Airworthiness Directives; Boeing Model 747-100, -200, -300, SP, and SR Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to all Boeing Model 747-100, -200, -300, SP, and SR series airplanes, that requires the installation of shielding and separation of the electrical wiring of the fuel quantity indication system (FQIS). This amendment is prompted by a failure analysis of the FQIS, and by testing results, which revealed that excessive energy levels in the electrical wiring and probes of the fuel system could be induced by electrical transients. The actions specified by this AD are intended to prevent electrical transients, induced by electromagnetic interference (EMI), or electrical short circuit conditions from causing arcing of the FQIS electrical wiring or probes in the fuel tank(s). Such arcing could result in ignition of the fuel tank(s).