Evolved at Farnborough during 1915 as a marriage of the B.E.2c airframe with the then-new R.A.F.4 air-cooled 12-cylinder Vee-type engine of 140hp, the B.E.12 prototype began test flying at the end of July that year. Although flown from the start as a single-seater, it was at first unarmed and was intended for such roles as bombing and photography rather than as a fighter.
The prototype was tested in France in September 1915 and its generally satisfactory performance encouraged the War Office to order production of the B.E.12 in that same month. Delivered from March 1916 onwards, production aircraft had the R.A.F.4a engine (with increased stroke), twin upright exhaust stacks, an auxiliary gravity fuel tank under the port upper wing and, after the first few, an enlarged rudder with curved leading edge. At first serving with RFC squadrons in France for general duties, the B.E.12 was fitted with a 7.7mm Lewis machine gun on an oblique mounting on the fuselage side, or over the wing centre section, but several other experimental installations were tried at Farnborough before the decision to adopt the newly-available Vickers-Challenger interrupter gear, using a Vickers gun firing through the propeller disc. Difficulties with the gear, combined with the excessive stability of the B.E.12 (to overcome which the B.E.2e-type tailplane and elevators were used on some B.E.12s), made the type ineffectual as a fighter, however, and it was soon withdrawn from France, having served with only two squadrons. B.E.12s remained in service with Home Defence squadrons through 1917, many alternative armament installations being tried, including a quartet of Lewis guns, and sets of Le Prieur rockets on the interplane struts. One Zeppelin was shot down by a B.E.12, in June 1917. At Farnborough, one was tested with a Davis six-pounder recoilless gun, firing upwards at 45° for anti-Zeppelin use, but this was not adopted for production. Contracts were placed with two companies for B.E.12 production, Daimler building 200 and Standard Motor Co, 50, against the original orders placed in 1915, and Daimler receiving a contract for 200 more in August 1917. Many of the latter, however, were completed as B.E.12b's.
With the B.E.12 established in production in 1916, based on the B.E.2c airframe with its equi-span two-bay wing and massive horizontal tail surfaces, a further marriage was arranged to combine the R. A.F.4a engine with the newer B.E.2e airframe. This introduced the single-bay cellule with overhanging upper wing and a smaller tailplane/elevator combination, together with the larger, rounded fin of the B.E.12. Designated B.E.12a in this form, the type was ordered from Coventry Ordnance Works and Daimler, each of which received contracts for 50 during 1916 (some of the Daimler batch being completed as B.E.12s). The B.E.12a's served briefly with Home Defence units and more extensively in Palestine, with the Australian-manned No 67 Squadron.
In an attempt to improve the performance of the B.E.12, primarily for the benefit of Home Defence squadrons, a 200hp Hispano-Suiza water-cooled eight-cylinder Veetype engine was substituted for the 150hp R.A.F.4a. The first such installation was completed in September 1917 by the Southern Aircraft Repair Depot at Farnborough and demonstrated a dramatic improvement in speed and climb performance. Consequently, it was decided that 150 of the 200 B.E.12s ordered from Daimler in August 1917 should be completed with the Hispano engines as B.E.12b's. Airframes built by Daimler were fitted with these engines at the Northern Aircraft Repair Depot at Aston, near Sheffield, and deliveries began late in 1917. As Zeppelin raids on the UK had by this time virtually come to an end, many B.E.12b's went straight into store, their urgently-needed engines being removed for use in other aircraft types, such as the S.E.5a. It is believed that production of B.E.12b's ended some 12-20 short of the intended total. The standard armament of the B.E.12b comprised a 7.7mm Lewis gun above the centre section, firing over the propeller disc. Dimensions similar to those of the B.E.12.
Engine: 1 x 150-h.p. R.A.F.4a
Wingspan: 11.3 m / 37 ft 1 in
Length: 8.31 m / 27 ft 3 in
Height: 3.39 m / 11 ft 1 in
Wing area: 34.47 sq.m / 371.03 sq ft
Max take-off weight: 1067 kg / 2352 lb
Empty weight: 742 kg / 1636 lb
Max. speed: 164 km/h / 102 mph
Ceiling: 3810 m / 12500 ft
Engine: 1 x 150-h.p. R.A.F.4a
Wingspan: 12.19 m / 40 ft 0 in
Length: 8.30 m / 27 ft 3 in
Height: 3.66 m / 12 ft 0 in
Wing area: 33.44 sq.m / 359.94 sq ft
Max take-off: weight: 1056 kg / 2328 lb
Empty weight: 730 kg / 1609 lb
Max. speed: 169 km/h / 105 mph
Engine: 1 x 200-h.p. Hispano-Suiza
Span: 37ft 0in
Royal Aircraft Factory B.E.12a