Airworthiness Directives; Boeing Model 737-100, -200, -300, -400, and -500 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737-100, -200, -300, -400, and -500 series airplanes, that requires 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. This AD also requires 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, terminates the repetitive testing. This amendment is prompted by reports of engine power loss caused by unsatisfactory performance of the fuel boost pumps. The actions specified by this AD are intended to prevent fuel suction feed operation on both engines without flight crew indication, and possible consequent multiple engine power loss.