Ch-47C Fixed-System Stall-Flutter Damping
Final rept. Feb 1974-Mar 1975
BOEING VERTOL CO PHILADELPHIA PA
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This program was conducted to evaluate the effect of fixed-system damping on stall-induced control loads. Damping was introduced into the CH-47C aft-rotor control system by connecting the housing portion of the linear damper to the longitudinal-trim system and grounding the piston portion of the damper to the aft transmission. Five damper-rate configurations were evaluated on a helicopter with a gross weight of 40,000 pounds. Data obtained in speed sweeps at five density altitudes to 10,000 feet indicate that the rotating-system loads were reduced by 16 percent and the fixed-system loads were reduced by 22 percent. The program proved that fixed-system damping is effective in reducing stall-induced control loads. Recommendations are presented for reducing these loads by softening the swashplate support as well as by increasing the effectiveness of the fixed-system damper.
- Fluid Mechanics