Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to various Boeing and McDonnell Douglas transport category airplanes. This proposal would require revising the Airplane Flight Manual (AFM) to advise the flightcrew to don oxygen masks as a first and immediate step when the cabin altitude warning horn sounds. This action is necessary to prevent incapacitation of the flightcrew due to lack of oxygen, which could result in loss of control of the airplane. This action is intended to address the identified unsafe condition..