Avro 555 Bison

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Contents

Type Description

• Type 555 Bison
• Three seat two bay biplane to meet Specification DofR Type 7A (later Air Ministry Specification 3/21) for a deck landing sea reconnaissance and fleet gunnery spotting aircraft. 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. A ply clad enclosed cabin with two portholes and a large rectangular window 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 high lift mainplanes, mounted directly on the upper and lower longerons, were built around two spruce spars and fitted with full span ailerons on both upper and lower wings. There was dihedral on both upper and lower wings, which were rigged with 5 in of back stagger and arranged to fold for stowage. The tail had aerodynamically balanced rudder and elevators, but no fixed fin. One 480 h.p. Napier Lion II powerplant, with its radiator mounted above the centre section.
  The second prototype featured the upper mainplane raised above the upper fuselage with no dihedral, plus an enlarged rudder and two auxiliary fins on the underside of the tailplane. The radiator was moved to below the nose.
  The third prototype was similar to the second, but with the wing mounting on the upper longerons as the first.

• Type 555 Bison Mk.I
• As the Type 555 Bison third prototype, but with the cabin portholes eliminated and the rectangular windows enlarged, to meet Air Ministry Specification 3/21 (later 16/23).

• Type 555 Bison Mk.IA
• Mk.I aircraft converted to Mk.II standard to meet the requirements of Air Ministry Specification 24/24.

• Type 555A Bison Mk.II
• As the Type 555 Bison second prototype, with a large dorsal fin replacing the auxiliary fins on the underside of the tailplane. The cabin portholes were eliminated, but the retangular windows remained their original size. Produced to meet the requirements of Air Ministry Specifications as indicated.

• Type 555B Bison Mk.I
  Amphibian
• Mk.I aircraft converted to an amphibian, to meet the requirements of Air Ministry Specification 8/23.

Production Details

Production References

1. Avro Aircraft Since 1908, A.J. Jackson (Putnam, 1990)
2. Fleet Air Arm Aircraft, Units and Ships, 1920 to 1939, Ray Sturtivant with Dick Cronin (Air Britain Publications, 1998)
3. Avro An Aircraft Album, E.A. Harlin and G.A. Jenks (Ian Allen, 1973)