The Boulton Paul P.75 Overstrand was a twin-engine biplane medium bomber designed and produced by the British aircraft manufacturer Boulton Paul. It was the final example of a series of biplane medium bombers that had served in the Royal Air Force since the First World War, starting with the likes of the Vickers Vimy and Handley Page Type O. The Overstrand was also the first aircraft to be fitted with a fully-enclosed power-operated turret. First flown in 1933, the Overstrand was essentially an improved model of the Boulton Paul Sidestrand of the 1920s, thus early references to the type referred to it as the Sidestrand Mk IV instead. It demonstrated a higher maximum speed than its predecessor and was procured for the RAF in limited numbers. As such, the type entered service during the mid 1930s, but became increasingly overshadowed by the new generation of monoplane medium bombers, such as the Vickers Wellington and Armstrong Whitworth Whitley. Nevertheless, the Overstrand remained operational during the early years of the Second World War, albeit only being flown by training units. The few surviving aircraft were withdrawn from service during 1941, having been rendered surplus to requirements. The Overstrand was a development of the Boulton Paul Sidestrand, which had first flown in 1928 and like the Sidestrand, it was named after a village in Norfolk, home also of Boulton Paul's Norwich factory. The earlier Sidestrand had been largely similar to its predecessors of the First World War, featuring open cockpits and hand-operated defensive machine guns. Unlike its predecessors, the Sidestrand could fly at speed of up to 140 mph (230 km/h), which made operating the guns in exposed positions difficult, particularly in the nose. To address this difficulty, the Overstrand was furnished with an alternative nose turret design, which was both enclosed and powered. At the time this was a relatively novel feature, the resulting aircraft being the first in the world to feature a fully-enclosed power-operated turret. The Overstrand's innovative turret was largely developed in-house by Bolton Paul's chief armament designer H. A. Hughes.[4] In terms of its basic design, the turret was a metal-framed cylinder with a domed upper and lower area; Perspex was used as glazing, in which there was a vertical slot for the single Lewis gun, which was covered by a canvas strip with a zip fastener to facilitate movement of the gun itself. Traverse motion of the turret was driven by pneumatic motors, powered by air bottles on board that were pressurised to 200 psi (1,400,000 Pa) using an engine-driven air compressor. The turret could move through a fully 360-degree circle if the gun was raised sufficiently, helping the turret to cover the widest area of any turret system. A geared spindle at the base of the turret was supported by a series of ball bearings. Elevation was achieved manually. n addition to the turret, various other revisions and improvements were also incorporated. It was decided that the cockpit ought to also be fully enclosed within a canopy of anti-glare Perspex, complete with a sliding hood. The airframe was strengthened considerably in many areas, which facilitated an increased bomb capacity of up to 1,500 lb (680 kg), up to two 500 lb (230 kg) bombs could be carried in the aircraft's recessed bomb cell in addition to two 250 lb (110 kg) bombs on external carriers. A new levered main undercarriage, complete with larger wheels, was also fitted, while the tailskid of the Sidestrand was replaced by a tailwheel. The wing design was also revised, a noticeable sweepback was added to the outer sections in order to compensate for the aircraft's heavier nose section. For more details. including operational history, click here.
