborough to continue trials. A month after the first flight, the existence of the P.1040 was revealed to the general public. Early flight trials encountered aerodynamically related teething problems, such as airframe vibrations and tail buffeting, which led to a redesign of the rear jet pipe fairings and the addition of a bullet-shaped anti-shock body on the tail. Other minor issues were addressed, including high stick forces and windscreen distortion; VP401 needed long take-off runs which were attributed to the "low-thrust" Nene 1. The Nene 2/Mk.101 for production aircraft would have a higher take-off thrust.On 31 August 1948, a naval prototype, VP413, equipped with folding wings, catapult spools and armament, conducted its first flight. VP413 was quickly subjected to a series of deck assessment trials using a mock-up deck at Boscombe Down. In April 1949, VP413 was transferred to the aircraft carrier to conduct general deck and handling trials at sea. These trials revealed the need for the wing span to be increased by 30 inches, the low-speed handling of the prototype having been found to be lacking. In November 1949, VP413 returned to Illustrious, performing around 25 deck landings without issue.
On 17 October 1949, the third prototype, VP422, made its maiden flight. Being representative of the production aircraft, VP422 incorporated a number of modifications as a result of experience gained from trials with the second prototype, these alterations included the fitting of a longer arrester hook when a number of "bolters" were experienced during the early dummy deck trials. After the longer hook was incorporated, this modification was carried though the remaining production runs. Other changes included the addition of fixtures for rocket-assisted take-off gear and hard points plumbed for external drop tanks. On 22 November 1949, Hawker received an initial production contract for 151 aircraft named Sea Hawk. Throughout 1950, both VP413 and VP422 were used for preliminary service trials.
VP422, the third prototype, later joined a specially-prepared Vampire Mk 21 in testing the feasibility of operating without an undercarriage, using a flexible deck. Flying from Farnborough, VP413 made the only flight with undercarriage raised from catapult launch to arrested landing on 12 November 1953. This flight was the final phase of the flexible deck project and was the only launch of an aircraft from the slotted tube catapult developed from the slotted tube launchers used for the V-1 flying bomb. Although the trials were successful, the project was abandoned when the introduction of more powerful engines obviated the need radically to adapt the design to the concept of combat aircraft without undercarriages.
VP401, the first prototype, had continued to serve in the flight test programme and was involved in two significant events prior to its retirement. On 1 August 1949, the Royal Navy entered VP401 in the National Air Races, in which it won the Society of British Aircraft Constructors Challenge Cup Race, beating a Vampire 3 and de Havilland DH.108. VP401 was later converted into a further prototype, the Hawker P.1072, the principal addition being in the form of an auxiliary rocket engine; configured as such, it became the first British rocket-powered aircraft. After a few flights were made in 1950, the rocket engine blew up during a test and although repaired, the airframe was scrapped soon after.
Production
Immediately following the receipt of the first order in November 1949, Hawker set about establishing a manufacturing line for the Sea Hawk at their Kingston facility. Shortly after the outbreak of the Korean War, an urgent operational demand for aircraft carriers and aircraft became apparent. The rate of production was substantially increased and more orders for the Sea Hawk were placed. The issuing of a 'Super-Priority' status for the Sea Hawk by Prime Minister Winston Churchill in 1951, served to speed up production considerably as well as aid the supply of vital materials for its manufacture.To cope with demand, address production shortcomings and cope with the parallel pressure that Hawker was facing for the development of another aircraft, the newer Hunter, it was decided that production would be transferred to a new assembly line run by Armstrong Whitworth Aircraft, part of the Hawker group, at Coventry. Prior to the transfer, 35 Sea Hawk F1, the initial production standard, were completed at Kingston. On 14 November 1951, the first production Sea Hawk F1, WF143, conducted its maiden flight. It possessed a 39 ft wingspan and a tailplane of increased area. The first Coventry-built Sea Hawk F1 made its first flight prior to the end of 1953; a total of 60 would be produced.
While some of the initial batch of Sea Hawks would see operational service, many of the F1s would be used for various service trials. Amongst these, WF143 would later be rebuilt as the prototype for the Sea Hawk F2, featuring power-assisted ailerons in place of their unpowered counterparts on the F1, to which flight trials had demonstrated a weakness in lateral control leading to instances of oscillation. On 24 February 1954, the first production Sea Hawk F2, WF240, conducted its maiden flight at Bitteswell. A total of 40 F2 aircraft would be produced.
Another Sea Hawk F1, WF157, was developed into a prototype for the FB 3 standard, the initial fighter bomber variant of the type and later most common of the Sea Hawk variants. To suit this role, much of the development work went into its range of external stores, although the clearance of these for service was disrupted by a lack of Royal Navy personnel. On 13 March 1954, the first production Sea Hawk FB 3, WF280, made its first flight. A more refined Sea Hawk FGA 4 variant followed, partially to remedy stores handling problems that had been experienced with the FB 3 variant; the first FB 4 aircraft, WV792 conducted its first flight on 26 August 1954.
In 1950, it was acknowledged that the Nene 101 engine was transitional powerplant; upon availability of the 4 per cent more powerful Nene 103, the Admiralty quickly ordered many of its Sea Hawk FB 3 and FGA 4 to be re-engined. Another two Sea Hawk variants were developed; the first of these, the FB 5, was more or less identical to the FB 3 apart from the newer, more powerful Nene 103 engine, which greatly improving the aircraft's low-speed handling and take-off performance. The final Sea Hawk standard, FGA 6, was a fighter ground-attack variant, the same as its FB 5 predecessor, though they were new-build aircraft rather than re-engined ones. A total of just under 90 FGA 6s were completed.