Producing a theoretical model for determining the appropriate propeller for a given model aircraft application

Abstract

This paper investigates a method of determining the most suitable propeller for any given model aircraft application based on simple inputs such as desired airspeed and powerplant requirements. This method has been embodied through a spreadsheet-based tool which is directed at the end users of model aircraft for establishing the propeller that will best suit their specific needs. The aims of this paper have been addressed through the aid of a case study, which outlines specific operating conditions and assists in putting the background theory into perspective. The ultimate goal for the case study was to determine the most suitable off-the-shelf propeller, in addition to establishing the theoretically ideal propeller for this application. The propeller selection tool itself is based on the operating data of numerous off the shelf propellers and motors, which have in turn been processed in such a way that optimal combinations can be automatically established under given operating conditions. The outputs from the selection tool have also been compared to those obtained from a number of different validation methods in order to determine their accuracy. The results ultimately indicated that the “7x5” propeller was the most suitable off-the-shelf component for the case study, achieving remarkably similar performance to that of the theoretically ideal propeller for the application. Although the chosen validation methods essentially exposed the questionable accuracy of the tool in its current form, this study clearly concludes that the errors do not lie so much within the methods of the tool itself, but rather within the propeller and motor data on which it is based. Therefore, input data of greater accuracy would result in a tool which could be considered fit for purpose in its intended role.