Action
Supplemental notice of proposed rulemaking (NPRM); reopening of comment period.
Summary
We are revising an earlier proposed airworthiness directive (AD) for certain The Boeing Company Model 737-700, -700C, -800, and - 900ER series airplanes, Model 747-400F series airplanes, and Model 767- 200 and -300 series airplanes. That NPRM proposed to require an inspection for affected serial numbers of the crew oxygen mask stowage box units; and replacement of the crew oxygen mask stowage box unit with a new crew oxygen mask stowage unit, if necessary. That NPRM was prompted by reports indicating that certain crew oxygen mask stowage box units were possibly delivered with a burr in the inlet fitting. The burr might break loose during test or operation, and might pose an ignition source or cause an inlet valve to jam. This action revises that NPRM by adding a step to identify and label certain crew oxygen mask stowage box units that have already been inspected and reworked by the supplier, and allowing operators to install new or serviceable crew oxygen mask stowage box units. We are proposing this supplemental NPRM to prevent an ignition source, which could result in an oxygen-fed fire; or an inlet valve jam in a crew oxygen mask stowage box unit, which could result in restricted flow of oxygen. Since these actions impose an additional burden over that proposed in the NPRM, we are reopening the comment period to allow the public the chance to comment on these proposed changes.