Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747-100, 747-200B, 747-200C, 747-200F, 747SP, and 747SR series airplanes. This proposal would require a one-time inspection for chafing of certain wire bundles behind the flight engineer's panel; repairs, if necessary; and a modification to reroute a certain electrical wire bundle to ensure sufficient clearance between that wire bundle and an adjacent flood light support bracket. This action is necessary to prevent chafing of certain electrical wire bundles, which could result in smoke in the cockpit, and uncommanded discharge of fire extinguishing bottles for the No. 4 engine and consequent reduction of the ability to fight a fire in the No. 4 engine. This action is intended to address the identified unsafe condition.