Airworthiness Directive 2015-21-11
one-timeAirworthiness Directives; The Boeing Company Airplanes
What this AD requires
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.
Which aircraft AD 2015-21-11 applies to
Model 737-100 through -500 series airplanes as identified in Boeing Special Attention Service Bulletin 737-21-1164, Revision 2, dated August 23, 2013; Model 737-600 through -900ER series airplanes as identified in Boeing Special Attention Service Bulletin 737-21-1165, Revision 3, dated July 16, 2014.
Whether AD 2015-21-11 actually applies to your aircraft (by serial and installed parts) and whether it’s already complied with comes from that aircraft’s records.
How AD compliance is recorded
A valid compliance record (14 CFR 43.9) states:
Tailplate reads a tail number’s logbooks and matches every applicable AD — including this one — to its compliance evidence, with recurring next-due dates computed.
Look up a tail number →Read the full directive (Federal Register)Applicability is derived from the FAA directive corpus and is advisory, not a legal airworthiness determination. Compliance is established only from an aircraft’s actual records.