EASA AD US-2021-08-04
Oxygen - Oxygen Mask Stowage Box Unit - Inspection / Replacement
Summary
Airworthiness Directive 2021-08-04 is a final rule issued by the Federal Aviation Administration addressing crew oxygen mask stowage box units on certain Boeing airplanes, including Model 737-700, -700C, -800, -900ER, Model 747-400F, and Model 767-200 and -300 series. The directive requires inspections and possible replacement or re-identification of affected oxygen mask stowage box units to prevent potential ignition sources or valve jams. This AD expands the applicability beyond the original scope of AD 2013-07-09 to include additional airplane models.
What Changed
This AD supersedes AD 2013-07-09 by retaining its inspection and replacement requirements while expanding the affected airplane models. It clarifies compliance methods, including acceptance of records review to conclusively determine affected serial numbers, and adjusts manufacturing date criteria for affected parts. The AD also confirms that installation of certain winglet Supplemental Type Certificates does not affect compliance.
Why It Matters
This directive addresses a safety risk where burrs in oxygen mask stowage box units could cause ignition or valve jams, potentially leading to oxygen-fed fires or restricted oxygen flow. Operators, maintenance organizations, and compliance teams must ensure affected parts are inspected and corrected to maintain airworthiness and crew safety. Expanding the applicability ensures broader fleet coverage, reducing the risk of unsafe conditions on more aircraft.
What To Do
Operators must perform a general visual inspection of crew oxygen mask stowage box units for affected serial numbers and replace or re-identify units as necessary. Records reviews are acceptable if they conclusively show the unit is not affected. Compliance with this AD is required by May 26, 2021, and maintenance actions may be performed using the applicable Aircraft Maintenance Manual without needing an alternative method of compliance.
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