Following the 1917 recommendation of the Bolling Airplane Mission that great energy be devoted to the development of means to maintain a high proportion of the power of airplane engines at great altitudes, some very creditable work was done. A recent flight test at 20,000-ft. altitude indicates a resultant marked increase in airplane performance. Interest in this development should be extended. The purpose of the paper is to indicate the possibilities and limitations of increasing airplane speed by introducing means to maintain high engine power at great altitudes. The DeHaviland-Four is selected as being, an airplane typical of present practice and the performances that might be obtained at different altitudes are approximately computed, with various assumed ratios of the actual engine power at the altitude to the total weight of the airplane in every case.
The accompanying series of curves give the various coefficient results. The method by which the values of the coefficients were obtained is stated and is of assistance in reading and applying the charts. All values are based upon results obtained from full-scale flight computations and not solely upon wind-tunnel tetests.
The mathematical notation employed throughout is specified. The computations are followed through, showing how the algebraic values of the coefficients are determined, the gains from maintaining engine power at great altitudes being stated in a somewhat similar manner and directions given for entering the charts and obtaining the desired values. A comparison between actual and hypothetical airplanes is then made by mathematical analytic methods, and the suggestion advanced that engineers go through a few numerical examples, following the methods shown, using the accompanying charts and noting results.


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