Propulsive Efficiency and Aircraft Drag Determined From Steady State Flight Test Data

A method is presented which permits determination of of propulsive efficiency and airplane drag terms from steady level flight speed-power data. The method is based on a computer formulation of Lock's equivalent propeller model which makes it suitable for use in parameter identification. The results are in the form of coefficients of polynomials defining the airplane and the propeller. These coefficients, determined from steady flight data, then permit easy calculation of propeller characteristics and airplane performance for other flight conditions. The method is particularly applicable to performance prediction and to simulation because the airplane and propeller are represented by a simple analytical model rather than by tables or graphs.

The method is described, computer formulation of the propeller model is verified with wind tunnel data, airplane and propeller characteristics are determined from actual flight test data, and predicted power is compared with measured power for a given flight test condition.