The Boulton Paul P.88 was a design for a cannon armed fighter, designed in response to the increased speed of bomber aircraft in the mid 1930s.
For a time in the mid 1930s bomber aircraft were increasing in speed quicker than fighter aircraft, making it unlikely that contemporary fighters, which often carried two machine guns, would be able to shoot them down. One way to deal with this problem was the turret fighter (such as the Boulton Paul Defiant), but an alternative route was the cannon armed fighter. The Air Ministry issued Specification F.37/35, which called for a single engined fighter armed with four cannon. The new aircraft was to be 40mph faster than any likely bombers and have a ceiling of 30,000ft. The possibility of movable guns was also mentioned. The new aircraft also had to have a retractable undercarriage, wheel brakes and an electric starter.
Although the cannon armed fighter would become one of the standard types of the Second World War, in the mid 1930s the weight of the cannon made it difficult to find powerful enough engines. In April 1936 the specification was modified to allow twin engined designs, and at the same time the movable gun idea was dropped.
Hawker, Supermarine, Bristol, Westland and Boulton Paul all offered designs to fit F.37/35. Hawker's was for a cannon armed version of the Hurricane (eventually produced as the Hurricane Mk IIC in 1941). Supermarine, Bristol and Westland all offered conventional twin engined designs, of which the Westland Whirlwind was selected for production.
Boulton Paul put forward two designs - the twin engined P.89 and the technically single engined P.88. Two versions were offered. The P.88A, powered by a Hercules HE-ISM radial engine and the P.88B, which used the Rolls Royce Vulture, a new 24 cylinder 'X' shaped engine, using four cylinder blocks from the Rolls Royce Peregrine, a development of the Kestral. The Vulture was expected to produce 2,000hp, but this engine was never really reliable, and helped doom the Avro Manchester to failure. The P.88 was a low wing monoplane, with level equal chord central sections and tapered outer sections with limited dihedral. The cannon were arrived in the outer section of the level wing section. The retractable undercarriage was in a similar position.
A provisional order was placed for two prototypes of the P.88A, but by the start of 1937 the Air Ministry had decided that current engines weren’t powerful enough for the design, while the Vulture and other more powerful engines weren't advanced enough. On 11 February 1937 the P.88 was cancelled, and development focused on the two-engined Westland Whirlwind instead.
Engine: Hercules HE-ISM (A)/ Rolls Royce Vulture (B)
Span: 39ft 6in (A)/ 44ft (B)
Length: 32ft 8in (A)/ 36ft 3in (B)
Max speed: 337mph at 15,000ft (A)/ 358ft at 15,000ft, 326mph at 30,000ft (B)
Climb Rate: 3,500ft/ min (A)/ 3,400ft/ min (B)
Service ceiling: 39,500ft (A)/ 38,000ft (B)
Armament: Four 20mm Hispano cannon in the wings