Avro Bison

The Avro 555 Bison was a British single-engined fleet spotter/reconnaissance aircraft built by Avro. 

Avro Bison
Class Aircraft
Type Reconnaissance
Manufacturer Avro
Production Period 1922 - 1929
Origin United Kingdom - UK (Great Britain)
Country Name Origin Year
United Kingdom - UK (Great Britain) 1921
Country Name Operational Year Retirement Year
United Kingdom - UK (Great Britain) 1922 1929 View
ManufacturerName Production From Production To Quantity
Avro 1922 1929 55 View

The Bison was designed to meet the British Specification 3/21 for a carrier based fleet spotter and reconnaissance aircraft. An order for three prototypes was placed in October 1921, together with three of the competing design from Blackburn Aircraft, the Blackburn Blackburn. Avro's design, the Type 555 Bison, was a two-bay biplane, powered, like the Blackburn, by a Napier Lion engine. The deep slab-sided fuselage was constructed of steel tube, with the pilot sitting in an open cockpit forward of the wings, and the engine cowling sloping steeply down ahead of the pilot. An enclosed cabin with large rectangular windows on each side housed the navigator and radio operator and all their equipment, with sufficient headroom to stand upright, while a cockpit for a gunner armed with a Lewis gun on a Scarff ring was provided in the rear fuselage. The upper wings were mounted directly on the top of the fuselage.

The first prototype flew in 1921, with an order for 12 Bison Is following. The aircraft had handling problems, however, caused by interference of the pilots cockpit with the airflow over the upper wing. This was resolved by revising the wing design of the second prototype, raising the centre section of the upper wing by 2 ft (0.6 m) and removed dihedral from the upper wings, flying in this form in April 1923. Further production orders followed with these modification incorporated as the Bison II, while some Bison Is were modified to a similar standard, sometimes known as the Bison IA. A Bison I was fitted with floats and retractable wheels but tests proved the design was not suitable for seaborne use.


  • Avro 555 Bison : Three prototypes to Air Ministry specification 3/21.
  • Avro 555 Bison I : Twelve Lion II powered production aircraft, survivors re-built as IAs
  • Avro 555 Bison IA : Bison Is modified with a biplane gap and additional dorsal fin.
  • Avro 555A Bison II : Improved variant with biplane gap modification, 23 built.
  • Avro 555B Bison I : One Bison I converted to an amphibian to meet Air Ministry Specification 8/23, not ordered into production. 

Although designed for a naval requirement the first deliveries were to the Royal Air Force in 1922 to replace the Westland Walrus for coastal reconnaissance work with No. 3 Squadron RAF. In April 1923, 3 Squadron was broken up to form a number of Fleet Spotter Flights of the Fleet Air Arm, Naval aircraft served on HMS Argus,HMS Eagle and Furious and on-shore at Gosport, England and Hal Far, Malta. The aircraft were retired in 1929 when they were replaced by the Fairey IIIF.

Role Fleet Spotter/Reconnaissance
Manufacturer Avro
First flight 1921
Introduction 1922
Retired 1929
Status Retired
Primary user Royal Air Force
Number built 55

General characteristics

  • Crew: 4
  • Length: 36 ft (10.97 m)
  • Wingspan: 46 ft (14.02 m)
  • Height: 13 ft 10 in (4.22 m)
  • Wing area: 620 ft (57.60 m)
  • Empty weight: 4,160 lb (1,887 kg)
  • Max takeoff weight: 5,800 lb (2,631 kg)
  • Powerplant: 1 x Napier Lion II, 450 hp (336 kW)


  • Maximum speed: 110 mph (177 km/h)
  • Range: 340 mi (547 km)
  • Service ceiling 14,000 ft (4,265 m)


  • 1 Lewis gun

End notes