Aerodynamic analysis relates mainly to questions of performance and stability, the latter including both maneuverability and control, but the designer's problems concern chiefly the prediction of the best possible performance. Accurate analysis, which would include a summation of the elemental resistances of an aircraft part by part and the making of many corrections, supplemented by tests of models in a wind-tunnel, involves much labor and expense.
When a preliminary choice of dimensions and specifications for a new type of an airplane is to be made or there is a question of the performance attainable with a given load and power, a shorter method becomes necessary. This is to be found in the derivation of simplified formulas and graphs.
The author illustrates by examples the process of deriving these formulas and considers in turn such elements as minimum and maximum speeds; climbing ability and the conditions under which an airplane will have a zero ceiling, that is, the limiting conditions under which flight is possible; rate and angle of climb, the latter controlling the possibility of getting out of a small field over a barrier; and the best ceiling possible. Under these heads he takes up such questions as fineness, which is the ratio of the parasite resistance to the wing area; and lift, weight and power and their relations in determining the various coefficients that are used. Values obtained theoretically from the formulas were checked by comparison with those of about 50 airplanes of various types of which the measurements and performance are known and application is made to specific examples. Numerous curves show the relation of the various coefficients that enter into the design and performance of the airplane.