G.Swanborough, P.Bowers United States Military Aircraft Since 1909 (Putnam)
Engineering Division XB-1
The Bristol F.2B Fighter, which served the R.F.C. with distinction from April 1917 until the end of World War I, and thereafter remained in service with the Royal Air Force until 1932, was the subject of extensive but less successful design and production development in the U.S. Its adoption for production in the U.S. followed a recommendation in August 1917 by the Bolling Commission, and a sample F.2B arrived in Washington on September 5. Powered by the standard 200 h.p. Hispano-Suiza engine, it was assigned to the Curtiss Aeroplane and Motor Co., which received contracts for 2,000 examples in October and December.
The Curtiss-built Bristols, officially known as U.S.A. O-1s, had 400 h.p. Liberty 12 engines and changes in construction necessary to accommodate the greater power. The first O-1 flew on March 5, 1918, followed by a further batch of 25 with modifications. Further production was cancelled when the re-engined F.2B proved to be over-powered and unsafe, but Curtiss completed and tested one other example - a second British-built specimen imported without an engine and fitted with the 300 h.p. Hispano-Suiza unit. This same engine was also fitted in the first British sample at McCook Field in April 1918, where it was allocated the project number P-30 and became the prototype U.S. B-1. The other British airframe, project number P-37, later flew with the Liberty 8 engine.
At McCook Field, plans were then made to produce four examples each of the O-1 with ply-covered fuselages and the 300 h.p. Wright Hispano and 290 h.p. Liberty 8 respectively. These were to be known as U.S. B-1 and U.S. B-2, while two more examples with each engine and an entirely new plywood fuselage were to be the U.S. B-3 and U.S. B-4 respectively. The original B-1 and B-2 were dropped, whereupon the B-3 and B-4 became the XB-1 and XB-2; the new XB-2 also was eventually abandoned.
The U.S. XB-1 was damaged before its flight test, and was rebuilt with Browning instead of Marlin guns. Redesignated XB-1A, and numbered P-90, it flew on July 3, 1919. With the war over, only small quantities of the aircraft were procured: a production batch of 40 XB-1As, with 300 h.p. Wright Model H engines, was built in 1920-21 by Dayton-Wright. One of these was tested in 1921 with a 350 h.p. Packard 1 A-1237 engine, and another flew with a Curtiss D-12 engine.
TECHNICAL DATA (XB-1A)
MANUFACTURER: U.S. Army Engineering Division, McCook Field, Dayton, Ohio.
TYPE: Fighter.
ACCOMMODATION: Pilot and gunner.
POWER PLANT: One 300 h.p. Wright H. piston vee in-line.
DIMENSIONS: Span, 39 ft. 4 1/2 in. Length, 25 ft. 6 in. Height, 9 ft. 9 1/2 in. Wing area, 406 sq. ft.
WEIGHTS: Empty, 2,201 lb. Gross, 3,679 lb.
PERFORMANCE: Max. speed, 121-5 m.p.h. at sea level. Cruising speed, 107 m.p.h. at 15,000 ft. Initial climb 8-4 min. to 6,500 ft. Service ceiling, 16,750 ft. Endurance, 3-8 hr. at 10,000 ft.
ARMAMENT: Two fixed forward firing and two flexible 0-30-in. guns.
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J.Bruce British Aeroplanes 1914-1918 (Putnam)
Bristol F.2A and F.2B
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The United States of America entered the war on April 6th, 1917, and set about the production of aircraft on a characteristically ambitious scale. The initial “Procurement Program” planned for the immediate acquisition of 7,375 aircraft, and the ultimate aim was the production of no fewer than 20,475 machines in twelve months. A substantial number of these aircraft were of British design. Towards the end of 1917 it was arranged that the Bristol Fighter would be produced by the Curtiss Aeroplane and Motor Corporation, and 2,000 were ordered. Two Bristol-built airframes were sent as samples to the Curtiss works.
The Curtiss-built machines were to have had the 300 h.p. Wright-built Hispano-Suiza engine, but political pressure was brought to bear in favour of the American Liberty 12, which was substituted for the Wright-Hispano. This was done in defiance of the strenuous opposition of the British & Colonial Aeroplane Co., for Captain Barnwell knew that the Liberty was too bulky and too heavy for the aeroplane.
Responsibility for the engineering behind the production of the Liberty-powered Bristol Fighter rested with the U.S. Government until the production programme was well advanced. Even when the Government relinquished that responsibility, the Curtiss company were not allowed to make changes of any magnitude. At an early stage, Curtiss engineers realised that Barnwell was correct in thinking that the installation of the Liberty engine in the Bristol Fighter would not be satisfactory; they therefore began to design a completely new aircraft (the Curtiss CB) to use the Liberty and to perform the same duties as the Bristol.
The installation of the Liberty engine in the Bristol Fighter was clumsy; the radiators were badly placed; and the aeroplane was nose-heavy and thoroughly unpleasant to fly. The first machine was completed in March, 1918, and was delivered to the U.S. Air Service during the following month. Twenty seven were built before production was halted and the remainder of the contract cancelled. Blind to their own blunder in fitting the Liberty to an aeroplane unsuited to the engine, the U.S. Army shifted the blame on to the innocent aircraft and condemned the Bristol Fighter as dangerous.
Another version of the design was, however, ordered in large quantities in America. The Engineering Division of the Bureau of Aircraft Production undertook the fairly extensive re-design of the Bristol Fighter and evolved two designs, both for aircraft which had completely re-designed structures: one version was powered by the 300 h.p. Hispano-Suiza, and was designated USB-1; the other was designed for the 290 h.p. Liberty 8, and was designated USB-2. An optimistic order for 2,000 machines of the USB type was placed.
These aircraft had veneer-covered fuselages of faired contours, and the area of their vertical tail assembly was increased. Many other detail modifications were made, and the equipment of the machines was different from that of the standard British-made Bristol F.2B.
Some standard Bristol Fighter airframes had been sent to America for experimental purposes. One was fitted with a 300 h.p. Hispano-Suiza, and had the McCook Field Project No. P.30; a second had one of the first eight-cylinder Liberty 8 engines of 290 h.p., and the Project No. P.37. The latter Bristol crashed before performance tests were carried out. These two Bristol Fighters have been referred to as the USB-1 and USB-2 respectively, but that is incorrect. In the summer of 1918, the construction of twelve Bristol Fighters was begun at McCook Field. The intention was to build eight machines to the basic Bristol design, four with Hispano-Suiza engines and four with the new and re-designed Liberty 8; and the remaining four were to be structurally similar but with veneer-covered fuselages, two having Hispano-Suizas and two Liberty 8s. Work lagged badly, however, and the construction of the first eight aircraft was finally stopped in September, 1918.
Work was still proceeding on the design of the USB-1 and USB-2, which were re-designated USXB-1 and USXB-2 at about this time. A number of fuselages of slightly different design were tested statically, and construction of two prototypes was begun.
The four Bristol F.2Bs with veneer-covered fuselages were still in hand, but in October, 1918, the construction programme was altered to consist of only two USXB-1s and two USXB-2s. This plan was retained until the Liberty 8 engine was abandoned in 1919, whereupon the USXB-2s were modified to take the 300 h.p. Hispano-Suiza, and all four machines emerged in July, 1919, under the designation Engineering Division XB-1A.
The order for 2,000 aircraft of USB type was cancelled at the time of the Armistice, but during 1920 and 1921 forty XB-1As were built by the Dayton-Wright concern. These production machines had the 330 h.p. Wright H engine, and their all-up weight was about 800 lb greater than that of the original XB-1A. In 1921, one of the production XB-1As was fitted with the 350 h.p. Packard 1A-1237 engine; and another (A.S.64156) was used as a test-bed for the Curtiss D-12.
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