Airworthiness Directives; Boeing Model 737, 757, and 767 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737, 757, and 767 series airplanes. This AD requires repetitive operational checks of certain motor- operated hydraulic shutoff valves to detect malfunctioning; replacement with new valves, if necessary; and eventual replacement of certain existing valves with new valves, which terminates the repetitive inspections. This amendment is prompted by reports that various intermittent limit-switch problems have caused valve failures. The actions specified by this AD are intended to prevent failure of the motor-operated hydraulic shutoff valves, which could result in leakage of hydraulic fluid to the engine fire zone, reduced ability to retract the landing gear, loss of backup electrical power or other combinations of failures; and consequent reduced controllability of the airplane.