NACA Report No. 133

NACA Report No. 135 - The Tail Plane was issued by the United States National Advisory Committee for Aeronautics in 1923.
Summary
NACA Report No. 135 presents the results of a test made upon a B. M. W. engine in the altitude chamber of the Bureau of Standards, where controlled conditions of temperature and pressure can be made to simulate those of the desired altitude.
Conclusions
A remarkably low value of fuel consumption - 0.41 pound of fuel per B. H. P. per hour - is obtained at 1,200 rpm at an air density of 0.064 pound per cubic foot and a brake thermal efficiency of 33% and an indicated efficiency of 37% at that speed and density. In spite of the fact that the carburetor adjustment does not permit the air-fuel ratio of maximum economy to be obtained at air densities lower than 0.064, the economy is superior to most engines tested thus far, even at a density lower than 0.064, the economies superior to most engines tested thus far, even at a density (0.03) corresponding to an altitude of 25,000 feet. The brake mean effective pressure even at full throttle is rather low. Since the weight of much of the engine is governed more by its piston displacement than by the power developed, a decreased mean effective pressure usually necessitates increased weight per horsepower. The altitude performance of the engine is, in general, excellent, and its low fuel consumption is the outstanding feature of merit.

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