Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Lockheed Model 188A and 188C series airplanes. This proposal would require a revision of the Airplane Flight Manual (AFM) to add procedures for donning the flightcrew oxygen masks when the cabin altitude warning horn is activated. This action is intended to prevent incapacitation of the flightcrew as a result of lack of oxygen and consequent loss of control of the airplane due to absence of AFM procedures for donning the flightcrew oxygen masks when the cabin altitude warning horn is activated.