Tuesday, 14 March 2017

R. J. Mitchell's Giant

Whilst the early Dornier Wal series had had a very obvious effect on the design of Mitchell's Air Yacht [see my Blogpost:"R.J. Mitchell's Air Yachts"], the huge Mark X version made a far wider impression when it arrived at Calshot in November, 1930, for a two week stay. With a wingspan of over 157 feet and something approaching steamship luxury, including a smoking room with its own bar, and a dining salon, it had a crew of ten and was capable of carrying 66 passengers on long distance flights and 100 travellers on shorter ones. It was powered by twelve 610 hp engines which could be accessed via a passageway within the wings.
Type 179 GIANT
Not to be entirely outdone, in 1929, the Air Ministry sent Supermarine a specification for a forty-seat civil flying-boat which Mitchell first projected as a high-winged monoplane, with three fins, a relatively flat-sided fuselage and with bulbous floats attached to the underside at each wing root, bulky enough to act as sponsons. Six engines were to be mounted in tandem on pylons above the wing, Dornier X fashion, and the very thick wing allowed the innovation of passenger seating in its leading edge. And this wing also distinguised by the first appearance in a Supermarine design of an elliptical planform, the distinctive feature of Mitchell’s famous fighter; its proposed torsion-resisting nose section also looked forward to the wing structure of the Spitfire, as did the use of a single spar – although in this case it was to be six feet in depth.
  Had Mitchell’s design been completed, its size would certainly have put his company well ahead of other large flying-boat contenders: it was to have a wingspan sixty-five feet more than the contemporary six-engined Short Sarafand and nearly three feet more than that of the Dornier X. About this time, there was another very large, seven-engined aircraft – the K-7 designed by Constantin Kalinin – which, interestingly, also featured an early example of the elliptical wing. It should, however, be pointed out that, whilst the Russian plane has always attracted the attention of air historians because of its size (and because it flew), Mitchell’s projected machine would have had a wingspan ten feet greater. With a wingspan of 185 feet, its name ‘Giant’ was therefore appropriate and it would have represented a significant departure from the almost universal formula of braced, fabric-covered biplanes.
Nearly a year later, the rather untidy general arrangement with three rows of forward-facing engines was revised, whereby two inner nacelles now housed two engines apiece, facing fore and aft, and two outer nacelles had a single engine each, driving a tractor propeller. Rolls-Royce steam-cooled engines were now proposed, with the leading edge of the wing used as a steam condenser for the cooling system, a variation on the wing surface radiator system of the S.5 and 6 types. The three rudders were to be replaced by a single one and an auxiliary tailplane was to be mounted above the main unit; additionally, the passenger seating in the wings was to be eliminated in order to accommodate the evaporative cooling system. Mitchell had also decided upon a return to conventional wing-tip floats instead of the high-drag sponson-type arrangement.
Thus by early 1931, when the keel of the Giant was laid down, most of the Dornier X influence had disappeared:
Supermarine publicity photograph
Whilst the first proposals for the Giant showed a tentative move forward from the angular Air Yacht,  the upswept tail section, the nicely streamlined engine nacelles  and the fore part of the hull, reveal Mitchell’s thinking to be in advance of forthcoming larger American flying-boats. For example, the Sikorsky S-40, of the same year as the keel of the Giant was laid down, represents a traditional approach of struts and wires and the ‘canoe’ hull and the necessary twin booms for the tail section, which no doubt achieved a good weight/strength ratio, did not represent the way forward for later flying-boat designs

By 1934, the Sikorsky S-42 had a tail unit integral with the main fuselage and had lost most of its predecessor’s struts and wires; and, coming a few years later than the proposed Giant, it had its engines neatly faired into the wing but it did, however, still retain wing and tailplane struts – compared with the Giant’s projected cantilever structures – and this in a machine that was to have a wingspan of 185 feet, compared with the 118 foot span of the American flying-boat.


Unfortunately, early in 1932, the Supermarine project was cancelled in view of the continued economic problems that faced the country and consternation was not limited to Supermarine, for questions were asked in the Parliament – where the Under Secretary for Air justified the government’s decision by claiming that over 70% of the estimated cost would be saved by cancellation. [In its defence, it might be noted that the Germans did not put their Do.X into quantity production either.] 

Had the Giant been built, perhaps Mitchell’s bomber [see my Blogpost: 'R.J.Mitchell's Bomber and his Death'] might have been designed earlier and might even have been in the air when the need for a large British bomber became critical. It was also thus fated that Mitchell would not be remembered (as might otherwise have been predicted) for his contribution to the  proliferation of the Imperial Airways routes or for the creation of later equivalents of the well-known wartime monoplane flying-boats, the Sunderland and the Catalina.

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For reference sources, see my Blogpost: “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. 

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