COMPARISONS OF PREDICTED AND MEASURED ROTOR PERFORMANCE IN VERTICAL CLIMB AND DESCENT

An experimental and theoretical investigation was conducted to provide accurate measurements of rotor performance in vertical climb and descent, and to assess the ability of various analyses to predict that performance. The experiment was performed in the Princeton Long Track, which effectively eliminated the uncertainties in rotor thrust and axial flight speed which have plagued earlier measurements of axial flight performance in wind tunnel and flight tests. Three analytical approaches were examined: momentum theory, a prescribed wake analysis, and a free-wake analysis. This paper presents the experimental data, and assesses the accuracy of the various analytical approaches.