Bristol F.2 Fighter

Origins

In the Autumn of 1915, the Royal Flying Corps (RFC) needed a new aerial reconnaissance and artillery spotting aircraft to replace the pre-war Royal Aircraft Factory B.E.2c. Among other attributes and performance requirements, emphasis was placed upon the ability to defend itself in aerial combat.^[1]

Several new types were developed; the Royal Aircraft Factory offered its R.E.8 design and Armstrong Whitworth produced the design that eventually emerged as the F.K.8.^[1] In March 1916, Frank Barnwell of the British and Colonial Aeroplane Company (later the Bristol Aeroplane Company), commenced work on a replacement for the B.E.2.^[1] This initially took two forms, the Type 9 R.2A, to be powered by the 120 hp Beardmore engine and the similar Type 9A R.2B, powered by the 150 hp Hispano-Suiza.^[2][3] Both designs had the fuselage mounted between the wings, with a gap between the lower longerons and the wing, along with a substantial part of the fin beneath the fuselage. These features were intended to improve the field of fire for the observer; the positioning of the fuselage also resulted in the upper wing obscuring less of the pilot's field of view.^[2][1] The crew positions were placed as close together as possible, to help communication between the pilot and observer.

Before either the R.2A or R.2B could be built, the new 190 hp (142 kW) Rolls-Royce Falcon inline engine became available.^[1] Barnwell drafted a third revision of his design around the new engine, with its decidedly superior power/weight ratio. The anticipated improvement in performance changed the emphasis in its intended operational use; it was now seen as a replacement for the F.E.2d and Sopwith 1½ Strutter two-seat fighters, rather than a competitor with the pedestrian reconnaissance designs that were to replace the B.E.2. The resulting Type 12 F.2A, was a two-bay equal-span biplane, closely based on the R.2A and R.2B designs.

Prototypes

In July 1916, work commenced on the construction of a pair of prototypes; on 28 August 1916, an initial contract was awarded for fifty production aircraft.^[1] On 9 September 1916, the first prototype performed its maiden flight, powered by a Falcon I engine.^[4] It was fitted with B.E.2d wings (Bristol were major contractors for the type) to save time; its lower wings were attached to an open wing-anchorage frame and had end-plates at the wing roots.^[5] On 25 October 1916, the second prototype was completed, powered by a Hispano-Suiza engine and differing from the first prototype in its tail-skid, which was integrated into the base of the rudder.^[1]

It was found that the prototype's radiator arrangement obscured the pilot's field of view and the nose was redesigned around a new circular-shaped frontal radiator in the cowling.^[1] Other changes made to the first prototype during flight testing included the elimination of the end-plates from the lower wing roots and the addition of a shallow coaming around the cockpits.^[6] Between 16 and 18 October 1916, the type underwent its official trials at the Central Flying School, Upavon, during which it was tested with a four-bladed 9 ft 2 in propeller and a two-bladed 9 ft 8 in propeller. By the time of its arrival at the experimental armament station at Orfordness it had also been fitted with a Scarff ring mounting over the rear cockpit and an Aldis optical sight.^[7]

Only 52 F.2A aircraft were manufactured before production began of the definitive model, the F.2B (retrospectively named Bristol Type 14), which first flew on 25 October 1916. The first 150 or so F.2Bs were powered by either the Falcon I or Falcon II engine but the remainder were equipped with the 275 hp (205 kW) Falcon III. The additional power gave the F.2B a 10 mph (16 km/h) advantage in level speed over the F.2A, while it was three minutes faster in a climb to 10,000 ft (3,000 m).

Armament

The Bristol F.2 Fighter was armed in what had by then become standard for a British two-seater military aircraft: one synchronised fixed, forward-firing .303 in (7.7 mm) Vickers machine gun (in this case mounted under the cowling to avoid freezing) and a .303 in (7.7 mm) Lewis Gun on a Scarff ring over the observer's rear cockpit. The F.2B often carried a second Lewis gun on the rear cockpit mounting, although observers found the weight of the twin Lewis gun mounting difficult to handle in the high altitudes at which combat increasingly took place in the last year of the war, many preferring one gun. Attempts were made to add a forward-firing Lewis gun on a Foster mounting or similar on the upper wing either instead of (or with) the Vickers gun. Among other problems this caused interference with the pilot's compass, which was mounted on the trailing edge of the upper wing: to minimise this effect the Lewis gun was offset to starboard.^[8]

Alternative engines

Rolls-Royce aero engines of all types were in short supply, which frustrated plans to increase production to enable the F.2B to become the standard British two-seater, replacing the R.E.8 and F.K.8. Efforts were made to find an available alternative powerplant that was both reliable and sufficiently powerful.^[9] The Type 15 was fitted with a 200 hp (150 kW) Sunbeam Arab engine. In expectation of a reduction in performance with the less powerful engine, it was planned to supply the Arab-powered Fighters to the "corps" reconnaissance squadrons, reserving Falcon-powered examples for fighter–reconnaissance operations.^[10] The Arab engine was to be fitted to Fighters produced by subcontractors under licence, while Bristol-built Fighters would continue to use the Falcon.^[9]

In the event the Arab engine was not a success; it was found to suffer from serious weaknesses in cylinder and crank-chamber design that led, among other faults, to chronic and severe vibration, while the cooling system also required repeated modification. The "Arab Bristol" was never to become a viable combination, in spite of prolonged development. A few Arab-engined Bristols were at the front late in the war but the British reconnaissance squadrons had to soldier on with the R.E.8 and F.K.8 until the end of hostilities.^[10] The Type 16 was fitted with a 200 hp (150 kW) Hispano-Suiza engine. This worked better than the Arab but there was already a severe shortage of Hispano-Suizas for other types, such as the S.E.5a and the Sopwith Dolphin. The 300 hp (220 kW) version of the Hispano-Suiza, suggested for the Type 17, was not available in quantity before the end of the war.

Other engines tried or suggested for the F.2B were the 200 hp (150 kW) RAF 4d, the 180 hp (130 kW) Wolseley Viper and the 230 hp (170 kW) Siddeley Puma.^[11] Trials of the Puma engine were carried out in February 1918; it was found to confer marginally better performance than the Hispano-Suiza and Arab engines but was difficult to install and unreliable. In September 1918, trials of a high-compression model of the Puma were carried out but it was found to have no significant performance benefit and this avenue was not pursued.^[12] The Type 22 was a proposed version adapted for a radial or rotary engine, either a 200 hp (150 kW) Salmson radial, a 300 hp (220 kW) ABC Dragonfly radial (Type 22A) or a 230 hp (170 kW) Bentley B.R.2 rotary (Type 22B). The type number was eventually used for the Bristol F.2C Badger, a completely new design.

The All-Metal Bristol Fighter

The Bristol M.R.1 is often described as an all-metal version of the F.2B but was a new design, although its fuselage was positioned between the upper and lower wing as with the F.2B. Two prototypes were built; the first flew on 23 October 1917, but the M.R.1 never entered mass production.

American versions

When the US entered the war, the Aviation Section, U.S. Signal Corps of the United States Army lacked any competitive combat aircraft either in inventory or under construction.^[12] On 1 August 1917, General John Pershing, the commander of the American Expeditionary Forces on the Western Front, issued his personal recommendation for the Bristol Fighter to be built in the United States, leading to plans for the development and production of an American version of the Fighter by the United States Army Engineering Division.^[12]

Original proposals for American production had the 200 hp (149 kW) Hispano-Suiza engine.^[12] On 5 September 1917, a F.2B Fighter was delivered to the Smithsonian Institution, Washington, United States. Attempts to begin production in the United States floundered due to the decision by Colonel V. E. Clark of the Bolling Commission to redesign the Fighter to be powered by the 400 hp (298 kW) Liberty L-12 engine. The Liberty was unsuitable for the Bristol, as it was far too heavy and bulky, so that the aircraft was chronically nose-heavy.^[13][12]

A contract for 1,000 aircraft was placed initially with the Fisher Body Corporation then cancelled and reallocated to the Curtiss Aeroplane and Motor Company.^[12] On 7 December 1917, the order was doubled to 2,000 aircraft. On 25 January 1918, the first aircraft, which was given the name U.S.A 0-1, was completed, despite the misgivings of Barnwell, who was not satisfied with some of the modifications made, particularly in the use of the Liberty L-12 engine.^[14] According to Bruce, misdirections attributed to Major E. J. Hall of the U.S. Signals Corps had led to roughly 1,400 production drawings produced by Curtiss being rendered obsolete. The reputation of the type was also tarnished by three early crashes, although one had been attributed to pilot error and the other two to faulty workmanship.^[15] Only 27 O-1s were completed.^[16]

Efforts to change the engine of American-built Bristol Fighters to the more suitable Liberty 8 or the 300 hp (224 kW) Wright-Hisso came up against political as well as technical problems. By July 1918, the only specimen of the American-built Hispano-Suiza engine had been installed in a Fighter; the combination soon gained the favour of the U.S. Air Board, which suggested to Curtiss that all work on the 400 hp Liberty L-12 version of the aircraft be abandoned in favour of the Hispano-Suiza version.^[15] In spite of protests by Curtiss, the contracts for the U.S.A. 0-1 were terminated, leading to only a pair of prototypes and 25 production aircraft out of the planned 2,000 aircraft being constructed.^[13][15]

W. C. Potter, Assistant Director of Aircraft Production, suggested that the original Bristol Fighter should be produced exactly as per Barnwell's original design, save for the use of either the Liberty 8 or Hispano-Suiza engine.^[15] Potter's proposal was overlooked; instead it was decided to produce eight aircraft, four being fitted with the Hispano-Suiza engine, as the Engineering Division USB-1A and four being powered by the Liberty L-8 engine, as the Engineering Division USB-1B; only one each were built.^[13][15]

In 1918, the Dayton-Wright Company designed a modified version, designated as the B-1A or XB-1A which used a 330 hp Wright-Hispano engine in a "new fuselage of wood-veneer monocoque construction". A later version was designated as the XB-1B and was equipped with the same engine.^[15][16] The XB-1A was armed with a pair of Marlin machine guns at the pilot's position while the XB-1B was armed with a pair of Browning machine guns. These aircraft were reportedly intended for use as night observation aircraft.^[15] Three prototypes were built by the Engineering division at McCook Field, with a further 44 aircraft built by the Dayton-Wright Company.^[17] According to Bruce, despite substantial efforts to differentiate and modify the aircraft's design, none of the American-built Fighters performed any better than the original Bristol.^[15] While some of the modified versions of the F.2 were used in the US, no American-built Bristol Fighters reached the American Expeditionary Forces in France.^[16]

Postwar developments

Postwar developments of the F.2B included the F.2B Mk II, a two-seat army co-operation biplane, fitted with desert equipment and a tropical cooling system, which first flew in December 1919, of which 435 were built. The Type 96 Fighter Mk III and Type 96A Fighter Mk VI were structurally strengthened aircraft, of which 50 were built in 1926–1927. Surplus F.2Bs were modified for civilian use. The Bristol Tourer was an F.2B fitted with a Siddeley Puma engine in place of the Falcon and with canopies over the cockpits; The Tourer had a maximum speed of 128 mph (206 km/h).

Postwar

Following the end of the war, the F.2B Fighter was soon adopted by the RAF as its standard army cooperation machine.^[15] The type continued to operate in army cooperation and light bombing roles in the British Empire, in particular the Middle East and India. In line with this role, which led to its use in a hot climate, Bristol introduced models of the Fighter equipped with 'tropical' radiators and provision for desert equipment.^[15] There had also been considerations made into deploying the Fighter as a carrier-based aircraft, which led to an engineless airframe participating in immersion trials in November 1918 and an aircraft being used in deck landing tests, reportedly on board HMS Eagle.^[15]

It was not until 1932 that the F.2B was withdrawn from RAF service, the last "Brisfit" unit being 20 Squadron stationed in India.^[21] The type lasted a further three years in New Zealand. Surplus aircraft were allocated to ADC Aircraft, a British company established to act as a seller for wartime aircraft, which passed on large quantities of Fighters to other nations, normally to military operators.^[21] Bristol also continued to manufacture and refurbish the type for some time. During the 1920s Bristol proceeded to develop and introduce numerous variants and derivatives of the Fighter, typically capable of carrying higher loads, with revised tail units and strengthened undercarriages.^[22]

The F.2B Fighter was adopted by the New Zealand Permanent Air Force and the Royal Australian Air Force (RAAF), as well as by the air forces of Belgium, Canada, Ireland, Greece, Mexico, Norway, Peru, Spain and Sweden. According to Bruce, relatively few Fighters entered service with the air forces of the various Commonwealth nations, greater quantities having been sold to other nations.^[21] Belgium purchased several from ADC Aircraft, and later arranged to produce the Fighter under licence at Sociétés Anonyme Belge de Constructions Aéronautiques (SABCA).^[22]

In 1920 Poland bought 106 Bristol Fighters (104 with Hispano-Suiza 300 hp/220 kW engines, two with Falcon IIIs) (other sources claim 107).^[23][24] Thus it became the second largest user of this type. It was also one of the most numerous Polish aircraft at that time. Forty Fighters were used during the Polish-Soviet War from July 1920, among others in the Battle of Warsaw, performing reconnaissance and close air support.^[24] The rest of the order became operational only after the end of hostilities. During the war, a pair were shot down by ground fire, while another was captured by the Soviets and several more were lost in crashes.^[24] Survivors of the conflict continued in Polish service in the reconnaissance and training roles until 1932.^[24]