Supermarine Walrus

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, and although 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.
Development.
Origins.
The Walrus was initially developed as a private venture in response to a 1929 Royal Australian Air Force (RAAF) requirement for an observation seaplane to be catapult-launched from cruisers and was originally called the Seagull V, although it only resembled the earlier Supermarine Seagull III in general layout. During 1930, the company commenced construction of a prototype; however, as a consequence of divided attention in favour of other commitments, Supermarine did not complete this aircraft until 1933.
The prototype was first flown by "Mutt" Summers on 21 June 1933. Five days later, it made an appearance at the SBAC show at Hendon, where Summers startled the spectators (R. J. Mitchell among them) by looping the aircraft. Such aerobatics were possible because the aircraft had been stressed for catapult launching. On 29 July Supermarine handed the aircraft over to the Marine Aircraft Experimental Establishment at Felixstowe. Over the following months extensive trials took place; including shipborne trials aboard "Repulse" and "Valiant" carried out on behalf of the Royal Australian Navy, as well as catapult trials carried out by the Royal Aircraft Establishment at Farnborough, becoming the first amphibious aircraft in the world to be launched by catapult with a full military load, piloted by Flight Lieutenant Sydney Richard Ubee.
The strength of the aircraft was demonstrated in 1935, when the prototype was attached to the battleship "Nelson" at Portland. With the commander-in-chief of the Home Fleet, Admiral Roger Backhouse on board, the pilot attempted a water touch-down, forgetting that the undercarriage was in the down position. The Walrus was immediately flipped over but the occupants only received minor injuries; the machine was later repaired and returned to service. Soon afterwards, the Walrus became one of the first aircraft to be fitted with an undercarriage position indicator on the instrument panel. Test pilot Alex Henshaw later stated that the Walrus was strong enough to make a wheels-up landing on grass without much damage, but also commented that it was "the noisiest, coldest and most uncomfortable" aircraft he had ever flown.
Production.
The RAAF ordered 24 examples of the Seagull V in 1933, these being delivered from 1935. Production aircraft differed from the prototype and the aircraft flown by the RAF in having Handley-Page slots fitted to the upper wings. The first order for 12 aircraft for the RAF was placed in May 1935; the first production aircraft, serial number "K5772", flying on 16 March 1936. In RAF service the type was named Walrus and initial production aircraft were powered by the Pegasus II M2, while from 1937 the Pegasus VI was fitted. Production aircraft differed in minor details from the prototype; the transition between the upper decking and the aircraft sides was rounded off, the three struts bracing the tailplane were reduced to two, the trailing edges of the lower wing were hinged to fold 90° upwards rather than 180° downwards and the external oil cooler was omitted.
A total of 740 Walruses were built in three major variants: the Seagull V, Walrus I and the Walrus II. The Mark IIs were constructed by Saunders-Roe and the prototype first flew in May 1940. This aircraft had a wooden hull, which was heavier but economised on the use of light metal alloys. Saunders-Roe license-built 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 Walrus and both were used for air-sea rescue 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, air-sea rescue helicopters were taking over the role from small flying-boats. The Walrus was known as the "Shagbat" or sometimes "Steam-pigeon"; the latter name coming from the steam produced by water striking the hot Pegasus engine.
Design.
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 . The single 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. The nacelle contained the oil tank, arranged around the air intake at the front to act as an oil cooler, as well as electrical equipment, and had a number of access panels for maintenance. A supplementary oil cooler was mounted on the starboard side. Fuel was carried in two tanks in the upper wings.
The Walrus' pusher configuration had the advantages of keeping the engine and propeller further out of the way of spray when operating on water and reducing the noise level inside the aircraft. The propeller was safely away from any crew standing on the front deck, when picking up a mooring line. The engine was offset by three degrees to starboard, to counter any tendency of the aircraft to yaw due to unequal forces on the rudder caused by the vortex from the propeller. A solid aluminium tailwheel was enclosed by a small water-rudder, which could be coupled to the main rudder for taxiing or disengaged for takeoff and landing. Although the aircraft typically flew with one pilot, there were positions for two. The main, left-hand position had a fixed seat with the instrument panel in front, while the right-hand seat could be folded away to allow access to the nose-gun position via a crawl-way. An unusual feature was that the control column was not fixed in the usual way but could be inserted in either of two sockets in the floor. It became a habit for only one column to be in use; 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 the navigator and radio operator.
Typical armament configurations for the Walrus consisted of a pair of .303 in (7.7 mm) Vickers K machine guns, one each in the open positions in the nose and rear fuselage. In addition, there were provisions for carrying either 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. 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 Walrus lifting-gear was kept in a compartment in the section of wing directly above the engine. A crewmember would climb onto the top wing and attach this to the crane hook. Landing and recovery was a straightforward procedure in calm waters but could be very difficult if the conditions were rough. The usual procedure was for the parent ship to turn through around 20° just before the aircraft touched down, creating a 'slick' to the lee side of ship on which the Walrus could alight, this being followed by a fast taxi up to the ship before the 'slick' dissipated.
Operational history.
Initial use.
The first Seagull V, "A2-1", was handed over to the Royal Australian Air Force in 1935, with the last, "A2-24" delivered in 1937. The type served aboard , , , and .
Walrus deliveries to the RAF started in 1936 when the first example to be deployed was assigned to the New Zealand Division of the Royal Navy, on – one of the light cruisers that carried one Walrus each. The Royal Navy s carried two Walruses during the early part of the war and Walruses also equipped the and heavy cruisers. Some battleships, such as and carried Walruses, as did the monitor and the seaplane tender .
By the start of the Second World War, the Walrus was in widespread use. Although its principal intended use was gunnery spotting in naval actions, this only occurred twice: Walruses from and were launched in the Battle of Cape Spartivento and a Walrus from was used in the Battle of Cape Matapan. The main task of ship-based aircraft was patrolling for Axis submarines and surface-raiders and by March 1941, Walruses were being deployed with Air to Surface Vessel (ASV) radars to assist in this. During the Norwegian Campaign and the East African Campaign, they also saw very limited use in bombing and strafing shore targets. In August 1940, a Walrus operating from "Hobart" bombed and machine-gunned an Italian headquarters at Zeila in British Somaliland. By 1943, catapult-launched aircraft on cruisers and battleships were being replaced by improved radar. A hangar and catapult occupied a considerable amount of space on a warship. Walruses continued to fly from Royal Navy carriers for air-sea rescue and general communications. The low landing speed of the Walrus meant they could make a carrier landing despite having no flaps or tailhook.
Air-sea rescue.
The Walrus was used for air-sea rescue in the Royal Navy and the Royal Air Force. The specialist RAF Air Sea Rescue Service squadrons flew a variety of aircraft, using Spitfires and Boulton Paul Defiants to patrol for downed aircrew, Avro Ansons to drop supplies and dinghies and Walruses to pick up them up from the water. RAF air-sea rescue squadrons were deployed to cover the waters around the United Kingdom, the Mediterranean Sea and the Bay of Bengal. Over a thousand aircrew were picked up during these operations, with 277 Squadron responsible for 598 rescues.
Experimental use.
In late 1939, a pair of Walruses were used at Lee-on-Solent for trials of ASV (Air to Surface Vessel) radar, the dipole aerials being mounted on the forward interplane struts. In 1940, a Walrus was fitted with a forward-firing Oerlikon 20 mm cannon, intended as a counter-measure against German E-boats. Although the Walrus proved to be a stable gun-platform, the muzzle flash rapidly blinded the pilot and the idea was not taken up.
Other users.
Three Walruses N.18 (L2301), N.19 (L2302) and N.20 (L2303) were to be delivered on 3 March 1939, and used by Irish Air Corps as maritime patrol aircraft during the Irish Emergency during the war. They were scheduled to fly from Southampton to Baldonnel Aerodrome, Ireland. N.19 arrived but N.20 had to be rerouted to Milford Haven and N.18 and its crew of two (LT Higgins and LT Quinlan) were left with no choice but to go down during high seas causing damage to the hull. N.18 ditched near Ballytrent, just south of the former United States Naval Air Station, Wexford. It was decided to tow N.18, with help of the Rosslare Harbour lifeboat and a local fishing boat to the launch slip once used for the Curtiss H-16s during the First World War. It was then loaded on a truck to complete its journey to the Baldonnel Aerodrome where it was repaired. N.18 (also identified as L2301) is currently on display at the Fleet Air Arm Museum in Yeovilton, England and is one of only three surviving aircraft of the type.
A Walrus I was shipped to Arkhangelsk with other supplies brought on the British Convoy PQ 17. After sustaining damage it was repaired and supplied to the 16th air transport detachment. This sole Walrus flew to the end of 1943. After the war, some Walruses continued to see limited military use with the RAF and foreign navies. Eight were operated by Argentina, two flew from the cruiser as late as 1958. Other aircraft were used for training by the French Navy's "Aviation navale".
Civil use.
Walruses also found civil and commercial use. They were briefly used by a whaling company, United Whalers. Operating in the Antarctic, they were launched from the factory ship "Balaena", which had been equipped with a surplus navy aircraft catapult. The aircraft used were slightly modified; they were fitted with electrical sockets to power the electrically heated suits, worn by the crew under their immersion suits. A small, petrol-burning cabin heater was fitted to help keep the crews comfortable during flights that could last over five hours. A Dutch whaling company embarked Walruses, but never flew them. Four aircraft were bought from the RAAF by Amphibious Airways of Rabaul. Licensed to carry up to ten passengers, they were used for charter and air ambulance work, remaining in service until 1954.
Surviving aircraft.
Three examples survive in museums in addition to one that is privately owned.
Wreckage that is thought to be that of the Walrus assigned to the cruiser HMAS "Sydney" was photographed when the wreck of the vessel was rediscovered in 2008.