Action
Notice of proposed rulemaking (NPRM).
Summary
We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD would require installing two warning level indicator lights on each of the P1-3 and P3-1 instrument panels in the flight compartment. This proposed AD would also require revising the airplane flight manual to remove certain requirements of previous AD actions, and to advise the flightcrew of the following changes: Revised non-normal procedures to use when a cabin altitude warning or rapid depressurization occurs, and revised cabin pressurization procedures for normal operations. This proposed AD was prompted by a design change in the cabin altitude warning system that would address the identified unsafe condition. We are proposing this AD to prevent failure of the flightcrew to recognize and react to a valid cabin altitude warning horn, which could result in incapacitation of the flightcrew due to hypoxia (lack of oxygen in the body), and consequent loss of control of the airplane.