The Grumman FF "Fifi" (company designation G-5) is an American biplane fighter aircraft operated by the United States Navy during the 1930s.

[4] The prototype XFF-1 (serial number A8878) was built to a contract placed on 22 April 1931, first flying on 29 December of that year,[2][5][6] a two-seat design, with an enclosed cockpit, fuselage of all-metal construction, and wings covered largely with fabric.

The XFF-1 was powered initially by a 616 hp (459 kW) Wright R-1820-E Cyclone radial engine, it achieved 195 mph (314 km/h) during service trials.

Later the original engine was exchanged for a 750 hp (560 kW) Wright R-1820-F Cyclone and the XFF-1 reached a top speed of 201 mph (323 km/h), faster than any US Navy fighter in service at the time.

[9] The Canadian Car and Foundry Co acquired a manufacturing license for the G-23, an improved FF-1, of which it completed a total of 52, some of which were assembled from US-built components.

[3] Referred to as the GE-23 Delfin (en:'Dolphin') by the Spanish Republican Air Force, the aircraft fought in the conflict, but were outclassed by opposing fighters and losses were high.

[1] Although initially rejected as a fighter by the Royal Canadian Air Force as outdated and too slow, with the advent of war, the last 15 of the CC&F production batch were taken on strength as Goblin Is.

In 1966, Grumman restored the aircraft before passing it to the US Navy where it remains as one of the displays at the Naval Aviation Museum at Pensacola, Florida.