A Reassessmemt of Rotor Hovering Performance Prediction Methods
Abstract:Recent test results from rotors operating at higher blade loadings with larger numbers of blades have pointed up the inadequacies of some of the simpler conventional methods for computing hover performance. As a result, the validities of the classical methods have been reassessed, and a series of improvements of the methods have been introduced. In this paper, the predictions of several methods are compared with representative full scale test data. The discrepancies which arise are shown to increase with blade loading, tip Mach number and number of blades. It is proposed that a major part of the discrepancy is due to wake contraction in close proximity to the rotor. Photographs of model and full scale flow patterns including high speed photographs of the details of wake formation and wake trajectories are used to illustrate the point. Finally a method for considering the effects of flow contraction on hovering performance is presented and it is shown that including this effect promises to provide improved accuracy in the prediction of hover performance.
Document Type: Research Article
Affiliations: Sikorsky Aircraft, Stratford, Connecticut
Publication date: April 1, 1968
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