Wednesday, 22 March 2017

R.J. Mitchell's Ugly Ducklings: The Scylla and the Swan

During World War I, Felixstowe F 2 and 3 flying-boats had been operated successfully on coastal-reconnaissance duties, despite their various problems,  and they were replaced after the armistice by the F.5 from the same makers. However, D’Arcy Greig (later to figure in the Supermarine S.5 story) recorded that: 
they were grossly underpowered by two Rolls-Royce Eagle VIII engines, and if there happened to be a flat calm at time of take-off, they frequently refused to unstick. On such occasions the pilot had to taxi frenziedly up and down the Solent and around in circles in order to disturb the surface of the water before trying again, but even then they sometimes failed to get airborne.
These flying-boats had slab-sided hulls which were prone to leakage and so the Air Ministry was concerned to see if the Linton-Hope type of hull (see my Blog: "R. J. Mitchell’s Wooden Hulls – structure and finish"), which they regarded as a success on the early Supermarine seaplanes, could be adopted on aircraft of the Felixstowe size.

The slow process of addressing this concern by various manufacturers around the country lasted well after the war, by which time Supermarine came into contention in 1921 with the Scylla, a triplane with biplane stabilizers. It was to be powered by two main engines and a much smaller, auxiliary one, sited in the hull to drive a water propeller for taxiing [and perhaps to assist with take-offs?]. This last feature seems particularly old-fashioned, looking back to the earlier Pemberton Billing days of the company, in particular, the P.B.7, and to a proposed Torpedo Carrier triplane of 1921.
Why only the hull of the Scylla was completed is unknown, as was its final fate. Most likely, Mitchell’s rapidly developing confidence as a designer was an important factor: as a new contract was received soon afterwards (Spec. 21/22) for a large commercial amphibian, his thoughts could turn from the traditional thinking represented by the Scylla to a more forward-looking aircraft. Also, required to carry twelve passengers, it would come out at about the same size as the military Scylla and therefore it might be that the first machine was soon relegated to merely providing information for the new design – which, as a biplane, Mitchell must have predicted would be a more efficient aircraft; it could also surely be easily retro-fitted for such military purposes as might have been envisaged for the Scylla. Certainly the former machine seems to have been used only for water taxiing trials and a photograph in Supermarine Aircraft shows a very basic framework erected on the hull to accommodate (temporarily?) the two engines for this purpose.
When the new machine, to be named the Swan, first appeared in 1924, it was a considerable re-design, being an equal-span biplane with a forward-folding wing arrangement like the Sea Eagle of the previous year. Indeed the Swan might, in some ways, be regarded, rather, as a scaled-up Sea Eagle although doubling the number of passengers to be carried necessitated accommodating them in the main body of the hull rather than in the fore position of the earlier aircraft. Again, the fuel tanks were placed high enough to provide gravity feed to the engines which were situated between the wings, as well as to provide unusually roomy and fume-free accommodation for the passengers. The fin and rudder outlines also resembled those of the Sea Eagle.
     On the other hand, Mitchell’s less complex use of dihedral only on the outer sections of the lower mainplane was new and the three vertical tail surfaces anticipated his larger designs of the next decade. The single plane stabiliser was also new to larger Supermarine aircraft and was kept well clear of the water by the upward slope of the rear section of the hull – very unusual for the time although not quite an innovation in flying-boat design (see the much smaller French Tellier T3 or Latham HB3); nor was it as graceful as the upward sweep of the future Southampton rear fuselage but, at least, it represented a bold new step in Mitchell hull design, without there being previous experimentation with smaller hulls.

Supermarine Swan

The need to mount three fins had also led to a reversal of his earlier practice, whereby the tailplane had been supported by the fin (with the aid of numerous struts). The new feature also anticipated most of Mitchell’s later seaplanes and was a more elegant configuration than the traditional biplane-tail approach proposed for the Scylla. On the other hand, the upswept fuselage and the boat-like prow, flared outwards at the top to counteract spray, were features in common with the earlier machine which had presumably been proven to be effective by its taxiing trials.
     The raised cockpit superstructure was also very reminiscent of the unfinished Scylla and it contributed significantly to the clumsiness of the hull profile. Cozens’ comments:
The Swan had several features which showed improvements on previous designs, and no doubt these led to its success. The keel had an upward curve towards the tail that enabled it to take off more readily and this feature was noticeable in all later flying boat hulls built throughout the flying boat era, even to the Saunders-Roe Princess of the nineteen fifties, and it is very apparent if one compares the pictures of the Swan with that of the [Supermarine] Channel I. The struts of the Swan’s centre section formed large W’s which made for great strength and the large fins and rudders and the considerable spacing between the wings made this aircraft a success from a handling point of view. At any rate, Captain Biard was pleased and so was the Air Ministry, but no-one could say that the Swan was a handsome machine with its rounded bow and strange looking cabin and the pilot’s cockpit at the top.
The “strange looking cabin”, which housed a crew of two, sat on the top of the main fuselage so as not to interfere with the passenger space and, as the proposed passenger windows had yet not been fitted, the offending side-view was unrelieved. The same had been true of the Scylla and, whilst Supermarine had no doubt chosen the latter’s name to suit its proposed military role, it might seem to others that the name reflected its appearance: according to Ovid, the beautiful Scylla was turned into a thing of terror and in Homer Odysseus manages to sail past her but not before she catches and devours six of his men. As the new design was to have a more pacific role, the new aircraft was named ‘Swan” although, despite its size, “ugly duckling” comes more to mind. 

The Swan nearing completion.

Be that as it may, the new aircraft was first flown by Biard on 25 March, 1924 and, at this time, displayed the triangular cut-outs in the leading edges of the wings to enable them to fold forwards. The Swan also had the sort of retracting undercarriage arrangement that Mitchell had designed for his single-engined amphibians but the much increased size of the new machine necessitated the novelty of some form of servo assistance. Biard described the mechanism as follows:
it would have been quite impossible to wind down the six-foot wheels and powerful landing-carriage, which had to stand the weight of several tons of aircraft and passengers! So a neat device was fitted to the machine to do the work quickly and efficiently for us. This consisted of a small propeller, which, when not in use, was set sideways to the direction in which we were flying. When we wanted to lower the landing-gear, this propeller was swung round to face the direction of our course, and the whirling propeller was connected by cogs to a handle which wound very rapidly round and lowered the wheels into place; by turning the propeller rearward the wheels were wound up out of our way under the wings, and the machine was then able to descend on water. This gear, after one or two adjustments following minor troubles during tests, when the Swan behaved neither like fish, flesh, nor fowl, proved remarkably efficient, and wound the heavy landing-gear into place in about half a minute or less.
Biard also describes the visit of the Prince of Wales to Supermarine, and to the Swan in particular, on the 27th of June in the same year. :
An informal moment in the Royal visit, showing the impressive size of the Swan.
(Note the substantial samson post at the prow. Mitchell to right of Prince of Wales).

By the time of the Prince’s visit, the Swan’s two 360 hp Rolls-Royce Eagle engines had been replaced by Napier Lion engines, each developing 90 hp more than the Rolls-Royce units, which increased the Swan’s top speed by 13 mph; and the folding of the wings and the leading edge cut-outs had also been dispensed with. Plans for an RAF version of the Swan were also being actively pursued at this time – which may also have had some influence on the change to the fixed-wing layout and possibly throws more light upon the decision to terminate the development of the military Scylla.
Successful trials at the Marine Aircraft Experimental Establishment, Felixstowe, followed which were to have important results for the fortunes of Supermarine (see my Blogpost: “Annus Mirabilis, Pt.1) and, on its return to Supermarine, it was now fitted out for its passenger-carrying role. Company publicity pointed out that the machine was not only the first twin-engined commercial flying-boat/amphibian but that the provision of accommodation set new standards:
This is the first twin-engined amphibian flying-boat to be built in the world and it may also be fairly claimed to be the first twin-engined commercial flying-boat.
An important feature of this machine is that the whole of the hull is devoted to passenger accommodation. There are no internal obstructions of any kind, and the amount of room in the saloon far exceeds that of any commercial landplane. The internal accommodation consists of one large passenger saloon, elaborately furnished and upholstered and with every comfort. Forward of the saloon is the luggage compartment, fitted with racks for the stowage of passenger baggage. Aft of the saloon is the buffet, with all necessary fittings to supply light refreshment during the journey. Still further aft are the lavatories, which are efficiently and fully equipped.

As such it was registered as G-EBJY and first flew on June the 9th, 1926, carrying a representative of the newly formed Imperial Airways and eight excited female employees of Supermarine. A slight reduction in passenger seating had further allowed Supermarine to address the new standards in passenger accommodation, which The Aeroplane fully confirmed:  ‘the appointments are exquisite’ with ‘a commodious passenger saloon padded luxuriously and in which there are ten cosy armchairs. An ample porthole is provided for each chair.’

Mitchell (front left) in the Swan.
(Note the Linton-Hope fuselage structure of close-spaced hoops on longitudinal stringers)

The aircraft was loaned by the Air Ministry to Imperial Airways in order to supplement the service of Supermarine’s remaining two Sea Eagles, on their Channel Isles service. It operated during 1926 and 1927 but, as The Guernsey Evening Press reported, ‘during the normal rigorous inspection prior to leaving Southampton on April 12, a structural defect was discovered which necessitated the stripping of the whole machine’. As a result, the Swan was scrapped; Imperial Airways’ next long-distance seaplane was not to be the Swan, however, and so its main significance remained that of providing the prototype for the Royal Air Force’s next standard maritime reconnaissance aircraft, the far more attractive Supermarine Southampton of 1925.

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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 which also provides material for wider reading, grouped according to specific areas of interest. More information, photographs and a three-view drawing of the Swan, 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.


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