Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Boeing Model 777- 200 series airplanes, that currently requires a one-time inspection to determine the serial numbers of various switch modules on the overhead panel and control stand, and replacement of switch modules with new, improved modules. The existing AD also requires repetitive tests of the cargo fire extinguishing system, and one-time tests of the fuel crossfeed valve, pack, trim air, and alternate flap control switches; and repair or replacement of switch modules with new improved modules, if necessary. This action would revise the applicability of the existing AD. This action also would require replacement of the existing switch modules with new switch modules; replacement of the existing module assemblies with new module assemblies; or reworked module assemblies; as applicable. This proposal is prompted by the FAA's determination that certain switches are susceptible to contamination. The actions specified by the proposed AD are intended to minimize contamination of the switch contacts and consequent failure of the switches, which, if not corrected, could result in inability of the flight crew to activate the cargo fire extinguishing, fuel, air conditioning, and alternate flap systems.