Cozens has left the following recollections of the Sea Eagle service:
The land planes flying from Croydon to the Continent carried wireless transmitters and receivers and had the benefit of a simple direction finding service, by which stations at Pulham in Norfolk and Lympne in Kent and Croydon could take bearings on an aircraft when its generator was running. Then Pulham and Lympne passed their bearings to Croydon, who would plot them, together with its own bearing, and so reach a ‘fix’ which would be passed to the aircraft pilot. The Sea Eagles carried the same equipment but they could not use it for direction finding purposes because they operated outside the sector where the system could be applied, but they could speak to their bases at Woolston and Guernsey.
I lived a mile from the Supermarine works and could hear an engine start, in those days a rare sound and quite distinctive from the riveters at Thornycroft or the rumble from the coaling wharf in the docks. These were the main sources of ‘noise pollution’ at that time. From the front gate I could watch the machine fly across the Dock Head and then go indoors and pick up the headphones of my crystal set. Soon I would hear ‘leaving the coast at Beaulieu’, and ‘passing the Needles’, and about 90 minutes later and hoping the cat’s whisker [fine wire detector] had not moved I would hear ‘passing the French coast at Ushant’ and sometimes very faintly ‘approaching Guernsey and winding in’.
When the time came for the return trip I would hear the call in the reverse order, passing Ushant, the Needles, Beaulieu, and ‘approaching Hythe and winding in’. Then I would cycle to the Floating Bridge in time to see the flying boat taxi up to its mooring. It was the flight engineer who operated the wireless [which] was powered by a wind-driven generator fixed to the cabin roof and the expression ‘winding in’ referred to the trailing aerial, a long wire with a weight on the end, which had to be wound on to a drum before the Sea Eagle could touch down …
By this time the airline’s operations were carried out from buildings along the side of the works and the staff were glad to have proper offices instead of the exposed Jopling’s Wharf and along the side of the boat shop the words ‘Woolston to Guernsey in 90 minutes’ were painted in blue and white. The Sea Eagles were finished in copal varnish and white, and the windsock was an orange colour and the motor boat varnished, making the whole operation smart and attractive …
Nearly four years later, the fleet of three Sea Eagles was down to one. G-EBFK had crashed on 21 May 1924, due to a bird strike, according to Cozens, and G-EBGS was rammed and sunk when moored at St Peter Port on 10 January 1927 (a reward of £10 for the identity of the culprit was never claimed).
A Sea Eagle in Imperial Airways livery at the Woolston terminal. Note the word ‘Airport’ on the roof of terminal (is this the first use of the word?). It has leading edge cut-outs for forward wing folding, and fuel tanks above the top wing, as well as fixed ladders for passengers and crew. (Courtesy of Solent Sky Museum)
But, for four years, two of 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 became part of Imperial Airways and eventually British Airways. On 31 March 1924, Imperial Airways Ltd had been 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 the four companies taken over for this purpose.
Scott-Paine became a member of the Imperial board of directors and so was able to use his influence to keep the Solent area, and Southampton in particular, to the fore in British commercial flying boat operations. The two Sea Eagles remaining at that time now had their fuselages painted with prominent ‘Imperial Airways’ lettering.
In the following year, it was reported in the Aeroplane that the Sea Eagles, ‘during their hibernation have grown another 100hp’ and are ‘now equipped with Napier “Lions”’. 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 for the Aeroplane showed a Sea Eagle hull at Heston Airport in 1954. At this time, the Imperial Airways marking had been painted out and the extant letters G-EBGS were now of a different character from those seen in photographs of the machines when in service. Andrews and Morgan, the authors of Supermarine Aircraft since 1914, state that the hull in question was that of G-EBGR, the last survivor of the Eagle fleet, rather than that of the retrieved G-EBGS. Whatever the truth of the matter, a hull was presented to the British Overseas Airways Corporation 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.
EARLY
MILITARY ORDERS
Supermarine Scarabs for the Spanish Navy. (From a painting by author)
PRECURSORS OF THE WALRUS
The Commercial Amphibian, Mitchell’s first success as chief designer, brought an order from the Air Ministry for a military development of the type as part of its policy to assist the struggling aviation companies to stay in business. This was a recognition that British air power needed the support of a healthy aviation industry, especially as the RAF had been in action again with a new military tactic. ‘Control without occupation’ was a very economical and swift-acting aerial alternative to the employment of army land forces in the policing of colonial and League of Nations mandated territories, and it was used against tribesmen in Mesopotamia, Transjordan, the Sudan and Somaliland, against the Bolsheviks in Russia and against the Afghans on the Indian frontier.
The Air Estimates of that year accordingly allocated £1,389,950 (although far less than the £54,282,064 of 1919) for the purchase of aeroplanes, engines and spares, and recognised that contracts for new, more advanced types would have to be spread around the various aviation firms in order to maintain the technical staff which had been built up. (Sopwith had already turned to making motorcycles, and Fairey, Gloster, Blackburn, Shorts and Bristol were manufacturing bus or car components.)
In order to fulfil the new Air Ministry requirement, Mitchell’s next design was to be a three-seat amphibian for use as a fleet spotter, to be extremely seaworthy and to have the lowest possible landing speed with good control in order to land onto aircraft carriers. Mitchell’s response was known as the Seal II, presumably with the Commercial Amphibian being regarded as the Mark I predecessor, which had also been a three-seater, as well as being fitted with a retracting undercarriage. However, many design changes show Supermarine’s young designer eager to improve upon his previous effort.
Seal II
The Seal II had the outwardly retracting landing wheel geometry first introduced on the Commercial Amphibian, but the detail of the Seal’s system shows that something had been learned from the criticisms of the earlier plane’s mechanism. The earlier machine had an undercarriage consisting of two steel tubes, hinged below the lower centre-section join with the lower main planes, and the wheels were raised or lowered by sideways movements of a tube in the hull to the wheel axles. The new undercarriage now had a single strut, suspended from the lower wing and braced by two tubes hinged to positions on the hull.
For retraction, the top of this main strut was moved inwards by means of a worm and bevel gear, thus reversing the previous method and siting the retracting mechanism further from the water. It was utilised on all future Supermarine amphibians up to, and including, the Sheldrake of 1927.
Mitchell also improved on the previous aircraft by siting the tailskid/water rudder further back, at the stern-post. This had the effect of increasing the wing incidence during taxiing and so improved the take-off performance (on land at least) which had not been very impressive in the earlier machine. A Flight commentator added a further design consideration: ‘it is much easier to provide the necessary strength and watertightness than
it is with a rudder working in the trunk of the hull. Also the tail loads, which are considerable, are lessened.’
Of the flying surfaces, only the tailplane followed the previous Hargreaves Sea Lion outlines and, although Mitchell now placed the stabiliser lower on the fin, he retained the inverted aerofoil principle. This feature was also continued until 1927, being necessitated by the customary high thrust line of the engine, which caused increasing nose-down forces as power increased. The need for constant back pressures on the stick was thereby reduced or eliminated as cruising speeds were reached.
On the other hand, the wing shape was new and this planform was retained by Mitchell for all his subsequent medium-sized naval aircraft, again, up to and including the Sheldrake (see drawing opposite). But the rearward-folding wing requirement for a shipboard aircraft had not been tackled by the Supermarine Company since the Baby of the First World War, and Mitchell adopted a similar approach – and one which he, again, continued with in military aircraft until the Sheldrake – the forward wing strut at the joint between the wing centre-section and the main plane was doubled so that one of these members carried the weight of the leading section of the wing when folded back.
The need for wing folding also required large cut-outs to be made in the trailing edges of the wings, so that they could fold close to the plane’s centre line to keep storage space to a minimum, and the wings were placed further forward than in the Commercial Amphibian so as not to project behind the trailing edges of the tail assembly when folded.
The wing-tip floats, with their decreased side areas, were less clumsy than before and offered less drag, as they could now be carried on struts to the waterline. The pilot was placed well forward and supplied with a machine gun which could be retracted and shielded during take-off and landing. The wireless operator was just aft of the wings and the rear gunner was behind him, with the fuel tanks separating off the pilot from the other two crew members.
A Seal II at the Supermarine slipway, showing retracted undercarriage arrangement. (Courtesy of Solent Sky Museum)
A Seal II with the wing folding cut-outs and new float configuration. (Courtesy of RAF Museum)
Because two of the crew members were placed behind the wings, a tractor layout had to be chosen for the engine to prevent the centre of gravity moving too far back. Flight believed this to be ‘the first British flying boat to be designed as a tractor’. The pusher configuration was also the most obvious way to keep the propeller as far back as possible from the spray at take-off and landing. In Supermarine’s publicity for the Seal, attention is drawn to this placement, no doubt because of its novelty (at least in single-engined machines):
The engine is the Napier of 450hp. The engine mounting is unusual in that it is of the tractor type. This has been rendered possible by the fact that in this case the greater part of the useful load carried is aft of the wings in the tandem cockpits, and the success of the tractor mounting will allow this type of boat to be arranged either as a tractor in such a case as this or as a pusher in cases where the greatest useful load is concentrated forward. Very great attention has been paid in designing this engine installation to securing accessibility for inspection and adjustment of the engine and its accessories.
One notices the offer of the more conventional pusher layout – presumably in the hope of a civilian version which would not, one might reasonably assume, need a gunner behind the wings. The company publicity also draws attention to the new designer’s typical concern with the practicality of his machines – in this case, the ease of access to the engine.
N146, the prototype Seal, first flew in May 1921 and, in the following year, one machine was sold to Japan, who were keen to be kept abreast of Western technological developments. Despite this general lack of orders, the Seal is important in our story as it is the one early Mitchell design that most clearly looks forward to one of his three main aircraft types – the Seagull II to Seagull V/Walrus series of medium-sized amphibians.
Meanwhile, the company had to come to terms with the post-war Anti-Waste League and the resultant Geddes Committee Report, which led to a drastic reduction in government expenditure. The new Secretary of State for Air, Sir Samuel Hoare, reported that in 1923 only 371 front-line aircraft remained, either in the British Isles or abroad, and thus assessed the current situation: ‘Orders for military planes had almost come to an end and a demand for civil planes did not yet exist … Only 2,500 men and women were left in the industry and the few firms engaged on machines and engines were on the verge of closing down.’
On the other hand, ‘control without occupation’ had to be backed up by support for the ailing aircraft industry if there were to be an adequate response from the depleted RAF. Thus it had been decided that, over the next five years, thirty-four new squadrons would be formed, bringing the number up to fifty-two squadrons by 1928. In the event, the total home squadron numbers only rose to thirty-four by the date proposed, but at least the 1923 Air Estimates of £10,783,000 had risen to £16,042,000 by this time.
Seagulls II–IV
The first positive result of the new situation was seen when Commander James Bird, who had taken over Supermarine at the end of 1923, approached the Air Ministry and subsequently received a letter which cautiously suggested that it ‘might be inexpedient’ to close down the works entirely as Supply & Research were considering an order, ‘the exact amount of which cannot yet be stated, but which might approach eighteen machines, spread over the period ending March 31st, 1924’.
A first Air Ministry lifeline came in the form of an initial order for two flying boats of the type Mitchell, in anticipation, had begun developing from the Seal. A more powerful Napier Lion II engine was now envisaged – again in a tractor layout – and the fin consequently increased in area and the wingspan reduced.
Thereafter, two new aircraft with these modifications, N158 and N159, were renamed ‘Seagull’ and were completed by March 1922. The type was displayed in the same year at the third annual RAF Pageant, Hendon, by which time the wing-tip floats had been redesigned, the wings given a slight sweep back, the ailerons redesigned, and the fin area further enlarged. The number of modifications resulted in these first production Seagulls, in fact, being designated Mark II.
There was one particular modification of the Seal type which ought to be mentioned: the fuel tanks had now been moved from the fuselage to positions under the top wing centre-section, supplying petrol to the engine by gravity feed. In the First World War, the Felixstowe flying boats, which had fuel tanks more conventionally placed in the fuselage, had suffered so many forced landings from blocked pipes and fuel-pump failures that a contemporary report stated, ‘our real enemy is our own petrol pipes’. It is a reflection of the very slow pace of aircraft development after the Armistice that Supermarine drew particular attention to their adoption of gravity feed as late as 1923, with the Seagull II.
Previous experience of the high position of the Sea Eagle’s fuel tankage would have shown Mitchell that the basic Supermarine amphibian configuration, with a suspended boat-like hull, made possible such new fuel arrangements without stability problems. There was also an additional bonus: as a consequence of moving the fuel tanks from the hull, Supermarine was able to announce that ‘inter-communication between crew has been considered fully, and a through passage is arranged for this purpose’. Thus Mitchell was not only solving possible supply problems from petrol in lower positions, but was also making an important step forward in the matter of military crew communication – something that was particularly appreciated when the Southampton flying boat came into service two years later.
In passing, it should be noted that the constructional methods of the Linton Hope hull that Supermarine had adopted conferred another advantage, in that there were no internal bracings or structural bulkheads to be weakened when opening up a passageway between the pilot and the other members of the crew.
A competitive test on HMS Argus between the Seagull and the Mark VII v
ersion of the Viking (whose predecessor had competed successfully with Mitchell’s Commercial Amphibian in 1920) had found in favour of Mitchell’s machine and, thereafter, Vickers concentrated upon land planes.
An RAF order for five Seagulls, N9562–N9566, was received in February 1923 and the Undersecretary of State for Air, the Air Vice-Marshall and the Director of Research visited the Supermarine works on 23 February 1923, to view the progress of the order. The Ministry were sufficiently pleased with the aircraft that a further order for five additional Seagulls (N9603–N9607) was received, and this was followed by a requirement for another thirteen (N9642–N9654). These aircraft equipped No. 440 (RAF) Fleet Reconnaissance Flight, and six were placed aboard the aircraft carrier HMS Eagle. An additional machine was again sold to Japan.
Further orders for the Seagull came in when the Australian Government decided that their Air Force should assist in the hydrographic survey of the Great Barrier Reef. No. 101 (Fleet Co-operation) Flight was formed on 1 July 1925, and six Supermarine Seagull III amphibians were ordered. These machines were essentially Mark IIs with larger radiators, and the first of these was ready by February 1926.
A Seagull II of 440 Flight, off the south coast of Malta. Note the rungs on the rear centre-section strut for access to fuel tanks. (Courtesy of RAF Museum)
By this time, six of the RAF aircraft had served a tour of duty with HMS Eagle, but the type had then been pronounced as having ‘no potential naval use’, particularly because of their habit of porpoising on take-off. They were then confined to coastal (non-carrier) reconnaissance duties and so the type did not come into contention as a future replacement for the long-serving Fairey III series. However, it was given a place in the popular final set piece of the fifth RAF Pageant, where it summoned Flycatchers, followed by Blackburn Darts, to destroy two large replica warships.
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