Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747 series airplanes. This proposal would require identification of the valves installed on the engine struts as hydraulic supply (fire) shutoff valves for the engine-driven pump, corrective action if necessary, and eventual replacement of discrepant valves with serviceable parts. This action is necessary to prevent leakage of hydraulic (flammable) fluid into an engine fire, which could result in an uncontrolled fire. This action is intended to address the identified unsafe condition.