The Boulton & Paul P.32 was a design for a heavy bomber that reached the prototype stage, but wasn't ordered into production.
The P.32 was produced in response to specification B.22/27, for a three engined heavy night bomber. The specification called for a metal structure, crew of four, and three engines, but with the nose left free for the gunner/ bomber-aimer.
Boulton & Paul produced a large three bay biplane, with a hull rather resembling a flying boat, and with some features taken from the P.29 Sidestrand. It used the same locked joint construction system as the P.29 Sidestrand, and also shared a number of components with the earlier aircraft. It was powered by three engines, one mounted above the centre of the upper wing and the other two mounted above the lower wing, just inside the inner wing struts. The tail had two vertical surfaces. The P.32 had two sets of main wheels, giving it four wheels in a row, and a single tail wheel. The wings had the standard Boulton & Paul square shape. They could be folded to give the aircraft a width of 47ft 6in for storage and to get into hangers. The upper wing was straight, the lower wing had anhedral.
Work on the P.32 progressed slowly. Originally Boulton & Paul quoted a price of £33,000 for the single prototype, which was to be delivered on 31 March 1929. The first mock-up conference was held on 8 August 1928, by which time delivery had been pushed back to January 1930. Development was then slowed up by problems with the Bristol Mercury engines, and by changes requested by the Air Ministry. The last design conference was held on 26 November 1930, well after the first two delivery deadlines, at which time the aircraft was expected to be ready by February 1931.
In its eventual form the P.32 (J9950) could carry a crew of five, with space for a sixth man who could serve as a co-pilot or instructor. The pilot's cockpit was ahead of the wings on the port side of the fuselage, with the second pilot just behind. The nose gunner/ bomb-aimer/ navigator had a large cockpit, with a Scarff ring for a Lewis gun, bomb sight in the lower front and chart table and navigation equipment at the rear. In order to allow him to use both sets of equipment he was given a swivel chair.
A series of internal walkways ran along the entire length of the aircraft. They started at a door in the nose cockpit, which led to a walkway that ran past the pilot, on the starboard side of the fuselage, to reach the wireless and camera compartment. The second walkway began at the back of this compartment, and ran past the fuel tanks in the wings (and over the bomb bay), passed the dorsal gunner's position and ended at the rear gunner's position, behind the twin rudders. One crew member was meant to operate both of these gun positions, and a parachute was provided in each.
The P.32 carried its bombs in a recessed but semi-exposed bomb bay that could take four 520lb or 550lb or six 250lb bombs. Another six 120lb bombs could be carried below the wings. The aircraft could also carry a single 1,000lb bomb.
Boulton & Paul took some time to decide what engine to use, and as a result the P.32 wasn't delivered to Martlesham Heath for its official tests until 1931. The original Bristol Mercury V was delayed, as was the Bristol Jupiter XF that was chosen to replace it. The high position of the third engine also caused problems, making it very hard to service. The prototype ended up with 575hp Jupiter XFBM engines, but production aircraft would have used the Mercury engines.
The prototype finally made its maiden flight on 23 October 1931. Two further flights followed on 26 October, another on 27 October and two more on 30 October. It then went to Martlesham Heath for official trials, by which time official interest in the project had disappeared. The P.32 prototype was displayed at Hendon in 1932, but that was the high point of its career.
Neither the P.32 nor its rival, the rather similar de Havilland D.H.72, were placed into production, and instead the Air Ministry decided to order the lighter Handley Page Heyford, designed in response to Specification B.19/27.
Engine: Three Bristol Jupiter XFBM radial engines
Power: 575hp each
Loaded Weight: 22,700lb
Armament: Three Lewis guns, one each in nose, dorsal and tail positions
Bomb load: Four 520/550lb bombs or six 250lb bombs in bomb bay, six 120lb bombs under wings