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12          U.S. AIR SERVICES          November, 1931


B. H. P. (during race--throttled)..........I,900
Bore....................6 inches
Strike....................6.6 inches
Weight of Engine....................1,530 lbs.
Wight per H. P. ....................0.805 lb.
Overall length....................91 3/4 inches
Overall height....................40 inches
Overall width....................30 inches
Gear Ratio (Propeller to Crank Speed)  0.68

The engine is a 12-cylinder water-
cooled vee type and is fitted with an enor-
mous supercharger to which much credit is given for the remarkable output of these engines. 

PUBLISHED reports concerning French and Italian preparations for this year's race indicate that engine de-
velopment in these two countries has also been making rapid strides. The Fiat Company of Italy is reported to have de-
veloped a new 18-cylinder engine with an output of 2,300 h.p. The French are understood to have produced new [[italicized]]Hispano Suiza][[italicized]] and [[italicized]]Lorraine Dietrich[[/italicized]] engines of about 2,000 h.p. The [[italicized]]Lor-
raine[[/italicized]] engine is reported to weigh only 1,200 pounds, which gives it a weight per horsepower rating of 0.575 pounds.
truly and astounding figure. It is re-
ported that all of these are exceptionally high compression engines without and extensive amount of supercharging such as is so successfully used in the big[[italicized]] Rolls Royce[[/italicized]] racing engine. Although it is probable that the [[italicized]]Rolls[[/italicized]] engine is the more highly developed of the engines dis-
cussed, nevertheless the value and benefit of the technical development due to Schneider race preparations is not con-
fined to British aviation. The French and Italian efforts are rewarded by ad-
vanced technical experience and knowl-
edge which would otherwise have been unavailable to them for years to come. Many features of our own pre-
sent liquid cooled engines owe their use to lessons learned during our own offi-
cial participation in national and inter-
national air racing some years ago. 

HIGH power and high speed develop-
ments bring many research prob-
lems which must be successfully solved before a new racer or high speed plane can be flown. Probably the greatest of these problems is the effective dissapa-
tion of waste heat from the energy. No engine is thermodynamically 200 per cent efficient and a very large portion of the energy present in the fuel appears as

[[second column]]

heat losses and must be carried i=off by the cooling substances (air or liquid) and the lubricating oil. 
Some idea of the magnitude of this cooling problem is shown by the fact that the heat losses in the 1931 [[italicized]]Rolls Royce[[/italicized]] racing engine total about 40,000 British thermal units a minute. This in more familiar terms means that the equivalent of one thousand horsepower must be dissipated to the atmosphere in order to keep the engine temperature withing safe limits. All of this heat must be carried off by the cooling liquid and the lubricating oil and these liquids must in urn be cooled by the passage of the airplane through the air. 
Hence the racing airplane is literally a flying radiator and practically every square foot of exposed surface on the 1931 [[italicized]]Supermarine S-6B[[/italicized]] racer is taken up by radiator elements. The wing cov-
ering is a hollow shell through which the cooling water is passed and both the inner and outer surfaces of the wing are utilized for cooling. Additional radiator surfaces are provided on the floats and even the struts come in for their share of the cooling system. The fuselage surface is employed as an oil cooler and the hollow vertical fin is util-
ized as an oil tank in which the hot oil from the engine is sprayed against the inner surfaces to increase the rate of oil cooling.

ANOTHER very troublesome ques-
tion in high powered internal com-
bustion engines is the fuel problems and each new development brings its own fuel difficulties. Gasoline is a fuel of widely varying characteristics, as the average motorist knows to his sorrow. As the unit output of an engine is in-
creased we soon find that even the very best gasoline becomes unsatisfactory and the engine overheats and loses power due to the detonation of the fuel. For this reason various doped fuels are used to obtain high output from the high com-
pression engines now found in many motor cars. 
The problem in a racing airplane is magnified tremendously and gasoline be-
comes practically useless as a fuel. it is reported that the fuel used in the record breaking [[italicized]]Rolls Royce[[/italicized]] engine is a blend of motor benzol, alcohol, and tetra ethyl lead (anti detonating agent). The characteristics of such a fuel would indicate its suitability for use in engines   

[[third column]]

of extreme power and the performance obtained during the race seems to be sufficient proof that a satisfactory fuel was found. 

THE heat dissipation of fuel prob-
lems are always present in any air-
plane or engine and these two items will probably continue to be the most diffi-
cult tasks for the designer. The cease-
less battle between direct, or air, cooling and indirect cooling in which liquid such as water, steam, or ethylene glycol (prestone) circulates in the cylinder jackets, continues unabated and without any semblance of finality. 
The indirectly cooled engine, reach-
ing its maximum development to date in the Schneider racing engines, holds a present advantage over the air or directly cooled engine because of its small frontal area which results in reduced air resist-
ance and therefore better efficiency. It is also very doubtful if power output of the magnitufe obtained in the big [[italicized]]Rolls Royce[[/italicized]] engines would be possible in an air-cooled engine of comparable cylinder dimensions due to the impossibility of carrying swat the waste heat with suffi-
cient rapidity to prevent the engine from burning up.
Thus, although the radical air-cooled engine, with its rugged simplicity of de-
sign and its well earned reputation for reliable service, will continue too dom-
inate the field for air transport and gen-
eral commercial use, it seems likely that the liquid coolies engine is the only pos-
sible type yet developed which is suitable for extremely high output and for use in what might be termed super perform-
ance aircraft. 
Another and possibly a more extensive field of usefulness for the larger power units is foreseen in the modern tendency [[red line]] toward aircraft of vastly increased physi-
cal dimensions and load capacity. The German [[italicized]]DOX[[/italicized]] and our own Sikorsky-
built [[italicized]]American Clipper[[/italicized]] are existing ex-
amples of this trend.

FLYING boat designers are already discussing plans for boats whose full load weight may exceed 75 tons and which will possibly require 10,000 h.p. or more. Obviously the provision of this power by some twenty engine units of the present 500-600 h.p. range would involve almost insuperable difficulties of installation and control. On the other