Scouting Experimental 5a; British fighter aircraft of World War I. One of the great combat machines of the war it was agile, robust, and easy to fly, though the first models suffered from an unreliable Hispano-Suiza engine.
It was developed by the Royal Aircraft Factory as a single-seat fighting scout biplane and was the best aircraft that factory ever produced. Later models had the 200 hp Wolseley Viper engine, giving them a top speed of 190 kph/120 mph and a range of 480 km/300 mi. Armed with a synchronized Vickers machine gun firing through the propeller and a Lewis machine gun mounted on the top wing, it could also carry four 25 lb bombs. About 5,000 were built in Britain for the Royal Flying Corps and US Army, and the US company Curtis were starting on a contract for 1,000 when the war ended.