Summary
This document revises an earlier proposed airworthiness directive (AD), applicable to certain Boeing Model 737-100, -200, -300, -400, and -500 series airplanes, that would have required repetitive testing of certain main tank fuel boost pumps to identify those with degraded performance, and replacement of degraded pumps with new or serviceable pumps. That originally proposed AD also would have required eventual replacement of the existing low pressure switches for boost pumps located in the main fuel tanks with higher threshold low pressure switches, which, when accomplished, would terminate the repetitive testing. That proposal was prompted by reports of engine power loss caused by unsatisfactory performance of the fuel boost pumps. This new action revises the proposed rule by reducing the compliance time for certain airplanes. The actions specified by this new proposed AD are intended to prevent fuel suction feed operation on both engines without flight crew indication, and possible consequent multiple engine power loss.