Saunders-Roe (Saro) was formed in July 1929, continuing the aviation business of S. E. Saunders Ltd, which was already established at Cowes. They occupied premises at West Cowes on the banks of the River Medina. Along with Samuel White, they were the major employers in the town. During the First World War a large number of seaplanes and flying boats, such as Felixstowe F2s and F5s, had been built under subcontract for the RNAS. During the 1920s the company produced two flying boat designs of its own. First was the large, wooden-hulled Saunders A3 Valkyrie powered by three Rolls-Royce Condor engines and having a wing span of 97 feet. A prototype was ordered by the Air Ministry and flown in the spring of 1926, but trials showed the weakness of using a wooden hull. The smaller A4 Medina biplane was intended for civilian use, but again trials showed the disadvantage of wooden hulls, which Saunders had traditionally used in their boat-building business.
The formation of Saunders-Roe saw further finance introduced, which was used for the development of metal-hulled flying boats. First was the three-engined A7 Severn reconnaissance flying boat (N240) which was flown in July 1930 but, after lengthy trials, proved to be a one-off. Alongside this military development, there was a line of smaller, civilian boats, commencing with the Cutty Sark. These had Alclad metal hulls, although still retained traditional wooden wings and tail. The Cutty Sark had accommodation for three passengers who had the benefit of large cabin windows. Flown in the summer of 1929 it was followed by the larger Cloud, which was initially known as the Flying Cloud. Accommodation was for six to eight passengers and sixteen were purchased by the RAF in 1932 as navigation and pilot trainers. Both of these flying boats could be fitted with a variety of in-line or radial engines, and were also offered as amphibians. The RAF was still looking for additional general-purpose flying boats and in 1933 the Air Ministry ordered the prototype Saro A27 London K3560. The twin-engine London met the need for a sturdy flying boat where speed was not the main requirement. First flown in January 1934, successful trials resulted in an initial order for ten, which were built in the large new works at East Cowes – the Columbine Works. Entering service in the spring of 1936, further London orders saw construction continuing until the spring of 1938. They remained in RAF service until April 1941.
Saro produced a long-range patrol flying boat to the same RAF requirement as the Short Sunderland. Development of the four-engined A33 was slow with prototype K4773 not flying until October 1938. At the end of the month it was badly damaged when it bounced during a high-speed taxi test and was never repaired. By then the ‘rival’ Sunderland had already entered service. The RAF had also been looking for a smaller general purpose boat and Saro produced the twin-engine S36 Lerwick. With war looming, a prototype was dispensed with and the Lerwick went straight into production with an initial order for twenty-one. L7248 first flew in November 1938 but showed a number of aerodynamic problems. Modifications to following aircraft did not improve matters very much and so no further orders were placed. The Lerwick entered limited RAF service in the autumn of 1939, but still proved troublesome and was disliked by its crews. Saro’s publicity described it as ‘the RAF’s fastest flying boat’ and as late as the spring of 1941 it was still being described as ‘doing excellent work as a long range flying boat’. In fact it was about to be taken out of front-line service. As only a small number were produced, there was a suggestion that Saro should build Sunderlands at Cowes in order to keep up with the RAF’s demand for reconnaissance boats. This did not happen and Saro spent the wartime years in assisting Supermarine by producing Walrus and Sea Otter amphibians on their behalf. This work continued until the summer of 1946.
Towards the end of the Second World War Saro produced the radical design of a waterborne jet fighter – the SR A1. Intended to serve in the Far East, where there were few runways, three prototypes were ordered in the spring of 1944. Construction delays meant that the first – TG263 – did not fly until July 1947, by which time the need for such a fighter had disappeared. During flight trials two of the prototypes were lost in crashes. At the other end of the scale, Saro also worked on the design of a large civil flying boat for luxury transatlantic travel. BOAC showed an initial interest and three SR45s were ordered by the Ministry of Supply in May 1946, later receiving the name Princess. The boats were intended to carry 105 passengers in luxury at 370 knots, with Saro planning an initial batch of twelve with construction undertaken in the Columbine works. Problems over finding the definitive engine for the Princess delayed progress, before ten Bristol Proteus boats were finally selected. The first Princess would fly with the underpowered Proteus 2s, but the next two would have improved Proteus 3s. By the summer of 1948 BOAC had lost interest but, backed by the Government, construction continued as BSAA were now showing interest. When BSAA was absorbed into BOAC, interest disappeared again. Although the first aircraft was almost complete by the autumn of 1951, continued delays with the engines meant that G-ALUN did not fly until the following August, with work continuing on the other two aircraft. By that time Saro’s adverts were showing the Princess in RAF markings as no airlines were interested. It was also admitted that costs of the project had reached £10,800,000 – a very large sum in those days. In November 1953 the Prime Minister said that a use must be found for the aircraft. Bristol Engines said that it would be possible to use six Proteus engines, not ten, or maybe their new Orion under development. BOAC said that with the prospect of more powerful Proteus engines they would reconsider using the Princesses. In any event it would still be some years before the airliners could be ready for commercial service – at least 1958. G-ALUN completed its flight-test programme, during which time it was frequently seen flying over the Solent and South Coast. The second two aircraft (G-ALUO/UP) were never flown, being cocooned by February 1953 and stored at the former RAF base at Calshot. G-ALUN continued flying until May 1954 when it too was cocooned and stored at West Cowes awaiting the availability of more powerful engines. Bristol still had problems with the newer Proteus engines and interest in re-engining the Princesses passed. During the late 1950s various plans were put forward for use of the Princesses, including nuclear propulsion, but none came to fruition. The three Princesses were put up for auction in June 1961, but there were no takers. They then lay neglected until being scrapped in 1967.
In late 1948 the RAF issued a requirement for a maritime reconnaissance flying boat to replace the outdated Sunderland. Saro came up with the P162 powered by six Ghost jet engines, continuing design work until 1955 when the RAF finally decided that it would give up operating flying boats. At the beginning of 1950 Saro also started working on a civilian version – the Duchess – which would carry seventy-four passengers at 500 mph. But the age of the flying boat had passed and Saro moved into diverse aviation projects such as helicopters, space rockets and hovercraft.
Saro undertook the overhaul of former BOAC Sandringham G-AKCO following its sale to Australia. It arrived from storage at Poole in the summer of 1954, departing for Sydney in November.