The Scimitar was developed out of an earlier effort, internally designated Type 505, an undercarriage-less fighter aircraft intended to be flown from rubber decks. Much of the aircraft's features, including its unorthodox V-tail (or "butterfly tail") and its thin straight wing, were shared with this ancestor; however, the Admiralty reconsidered their requirements and specified a conventional undercarriage be used. Accordingly, Supermarine produced the closely related Type 508, equipped with an enlarged wing and retractable undercarriage. On 31 August 1951, the Type 508 performed its maiden flight, it was closely followed by the redesigned Type 529 and Type 544, the latter serving as a direct prototype for the production model, making its first flight in January 1956.
During 1957, the first production aircraft were delivered, enabling the Scimitar to enter service with the Royal Navy during the following year. The aircraft was operated by the Royal Navy as a low level strike aircraft, which included potentially being armed with nuclear weapons, having been superseded as a fighter even prior to its introduction by other aircraft such as the de Havilland Sea Venom and the de Havilland Sea Vixen. It experienced a relatively high attrition rate due to a spate of accidents. Towards its latter years of operation, the type was frequently used as an aerial refuelling tanker. During 1969, the Scimitar was permanently withdrawn, having been replaced in service by newer and more capable aircraft such as the Blackburn Buccaneer.
The Scimitar stemmed from a number of designs produced by Supermarine for a naval jet aircraft. Work on what would eventually lead to the Scimitar officially commenced in 1945 following the release of a requirement for an undercarriage-less fighter aircraft, which was intended to land on flexible "sprung" rubber decks.[1] According to aviation authors C. F. Andrews and E. B. Morgan, it was commonly believed amongst officials that such an arrangement would enable aircraft to be built with a lighter and simpler structure, and thus be capable of achieving greater performance in comparison to their conventional peers, particularly amongst those being operated from aircraft carriers. Specifically, the weight reduction achieved by eliminating the reinforced undercarriage used on naval aircraft would lead to substantially great rates of climb and acceleration.[1] Seeking to keep the airframe compact and fairly lightweight, it was also desirable to adopt the most powerful powerplants available while restricting its diameter and thus its overall size; it was promptly determined that placing a pair of engines in a side-by-side configuration resulted in a relatively flat fuselage cross-section that generated favourable characteristics for undercarriage-less landings.[2]
Supermarine's design to meet this requirement, internally designated Type 505, featured an unusual V-tail (or "butterfly tail") arrangement that kept the tail surfaces away from the jet exhausts. Pitch control was performed via movements of the whole tail, the elevators being capable of working in tandem to provide additional pitch control, while also replacing the rudder of a conventional tail when being worked differentially. Wide-chord ailerons were installed for lateral control while leading and trailing edge flaps were also fitted, including dive flaps to aid in recovery during high speed flight by restoring lift.[3] [4] A cockpit akin to the earlier Supermarine Attacker was positioned within the aircraft's nose, it was pressurised to better facilitate flying at altitude. The powerplant selected was the Rolls-Royce Avon turbojet engine, a pair of which being installed side by side within the fuselage; it was accessed via removable panels on the upper fuselage. A relatively thin wing could also be adopted, having been freed from the necessity of bearing elements of the undercarriage; while considerations towards a swept wing configuration were made, the option was discounted due to it presenting too many unknown factors at the time. Instead, a straight wing with a constant airfoil section was adopted; its leading edge section was as large as was feasible to minimise premature breakaway of airflow, a phenomenon that could lead to stalls.[5]
During 1948, the Admiralty had second thoughts about the undercarriage-less fighter, leading to Supermarine reworking their design by including a nosewheel undercarriage, the resulting redesign being designated the Type 508.[6] This led to the adoption of a retractable nosewheel undercarriage; redesign work was aided by considerations that had already made for the installation of a conventional undercarriage upon the Type 505 during its initial test flights. Furthermore, the viable landing speed was also reduced at this time, necessitating various alterations, such as the wing thickness being increased from seven to nine percent for a higher lift coefficient, while the wing's area was also expanded.[7]
The Type 508 was the first Scimitar ancestor; it shared the broad layout of the unflown Type 505, both possessing a straight-wing paired with a V-tail and twin jet engines. The redesign was done in a manner that, if desired, an undercarriage-less configuration was still viable; furthermore, it was designed in such a manner that it could be readily adapted to Royal Air Force (RAF) requirements as well. The primary structural change between the two designs affected the wing spars, which were redirected underneath the engines to accommodate the undercarriage.[8] During November 1947, Supermarine received an initial order for three Type 508s to fulfil Specification N.9/47.[4]
On 31 August 1951, the first Type 508 performed its maiden flight from RAF Boscombe Down; by May 1952, the aircraft had commenced carrier-based trials aboard HMS Eagle.[9] The second aircraft featured significant differences, carrying a cannon armament and was different enough in detail to be renamed the Type 529. It flew for the first time on 29 August 1952.[4] One unusual modification was the larger tailcone, which had been implemented so that a proposed tail-warning radar could be accommodated.[10] The maximum speed of the straight-winged Type 508 and 529 was relatively modest, with the Type 529 reaching 607 mph (977 km/h) and it had already been decided when the Type 508 first flew, to redesign the third prototype with swept wings to improve performance.[11] The resulting Type 525 also featured conventional swept tail surfaces as well as blown flaps to reduce the aircraft's landing speed and first flew on 27 April 1954.[12]
While the aircraft was subsequently lost as a result of a crash, numerous favourable performance improvements had been observed, including a reduction in its stalling speed, a reduced angle of attack, increased stability and control at low speeds, and more stable airflow over the wing's trailing edge.[13] Thus, the basic design was considered to have been sufficiently proved to the extent that officials decided to proceed with an outwardly fairly similar looking aircraft, the Type 544, to fulfil Specification N.113.[14] A total of 100 aircraft were ordered, although the Royal Navy had changed the specification to a low level strike aircraft with nuclear capability, despite having originally been designed as a fighter.[15]
The first of the Type 544s, serving as prototypes for the later production series, flew on 19 January 1956. The aircraft evolved more with the third Type 544, incorporating different aerodynamic changes and a stronger airframe for the new low level role - to quote Flight; "To permit uninhibited manoeuvring in thick turbulent air at low levels while carrying heavy loads of strike weapons, the structure is extremely sturdy".[14] Various aerodynamic "fixes" were implemented in an effort to counter undesirable pitch-up effects present during high speed flight and at high altitudes; these included flared-out wing tips and wing fences, while the tailplane was also changed from dihedral to anhedral. These combined modifications led to the final Type 544 being considered the "production standard". The first production Scimitar flew on 11 January 1957.[16]
The Scimitar pioneered fuel flow proportioning and integral main-plane tanks, along with "blown" flying surfaces to reduce landing speeds. It also featured the first use of duplicated fully-powered flight controls by a British naval aircraft.[17]
At the point of its introduction, the Scimitar was the largest, heaviest and most powerful aircraft to have entered service with the Fleet Air Arm.[18] In June 1958, operational training on the type commenced with 803 Naval Air Squadron at RNAS Lossiemouth, prior to their embarkment upon the aircraft carrier HMS Victorious during September of that year. Multiple squadrons formed around the Scimitar shortly thereafter, leading to its use upon the carriers HMS Ark Royal, HMS Centaur, HMS Eagle and HMS Victorious as well.[19]
Early on in the Scimitar's flying career, the majority of the Royal Navy's carriers were relatively small while the Scimitar was a comparatively large and powerful aircraft. This combination likely contributed heavily to the frequent landing accidents with the type; perhaps the most high profile of these occurred during the type's introduction. It was a fatal accident, taking the life of Commander John Russell, commanding officer of 803 Naval Air Squadron, the first squadron to operate the Scimitar. Overall the Scimitar suffered from a high loss rate; 39 were lost in a number of accidents, amounting to 51% of the Scimitar's production run.[20]
Although the Scimitar could operate as a fighter, the interceptor role was covered by the de Havilland Sea Venom and then the de Havilland Sea Vixen.[21] The Scimitar itself was replaced by the Blackburn Buccaneer.[22] It was kept initially as a tanker to allow the underpowered Buccaneer S.1 to be launched from aircraft carriers with a useful weapons load. To save weight, the Buccaneer would take off with a reduced fuel load then refuel from a Scimitar immediately after.[23] Late in the Scimitar's operational career, 16 examples were flown between 1965 and 1970 by the Fleet Requirements Unit (FRU) based at Bournemouth Airport (Hurn).[24] [25] The FRU was managed by Airwork Services and provided realistic flight operations for land and sea-based naval training units.[26]