The Supermarine Walrus is a British single-engine amphibious biplane designed by Supermarine's R. J. Mitchell. Primarily used as a maritime patrol aircraft, it was the first British squadron-service aircraft to incorporate an undercarriage that was fully retractable, enclosed crew accommodation, and a fuselage completely made of metal.
Supermarine originally named the type the Supermarine Seagull V, before changing it to the Walrus. The type first flew in 1933, its design process had begun four years earlier as a private venture. It shared its general arrangement with that of the earlier Supermarine Seagull. Having been designed to serve as a fleet spotter launched by catapult from cruisers or battleships, the aircraft was employed as a maritime patrol aircraft. Early aircraft had a metal hull for greater longevity in tropical conditions, while the later variant, the Supermarine Walrus II, had a wooden hull to conserve the use of light alloys.
The Supermarine Seagull V entered service with the Royal Australian Air Force in 1935. The type was subsequently adopted by the Fleet Air Arm, the Royal Air Force (RAF), the Royal New Zealand Navy, and the Royal New Zealand Air Force. Walruses operated against submarines throughout the Second World War, and were also used by the RAF Search and Rescue Force to recover personnel from the sea. It was intended to replace the Walrus with the more powerful Supermarine Sea Otter, but this did not happen.
Stothert & Pitt of Bath manufactured the ship mounted cranes used for hoisting the seaplanes from the water
After the end of the war the Walrus continued in service, and some aircraft operated in a civil capacity in regions such as Australia and the Antarctic. The Walrus was succeeded in its air-sea rescue role by the first generation of helicopters.
Development The Supermarine Walrus, originally called the Supermarine Seagull V, was initially developed by Supermarine as a private venture in response to a Royal Australian Air Force (RAAF) requirement for an observation seaplane to be catapult-launched from cruisers. Designed by a team led by Supermarine's chief designer, R.J. Mitchell, it resembled Mitchell's earlier Supermarine Seagull III in general layout.
Supermarine began construction of a prototype during 1930, but due to other, more pressing, commitments did not complete it until 1933. The prototype of the Seagull V, known as the Type 228, following modifications to the design, was first flown by "Mutt" Summers on 21 June 1933. Five days later, the aeroplane (now marked N-1) made an appearance at the SBAC show at Hendon, where Summers made an unscheduled loop during the display, startling the spectators (Mitchell included).
On 29 July Supermarine handed the aircraft (re-marked as N-2) over to the Marine Aircraft Experimental Establishment at Felixstowe. Over the following months extensive trials took place; including shipborne trials aboard the HMS Repulse and the HMS Valiant carried out on behalf of the Royal Australian Navy. There were also catapult trials carried out by the Royal Aircraft Establishment at Farnborough, when the Seagull V became the first piloted aircraft in the world to be launched by catapult, piloted by Flight Lieutenant Sydney Richard Ubee.
The strength of the aircraft was demonstrated in October 1935, when a Seagull V carrying the Commander-in-Chief of the Home Fleet, Roger Backhouse, landed in the water in Portland Harbour with its wheels unretracted. The aircraft's hull flooded following the impact of the landing, which caused it to flip over, but Backhouse and the crew managed to escape with minor injuries. An automatic horn and indicator lights were subsequently fitted to ensure the pilot checked the wheels before landing. The machine was later repaired and returned to service. Soon afterwards it 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.
Design Airframe The Type 236 Supermarine Walrus is a single-engine amphibious biplane, principally designed to conduct maritime observation missions. The all-metal hull, an innovation for its day, was constructed from an anodised 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.
Although the aircraft typically flew with one pilot, there were positions for two. The control column was not fixed, but could be inserted in either of two sockets in the floor, so that the column could be passed between the pilots. Behind the cockpit there is a small cabin with work stations for the navigator and radio operator.
Wings The fabric-covered wings are of equal span, with a noticeable sweepback, and have stainless–steel spars and wooden ribs. The lower wings are set in the shoulder position with a stabilising float mounted under each one. The elevators are high on the tail-fin and braced by a pair of struts on either side. The wings can be folded, giving a stowage width a little greater than that of the tailplane.
The Seagull V was the first British military aircraft to be fitted with a retractable undercarriage. A senior technical assistant at Supermarine suggested the idea of completely retracting the wheels into the wings, so as to make the aircraft more streamlined.
Powerplant
The single Bristol Pegasus radial engine is mounted 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 drives a four-bladed wooden pusher propeller. The nacelle contains the oil tank, arranged around an air intake at the front to act as an oil cooler, as well as electrical equipment, and has a number of access panels for maintenance. A supplementary oil cooler is mounted on the starboard side. Fuel is carried in two tanks in the upper wings.
The Seagull's pusher configuration has the advantages of keeping the engine and propeller out of the way of spray when operating on water and of reducing the noise level inside the aircraft; also the propeller was safely away from a crew member standing on the front deck when hooking on a hoisting cable. The engine is 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 is enclosed by a small water-rudder.
Armament The armament 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.
Operation from ships
Prior to the 1930s, aircraft catapults had been installed in any naval ship capable of launching an aircraft; by 1934, 25% of the FAA's aircraft were catapult-launched. 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 crew member 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 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.
Like other flying boats, the Walrus carried marine equipment for use on the water, including an anchor and a boat-hook.
Production
The RAAF ordered 24 Seagull Vs in 1933, to use as spotter-reconnaissance aircraft for the RAN. These were delivered during 1935 and 1936, with most of the aircraft being transported to Point Cook, Victoria, for use by the Seaplane Training Flight RAAF.
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 Walrus II. Of these, 462 aircraft were constructed by Saunders-Roe in Weybridge, Surrey, with fuselages built by Elliotts of Newbury. This variant had a wooden hull, which was heavier but economised on the use of light alloys. Saunders-Roe license-built 270 metal Mark Is and 191 wooden-hulled Mark IIs. The Walrus was called the "Shagbat", the "Steam Pigeon", and other names by its crews.
The successor to the Walrus was the Sea Otter, which was similar in design but more powerful. Sea Otters never completely replaced the Walrus, and both were used for air-sea rescue during the latter part of World War II. A post-war replacement for both aircraft, the 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.
Operational history Initial use The first Seagull V, A2-1, was handed over to the Royal Australian Air Force in 1935, with the last being delivered in 1937. The type served aboard the County-class cruisers and , and the Leander-class cruisers , 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 Leander-class light cruisers that carried one Walrus each. The Royal Navy s carried two Walruses during the Second World War, and Walruses also equipped the and County-class heavy cruisers. Some battleships, such as the Queen Elizabeth-class battleship and the Nelson-class battleship carried Walruses, as did the seaplane tender .
By the start of the war, the Walrus was already in widespread use. Although its principal intended use was gunnery spotting in naval actions, this only occurred twice: Walruses from the battlecruiser (the lead ship of her class) and the Town-class cruiser were launched in the Battle of Cape Spartivento, and a Walrus from the Town-class was used in the Battle of Cape Matapan. The main task of ship-based aircraft was patrolling for Axis submarines and surface-raiders. By March 1941, Walruses were being deployed with ASV radar systems to assist in this. During the Norwegian Campaign and the East African Campaign, Walruses saw limited use in bombing and strafing shore targets. In August 1940, a Walrus operating from HMAS Hobart bombed and machine-gunned the Italian headquarters at Zeila in British Somaliland.
By 1943, catapult-launched aircraft on cruisers and battleships were being replaced by radar, which occupied far less 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.
Other military uses