Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Lockheed Model L- 1011-385 series airplanes, that currently requires revision of the Airplane Flight Manual (AFM) to prohibit operation of the fuel boost pumps when fuel quantities are below certain levels, and to add maintenance procedures for operating the airplane with an inoperative fuel boost pump assembly or with an inoperative flight station fuel quantity indicating system. That AD also requires the installation of a placard on the engineer's fuel panel to advise the maintenance crew that operation of the fuel boost pumps when less than 1,200 pounds of fuel are in the corresponding wing fuel tank is prohibited. This action would add a requirement for modification of each fuel boost pump assembly, which would terminate the requirements of the existing AD. This proposal is prompted by reports of internal electrical failures in the fuel boost pump of the wing fuel tanks that could result in either electrical arcing or localized overheating. The actions specified by the proposed AD are intended to prevent such electrical arcing or overheating, which could breech the protective housing of the fuel boost pump and expose it to fuel vapors and fumes, and consequent potential fire or explosion in the wing fuel tank.