Correlation of Full-Scale Isolated Proprotor Performance and Loads

A full-scale isolated proprotor test was recently conducted in the USAF National Full-Scale Aerodynamics Complex (NFAC) at NASA Ames Research Center. The test article was a 3-bladed research rotor derived from the right-hand rotor of the AW609. For this test, the NASA Tiltrotor Test Rig (TTR) and rotor were installed in the 40- by 80-foot test section. This paper presents initial correlations between data and predictions of rotor performance and blade moments using the newly acquired test data and the comprehensive analysis CAMRAD II. Four low-speed conditions were studied, including hover (actually, low speed vertical climb), cruise (airplane mode), conversion, and helicopter mode. Mean and 1⁄2 peak-to-peak quantities (hpp) are correlated; time-history correlation for the helicopter condition is also included. The hover calculations proved useful in providing reality checks on the test hardware. The correlation is reasonable. The mean midspan flap banding moments are predicted very well. The trends (with CT/σ) are largely captured, with some overprediction or underprediction (details in the paper). The time-history correlations (helicopter mode) show that, compared to the rolled-up wake (RW) model, the multiple-trailer wake model improves the correlation slightly; the collective is predicted well by the RW model, the lateral cyclic correlation is not good, and the longitudinal cyclic correlation is reasonable; the flap moment correlation is reasonable; the pitch link load and lag moment are underpredicted; and the torsion moment correlation is poor and needs further study.