Airworthiness DirectiveEASA AD US-2021-08-04

Oxygen - Oxygen Mask Stowage Box Unit - Inspection / Replacement

Published: Apr 26, 2021
Effective: May 26, 2021
Deadline: May 26, 2021
Replaces: 2013-07-09

Boeing 737 700 700C 800 900ER

AI-generated summary of the official EASA document. Verify against the PDF before acting.

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.

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.

More for Boeing 737

All 175

Get the next one by email

New ADs and bulletins for Boeing 737, 747, 757 and 767, summarized like this page, every Monday.