Supermarine Stranraer

The Supermarine Stranraer is a flying boat designed and built by the British Supermarine Aviation Works company at Woolston, Southampton. It was developed during the 1930s on behalf of its principal operator, the Royal Air Force (RAF). It was the RAF's last and fastest biplane flying boat.

Derived from the Supermarine Scapa, the aircraft's design was heavily shaped by Specification R.24/31, issued in 1931. After an initial rejection by the Air Ministry, Supermarine persisted with development as a private venture under the designation Southampton V. During 1933, a contract was placed for a single prototype; it was around this time that the type was named after Stranraer. First flown on 24 July 1934, the Stranraer entered frontline service with the RAF during 1937; most examples of the type were in service by the outbreak of World War II.

The Stranraers typically undertook anti-submarine and convoy escort patrols during the early years of the conflict. During March 1941, the model was withdrawn from frontline service, but continued to be operated in a training capacity until October 1942. In addition to the British-built aeroplanes, the Canadian Vickers company in Montreal, Quebec, also manufactured 40 Stranraers under licence for the Royal Canadian Air Force (RCAF). These Canadian Stranraers served in anti-submarine and coastal defence capacities on both Canada's Atlantic and Pacific coasts, and were in regular service until 1946. Following their withdrawal from military service, many ex-RCAF Stranraers were sold off to fledgling regional airlines, with whom they served in various commercial passenger and freighter operations into the 1950s.

Design and development

Background

thumb|[[Supermarine's works at Woolston, Southampton]]

The Supermarine Stranraer, which was directly derived from the Supermarine Scapa, was the final aircraft in a series of flying boats designed by R. J. Mitchell for the Royal Air Force (RAF). The Stranraer was produced by Supermarine at its works in Woolston, Southampton, with deliveries taking place between 1937 and 1939. Development of the series began during the early 1930s, with Supermarine's design team headed by Mitchell. The project was pursued as a response to the Air Ministry's issuing of Specification R.24/31 in 1931, which called for a general purpose coastal reconnaissance flying boat for the RAF.

This specification demanded a payload greater than that of the Scapa and the ability to maintain level flight on only a single engine, which the Scapa could not do. Supermarine's initial response to the specification was a larger model of the Scapa; the company competed against a bid from Saunders-Roe. The Air Ministry favoured Saunders-Roe's proposal and rejected Supermarine's design. Despite this, Supermarine chose to continue development work on the design as a private venture, which was first known as the Supermarine Southampton V.

Prototypes and production

In 1933 a contract was placed for a single prototype powered by two Bristol Pegasus IIIM engines, and the type was named the Stranraer. On 24 July 1934, the first prototype, K3973, made its maiden flight, piloted by Joseph Summers. Over the following months, a relatively intense initial flight test programme was conducted. On 24 October 1934 it was delivered to the Marine Aircraft Experimental Establishment (MAEE) at RAF Felixstowe for official trials.

On 29 August 1935, soon after the completion of proving flights, an initial order for 17 aircraft (serial numbers K7287 to K7303) was placed by the Air Ministry to fulfil Specification 17/35; six more aircraft (K9676 to K9681) were ordered in May 1936, but this order was subsequently cancelled. The first production standard aircraft made its first flight in December 1936, and entered service operation with the RAF on 16 April 1937. The final Stranraer was delivered on 3 April 1939. In addition, a total of 40 Stranraers were manufactured under licence in Canada by Canadian Vickers Limited, as both Supermarine and Canadian Vickers were subsidiaries of Vickers-Armstrongs.

Description

thumb|A 1935 [[cigarette card depicting the Supermarine Stranraer]]

The Stranraer was a twin-engined biplane flying boat accommodating a crew of 6–7. Its empty weight was , with a maximum take-off weight of .

As the design of the Stranraer progressed, it was changed from that of the Scapa, having a two-bay structure. The Stranraer's weight, and the surface area and span of its wings, were 12 per cent greater; the elevator was also 7 per cent larger, while the rudders featured trim tabs capable of holding the aircraft straight under single-engine flight. The moderately supercharged Bristol Pegasus IIIM radial engine was selected. Much of the airframe was alclad, while detailed fittings were made of stainless steel; metal components were anodised as an anti-corrosion measure.

For additional strength, a second pair of interplane struts were added. The hull was considerably larger, its cross-section being increased by 18 per cent, yet it had identical hydrodynamic performance. The forward gun was redesigned to be retractable, the middle gunner's position was lowered, and a tail gunner position was added just aft of the control surfaces, completed with a hooded windshield. In general, the equipment of which the aircraft was to be fitted with were the result of lessons learnt from operations of the earlier Southamptons. The production model of the Stranraer differed in a few ways from the first prototype, chiefly of which was the use of the more powerful Pegasus X engine. The engines were placed in nacelles under the upper wing, so that the propellers were well clear of any sea spray. This aircraft was built in 1940, one of 40 produced by Canadian Vickers. In service with the RCAF, it flew with several squadrons, on anti-submarine patrols, as a training aircraft and carrying passengers. In 1944, it was disposed of. It was flown by the civilian airline Canadian Pacific Airlines until 1947, then by Queen Charlotte Airlines, who replaced its original engines with American Wright R-1820 Cyclone engines. Queen Charlotte Airlines flew the aircraft on passenger flights until 1952, flying from Vancouver along the Pacific coast of British Columbia. It flew with several other private owners until it was damaged by a ship in 1966. In 1970, it was bought by the RAF Museum and transported to the UK.

Parts of a second Stranraer, 915/CF-BYJ, are owned by the Shearwater Aviation Museum, Halifax, Canada. This aircraft also operated with Queen Charlotte Airlines until it crashed on Christmas Eve 1949 at Belize Inlet, British Columbia. Initial parts of the aircraft were recovered in the 1980s, with additional wreckage transported to the museum in November 2008 for eventual restoration, excluding the forward fuselage and cockpit. As of 2025, the parts remain in storage at the museum awaiting restoration.