The Supermarine Walrus (originally known as the Supermarine Seagull V) was a British single-engine amphibious biplane reconnaissance aircraft designed by R. J. Mitchell and manufactured by the British aircraft company Supermarine. The Walrus made its maiden flight in 1933, the design effort having commenced as a private venture four years earlier. It shared its general configuration with that of the earlier Supermarine Seagull. Having been designed to serve as a fleet spotter for catapult launching from cruisers or battleships, the aircraft was largely employed in other roles, notably as a maritime patrol aircraft and as a rescue aircraft for ditched aircrew. The Walrus featured numerous innovations for the period, being the first British squadron-service aircraft to incorporate in one airframe a fully retractable main undercarriage, completely enclosed crew accommodation and an all-metal fuselage. Early-build aircraft featured the original metal hull design for its greater longevity in tropical conditions, while later-build examples instead used a wooden counterpart to conserve the use of light metal alloys. The first examples of the Seagull entered service with the Royal Australian Air Force (RAAF) in 1935. The type was subsequently adopted in quantity by the Fleet Air Arm (FAA), Royal Air Force (RAF), Royal New Zealand Navy (RNZN) and Royal New Zealand Air Force (RNZAF). Hundreds of Walruses were in operational service throughout the Second World War, where it was prolifically operated against Axis submarines. It was also adopted by the RAF Search and Rescue Force for recovering downed personnel. An intended replacement, the Supermarine Sea Otter, which possessed considerably more power, was introduced during the conflict but never fully displaced the Walrus. The Walrus continued to serve in a limited capacity with several militaries around the world during the postwar era, while some aircraft were also operated in a civil capacity in regions such as Australia and the Antarctic. It was largely succeeded by the first generation of rescue helicopters. The Supermarine Walrus was a single-engine amphibious biplane principally designed to conduct the maritime observation mission. The single-step hull was constructed from aluminium alloy, with stainless-steel forgings for the catapult spools and mountings. Metal construction was used because experience had shown that wooden structures deteriorated rapidly under tropical conditions. The fabric-covered wings were slightly swept back and had stainless–steel spars and wooden ribs. The lower wings were set in the shoulder position with a stabilising float mounted under each. The elevators were high on the tail-fin and braced on either side by 'N' struts. The wings could be folded, giving a stowage width of 17 ft 6 in (5.33 m). The single 620 hp (460 kW) Pegasus II M2 radial engine was housed at the rear of a nacelle mounted on four struts above the lower wing and braced by four shorter struts to the centre-section of the upper wing. This powered a four-bladed wooden pusher propeller. For more information on the development, design, operational history, civil use, and variants, click here.