The Sopwith B.1 was a failed design for a single seat bomber that appears to be have been produced because of a misunderstanding about what type of aircraft the French wanted, and that performed too poorly to be considered for production.
The B.1 was a two bay biplane, powered by a 200hp Hispano-Suiza engine. The pilot’s cockpit was below the upper wing, with the main fuel tank behind him, and an internal bomb bay behind that. This placed the bomb bay some way behind the centre of gravity, and perhaps in compensation the aircraft had a variable incidence mechanism on the tailplane (also used on the Strutter),.
The B.1 was designed in the spring of 1917 by Sopwith, probably as a possible replacement for the bomber version of the Sopwith 1 ½ Strutter. The prototype made its maiden flight in April 1917 and then underwent some basic trials. The tail mechanism wasn’t effective, and the aircraft was found to be nose heavy when empty and tail heavy when loaded. Controls were good in the air and on the ground, but at full power the torque from the engine required considerable left rudder to keep the aircraft flying straight, making it tiring to fly.
It appears to have been built in the belief that the French wanted a single seat bomber powered by the new 200hp Hispano-Suiza engine. When the prototype arrived in France in early May 1917 it became clear that there had been some sort of misunderstanding and the French had been expecting a two seat reconnaissance aircraft (possibly the Sopwith FR.2 two-seater which only reached the early design stage).
After being rejected by the French, the B.1 was flown from RNAS Dunkerque to No.5 Squadron, RNAS, at Petitie Synthe, for operational tests. It was given a fixed forward firing Lewis gun. On 20 May the B.1 and three DH4s attacked German destroyers off Zeebrugge. On 25 May and 28 May the same force bombed a German airfield at St Denis Westram. After three raids the pilot, Flt Sub Lt Bartlett, reported that the aircraft climbed well, could reach high altitude, but lateral control was heavy and manoeuvring was slow and difficult. As a result it would always be vulnerable to any attack from above and would need a fighter escort. As a result the senior officer at Dunkerque reported that the B.1 wasn’t suitable for production.
In early June the B.1 flew back to Britain, suffering an engine failure on the way and just reached Eastbourne safely. The aircraft was then sent to the Experimental Constructive Depot on the Isle of Grain to be converted into a two seat fleet reconnaissance aircraft with folding wings, radio and flotation gear. The conversion must have been completed by 22 November 1917 when the aircraft was flown again. The conversion was difficult, although the bomb bay did at least provide enough space for the observer’s cockpit. The aircraft was clearly not suitable for the role but it did become the basis of a larger aircraft, the Grain Griffin, of which seven were eventually built.
Despite the obvious failure of the design, a second prototype was built at Sopwith in the summer of 1917. This aircraft was nearly completed by 1 June, so was probably under construction alongside the first prototype. On 6 June a provisional order for 150 Sopwith Hispano bombers was placed, but it was cancelled on 22 June. Work on the second prototype must have slowed down after that, as it was probably not completed until January 1918. It went for official trials in April-May 1918 heading for Farnborough. After that it disappears from view. It had performed slightly worse than the first prototype in the trials.
Engine: Hispano Suiza
Span: 40ft 6in
Length: 27ft 6in
Height: 10ft in
Loaded Weight (trials): 2,945lb
Maximum Speed (trials): 118.5mph at 10,000ft; 97.5mph at 15,000ft
Climb rate (trials): 8min 55sec to 6,500ft; 15min 30sec to 10,000ft