Bristol Beaufighter, part twelve. Inception and early operational history

 

Note: This is our last post until September. See you back then!
The Bristol Beaufighter was a British twin-engined World War 2 heavy-fighter/strike aircraft that was initially conceived as a fighter variant of the Bristol Beaufort.
Its inception dates back to 1938 when the Beaufort was about to undertake its maiden flight, Bristol's chief designer, Leslie Frise and Roy Fadden, his assistant, put forward a design study on the Beaufort to check how much of it could be adapted into an interim fighter, as it was expected during the Munich Crisis, that the Royal Air Force (RAF) would be short of fighters in case of war. 
This idea was well received by the Air Staff because, theoretically, it reduced the time and cost for an entire new fighter, so a few days later Bristol was asked to build four prototypes of the so-called "Beaufort fighter".
Given that some preliminary studies have been carried out by Bristol of a heavy fighter powered by their own Hercules engine, this design, called 'Type 156', employed the Beaufort's wing, tail and landing gear and Bristol's engineers at Filton (where the headquarters of the company were located) managed to refine the design of the Type 156 in only six months to produce the first prototype.
The design differed so much from that of the Beaufort. A new narrower fuselage was added to the Beaufort's components, with a short solid nose housing a single-seat cockpit. A dorsal position for an observer was included aft the cockpit. 
With a serial number of R2052 , the Type 156's prototype made its maiden flight on 17th July 1939 and, although initially it was going to be armed with four 20 mm (.78 in) cannons, those were never installed in the prototype during the first flight. 
Now, further refinement work on the prototype was needed to convert the Beaufighter into an operational combat aircraft and almost a year had to pass before the RAF received its first operational Beaufighter. During that time Bristol refined the design, boosting its performance, which with early Hercules engines was similar to that of the Hawker Hurricane, the most numerous RAF fighter during the early war. 
Given that only Hercules III engines were immediately available, and they gave the Beaufighter the 'Hurricane performance', the Air Ministry issued a specification, F.17/39 which set up the production chain for the Beaufighter and ordered a first batch of 300 aircraft. Given that the engine supply was not certain, agreements were made to foresee another variant powered by the in-line Rolls-Royce Griffon engines, with minimum modifications to the wings being made, as an alternative to the radial Hercules engines.
Four prototypes were built by Bristol, R2052 to R2055, which served for pre-testing purposes, with some handicaps in testing during the summer of 1940 as the Battle of Britain progressed. The second prototype, R2053 was also unarmed, but the third prototype, R2054 had four 20 mm cannons installed with its blast tubes integrated under the forward fuselage, together with armour plate, a bullet-proof windshield and a gun camera. This camera became very distinctive as it produced a bulge on top of the nose.
The first three prototypes were tested by the Aeroplane and Armament Experimental Establishment (A&AEE) in April and June 1940 and, except for some slow speeds, it achieved good test results. 
In order to improve Beaufighter's performance, while the Hercules VI engine became available, was to fir alternative power plants to the fuselage, as previously agreed upon, so the most logical alternate engine was the Rolls-Royce Merlin, the same one that powered both the Hawker Hurricane and the Supermarine Spitfire. 
After making some modifications to the engine nacelles, a new model, which was designated as Beaufighter Mk. II, was made with the Merlin XX engine installed on the 450th Beaufighter of the 1.218 Beaufighters on the Filton production line by mid-1940 and three airframes, R2058, R2061 (this one powered by the Rolls-Royce Exe nacelle engines and nacelle configuration) and R2062, were put aside to serve as testbeds for the Mk. II.
Regarding armament, only the first fifty production Beaus were fitted with just four 20 mm Hispano cannons, but subsequent Mk. Is had six additional .303 in Browning machine guns placed in the wings, two on the port side and four on the starboard. This made the Beaufighter the most heavily armed fighter of the RAF for the whole war. 
Some additional solutions were investigated to improve Beaus' performance, such as fitting twin fins on a single prototype, R2268, in order to improve directional stability, however trials were not satisfactory and no production on this configuration was undertaken.

Sources:
1st Signal Squadron - Aircraft In action 153 - Bristol 'Beaufighter' in Action
2nd Scale Aircraft Modelling - Modellers Datafile 6 - Bristol Beaufighter
3rd https://en.wikipedia.org/wiki/Bristol_Beaufighter