Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Gulfstream Aerospace LP Model Astra SPX and 1125 Westwind Astra series airplanes. This proposal would require revising the airplane flight manual to advise the flightcrew to don oxygen masks as a first and immediate step following a cabin altitude alert. This action is necessary to prevent incapacitation of the flightcrew due to lack of oxygen. This action is intended to address the identified unsafe condition.