Supermarine Walrus - Development

Development

The Walrus was initially developed for service from cruisers in response to a request from the Royal Australian Air Force (RAAF), and was originally called the Seagull V; although there was little resemblance to the earlier Supermarine Seagull III. It was designed to be launched from ship-borne catapults, and was the first amphibious aircraft in the world to be launched by catapult with a full military load.

The lower wings of this biplane were set in the shoulder position with a stabilising float mounted under each one, with its horizontal tail-surfaces being positioned high on the tail-fin. The wings could be folded on ship, giving a stowage width of 17 feet 11 inches (5.46 m). The single Bristol Pegasus VI radial engine was housed in a nacelle slung from the centre section of the upper wing and powered a four-blade propeller in pusher configuration. The propeller consisted of two, two-bladed wooden propellers that were bolted onto the same hub, but offset by 90 degrees. The vortex of air created by the propeller created unequal forces on the rudder, making the aircraft yaw. The engine was offset by three degrees to starboard to counter this.

Although the aircraft typically flew with one pilot, there were positions for two. The left-hand position was the main one, with an instrument panel and a fixed seat; while the right-hand, co-pilot's seat could be folded away to allow access to the nose gun-position via a crawl-way. One of the more unusual characteristics of the aircraft was that the control column was not a fixed fitting in the usual way, but could be unplugged from either of two sockets at floor level. It became a habit for only one column to be in use; and when control was passed from the pilot to co-pilot or vice-versa, the control column would simply be unplugged and handed over. Behind the cockpit, there was a small cabin with work stations for a navigator and a radio operator.

As the Walrus was stressed to a level suitable for catapult-launching, rather surprisingly for such an ungainly-looking machine, it could be looped and bunted. This was first done by the test pilot Joseph Summers, flying the prototype at the SBAC show at Hendon in June 1933; this feat surprised even R. J. Mitchell, who was amongst the spectators. However, in practice any water in the bilges would make its presence felt when the aircraft was inverted. This usually discouraged the pilot from any future aerobatics on this type.

In 1934 an early pre-production Walrus became (according to its manufacturer) the first amphibian to be launched from a land-based catapult.

The strength of the aircraft was demonstrated in 1935, when the prototype was attached to the battleship HMS Nelson at Gibraltar. With the naval commander-in-chief on board (Admiral Roger Backhouse) the pilot attempted a water touch-down, but with the undercarriage accidentally lowered. The Walrus was immediately flipped over but the occupants only had minor injuries; the machine was later repaired and returned to flight. Soon afterwards, the Walrus became one of the first aircraft to be fitted with an undercarriage position indicator on the instrument panel.

When flying from a warship, the Walrus would be recovered by touching-down alongside, then lifted from the sea by a ship's crane. The aircraft's lifting-gear was kept in a compartment in the section of wing directly above the engine – one of the Walrus' crew would climb onto the top wing and attach this to the crane hook. This was a straightforward procedure in calm waters, but could be very difficult if the conditions were rough. One procedure was for the parent ship to slew several degrees just before the aircraft touched down, thus creating an evanescent 'smooth' astern of the ship on which the Walrus could alight, this being followed by a fast taxi up to the ship before the 'smooth' dissipated.

Armament usually consisted of two .303 in (7.7 mm) Vickers K machine guns, one in each of the "open" positions in the nose and rear fuselage; with the capability of carrying 760 pounds (340 kg) of bombs or depth charges mounted beneath the lower wings. Like other flying boats, the Walrus carried marine equipment for use on the water, including an anchor, towing and mooring cables, drogues and a boat-hook.

The RAAF ordered 24 examples of what was originally Seagull V directly off the drawing boards which were delivered for service from cruisers from 1935; this was followed by orders from the RAF with the first production Walrus, serial number K5772, flying on 16 March 1936. It was also hoped to capitalise on the aircraft's successful exports to Japan and Spain among others.

A total of 740 Walruses were built in three major variants: the Seagull V, Walrus I, and the Walrus II. The Mark IIs were all constructed by Saunders-Roe and the prototype first flew in May 1940. This aircraft had a wooden hull, which was heavier but had the advantage of using less of the precious wartime stockpiles of light metal alloys. Saunders-Roe would go on to build under license 270 metal Mark Is and 191 wooden-hulled Mark IIs.

The successor to the Walrus was the Supermarine Sea Otter – a similar but more powerful design. Sea Otters never completely replaced the Walruses, and served alongside them in the air-sea rescue role during the latter part of the war. A post-war replacement for both aircraft, the Supermarine Seagull, was cancelled in 1952, with only prototypes being constructed. By that time, helicopters were taking over from small flying-boats in the air-sea rescue role.

The Walrus was affectionately known as the "Shagbat" or sometimes "Steam-pigeon"; the latter name coming from the steam produced by water striking the hot Pegasus engine.