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, 747-300, 747-400, 747-400D, 747-400F, and 747 SR series airplanes. This proposal would require inspection of fire extinguisher bottles in the engine and the auxiliary power unit (APU) to determine the part number; and replacement of the fire extinguisher bottles with new fire extinguisher bottles, if necessary. This action is necessary to prevent fractured discharge heads, which could cause the fire extinguishing agent to leak, which could result in an uncontrolled engine fire that could spread to the strut and wing, or an uncontrolled APU fire that could spread to the airplane structure. This action is intended to address the identified unsafe condition.