U.S. Patent Specifications

In an airplane control system including a movable airfoil, manually operable means for controlling the said airfoil, and hydraulic and linkage means for multiplying the manual energy and transmitting load feel to the said manual means, the second said means comprising a pivotal lever spaced from said movable airfoil and a hydraulic valve and piston unit floatingly suspended therebetween, a linkage connecting said manual means with the valve and a rod connecting said manual means with said pivotal lever, whereby operation of said manual means reciprocates the said valve thereby directing pressure fluid to the said piston which is displaced and transmits force both to the airfoil and the pivotal lever, the force to the airfoil rotating same and the force to the lever transmitting load feel to the manual means in a sub‐multiple of the load required to actuate the said airfoil.