The Bristol Badger was designed to meet a British need for a two-seat fighter-reconnaissance aeroplane at the end of World War I. Despite the 1918 Armistice, three Badgers were delivered to the Air Board to develop air-cooled radial engines, particularly that which became the Bristol Jupiter; two other Badgers were also built.
The Bristol Badger began life as the Bristol F.2C before receiving its official name, and was retrospectively given the Bristol Type number 23 in 1923. The Badger was designed at the end of 1917 to meet a two-seat fighter-reconnaissance role. It was a single-bay biplane with strongly staggered, unswept and unequal span wings. Pilot and observed sat in tandem, the pilot in front under the upper-wing trailing edge and the observer behind with a ring-mounted .303 in (7.7 mm) Lewis Gun. At first, the Badger carried almost no fixed fin. Construction was the traditional wood and fabric of the time and the undercarriage was a single axle plus tailskid arrangement.
During the design process, it became clear that at least 300 hp (230 kW) would be needed and such engines were in short supply. The Badger was initially designed to take the ABC Dragonfly, a new aircooled radial of 320 hp (240 kW). This proved unreliable and Bristol looked to an alternative, a new nine-cylinder, 400 hp (300 kW) radial produced by Brazil Straker and known then as the Cosmos Jupiter. Later, it became the Bristol Jupiter.
Bristol were awarded a contract to build three Badgers, two powered by the Dragonfly and one (the second) by a Jupiter. The first Badger flew on 4 February 1919 but crashed on this first flight with fuel supply problems. It was rebuilt with a larger rudder and delivered to the Air Board eleven days later. The second, Jupiter-engined Badger flew on 24 May but was re-engined with a Dragonfly and was purchased by the Air Board in September. It had full armament and a fixed, rounded fin, introduced to cope with the heavier Jupiter engine. The Badger proved to have a lateral stability problem, an adverse yaw effect caused by aileron drag, and because of this, the third machine was not accepted by the Air Board. These first three machines were designated Badger I.
Despite the instability and without having received a Jupiter-powered Badger, the Air Board were sufficiently encouraged by this engine's promise to order a fourth, fully armed Badger with this powerplant. After some testing the rudder was modified with a horn balance and larger ailerons were fitted. This aircraft was the sole Badger II and was loaned by the Air Board to Bristol for the development of the Jupiter and its cowling during 1920-1.
The lateral stability problems of the Badger worried its designer Frank Barnwell because a 1/10 scale model had been carefully tested in the NPL wind tunnel without any alarms. Scaling from model to full size was a problem because the Reynolds number reached in the atmospheric pressure wind tunnels of the time were much lower than those encountered in full size flight. Flight tunnel tests also often involved the use of simplified aircraft models, with no attempt made to model the fuselage shape in detail. Using a spare set of Badger wings and empennage, Barnwell designed a new, single-seat flat-sided and very simple fuselage made from plywood on a wooden frame for a fifth and final Badger, the Badger X. It first flew on 13 May 1919 and was Bristol's first civil registered aircraft, initially as K110 then G-EABU but was never able to provide the intended comparative data with tunnel models, crashing on 22 May.