Airworthiness Directives; Boeing Model 747 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to all Boeing Model 747 series airplanes, that currently requires revising the Airplane Flight Manual to include procedures to prevent dry operation of the center wing fuel tank override/jettison pumps and, for certain airplanes, to prohibit operation of the horizontal stabilizer tank transfer pumps in-flight. For certain airplanes, this amendment requires installation of improved fuel pumps, which terminates the requirements of the existing AD. This amendment is prompted by new information received from the fuel pump manufacturer. The actions specified by this AD are intended to prevent contact between the rotating paddle wheel and the stationary end plates within the center wing tank override/jettison fuel pumps or horizontal stabilizer tank transfer pumps, which could cause sparks and/or a hot surface condition and consequent ignition of fuel vapor in the center wing tank or horizontal stabilizer tank during dry pump operation (no fuel flowing).