The design was a development of the earlier Vickers F.B.12 prototypes;[2] and was a two-bay biplane with a high-mounted nacelle for the pilot and an initial armament of two .303 in (7.7 mm) Lewis Guns.

After modifications to the radiator layout and wing structure and re-armed with three Lewis guns in an Eeman mounting capable of firing up at a 45° angle to engage enemy bombers from below, being numbered B1484, the FB.26 was passed to the Aeroplane and Armament Experimental Establishment at Martlesham Heath for evaluation.

The prototype was destroyed on 25 August 1917 when Harold Barnwell, the Vickers test pilot failed to recover from a spin.

Service evaluation was unfavorable: although performance was satisfactory, its handling qualities were poor.

[3] A third aircraft, B1485, powered by a 230 hp (170 kW) Bentley rotary engine and modified for ground-attack was built in 1918 but by the time it was built the Sopwith Salamander had already been ordered for production and development was abandoned.