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. 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.
In 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 , up to two bombs could be carried in the aircraft's recessed bomb cell in addition to two 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.
Into flight
During 1933, the first Overstrand performed its maiden flight, at which point the type was still known as the Sidestrand Mk IV.
Modifications were made after the aircraft's return on 19 March to refine the design.
Continued flight testing revealed the vibration issues to be present still, but would be largely resolved upon later new-build Overstrands.
At one stage, plans were drawn up for an improved variant of the aircraft to be developed, the principal difference being the adoption of a retractable undercarriage, designated the P.80 "Superstrand"; however, this project was ultimately abandoned due to alternative options involving rival monoplane designs proving to be more attractive in the eyes of military planners.
Operational history
A total of 24 Overstrands would be procured for the RAF, a quantity that facilitated the complete replacement of the older Sidestrands flown by No. 101 Squadron, the only squadron equipped with the type, to commence in January 1935. The type was also briefly adopted by No. 144 Squadron, although it was quickly replaced by the more modern Bristol Blenheim bomber during 1938. The Overstrand proved to be relatively popular with its crews, who often appreciated the attention paid to crew comfort as well as the ability of the newly developed powered turret. The type would perform regular public displays of its capabilities, from mock interceptions to bombing demonstrations, throughout the 1930s; one particularly prominent occasion was during the Silver Jubilee of George V, with the King himself inspecting one such aircraft externally and internally. During 1935, an Overstrand of No. 101 Squadron was awarded to Sassoon Trophy for aerial reconnaissance, having the highest score achieved at that time.
Due to the rapid advances made in bomber technology during the late 1930s, the Overstrand had been effectively rendered obsolete by 1938, the final example of the type being withdrawn from frontline duties during the summer of that same year.
Operators
- Royal Air Force
- No. 101 Squadron
- No. 144 Squadron
- RAF Second line units
- No. 2 Air Observers School
- No. 10 Bombing and Gunnery School
- Balloon Development Unit
- Army Co-operation Development Unit
Accidents and incidents
A number of Overstrands were destroyed or beyond economic repair in accidents, the type had only two fatal accidents.
- 11 January 1937: K4564 of 101 Squadron flew into ground in fog at Swanbourne, Buckinghamshire, three crew killed.
- 22 April 1940: K8173 of 101 Squadron crashed off Chesil Beach, Dorset following an engine fire, three crew killed.