Saturday, 25 March 2017

R.J. Mitchell's Sea Eagle Fleet.

In 1922, the Air Ministry gave approval for an air service between Southampton, Cherbourg and Le Havre. The route, with a subsequent extension to the Channel Isles, was to be operated by an air service named the British Marine Air Navigation Company and Hubert Scott-Paine and James Bird of Supermarine were to be its directors.
The aircraft which Mitchell was to design for this service was to be powered by the Rolls-Royce Eagle IX engine, hence the chosen name – “Sea Eagle”. Despite the somewhat aspirational name, Mitchell went back to the more boat-like hull shape of the larger Channel and Commercial Amphibian designs and, in fact, the fore section of the Sea Eagle resembled a cabin cruiser of the time, with its high, pointed prow, enclosed accommodation for passengers, large windows and grab-rails running the length of the passenger compartment above the cabin and along the top of the hull. As the two planing steps were also joined by a continuous hard chine which ran three-quarters of the hull length, it embodied more than any other Mitchell design the original Pemberton Billing concept of ‘boats which fly’.
    Presumably because of a need to consider local hangarage for the aircraft, wing folding was again adopted. It would seem that width rather than length was the important consideration because a forward folding arrangement was again adopted, which also had the structural advantage of folding at the main spar, although this arrangement necessitated a cut-out in the leading edge of the wings, which did nothing for aerodynamic efficiency.
    Mitchell continued the practice of gravity feed for the engine of this latest flying boat with apparently little qualms about stability problems, for the fuel tank (and subsequently a second tank) was now attached to the top of the centre section. On 28 June, a Flight correspondent wrote that that ‘this machine represents a great step forward in the development of the seaworthy [commercial] amphibian’ having appreciated the ‘most important innovation’ that, in place of the usual tank in the hull, ‘the main petrol tank has been mounted on top of the top plane, so that direct gravity feed, with its attendant simplicity and freedom from breakdown, can be used’. The writer also added, ‘the fact that the engine is mounted high above and some distance aft of the cabin has resulted in reducing the noise audible in the cabin to a minimum, and as a matter of fact, in the “Sea Eagle” it is possible for the passengers to converse in ordinary tone of voice, without having to shout to one another’.
One departure from all previous (and future) practice was the use of a pronounced stagger of the two wings, as the weight of the forward passenger cabin and its six passengers necessitated bringing the centre of lift of the top wing well forward of the engine. (One suspects that Mitchell’s usual preference was for the simplicity of directly opposed biplane wings.)

Sea Eagle at Woolston
The first of the completed Sea Eagles had made its maiden flight in June 1923, and received its Certificate of Airworthiness on 11 July. Two days later, Supermarine entered the new aircraft in the King’s Cup Air Race that had been initiated by the Air Ministry the year before, also to encourage aviation development. As it was a handicapped event, the entry of a commercial flying boat might not seem too strange but the carrying of four passengers must have had much to do with the Company being mindful of publicity generated by air races. Unfortunately, circumstances involving a burst tyre and its replacement led to the aircraft being disqualified.
   On the 5th of the next month, the Director of Civil Aviation at the Air Ministry, Sir Sefton Brancker, came to Southampton and was given a display of the machine’s ability to negotiate the (usually) crowded seaway as well as a demonstration flight. He announced himself to be well satisfied with the Sea Eagle’s potential contribution to the development of civil aviation, both in terms of performance and comfort and, along with other senior members of his department, had another flight nine days later.
   Particular comment was made on the very sensible placing of the passengers and, in the following publicity, the Company makes reference to the advantages of this arrangement:
The passengers are accommodated in a roomy cabin in the fore part of the hull. This cabin is very comfortably fitted out. Its position in front of the engine makes it very quiet and free from engine exhaust, gases, oil, etc. . . It is very efficiently heated and ventilated, and is fitted with sliding triplex windows along the two sides for use in the warm weather.
One passenger recorded descending into the Sea Eagle and finding ‘a delightful little room’ that the Company had fitted with ‘reposeful armchairs’.

Regular daily services between Southampton and Guernsey began on 25 September, 1923, so constituting the very first British scheduled flying boat service; it was advertised to leave Woolston at 11.15 a.m. and return from St Peter Port at 3.30 p.m. (The French section of the service did not materialise.) The service, often with breaks due to bad weather, continued with the Sea Eagles for the next five years, even though the single fare to the Channel Isles was not cheap. Compared with boat transport, however, the normal flight time of one and a half hours was very attractive although, in adverse wind conditions, it might be almost an hour more.
   Nearly four years later, the fleet of three Sea Eagles was down to one: G-EBFK having crashed on May 21, 1924 (reportedly due to a bird strike) and G-EBGS was rammed and sunk when moored at St Peter Port on the 10th of January, 1927 – a reward of £10 for the identity of the culprit was never claimed.
In the event, Mitchell’s machines had not only operated the first scheduled flying boat service in Britain but they also had the distinction of forming part of the basic fleet of the organisation which eventually became British Airways – on 31 March, 1924, Imperial Airways Ltd was incorporated as the 'chosen instrument' of the British Government for developing national commercial air transport on an economic basis and the British Marine Air Navigation Co. was one of four companies taken over for this purpose. The two Sea Eagles which were remaining by that time now had their fuselages painted with prominent ‘Imperial Airways’ lettering and they continued their accustomed service to the Channel Isles under the control of the new national company from May 1, 1924.
The last of the three Sea Eagles, G-EBGR, was finally retired in 1928, thus justifying Supermarine’s claims that this type was ‘very strongly built and very seaworthy’. A photograph from a correspondent to The Aeroplane showed a Sea Eagle hull at Heston Airport in 1954. It had been presented to BOAC in September 1949 and intended for restoration and display at the new London Airport; but nothing came of this proposal and this piece of industrial archaeology was burnt on 13 February, 1954.


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For reference sources, see my Blog: “Source Material and References. " An extended bibliography is included in my R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire (details below) which also provides material for wider reading, grouped according to specific areas of interest. 

More information, photographs and three-view drawings of the Sea Eagle, as well as a full account of all Mitchell's completed designs and of the man behind them, will be available in a few weeks' time:
Advance Notice:  
R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire.
This is a much expanded, completely up-to-date, second edition of my earlier work with 50% more photos, and 25% more text – 380 pp. instead of 250. There are general arrangement drawings of Mitchell’s 21 main aircraft types which flew, as well as 40 other drawings. There are 24 photographs, featuring or including Mitchell, as befits the first fully detailed and, I hope,  definitive account of the man and his work at Supermarine.
To obtain a copy at pre-publication prices, please enquire via the contact form in the sidebar. 




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