Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 777 series airplanes. This proposal would require an inspection to determine the part number of the filter/regulator on the fire extinguishing system installed in the lower cargo compartment of the airplane, and replacement of the filter/regulator with a new filter/regulator, if necessary. This action is necessary to prevent leakage of fire extinguishing agent through the filter/regulator of the cargo fire extinguishing system, which could result in the inability of the fire extinguishing system to suppress a fire in the cargo compartment of the airplane. This action is intended to address the identified unsafe condition.