Airworthiness Directives; Boeing Model 777-200 Series Airplanes

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 777-200 series airplanes. This action 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. This 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 amendment is prompted by a report indicating that the flight crew received a warning of fire in the forward cargo compartment during flight; later inspection revealed that the metered fire bottles failed to discharge due to suspected contamination of the arming switch contacts of the cargo fire extinguishing system. The actions specified in this 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.