Vickers Supermarine ' Walrus ' Amphibian Flying Boat with a Bristol Pegasus engine . Walrus is a single engined ( pusher ) biplane amphibian flying boat constructed almost entirely of metal , stainless and duralumin , the hull is flush riveted and the fabric covered superstructure has spars of stainless steel . It is designed for service with naval cruisers and aircraft carriers for reconnaissance , fleet spotting , photographic and training purposes . A retractable undercarriage , hydraulically operated , provides for landing on an aerodrome or on the sea . In the raised position the wheels are housed in recesses in the bottom main planes . Walrus will be carried by vessels equipped with catapult launching gear . It was the first military aircraft with a retractable undercarriage to be adopted by the Royal Air Force and the first amphibian aircraft to be catapulted with full military load . Slinging gear is provided for hoisting on board on the conclusion of a flight . The pilot and observor have a clear field of view , unrestricted by floats or wings from the forward enclosed cockpit . For stowage purposes the wings can be easily and quickly folded . A production order for the Fleet Air Arm for the Royal Navy has been received . The same type known as ' Seagull ' V , has been supplied to the Royal Australian Air Force . 18 June 1936