Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Israel Aircraft Industries, Ltd., Model 1121, 1121A, 1121B, 1123, 1124, and 1124A series airplanes. This proposal would require removing the existing oxygen shutoff valve and installing a new oxygen shutoff valve. This action is necessary to prevent rapid adiabatic compression within the oxygen line between the oxygen shutoff valve and the pressure regulator due to a shutoff valve that can be opened quickly, which could result in overheating of the oxygen system, and consequent fire in the cockpit. This action is intended to address the identified unsafe condition.