Avro Bison

The Avro 555 Bison was a British single-engined fleet spotter and reconnaissance aircraft built by Avro to Specification 3/21 for carrier operation. Three prototypes were ordered in October 1921 alongside the competing Blackburn design, and both used a Napier Lion engine. Avro's Bison was a two-bay biplane with a deep slab-sided steel-tube fuselage, an enclosed cabin for the navigator and radio operator and a gunner's cockpit with a Lewis gun on a Scarff ring. The first prototype flew in 1921, and handling problems from the pilot's cockpit disturbing airflow over the upper wing were cured by raising the upper-wing centre section by 2 ft and removing dihedral, flying in this form in April 1923. Twelve Bison I and further orders followed, including 23 Bison II, and the aircraft were retired in 1929.