FLIGHT -INVESTIGATION-OF EFFECTS OF RETREATING-BLADE STALL ON BENDING AND TORSIONAL MOMENTS ENCOUNTERED BY A HELICOPTER ROTOR BLADE

摘要

Flight tests have been conducted with a medium-size single-rotor helicopter, one blade of which was equipped with strain gages, to determine the effects of retreating-blade stall on the rotor blade bending and torsional moments during high-speed flight and pull-up maneuvers.nThe results indicate that retreating-blade stall has a substantial effect on the periodic rotor blade moments. In the stalled condition, the higher harmonics can become almost as large numerically and. as impor¬tant from a fatigue standpoint as the lower harmonics. Since these increased moments, particularly the torsional moments, cause increased periodic control loads and increased vibration in the helicopter control system, they may tend to restrict the normal operating limits of future high-performance helicopters unless an adequate combination of means to reduce these moments and means to design for their fatigue-effects is devised.