The two-seat H.F.20 was in service with the French and Belgian military in 1913 and was basically a refined "Shorthorn”, with a 59.6kW Gnome rotary engine driving a pusher propeller. With the outbreak of World War I the type was used also by the British air services for scouting and light bombing but achieved only marginal success as a reconnaissance type and then trainer.
By substituting the Gnome for a Le Rhone engine of similar power it was hoped to extend the aircraft's capabilities, but the resulting H.F.21 was obsolete. In a final attempt to rectify the tremendous lack of power the H.F.27 was developed with a 104.3kW or 119kW Canton-Unne engine - as fitted to the equally light but far more successful early Voisin types. The resulting aircraft was sufficiently promising to be deployed on secondary war fronts.
Engine: 1 x Gnome, 59kW Max take-off weight: 660 kg / 1455 lb Empty weight: 360 kg / 794 lb Wingspan: 14.0 m / 45 ft 11 in Length: 8.3 m / 27 ft 3 in Height: 3.2 m / 10 ft 6 in Wing area: 35.0 sq.m / 376.74 sq ft Max. speed: 110 km/h / 68 mph Ceiling: 315 m / 1050 ft Range w/max.fuel: 250 km / 155 miles Armament: 1 machine-guns Crew: 2