Saunders Roe Company & the Princess Flying Boat

Tuesday 10th February 2015
Saunders Roe Company & the Princess Flying Boat Bob Wealthy – Solent Aeromarine.
The speaker, Bob Wealthy, spent a career in space engineering at what finally became Astrium part of EADS now known as Airbus Industries. During this time he retained a strong interest in aeronautics and in particular the history of aircraft construction in the Solent area. On retirement he formed Solent Aeromarine which specialises in publications and artefacts regarding the history of aircraft construction in the area. His presentation focused on the Saunders Roe company and the Princess Flying boats that were constructed in the late forties and early fifties.
In 1901 Sam Saunders opened a branch of his boat building business in Cowes to take advantage of a location which was a centre for British yachting. He was part of a syndicate that had developed a new method for the construction of plywood hulls known as “Consuta”. It involved the sewing together of plywood sections with copper wire. The process was a great success and gained international acclaim allowing him to form his own business which in 1908 become a private limited company known as S.E. Saunders Ltd and he started operations at his newly acquired Columbine yard on the river Medina.
As a sideline the company started to take interest in aviation building two gondolas for the first naval airships. This was followed by building Sopwith’s Bat Boat in 1912 which was one of the earliest flying boats. At the outbreak of the first world war he opened a number of plants on the Isle of Wight which produced a variety of aircraft for the war effort including the Avro 504 trainer, Short 184 seaplanes, Felixstowe F2A flying boats and Norman Thompson NT2B flying boats. After the war Saunders became more ambitious and hired aircraft designers in order for the company to move forward and undertake complete packages. Out of this four aircraft evolved, the T1 biplane, the Kittiwake, A3 Valkyrie and the A4 Medina. All were wooden hulled in line with the company’s expertise and many test and proving flights were flown but they failed to attract orders mainly because of their disappointing performance in comparison to their competitors. This was due in part to the fact that other designs used lighter weight metal hull and skin materials. Consequently their wooden type of construction was abandoned.
Sam Saunders realised that if the company was to survive a change to metal construction was essential but the cost of reinvestment in new equipment was beyond that which to company could manage to finance as a separate entity. After negotiations with other companies / investors failed to secure the capital needed S.E.Saunders was eventually taken over in 1928 by A.V.Roe and other investors to become what many of us will remember as Saunders-Roe Ltd which continued to trade until 1958 when it was taken over by Westland Aircraft.
During the 1930’s the company expanded apace and operated in ever more areas of boating and aviation producing both military and civilian aircraft, flying boats, speed boats and other craft. Amongst the successes of the marine section were the “Miss England II” in which Sir Henry Seagrave captured the water speed record of 98.76 mph in 1930 killing himself and one other crew member in the process of trying to improve it during further runs. Only the third crew member escaped relatively unharmed. Although the record was raised further in the 1930’s it was recaptured by Sir Malcolm Campbell in 1938 with a speed of 130.9 mph in “Bluebird” which was also built in Cowes by Saunders Roe.
The company was very active in the 30’s producing many aircraft to its own designs and fulfilling subcontracts to build aircraft for other companies including the Blackburn Bluebird IV an all metal two seat biplane. Additionally in 1931 it acquired Spartan Airlines operating the three engined Spartan Cruiser airliner designed by Spartan and built by Saunders Roe. After 1935 the aircraft were flown only by a number of early commercial operators.
With war upon us again in 1939 the company prospered producing aircraft designed by other companies which came with the benefit of a sustained workload whereby 453 Walruses and 290 Sea Otter amphibians were built on behalf of the Supermarine company (of “Spitfire” fame) for the RAF. Large numbers of damaged aircraft were also repaired and 336 Catalina amphibians updated to carry radar. During this time the company also sustained heavy damage to its Solent works during an air raid in 1942.
By the end of WW2 the company had grown enormously and had a widely dispersed collection of factories engaged on a variety work suited to wartime production. In the interest of efficiency it was decided to concentrate aircraft work at Eastleigh and the Isle of Wight. It was at this time that the company was awarded a contract from the Ministry of Supply to design and build three large passenger carrying flying boats type SR45 and later named the “Princess”. BOAC and other civil aircraft operators were involved to help define the operational requirements as it was those companies who were expected to purchase and commercially operate future production. Contract value was £2.8M a sum which would just about cover the cost of a design feasibility study in today’s world.
At the end of WW2 there were many companies in the UK eager to secure peacetime orders for aircraft to sustain a large workforce of talented personal acquired for wartime production so winning the SR45 contract was a considerable success for the company and a vote of confidence in their expertise. The principal design requirements were that it should have a range of 5000 nautical miles, fly at 34500 feet at 360mph carrying 100 plus passengers on transatlantic routes.
Whilst Saunders Roe were at ease with the design and production of the airframe major subcontracts were necessary for such items as engines, propellers, fuel systems, flight controls and instrumentation. Of these, of greatest importance was the engines required to meet the design requirements at a time when the use of jet engine propulsion was in its infancy and deemed too much of a risk. Consequently it was decided to use Bristol Proteus turbines driving contra rotating propellers i.e. turbo-props. On reflection these also represented considerable risk as they were still under development together with a newly designed gear train. Ten of these engines were fitted of which four were mounted in pairs with the other two as singles. The propellers were manufactured by De Havilland and were of hollow steel and 16.5ft in diameter. The table below gives some idea of the size of this aircraft which I’m sure you will appreciate was a mammoth undertaking in the late 40’s when designers never had the advantages of computers for simulation and design tasks to more readily obtain optimum performance of the aerodynamics and associated subsystems. All this in 6 years to flight testing from contract placement. Quite an achievement.

All up weight
330,000 lbs
Max wing loading
65 lb/sq.ft.
Empty weight (less fuel)
190,000 lbs
219.5 ft
Wing area
5019 sq.ft.
148 ft
55.75 ft
Fuel Capacity
14,500 gall (117,450 lbs)
Max landing weight
250,000 lbs
Floor area
1400 sq.ft.
Cabin volume
15,403 cu.ft.
8 lb p.s.i.
Engines (10)
3,350 shp or 3780 ehp (incl. exhaust thrust)
5,000 nmls
105 (on two levels)
Cruising speed
360 mph
Cruising height
34,500 ft
It was interesting to note that passenger accommodation was on two levels with a high level of comfort making the claims of modern aircraft manufacturers in this respect look dated but, of course, at that time a king’s ransom was required to join the mile high club across the Atlantic.
The speaker continued with an outline description of the many test and simulation facilities required to verify the design. Generally they are earlier versions of what can be seen today and very much less complex but still a necessary part of the design process and much of it was situated on the IOW.
The Princess, as it then became known, took its first test flight on 22nd August 1952 taking off across the Solent in perfect weather conditions with a backdrop of the liner “Mauretania” making her way to Southampton docks after an Atlantic crossing. That must have presented all those who turned out for the occasion with a remarkable sight. The roar of 10 Proteus turbines at full power in the days before noise abatement completed the picture. It was airborne for around 35 minutes in a flight around the south coast which was considered to be a great success. No significant problems were reported and it was said to have handled well. In September 1952 and 1953 it made showings at the Farnborough air show.
On 27th May 1954 it made its final flight at the end of the Ministry of Aviation contract after completing a test programme of 47 flights totalling nearly 98hrs. Its performance fell short of the design aims mainly due to the Proteus engines poor reliability in relation to engine and propeller gearboxes together with the fact that the engines supplied delivered only 2500 shp as opposed to the planned 3500shp, a shortfall of around 30%. It is clear that these shortcomings could have been resolved as the proteus power plant survived to serve many varied applications well. However, it was also quite clear that enthusiasm for this type of air transportation was on the wane.
The “Princess” G-ALUN at Cowes
It had been hoped that BOAC would have been a lead purchaser / operator but had earlier closed its maritime flight operations having made a decision to concentrate on land based operations. This was clearly a great blow and sullied any international confidence the “Princess” might have gained.
Eventually due to the lack of any orders all three Princesses were cocooned to prevent corrosion in the hope that buyers could be found. Ideas abounded but only one from the US department of defence led to any meaningful negotiations. They were in their final stages when, upon removing the cocooning, significant corrosion was identified, jeopardising any further hope of a sale. Consequently they were scrapped.
This was, quite obviously, the end of the company’s aspiration as a manufacturer for large maritime based civil aircraft. Having contributed so much to the evolving post war design of future turbine propelled and pressurised large civil aircraft the company had no alternative other than to reorganise to use these skills in other areas if it was to survive. So, in the late 50’s and early 60’s, it undertook a number of new projects including SR53 Rocket propelled Interceptor demonstrator and the Black Arrow satellite launch vehicle which successfully launched the “Prospero” satellite from a launch pad in Woomera, Australia.
Through takeovers and further reorganisations the Saunders Roe Company became a division of the Westland Aircraft Company in 1959 and later became the British Hovercraft Corporation in 1966 making the SRN series of hovercraft on the IOW. The original site in Cowes now houses GKN Aerospace Services, part of the GKN Group.