Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Boeing Model 747- 400 series airplanes, that currently requires replacement of electrical wiring to the fuel shutoff valve for each engine. This action would require replacement of the fuel shutoff valve wire and sleeve with a wire in two non-metallic sleeves in the conduit in the struts of each engine. This proposal is prompted by reports of additional occurrences of chafing and shorting of the wiring of the engine fuel shutoff valves. The actions specified by the proposed AD are intended to prevent such chafing and shorting, which could result in the pilot's inability to shut off the supply of fuel in the event of an engine fire.