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Many tests have shown that engine oil pumps are the limiting factor in providing satisfactory high-altitude aircraft oil system performance. As is pointed out in this paper, it is for this reason that both reciprocating and gas turbine engine manufacturers should design and provide their engines with a pump that will give satisfactory performance at an inlet pressure of 2 in. of Hg absolute with 10% (by volume) entrained air. Of the various oil systems investigated by the AMC, the closed-circuit system seemed to be most desirable in terms of both performance and installation, for use in high-altitude operational aircraft.

Consideration of the requirements of a realistic power-plant evaluation for air transport operations leads to the conclusion that the criterion must include the effect of the velocity at which the transportation is accomplished and some of the operating costs. A method of evaluating power plants for transport operations based on total operating cost per ton-mile is presented. An equation is developed for the purpose of expressing the total operating cost per ton-mile with the costs appearing in the equation as constants of proportionality. Methods are outlined to aid in the application of this equation to actual power-plant-evaluation problems. An approximate method of determining the flight altitude that results in the best performance for each combination of range and velocity is presented in order to simplify the power-plant evaluation. An example is included to illustrate the use of the equations and the methods developed.

The opinions and statements expressed herein are those of the writer and are not official views of the Navy Department or Associated Services.