Sopwith 3F.2 Hippo

Built as a private venture, the Hippo two-seat fighter featured negative wing stagger, the gap between the wings being completely filled by the deep fuselage, and the first of two prototypes was flown on 13 September 1917. A two-bay biplane powered by a 200hp Clerget llEb 11-cylinder rotary, the Hippo had an armament of two fixed synchronised 7.7mm and (initially) two free-mounted guns of similar calibre, or (later) one 7.7mm gun on a Scarff mount in the rear cockpit. Official trials were performed at Martlesham Heath in January 1918, these having been delayed by engine problems. The performance of the Hippo was considered inferior to that of the Bristol F.2B and lateral control was criticised, and, on 2 February 1918, the aircraft was returned to Sopwith. Despite official rejection, the manufacturer fitted new wings, plain ailerons and an enlarged fin. Wing dihedral was increased and stagger was reduced, and with these modifications the Hippo re-emerged in April 1918, with a second prototype following in June. By that time, the F.2B was giving satisfaction in service and it became apparent to Sopwith that the Hippo was too late, further development being discontinued.