SYSTEME POUR AUGMENTER LA SENSATION SUR LE LEVIER DE COMMANDE DE SURFACE AERODYNAMIQUE

In a helicopter, a pilot-actuated lever controls, through linkage mechanisms, a servo valve to drive a hydraulic piston; the piston moves a swash plate which in turn controls movement of rotor blade pitch positioning mechanisms against the force of blade loading, caused by aerodynamic forces. Blade loading, heretofore monitored visually by the pilot on a cruise guide indicator instrument, is used herein to control a secondary input to the servo valve, thereby to alter the position linkage mechanism which causes the force of a spring attached thereto to impose a force on the collective pitch control for blade loadings in excess of one-third of maximum allowable blade loads, in a direction tending to drive the control to lower collective pitch (lower blade loading). This provides "feel" to the pilot in proportion to blade loading when at critical magnitudes. A trim system is selectively actuatable to provide an input to the auxiliary valve which tends to maintain the collective pitch control in a selected position.