| A study was made to determine the feasibility of identifying concurrently an aircraft's propulsive efficiency and aerodynamic drag parameters using the Gradient Search technique along with the application of Lock's propeller model. The primary task was to perform a curve fitting process to represent the propeller blade lift and drag coefficients calculated by the extensive work that Lock conducted during the 1930's and 1940's. It was found that an iterative analysis was useful to reduce all the propeller chart interpolation into a numerical interpolation. The Gradient Search method was used to estimate the performance parameters because of stable convergence and its ability to handle the poor initial value guesses. For the present investigation, initial parameter guesses up to fifty percent off the actual values were tried, and convergence was obtained within an accuracy of 2.0 percent in about fifty iterations.; This parameter identification technique requires only steady state measurement of propeller blade angle and RPM, aircraft weight, speed, rate of climb, and atmospheric density. The use of this computational model of the propeller will enable engineers to explore more rapidly and accurately a much wider spectrum of aircraft performance and design options at low cost. This should be a valuable tool for the general aviation manufacturer. |
