Airworthiness Directives; Airbus SAS Airplanes

SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2022-13-11, Amendment 39-22097 (87 FR 39741, July 5, 2022) (AD 2022-13-11). AD 2022-13-11 applied to all Airbus SAS Model A350-941 and -1041 airplanes. AD 2022-13-11 was prompted by a report of inadvertent AFS altitude changes on the FCU; an investigation revealed that, depending on the ring selection, failure of the ALT knob on the FCU could change the target altitude. AD 2022-13-11 required revising the existing AFM to include a procedure on the use of the AFS control panel ALT knob. AD 2022-13-11 also required replacing any affected FCU with a serviceable FCU, which would terminate the AFM revision following that replacement. The FAA issued AD 2022-13-11 to address erroneous target altitude during descent, climb, or go-around, which could result in an unexpected vertical trajectory deviation and loss of correct situational awareness that could potentially result in uncontrolled impact with the ground.

The NPRM published in the Federal Register on April 23, 2024 (89 FR 30281). The NPRM was prompted by AD 2023-0215, dated December 11, 2023; corrected December 13, 2023; issued by EASA, which is the Technical Agent for the Member States of the European Union (EASA AD 2023-0215) (also referred to as the MCAI). The MCAI states that since EASA AD 2021-0260, dated November 18, 2021 (EASA AD 2021-0260), was issued, several operators reported additional incidents of inadvertent AFS altitude changes on airplanes equipped with serviceable FCUs. Airbus is investigating the cause of these reported events and, as a precautionary measure, expanded the applicability of the AFM Temporary Revision (TR) 121, Issue 1, to all airplanes, including those equipped with serviceable FCUs. For the reasons described above, EASA AD 2023-0215 partially retains the requirements of EASA AD 2021-0260, which is superseded, and requires amendment of the applicable AFM by incorporating AFM TR 121, Issue 1, for airplanes equipped with serviceable FCUs. EASA AD 2023-0215 is still considered to be an interim action, and further EASA AD action may follow.

In the NPRM, the FAA proposed to continue to require certain actions in AD 2022-13-11, including replacing any affected FCU with a serviceable FCU, as specified in EASA AD 2023-0215. The NPRM also proposed to require expanding the applicability of the requirement to revise the existing AFM to all Model A350-941 and -1041 airplanes, including those equipped with serviceable FCUs, as specified in EASA AD 2023-0215. The NPRM also proposed to prohibit the installation of affected parts. The FAA is issuing this AD to address erroneous target altitude during descent, climb, or go-around, which could result in an unexpected vertical trajectory deviation and loss of correct situational awareness that could potentially result in uncontrolled impact with the ground.

You may examine the MCAI in the AD docket at regulations.gov under Docket No. FAA-2024-1007.

Discussion of Final Airworthiness Directive

Comments

The FAA received a comment from Air Line Pilots Association, International (ALPA), who supported the NPRM without change.

The FAA received an additional comment from Delta Air Lines (Delta). The following presents the comment received on the NPRM and the FAA's response to the comment.

Request To Extend Compliance Time for Replacement of Affected FCUs

Delta requested that a new exception be added to paragraph (h) of the proposed AD to extend the compliance time for the replacement of affected FCUs from 25 months to 32 months, due to lack of parts availability. Delta pointed out that it is currently the only U.S. operator affected by AD 2022-13-11 and that Thales, the FCU manufacturer, focused on providing serviceable FCUs to European operators first, since EASA AD 2021-0260 was required to be accomplished sooner than AD 2022-13-11. Delta asserted that this resulted in Delta losing approximately 17 months of the time needed to accomplish the required replacement and therefore, requested the additional 7-month extension. Additionally, Delta pointed out that the replacement is secondary to the requirement to amend the AFM, which affects both serviceable and affected FCUs. Because the compliance time for the AFM amendment is retained as proposed, Delta maintained that an adequate level of safety is provided during the requested extension of the compliance time for replacing the affected FCUs.

The FAA does not agree to extend the compliance time for replacing the affected FCUs. Delta did not provide enough justification to support an extension of the compliance time. In developing an appropriate compliance time for this action, the FAA considered the recommendations of the manufacturer, the urgency associated with the subject unsafe condition, the availability of required parts, and the practical aspect of accomplishing the required replacement within a period of time that corresponds to the normal scheduled maintenance for most affected operators. According to EASA, as the State of Design, parts availability was taken into consideration during development of the compliance time, which was determined to be sufficient to allow for the replacement of the affected parts to address the entire global A350 fleet. In consideration of these items, the FAA has determined that the proposed compliance time will ensure an acceptable level of safety. However, under the provisions of paragraph (i)(1) of this AD, the FAA will consider requests for approval of an extension of the compliance time if sufficient data are submitted to substantiate that the new compliance time would provide an acceptable level of safety. Therefore, no change is necessary to this AD.

Conclusion

This product has been approved by the aviation authority of another country and is approved for operation in the United States. Pursuant to the FAA's bilateral agreement with this State of Design Authority, it has notified the FAA of the unsafe condition described in the MCAI referenced above. The FAA reviewed the relevant data, considered the 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 this product. Except for minor editorial changes, 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

EASA AD 2023-0215 specifies procedures for revising the existing AFM to include a procedure on the use of the AFS control panel ALT knob for all Airbus SAS Model A350-941 and -1041 airplanes, including the airplanes equipped with serviceable FCUs part number (P/N) C31006AD01; and replacing any affected FCU having P/N C31006AC01 or C31006AB01 with a serviceable FCU having P/N C31006AD01. EASA AD 2023-0215 also prohibits the installation of affected parts.

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.

Interim Action

The FAA considers that this AD is an interim action. The FAA anticipates that further AD action will follow.

Costs of Compliance

The FAA estimates that this AD affects 27 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD: