Bristol Scout F

The Bristol Scout F was a British single seat biplane fighter built in 1916 to use newer and more powerful engines. The Armistice ended hopes of production.

Development
By the end of 1916 there was a shortage of suitably powerful engines for single seat fighters needed for air superiority. One of the few available was the Hispano-Suiza, but this was reserved for the SE5a and was in any case none too reliable. F.S Barnwell at Bristol designed a single seat biplane, called the Scout E, around the proposed 200 hp (150 kW) Cruciform radial, but this engine failed to materialise and another powerplant was sought. The Company gained an Air Ministry contract for six aircraft and promised some 200 hp Hispano-Suizas, but by June 1917 these had been replaced by 200 hp Sunbeam Arabs. With the Arab engine the design was redesignated the Scout F.

The Scout F was a small biplane with staggered, unequal span wings with straight edges and rounded tips. Ailerons were carried only on the upper planes and there were smooth cut-outs in both to improve the view from the open cockpit, placed just behind the trailing edge. The tail was conventional, with unbalanced control surfaces. The Scout F had fuselage mounted single axle main undercarriage forward of the lower wing, plus a tailskid. The water-cooled V-8 Arab engine allowed a smooth and quite short installation, ending in a two blade propeller and conical spinner. There was a small bulge on top of the cowling for the coolant header tank and the radiator was placed in a tunnel fairing between the undercarriage legs, with a pair of shutters for coolant temperature control.

Persistent vibrations dogged the Arab and a decision was made to use it only in the first two Scout Fs. The first flew in March 1918. It was fast (138 mph (222 km/h)) at sea level and could climb to 10,000 ft (3,050 m) in 9.5 min. The second was flown by experienced pilots at the Central Flying School, amongst them Oliver Stuart who judged it a better aerobatic mount than the SE5a.

It was decided to fit the third machine with a new, small diameter and powerful new radial, the 315 hp (235 kW) Cosmos Mercury. It was installed under a low drag cowling with exposed cylinder heads, making the aircraft 10 in (40 mm) shorter than the Arab powered machines. The weight went up by 60 lb (27 kg). It became known as the Scout F.1 and it first flew on 6 September 1918. The greater power produced a slightly high top speed and a much better rate of climb.

The third Scout F was the last to fly, although a fourth aircraft was built as a spare frame. The Armistice brought an end to the Mercury contract, the cancellation of the two outstanding Scout Fs and the abandonment of hopes of its production.