The Boulton & Paul P.7 Bourges was a promising design for a fighter-bomber that was produced in 1918, and disappeared after the end of the First World War.
Work on the P.7 began in response to Specification A.2(b), for a twin-engined reconnaissance aircraft. The formation of the RAF then meant that a new set of specifications were issued, and Boulton Paul's designer John Paul decided to design an aircraft that could fit several of them - No.IV for a long distance photographic reconnaissance fighter, No.VI for a short distance day bomber and No.VIII for a long distance day bomber. Internally the aircraft was described as a fighter-bomber.
The Bourges was a three bay biplane, with its two engines carried in nacelles mounted between the wings on the innermost struts. It carried a crew of three - a nose gunner/ bomb aimer, pilot and rear gunner. It was armed with four machine guns (two in the nose position and two in the rear gunner's position) and could carry up to 900lb of bombs. Both the bomb aimer and pilot could release the bombs. A camera position was located just in front of the rear gunner, who also acted as the camera operator. The structure was made from spruce, with a fabric covering. The fuselage was a simple wire-braced box-section structure, with flat sides. The horizontal tail surfaces were level with the top of the rear fuselage, and supported by two struts. The Bourges has a wide track undercarriage, with the main wheels mounted on V struts below the engines, and extra bracing running to the base of the fuselage. The aircraft had an internal bomb bay carried between the lower wing spars.
Boulton & Paul received a contract to build three prototypes. These were completed in four different configurations.
The original plan was to use the 320hp Dragonfly I radial engine, but these weren't available in time to be used on the first prototype. The Dragonfly engines were the first powerful radial engines, and their development was very slow, and they were prone to overheating and losing power.
The first prototype (F2903) was completed with less powerful 230hp Bentley B.R.2 rotary engines that were mounted between the wings. It was given the designation Bourges Mk IIA. The 'A' designation indicated that the aircraft had a conventional upper wing, with a gap between the centre section and the fuselage. Once the Dragonfly engines became available they were installed on the first prototype. At first they were given close cowling, two-blade propellers and large spinners, but the spinners were soon removed to improve cooling, and the cowling modified. This aircraft was scrapped in May 1920.
The second prototype was built with the Dragonfly engines. In this configuration it was given the designation Bourges Mk IA. The IA was a promising design, with similar manoeuvrability to contemporary figures, despite have twice the wing span.
The second prototype (F2904) was then given a gull-wing upper wing, with the central section of the wings attached directly to the upper fuselage and dihedral as far as the engines, and a modified fin and rudder, in an attempt to improve the field of fire for the rear gunner. In this configuration it was given the designation Bourges Mk IB. This aircraft also had the engines moved from their original position in the middle of the wing gap, down to the lower wings, after this was proved to reduce drag. This aircraft was written off in a crash at Mousehold in 1919, and the parts were used to build the first Boulton & Paul P.8, a civil airliner built with the trans-Atlantic flight in mind.
The third prototype (F2905) was completed with 450hp Napier Lion engines mounted on the lower wings and the straight wings of the IA and IIA. The change of engine increased the top speed from 123 to 130mph. This version was given the designation P.7B. The P.7B had new lighter gun mountings that could take one or two Lewis guns. It retained the good manoeuvrability of the earlier prototypes, and was claimed to be the fasted twin-engined aircraft in the world. It performed at the RAF Pageant at Hendon in 1923,
A Mk III with 290hp Siddeley Puma engines was planned, but not built.
The Bourges performed well in its flight tests - it could be rolled, spun and looped and could fly on a single engine.
Although the Bourges was a promising design, it was still at the prototype stage when the First World War came to an end. A combination of the vast number of surplus military aircraft and cuts in military spending meant that the type never entered production, although it would probably have been ordered if the war had continued into 1919. It did become the basis of the sole Boulton & Paul P.15 Bolton, the first all-metal aircraft to be delivered to the RAF. This was perhaps doubly unlucky for Boulton & Paul, which gained a reputation as a designer of twin engined medium bombers, one type of aircraft that the RAF didn't use.
Mk IA and IB
Engine: Two A.B.C Dragonfly I radial engines
Power: 320hp each
Span: 57ft 4in (with horn-balanced ailerons), 54ft (without horn-balanced ailerons)
Length: 37ft 0in
Height: 12ft 0in
Empty weight: 3,820lb
Maximum take-off weight: 6,326lb
Max speed: 123mph at 6,500ft
Climb Rate: 11min to 10,000ft
Service ceiling: 20,000ft
Endurance: 9 hours 15 minutes
Armament: Two 0.303in Lewis guns in nose, two Lewis guns in rear cockpit
Bomb load: 900lb