The F.B.19 was designed by G. H. Challenger, and first flew in August 1916. It was a single-engine, single-bay, equal-span biplane, slightly smaller than either the Sopwith Camel or Nieuport 17, with a proportionally large engine fairing and tall fuselage giving it a relatively stubby appearance. It was armed with one synchronised 7.7mm Vickers machine gun, mounted unusually on the left-hand side of the fuselage, and fitted with the Vickers-Challenger synchroniser gear, also designed by Challenger.