AN EXPERIMENTAL INVESTIGATION OF A BEARINGLESS MODEL ROTOR IN HOVER

A 1.79-m diameter model rotor was used to investigate the aeroelastic stability of an isolated bearingless rotor blade in hover, and the results were compared with theory. Configurations tested included 1) an uncoupled configuration with a leading and trailing edge pitch link; 2) a cantilever pitch arm configuration with a single pitch link on the trailing edge of the blade (three pitch link radial locations were studied); 3) a cantilever pitch arm configuration with a single trailing edge pitch link (again three radial locations were studied); 4) a trailing edge pitch link location with –2.5° droop; and 5) a trailing edge pitch link location with 2.5° precone. Lead-lag damping was heavily dependent on pitch link radial location at higher pitch angles for the cantilever pitch arm configurations studied. Theoretical predictions show stability trends quite well in almost all cases but show discernible differences in damping at higher pitch angles.