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 a one-time inspection of the potable water and drain lines in the forward and aft cargo compartments for indications of overheating of the heater tape, exposed foam insulation, missing or damaged protective tape, or debris around the potable water fill and drain lines; and corrective action, if necessary. This action is necessary to prevent overheating of the heater tape on potable water fill and drain lines, which may ignite accumulated debris or contaminants on or near the potable water fill and drain lines, resulting in a fire in the airplane. This action is intended to address the identified unsafe condition.