Flight, August 1927

THE 1927 SCHNEIDER TROPHY CONTEST
Some Notes on Two of the British Challengers

The Supermarine-Napier S.5

   The Schneider Trophy challenger produced by the Supermarine Aviation Works, Ltd., of Southampton - the Supermarine-Napier "S.5" - undoubtedly looks as if it meant to win back the Trophy, as may be gathered from the accompanying illustrations. But what is more important, tests have demonstrated that we have something more than looks to count upon. Mr. R. J. Mitchell, Chief Engineer to the Supermarine firm is responsible for the design of the "S.5" (we understand three of these machines have been constructed), whilst thanks are also due to the very valuable research work and co-operation of the Technical Officers of the Air Ministry, the Royal Aircraft Establishment at Farnborough, and the National Physical Laboratory at Teddington, that have been rendered in connection with its design and construction.
   The "S.5" is a low-wing twin-float mono-seaplane developed from the "S.4" - to which it is very similar in general appearance - which took part in the 1925 contest and also won the world's speed record for seaplanes; incidentally, the "S.4" still holds the British speed record for both land and seaplanes.
   It may be of interest to note in passing that these machines were the first mono-seaplanes (float) to be used in the Schneider contests since the early days - the Italian Macchi being produced after the "S.4" made its debut.
   As we mentioned before we are unable to describe the "S.5" in detail, and can only refer to it in a general sort of way. It has, however, a number of very novel features which we give herewith, and these, together with our illustrations should provide our readers with some idea, at any rate, of its characteristics.
   All the fuel is carried in the starboard float, the fuel tank being constructed as a section of the float. The effect of this is partially to balance the engine torque and thereby improve the flying qualities of the machine. The fuel is carried up to the engine by means of an engine-driven pump.
   The wing surface radiators are an entirely new development and are a definite advance on anything previously used. They cool the engine without adding any resistance whatsoever to the machine, having a perfectly flat outer surface.
   The wing is built of wood and is covered with special laminated wood underneath the radiators. The fin, to which is hinged the rudder, is built integral with the fuselage, and the tail plane is also neatly faired into the latter.
   The fuselage is constructed entirely in metal, the skin taking practically all the stresses. The engine mounting consists of a cantilevered extension to the fuselage, the skin of the mounting taking all engine loads.
   It may be noted that the fuselage is probably smaller in cross sectional area than any fuselage previously designed, and the pilots have had to be specially "fitted" to the machine. The area of maximum section is only just over half that of the "S.4."
   In order to clear the cockpit of exhaust fumes and hot air during flight, it has been found necessary to fit fresh-air ducts.
   Oil cooling is effected by passing the oil along both sides of the fuselage in contact with the skin through specially-constructed oil coolers.
   As regards the floats, these are comparatively long and are constructed of Duralumin, being anodically treated to resist sea-water corrosion. They are connected to the fuselage by two pairs of V struts.
   Of the engine, the special racing Napier "Lion," particulars are given elsewhere, so we need only add here that the airscrews for the "S-5" have been designed and manufactured by the Fairey Aviation Co., of Hayes.
   The Supermarine Aviation Works, Ltd., will be represented in Italy, by Commander James Bird, Chairman and Managing director, Mr. R. J. Mitchell, Director and Chief Engineer, and the Supermarine crew will consist of Mr. A. Powell, Mr. B. Pickett, Mr. G. Broome, Mr. B. Tozer, Mr. G. Pearson, Mr. H. Grimes, and Mr. B. 15. Brown.
   It is anticipated that the machines will leave England in two consignments, one on or about August 16, and the other on or about August 26.

Flight, July 1929

BRITISH AIRCRAFT AT OLYMPIA

SUPERMARINE AVIATION WORKS, LTD.

   As a result of the purchase, some months ago, of the Supermarine Aviation Works by Vickers (Aviation), Ltd., the two firms are now practically one, with Supermarine's looking after the maritime side and Vickers after the aeroplane side. This division is probably not intended to be an absolutely rigid and unalterable one, but with the accumulated experience of 15 or 16 years of specialising on marine aircraft, it may be assumed that in the great majority of cases the Southampton designing office will deal with marine types. It is logical that, on the other hand, Vickers (Aviation), Ltd., should devote their energies to aeroplanes of all types and classes, their experience of which dates back to the early days of flying in Great Britain. The two firms thus united are both among the pioneer aircraft companies of Great Britain, and the combination should be a very powerful one. At Olympia the two firms will naturally exhibit their aircraft together, but for the sake of easy reference we have thought it preferable to deal with the exhibits separately.
   Supermarine's will, it is hoped, exhibit two complete marine aircraft: One of the metal "Southampton" flying-boats with Napier "Lion" engines which made the 27,000 miles' R.A.F. Far East Flight, and the other the Supermarine S.5 with Napier racing engine which won the Schneider Trophy for Great Britain in 1927, and which, in 1928, gained the British high-speed record of 319-57 m.p.h. .
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   The Supermarine-Napier "S.5" racing seaplane is, as already mentioned, the type which won the Schneider Contest in 1927. Two of these machines are being used by the high-speed flight of the Marine Aircraft Experimental Establishment of the R.A.F. as practice machines for this year's Schneider Trophy Contest, and as one "S.5," piloted by Flight-Lieut. D'Arcy Greig, has established a British speed record of 319-57 m.p.h., no visitor to Olympia should fail to inspect the "S.5" on the Supermarine stand.
   The "S.5" is a low-wing braced monoplane, with twin-float undercarriage. The fuselage is a duralumin monocoque, while the wings are of wood construction, covered with plywood 1/8-in. thick. Over the wing covering are placed the wing surface radiators.
   The duralumin floats are of the long, single-step type, and have a backbone in the form of one central longitudinal bulkhead of sheet duralumin, to which the transverse frames art attached.
   A special racing type of Napier engine is fitted in the nose and is entirely covered in. The water header tank is housed in the central cylinder block fairing, while the main petrol tank is situated in the starboard float of the undercarriage. An auxiliary gravity tank is housed in the fairing of the starboard cylinder block. The total petrol capacity is 55 gallons.
   With a wing span of but 26 ft. 9 in. and a wing area of 115 sq. ft., the "S.5," with direct-drive Napier, weight 3,100 lbs., and with the geared Napier, the weight is 3,250 lbs. The maximum speed of the machine with direct-drive engine is about 300 m.p.h., and with the geared engine about 320 m.p.h. The landing speed is approximately 90 m.p.h., so that it will be realised that the "S.5" is a very efficient aircraft, with a speed range of more than 3-5:1.
   It is worth recalling that in the Schneider Trophy Contest of 1927 at Venice, the winner, Flight-Lieut. Webster, on one of the "S.5" monoplanes averaged a speed over the 217 miles course of 281-65 m.p.h., while Flight-Lieut. Worsley, on the similar machine averaged 273 m.p.h. In the course of the contest also the winning machine established a new world record over a distance of 100 kms., with a speed of 283-68 m.p.h.

Flight, October 1931

The Supermarine S.6 B Monoplane
Main Particulars Published for the First Time

   HITHERTO it has not been possible to publish the data relating to the S.6B. monoplanes designed and built by the Supermarine Aviation Works for the 1931 Schneider Contest. The general appearance of the machines has been shown in the innumerable photographs which have been published all the world over, but essential data, such as weight, etc., have been kept secret. It has now become permissible to give such data, so that, taken in conjunction with the article on the Rolls-Royce "R" engines on pp. 989-995, it is now possible, for the first time, to form a true picture of the achievement of all concerned in the production of the British 1931 Schneider defenders.
   It has already been recorded in FLIGHT that, when Lady Houston came forward with her magnificent offer of ?100,000 for the building of new machines and engines for this year's Contest, time was getting so short that neither the Supermarine Aviation Works nor Rolls-Royce, Ltd., had time to produce entirely new designs, but had to do the best possible in the time available with the 1929 machines and engines. Some of the difficulties encountered by the Rolls-Royce firm are set out in the article referred to above. In the following will be found a brief outline of the improvements made by the Supermarine Aviation Works, and which resulted in the production of the 1931 S.6B. monoplanes.
   Although the 1931 machines were generally similar to the 1929 type, it was found that detail improvement in the following items could be made: The oil system, the water system, the fuel system, the floats, and the aircraft controls.
   The Oil System. - In the S.6B. machines the oil system is, as before, housed entirely in the fuselage. When the oil leaves the engine, it is forced along the fuselage side coolers to the top of the fin tank. By an arrangement of ribs and gutters, the oil is kept in contact with the shell as it falls to the normal level and passes through a filter into the return (suction) cooler, which is built on the same lines as the side coolers, but is of greater section. Oil cooling had to be improved considerably in order to cope with the increased engine power, and it was found that the difficulty lay not so much in transferring the heat from the cooler to the air as in transferring it from the oil to the surface of the cooler. Eventually, as a result of extensive research work carried out by the Supermarine Aviation Works and by the R.A.E., it was found possible to increase the efficiency of the coolers by as much as 40 per cent. This was done by sweating small vanes into the oil ways, but a great deal of experiment was necessary before the type and pitch of vanes could be determined. Excessive restriction in the flow increased the pressure difference between inlet and outlet by an enormous amount. The gutters in the fin tank performed a similar duty, and the capacity of the tank itself was greatly increased to carry the additional oil required. In actual practice, the temperature drop between oil outlet and oil inlet reached 60 degrees C, a figure probably never before approached on any aircraft.
   The Water System. - In order to keep the new engines at the correct temperature, it was necessary to dissipate approximately 40,000 British Thermal Units of heat per minute from the cooling surfaces. The efficiency of the wing radiators could not be improved appreciably, and, therefore, more surface had to be provided somehow. The only extra surface available was that presented by the topsides of the floats. These were covered with radiators instead of the usual shell plating, and the addition of this extra cooling surface was very effective. A new type of header tank with a steam separator was designed to prevent any loss of water. In other respects the water system was unaltered.
   The Fuel System. - The fuel is carried inside the floats, and is delivered to a small pressure tank in the fuselage by engine-driven pumps. Normally the engine is fed from the pressure tank, but this is of small capacity and intended only to be adequate for the short period when the aircraft is doing a steeply-banked turn and when, due to centrifugal force increasing the weight of fuel, the pumps are unable to supply the engine. The starboard float carries much more fuel than the port, in order to offset the tremendous engine torque during take-off. The effect of full engine torque is to transfer a load of approximately 500 lb. from one float to the other.
   The New Floats. - Extensive tests have been carried out on model floats both in the Vickers Experimental Tank at St. Albans and in the Wind Channels of the N.P.L. in order to produce floats combining the best possible compromise between aerodynamic and hydrodynamic requirements. As a result of these researches it was found possible to reduce considerably the air resistance per unit of float volume, and at the same time the take-off characteristics were materially improved, both by a reduction in hump resistance and by better stability and less tendency to "porpoising."
   The fitting of water coolers on top of the floats presented considerable structural problems, as the radiators expand nearly half an inch when the water approaches boiling point. This expansion had to be allowed for in the construction of the floats, and to prevent buckling of the float planking an elastic framework construction had to be devised.
   The Aircraft Controls. - On the Supermarine S.5 machines of 1927 it was found that aileron flutter developed if the controls were permitted to become slack. Calculations showed that at the increased speed of the S.6B machine there was a possibility of trouble from this source, and mass balances were, therefore, fitted as a precautionary measure to ailerons, rudder and elevators. These mass-balances were found effective, and flutter was not experienced in the machines as finished for the Schneider Contest.
   At the extremely high speeds attained by the S.6B machines the ordinary small inaccuracies in construction which are of no importance in slower machines, make themselves felt by producing air loads on fin and tailplane which must be countered by loads on the control column and rudder bar. As the tail unit is built into the fuselage no change in rigging was possible, and to overcome the difficulty very tiny fins or flaps were mounted on the trailing edges of rudder and elevators. These small flaps could be bent to one side or other, and when a suitable position had been found, they relieved the pilot of the task of continually exerting a pressure on control column and rudder bar. These flaps are only a few square inches in area, but they proved extremely effective in use.
   A curious point arose in connection with airscrews this year. The new airscrews produced by the Fairey Aviation Co., Ltd., for the 1931 machines were of 8 ft. 6 in. diameter, as compared with 9 ft. 6 in. for the 1929 machines. It was found impossible to take off with these airscrews, owing to the fact that at an early stage in the take-off the machine swung violently to port, even with full starboard rudder. With the old 9 ft. 6 in. airscrews the take-off was easy, and in fact a great improvement on the S.6A's, owing to the improved float design. Eventually 9 ft. 1 1/2 in. airscrews were found to give satisfactory takeoff, while with an 8 ft. 10 in. airscrew it was only just possible to get off under very favourable conditions.