Comparison of Wind Tunnel Tiltrotor Loads of Two Hub Types Under Different Pylon Angles with Multibody Dynamics Analyses

Loads and harmonics calculations for a wind tunnel tiltrotor model built by the U.S. Army are presented. Blade loads are calculated using the comprehensive analysis, CAMRAD II, and the multibody dynamics analysis, Dymore, for helicopter, airplane, and transition modes of flight at various velocity and pylon angles. These calculations were performed for both a gimballed hub and hingeless hub configurations. Mean variations show a primary trend along the radial station is consistent among both hub types. Half peak-to-peak comparisons show excellent agreement based on the analysis in helicopter and airplane mode. During transition flight some deviations occur within the hingeless hub type confiruation. The analytical vibratory blade loads generally match in waveforms for both the gimballed and hingeless hub configurations. Dymore and CAMRAD II show good agreement among the harmonics for both the gimballed and hingeless hub configurations with both the flapwise bending moment and chordwise bending moment cases relatively similar. Good agreement is identified particularly in airplane mode and higher flight speeds.