UNFORTUNATELY, there is an almost complete absence of technical information about any of the machines built for this year's Schneider Trophy Race. The two Governments concerned are unwilling as yet to allow anything but the most meagre details to be published. What data are available of the Supermarine “S.6” are given in the table on page 274 of the winners and performances since 1913. The engine‐power is not given there because it is not permitted by the Air Ministry to say more than that the super‐charged Rolls‐Royce “R” installed develops “over 1,500 h.p.” It has, consequently, been impossible to give the figure for weight per horsepower, but it may, perhaps, be said that this is believed to be, in spite of the increase in gross weight, quite considerably below that of the “S.5.” Indeed, when the power actually developed by the Rolls‐Royce is made public it will probably cause something of a sensation. Though, of course, test‐bench figures are not always achieved in the air, those obtained in this case were most remarkable, and it is only to be regretted that it is not possible to mention them. No more can be said than that with this engine, and the series from which it was developed, Messrs. Rolls‐Royce have at one bound come back to the foremost position they used to hold in the aero‐engine world. The continued improvement in engines is, in fact, perhaps the chief feature of the racing machines of 1929 compared with those of 1927. The 900‐h.p. “Lion” of two years ago seemed to have reached almost the limit of development for a single type, but the Napier Company showed this year that that was by no means the end of their resources. They have added probably about another. 500 h.p. and still further reduced the frontal area, the increase of power being largely owing to the addition of a supercharger, which is also a feature of the Rolls‐Royce. This has been spoken of as an innovation in racing aeroplane engines, but actually the example was set by Mr. Fedden in the Bristol “Mercury” fitted two years ago to the Short “Crusader,” an engine which is only just overcoming its teething troubles as a production type but will shortly, it is expected, begin to take its true place as the fine piece of work it is. So jealously guarded are the details of those high‐efficiency racing engines that no details whatever of either the “Lion” or the “R” are available, and in the ease of the latter a photograph giving merely a side view of the exterior of the engine was deemed too confidential for reproduction because it showed the blower casing. Of the Italian engines nothing whatever is known except that the Isotta‐Fraschini in the Macchi M.67 is rated at 1,700 h.p. and the Fiat C.R. 29's Fiat at 1,000 h.p. Whether these are purely nominal ratings or represent actual powers developed on the test bench, or in the air, it is impossible to say.
Lockwood Marsh, L.‐.W. (1929), "Schneider Trophy Reflections: Personal Opinions Formed from Observation and Some Talks with Others", Aircraft Engineering and Aerospace Technology, Vol. 1 No. 8, pp. 271-274. https://doi.org/10.1108/eb029189
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