• The Bristol Type 107 Bullpup was a British fighter aircraft built in the 1920s. It was not selected for squadron service and only the single prototype was built.
    The design of the Bullpup was an outcome of a series of design studies for a fighter undertaken by Frank Barnwell during the 1920s. In 1924 Barnwell had started work on a fighter powered by the Rolls-Royce Falcon to meet the requirements of specification F.17/24. This project was shelved since Bristol preferred to use their own engine designs, but was revived in 1926 when Barnwell started work on a design, designated the Bristol 102, to meet either F.9/26 for a day-and-night fighter or N.21/26 for a shipborne fighter. A subsequent proposal, designated Type 105 was for another aircraft to meet F.9/26, powered by the Mercury engine then under development at Bristol. These proposals were sufficient for a pair of mockups to be constructed for inspection by the Air Ministry in February 1927. The two aircraft were similar in design, the interceptor to specification F.17/24 design being slightly smaller and lighter and not equipped with radio. As a result, Bristol was asked to revise the design so that it met a later interceptor specification, F.20/27. Subsequently, a prototype was ordered for evaluation, but the other design did not gain official backing. Nevertheless, Bristol considered it promising enough to build a prototype to be entered for the F.9/26 trials as a private venture, powered by a Bristol Jupiter because the supply of Mercurys was expected to be limited. This became the Bristol Bulldog.

    In essence, it was a lightweight scaled-down version of the Bristol Type 105 Bulldog and when compared with the Bristol Type 105 Bulldog IIA, it was around 700 lb lighter and had a wing area of only 230 sq ft (compared to 307 sq ft).
    Design and development
    The Type 107 was an unequal span single bay biplane powered by a 480 hp (360 kW) Bristol Mercury air-cooled radial engine driving a two-bladed propeller. The structure was all-metal with a fabric covering, using members built up from rolled high-tensile steel strips riveted together. In order to optimise the pilot's field of view there was large semi-circular cutout in the trailing edge of the upper wing and the inboard section of the lower wing was of reduced chord. Frise ailerons were fitted to the top wing only. It was armed with a pair of 0.303 in (7.7 mm) Lewis guns mounted on either side of the cockpit.

    The prototype first flew on 28 April 1928, powered by a Bristol Jupiter engine since a flight-ready Mercury was not yet available, and the aircraft was not delivered to Martlesham Heath for evaluation until March 1929. The Bullpup prototype was subsequently fitted with a Jupiter F type head with twin compensator rods for the penthouse heads. Trials with this engine were carried out at Martlesham in 1929.

    Trials at A & A E E are reported to have shown that the Bristol Type 107 Bullpup recorded a climb to 15,000ft in 10 min 50 sec, compared with 18 min 38 sec for the Bristol Type 105 Bulldog IIA.

    Following the trials, The Bristol Type 107 Bullpup was also tested with different engine variations such as a short-chord Townend ring cowling, and a Bristol Jupiter VIIF engine, fitted for the 1930 RAF Display at Hendon. In 1931, a short-stroke Bristol Mercury engine was also fitted with a close-fitting NACA-style cowling.

    Engine trials continued into 1934, with a 200-hour endurance test of the sleeve-valve Bristol Aquila I engine. The Bristol Aquila also featured a long-chord, close-fitting cowling and the aircraft was displayed in this form at the SBAC show in June 1935.

    The aircraft was scrapped in 1935 at the end of the Bristol Aquila development programme. .
    General characteristics
    Crew: 1
    Length: 23 ft 6 in (7.16 m)
    Wingspan: 30 ft 0 in (9.14 m)
    Height: 9 ft 5 in (2.87 m)
    Wing area: 230 sq ft (21.37 m2)
    Empty weight: 1,910 lb (866 kg)
    Gross weight: 2,850 lb (1,293 kg)
    Powerplant: 1 × Bristol Mercury IIA , 480 hp (358 kW)
    Maximum speed: 190 mph (306 km/h, 170 kn)
    2 × .303 in (7.7 mm) Lewis guns
    The Bristol Bullpup at Filton in April 1928 with Jupiter VI and initial small rudder.

    The Bristol 107 Bullpup J9051 with Mercury IIA and metal wing struts, as tested ar Martlesham Heath.

    The Bristol Bullpup with Mercury IIA engine and narrow-chord Townend ring cowling.

    The Bullpup in its final form with AquilaI engine, as displayed at the SBAC Show in June 1935.
    Bristol Bullpup J9051

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