Summary
This document revises an earlier proposed airworthiness directive (AD), applicable to certain Boeing Model 727 and Model 737 series airplanes, that would have required replacement of the actuator of the engine fuel shutoff valve and the fuel system crossfeed valve with an improved actuator. That proposal was prompted by a report indicating that, during laboratory tests, the actuator clutch on the engine fuel shutoff and crossfeed valves failed to function properly. This action expands the applicability of the proposed rule by including an additional Kearfott actuator that is subject to the addressed unsafe condition. The actions specified by this proposed AD are intended to prevent improper functioning of these actuators, which could result in a fuel imbalance due to the inability of the flightcrew to crossfeed fuel; improperly functioning actuators also could prevent the pilot from shutting off the fuel to the engine following an engine failure and/or fire.