Airworthiness Directives; The Boeing Company Model 737-100, -200, -200C, -300, -400, and – 500 Series Airplanes

SUMMARY: We are adopting a new airworthiness directive (AD) for the products listed above. This AD requires installing two warning level indicator lights on the P2-2 center instrument panel in the flight compartment for certain airplanes. For a certain other airplane, this AD requires activating the cabin altitude warning and takeoff configuration warning lights. For all airplanes, this AD also requires revising the airplane flight manual to remove certain requirements included by previous AD actions, requires new pressure altitude limitations for certain airplanes, and advises the flightcrew of the following changes: revised emergency procedures to use when a cabin altitude warning or rapid depressurization occurs, and revised cabin pressurization procedures for normal operations. This AD was prompted by a design change in the cabin altitude warning system that would address the identified unsafe condition. We are issuing this AD to prevent failure of the flightcrew to recognize and react properly to a valid cabin altitude warning horn, which could result in incapacitation of the flightcrew due to hypoxia (lack of oxygen in body), and consequent loss of control of the airplane.

2011-03-14