AD FAA-2015-4207

We are superseding Airworthiness Directive (AD) 2015-16-01 for certain The Boeing Company Model airplanes. AD 2015-16-01 required incorporating design changes to improve the reliability of the cabin altitude warning system by installing a redundant cabin altitude pressure switch, replacing the aural warning module (AWM) with a new or reworked AWM, and changing certain wire bundles or connecting certain previously capped and stowed wires as necessary. For certain airplanes, AD 2015-16-01 also required prior or concurrent incorporation of related design changes by modifying the instrument panels, installing light assemblies, modifying the wire bundles, and installing a new circuit breaker, as necessary. This AD retains all actions required by AD 2015-16-01. This AD was prompted by the discovery of a typographical error in AD 2015-16-01 that referred to a nonexistent paragraph. We are issuing this AD to prevent the loss of cabin altitude warning, which could delay flightcrew recognition of a lack of cabin pressurization, and could result in incapacitation of the flightcrew due to hypoxia (a lack of oxygen in the body), and consequent loss of control of the airplane.