Airworthiness Directives; Safran Aerosystems (Formerly AVOX Systems Inc.; Scott Aviation) Oxygen Cylinder and Valve Assemblies, and Oxygen Valve Assemblies

SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2023-13-11, Amendment 39-22496 (88 FR 50011, August 1, 2023) (AD 2023-13-11). AD 2023-13-11 applied to certain AVOX Systems Inc. (formerly Scott Aviation) oxygen cylinder and valve assemblies, and oxygen valve assemblies, installed on but not limited to various transport airplanes. AD 2023-13-11 was prompted by reports of cylinder and valve assemblies having oxygen leakage from the valve assembly vent hole, caused by the absence of a guide that maintains appropriate spacing between certain parts, and by a determination that additional assemblies and parts are affected by the unsafe condition addressed by AD 2022-04-09, Amendment 39-21951 (87 FR 10958, February 28, 2022) (AD 2022-04-09) (which was superseded by AD 2023-13-11).

The NPRM published in the Federal Register on March 25, 2024 (89 FR 20558). The NPRM was prompted by a report that the manufacturer identified additional assemblies and parts subject to the unsafe condition. In the NPRM, the FAA proposed to continue to require the actions specified in AD 2023-13-11 and require similar actions for those additional assemblies and parts. The FAA is issuing this AD to address oxygen leakage from the cylinder and valve assemblies, which could result in decreased or insufficient oxygen supply during a depressurization event; and heating or flow friction, which could cause an ignition event in the valve assembly.

Discussion of Final Airworthiness Directive

Comments

The FAA received comments from four commenters, including Alaska Airlines (Alaska), American Airlines, Cathay Pacific Airways, Delta Air Lines (Delta), and SIAEC (SIA Engineering Company). The following presents the comments received on the NPRM and the FAA's response to each comment.

Request To Reference Later Revisions of Material Identified as Credit

Alaska requested adding the required revisions of the material (identified in paragraphs (l)(1) through (3) of the proposed AD) to the group of material identified as acceptable material in paragraph (p)(3) of the proposed AD for actions accomplished before the effective date of this AD.

The FAA disagrees with the request to revise paragraph (p)(3) of this AD. A global alternative method of compliance (AMOC) letter, 753-23-00200, was issued for AD 2023-13-11 that identified the required material in paragraphs (l)(1) through (3) of this AD as an acceptable AMOC. Accomplishment of the required material before the effective date of this AD to comply with the requirements of this AD is addressed by paragraph (f) of this AD. Paragraph (f) of this AD allows for the use of the required material before the effective date of this AD. No change to the AD has been made in this regard.

Request for Clarification on Acceptable Material for Credit Conclusion

SIAEC asked if credit can be granted for the actions specified in paragraphs (h) and (i) of the proposed AD if Revision 03 of the material was used.

The FAA agrees to clarify. Paragraphs (h) and (i) of this AD still reference Revision 03 of the material as the primary means of compliance for those parts identified in Appendices 1 or 2 of the referenced material. Paragraph (p) of this AD references the other revision levels that are acceptable for credit if they were used before certain effective dates. Paragraph (f) of this AD allows for the use of the required material before the effective date of this AD. No change to this AD is necessary in this regard.

Request To Require Actions for All Serial Numbers Instead of List of Affected Serial Numbers

American Airlines requested revising the applicability of the proposed AD to apply to all serial numbers of the affected part numbers, instead of adding groups of additional serial numbers in superseding ADs. Alaska requested revising the requirements for the serial number inspection, in particular, the ones in Appendix 3 of the required material referenced in paragraph (l) of the proposed AD. Alaska explained that the reading and recording of the serial numbers in three different places on the bottle leads to numerous discrepancies by personnel, which then leads to additional time spent trying to review all the numbers and identify the affected airplanes, possibly leading to affected bottles remaining on the airplane longer before being removed. Alaska suggested that a check for the manufacturer date, and then if a bottle has an affected manufacture date, an inspection to determine if the valve has a blue dot, would be sufficient to determine if an affected bottle is installed on the airplane. Alaska also suggested that once an affected bottle is found, the operator could then choose to accomplish the gap check and record the required serial numbers, or assume all affected bottles are suspect, and then send any suspected bottle back to the vendor instead of doing a gap check and subsequent serial number record-keeping.

The FAA does not agree to expand the applicability. Revising the applicability to refer to the date of manufacture instead of the serial numbers that must be inspected would increase the burden on some operators. However, operators choosing to inspect all the serial numbers of a part number may apply for an AMOC using the procedures specified in paragraph (q) of this AD. No changes to this AD have been made in this regard.

Request for Additional Compliance Time for Replacing Affected Parts

Alaska requested a revision to extend the compliance time to at least 90 days due to the large increase in number of affected bottles and potential effect on the limited supply of spare bottles. Alaska reasoned that a compliance time of 90 days would help repair vendors turn around the repair of faulty bottles in a timely manner. Although Alaska did not specify what action or paragraph the referenced compliance time would be for, the FAA infers that Alaska is referencing the replacement compliance time specified in paragraph (m)(2) of the proposed AD.

The FAA disagrees with the request. A global AMOC letter, 753-23-00200, was provided in December 2023 to provide relief for using later revisions of the material referenced in AD 2023-13-11, so knowledge of the additional numbers of affected bottles identified in the later revisions of the material would have been available since December 2023. In addition, the compliance time for most of the bottles affected by AD 2023-13-11 would have elapsed in early November 2023. Replacement before further flight ensures that airplanes are not knowingly flying with an unsafe condition. Operators may also apply for an AMOC under the provisions of paragraph (q) of this AD. The FAA has not changed the AD in this regard.

Request To Remove Inspection Report Requirement

Delta requested that the inspection report that was specified in paragraphs (j)(1) and (n)(1) of the proposed AD be removed. Delta pointed to guidance in the AD Manual (FAA-IR-M-8040.1C) ( https://drs.faa.gov/browse/excelExternalWindow/66DDD8E1D2E95DB3862577270062AABD.0001 ) that describes the general conditions for requiring inspection reports, and contrasted that with the material's description of the problem with the affected valve assemblies and the proposed AD's proposed requirements as the rationale for removing the inspection report.

The FAA agrees to remove the inspection report that was proposed in paragraphs (j)(1) and (n)(1) of the proposed AD for the reasons provided by the commenter. The subsequent paragraph identifiers have been revised, and the cost estimate has been updated accordingly.

Request To Address Discrepancy in Serial Numbers in Appendix of Material

SIAEC stated that there is a discrepancy within the tables of Appendix 3 of Safran Aerosystems Alert Service Bulletin 10015804-35-01, Revision 04, dated November 9, 2023. SIAEC noted that some of the affected valve serial numbers are erroneously listed in the affected “Cylinder Serial #” columns in the tables for the Cylinder and Valve assemblies P/Ns 89794077 and 891511-14.

The FAA agrees there are discrepancies in the serial number lists. Paragraph (l)(1) of this AD has been revised to correct the discrepancies.

Request for Clarification of Credit

Cathay Pacific Airways noted that the expanded serial number list from the latest revision of the Safran/AVOX service bulletins has a manufacturing date range from 2011 to 2017. The commenter asked whether the actions specified in the latest Safran/AVOX service bulletin must be redone on an affected serial number if maintenance can show that the part has been overhauled already.

The FAA contacted Safran for additional information regarding the comment, and provides the following clarification. The “overhaul kit” does not always have the necessary parts and therefore does not meet the intent of this AD. P/N 10015804 is a guide part number. If this part is missing, the gap check will fail. However, if the tank undergoes an overhaul as outlined in the Component Maintenance Manual (specified in paragraph 1.K of the applicable service bulletin), it will be equipped with the necessary guide, reassembled, and tested for leaks and hydrostatic pressure. This process aligns with the intent of this AD.

Additional Changes to This Final Rule

The FAA corrected the name of the publisher of the material identified in paragraphs (l)(1) through (3) of this AD from AVOX Systems Inc. to Safran Aerosystems. The FAA has also revised references to the manufacturer's name specified throughout this final rule to identify the manufacturer name as published in the most recent material for the affected models.

Conclusion

The FAA reviewed the relevant data, considered any comments received, and determined that air safety requires adopting this AD as proposed. Accordingly, the FAA is issuing this AD to address the unsafe condition on these products. Except for minor editorial changes, and any other changes described previously, this AD is adopted as proposed in the NPRM. None of the changes will increase the economic burden on any operator.

Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed the following material. This material specifies procedures for an inspection to determine the serial numbers of the oxygen cylinder and valve assemblies, and the oxygen valve assemblies, a detailed inspection for correct spacing of the gap between the bottom of the packing retainer and top of the valve body on the assemblies, parts marking, inspection report, and return of parts to the manufacturer. These documents are distinct since they apply to different assembly part numbers.

• Safran Aerosystems Alert Service Bulletin 10015804-35-01, Revision 04, dated November 9, 2023.
• Safran Aerosystems Alert Service Bulletin 10015804-35-02, Revision 06, dated August 30, 2023.
• Safran Aerosystems Alert Service Bulletin 10015804-35-03, Revision 05, dated September 29, 2023.

This AD also requires the following material, which the Director of the Federal Register approved for incorporation by reference as of September 5, 2023 (88 FR 50011, August 1, 2023).

• AVOX Systems Inc. Alert Service Bulletin 10015804-35-01, Revision 03, dated June 7, 2021.
• AVOX Systems Inc. Alert Service Bulletin 10015804-35-02, Revision 03, dated March 11, 2022.
• AVOX Systems Inc. Alert Service Bulletin 10015804-35-03, Revision 03, dated June 18, 2021.

This material is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section.

Costs of Compliance

The FAA estimates that this AD affects 3,777 oxygen cylinder and valve assemblies, and oxygen valve assemblies, installed on various transport category airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD: