Discussion
We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all Airbus SAS Model A318 and A319 series airplanes; Model A320-211, A320-212, A320-214, A320- 216, A320-231, A320-232, and A320-233 airplanes; and Model A321-111, A321-112, A321-131, A321-211, A321-212, A321-213, A321-231, and A321- 232 airplanes. The NPRM published in the Federal Register on April 16, 2018 (83 FR 16251). The NPRM was prompted by reports of missing assembly hardware on the THSA. The NPRM proposed to require repetitive inspections and checks of the lower and upper THSA attachments and applicable related investigative and corrective actions; a one-time inspection of the THSA lower attachment and replacement as applicable; and, for certain airplanes, activation of the ELSD and concurrent modifications.
We are issuing this AD to address uncontrolled movement of the horizontal stabilizer as a result of the latent (undetected) failure of the THSA's primary load path and consequent loss of control of the airplane.
The European Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Union, has issued EASA Airworthiness Directive 2017-0237, dated December 4, 2017 (referred to after this as the Mandatory Continuing Airworthiness Information, or ``the MCAI''), to correct an unsafe condition for all Airbus SAS Model A318 and A319 series airplanes; Model A320-211, A320-212, A320-214, A320-216, A320-231, A320-232, A320-233 airplanes; and Model A321-111, A321-112, A321-131, A321-211, A321-212, A321-213, A321-231, and A321- 232 airplanes. The MCAI states:
The Trimmable Horizontal Stabilizer Actuator (THSA) of Airbus A320 Family aeroplanes has been rig-tested to check secondary load path behaviour in case of primary load path failure. In that configuration, the loads are transferred to the secondary load path, which should jam, preventing any Trimmable Horizontal Stabilizer motion. The test results showed that the secondary load path did not jam as expected, preventing detection of the primary load path failure. To verify the integrity of the THSA primary load path and the correct installation of the THSA, Airbus issued Service Bulletin (SB) A320-27-1164, later revised multiple times, and SB A320- 27A1179, and EASA issued AD 2006-0223 [which corresponds to FAA AD 2007-06-02, Amendment 39-14983 (72 FR 12072, March 15, 2007) (``AD 2007-06-02'')], AD 2007-0178 [which corresponds to FAA AD 2008-09- 16, Amendment 39-15497 (73 FR 24160, May 2, 2008)(``AD 2008-09- 16'')], AD 2008-0150, and AD 2014-0147, each AD superseding the previous one, requiring one-time and repetitive inspections.
Since EASA AD 2014-0147 was issued, Airbus designed a new device, called Electrical Load Sensing Device (ELSD), to introduce a new means of THSA upper secondary load path engagement detection. Consequently, Airbus issued several SBs (Airbus SB A320-27-1245,A320-27-1246, and A320-27-1247, depending on aeroplane configuration) providing instructions to install the wiring provision for ELSD installation and to install ELSD on the THSA, and SB A320-27-1248, providing instructions to activate the ELSD. Airbus also revised SB A320-27-1164, now at Revision 13, including instructions applicable for aircraft equipped with ELSD.
Furthermore, following a visual inspection of the THSA, an operator reported that the THSA was found with a bush missing, inducing torqueing of the THSA lower attachment primary bolt against the THSA lug, which resulted in the application of a transverse force on the lug.
Prompted by several other identical findings, Airbus released Alert Operator Transmission (AOT) A27N010-17 to provide instructions for inspection and associated corrective actions.
For the reasons described above, this AD retains the requirements of EASA AD 2014-0147, which is superseded, and requires installation of ELSD on the THSA, ELSD activation, and a one-time inspection to verify the bush presence on the THSA lower attachment.
The unsafe condition is uncontrolled movement of the horizontal stabilizer as a result of the latent (undetected) failure of the THSA's primary load path and consequent loss of control of the airplane.
The required actions include repetitive inspections and checks of the lower and upper THSA attachments and applicable related investigative and corrective actions; a one-time inspection of the THSA lower attachment and replacement as applicable; and, for certain airplanes, activation of the ELSD and concurrent modifications.
Related investigative actions include an inspection of the upper THSA attachment, an inspection of the lower attachment, and a check of the upper and lower clearance between the secondary nut trunnion and the junction plate. Corrective actions include replacement of the THSA and repair.
You may examine the MCAI in the AD docket on the internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2018- 0298.
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Comments
We gave the public the opportunity to participate in developing this final rule. The following presents the comments received on the NPRM and the FAA's response to each comment.
Support for the NPRM
The Air Line Pilots Association, International, stated its support for the NPRM. United Airlines stated that it has no objection to the NPRM.
Request To Allow Future Revisions of Service Information
Delta Air Lines (DAL) requested that the proposed AD allow operators the opportunity to utilize the latest data and instructions available without the need to request an alternative method of compliance (AMOC). DAL proposed that after each reference made to service information in paragraphs (g), (h), (i), (j), (k), (m)(1), and (m)(2) of the proposed AD, the following statement is included:
Or using a method approved by the Manager, International Section, TransportStandards Branch, FAA; or the European Aviation Safety Agency (EASA); or Airbus's EASA Design Organization Approval (DOA).
DAL noted that the service information has been revised multiple times or has been revised within a short period of time. DAL observed that the statement quoted above is based on language used in paragraph (g) of AD 2018-03-12, Amendment 39-19185 (83 FR 5906, February 12, 2018) (``AD 2018-03-12''), and should be considered as standard wording for future ADs, as applicable.
We disagree with the commenter's request. We infer that the commenter is requesting a way for operators to comply with the requirements of an AD by using service information revisions that are issued after an AD is published without having to request an AMOC. We may not refer to any document that does not yet exist. In general terms, we are required by Office of the Federal Register (OFR) regulations for approval of materials ``incorporated by reference,'' as specified in 1 CFR 51.1(f),to either publish the service document contents as part of the actual AD language; or submit the service document to the OFR for approval as ``referenced'' material, in which case we may only refer to such material in the text of an AD. The AD may refer to the service document only if the OFR approved it for ``incorporation by reference.'' See 1 CFR part 51. To allow operators to use later revisions of the referenced document (issued after publication of the AD), either we must revise the AD to reference specific later revisions, or operators must request approval to use later revisions as an AMOC with this AD. However, we may consider approving global AMOCs to allow operators to use future revisions of the service information. We reserve the use of the wording requested by the commenter for situations where no service information is available or a service document, such as an aircraft maintenance manual, cannot be incorporated by reference in an AD. Therefore, we have not changed this AD in this regard.
Request To Specify Required Paragraphs in Airbus Alert Operators Transmission
DAL requested that paragraph (k) of the proposed AD specify only paragraphs 4.2.2 and 4.2.3 of Airbus Alert Operators Transmission (AOT) A27N010-17, Revision 01, dated October 17, 2017, including AOT Appendix_A27N010-17, because, as a whole, the service information contains data that are unrelated to the inspection process. Paragraphs 4.2.2 and 4.2.3 of the service information provide the inspection activities and corrective actions.
We agree with the commenter that the primary instructions for inspection and corrective actions are contained in paragraphs 4.2.2 and 4.2.3 of Airbus AOT A27N010-17, Revision 01, dated October 17, 2017, including AOT Appendix_A27N010-17. We have revised paragraph (k) of this AD to require only paragraphs 4.2.2 and 4.2.3 of Airbus AOT A27N010-17, Revision 01, dated October 17, 2017, including AOT Appendix_A27N010-17. Note that there is relevant information outside of those two paragraphs, such as references to part numbers, aircraft maintenance manual procedures, and an appendix. Procedures outside of paragraphs 4.2.2 and 4.2.3 can be deviated from, using accepted methods provided in an operator's maintenance or inspection program, provided the required AD actions can be done and the airplane can be put back in service in an airworthy condition.
Request To Modify Language Regarding Contacting the Manufacturer
DAL noted that paragraph (o) of the proposed AD provides exceptions to two Airbus service information documents--Airbus Service Bulletin A320-27-1164, Revision 13, dated August 8, 2016; and Airbus AOT A27N010-17, Revision 01, dated October 17, 2017, including AOT Appendix_A27N010-17, with respect to contacting the manufacturer. DAL proposed that this paragraph be rewritten to state:
Any approved method which specifies to contact the manufacturer: Before further flight, accomplish the corrective actions in accordance with the procedures specified in paragraph (v)(2) of this AD.
We acknowledge the commenter's request to clarify paragraph (o) of this AD. When specifying exceptions to required service information, we are unable to generalize the required documents by stating ``any approved method,'' as requested by the commenter. We must identify the specific service information. Therefore, we have not changed this AD in this regard.
Request for Clarification of Service Information Instructions
DAL observed that Airbus Service Bulletin A320-27-1245, Revision 00, dated March 6, 2017, indicates multiple configurations for certain aircraft. As an example, DAL pointed out that aircraft manufacturer serial number (MSN) 118 is shown as both configuration 078 and configuration 082. DAL stated the service information does not provide clear guidance on determining if both or only one set of material/ instructions is applicable. DAL requested that the service bulletin be revised to clarify the intent of the multiple configurations and how to address them.
We disagree with the commenter's request to revise the service information; however, we agree to clarify. The referenced service information is adequate because different aircraft configurations can be determined based on the type of placard installed. Airbus Service Bulletin A320-27-1245, Revision 00, dated March 6, 2017, provides airplane configuration definitions in paragraph 1.A.(5), ``Configuration Definition,'' of the ``Planning Information'' section. According to the configuration definition, configuration 078 has placard 33LM PN D11311117A00 installed and configuration 082 has placard 33LM PN 002051-09 installed. Once the placard installation is determined, an operator can follow the instructions based on each respective configuration. We have not changed this AD in this regard.
Request for One Comprehensive AD To Address THSA System
DAL noted that the Model A319, A320, and A321 THSA system has had a continually complicated maintenance and regulatory history. The THSA system has been subject to numerous ADs throughout the years that address numerous individual shortcomings. The
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proposed AD encompasses several different aspects (inspections and alterations), yet there are still other regulatory actions such as the replacement of No-Back Brake components or overhaul restrictions, which complicate the operators' maintenance activities. DAL requested that future regulatory actions related to the system be reviewed with a goal of providing a singular, coordinated over-arching regulatory and maintenance requirement.
We agree that there have been several ADs issued on the THSA system addressed in this AD, and we acknowledge the commenter's concerns. We understand that the EASA and the airplane manufacturer are making an effort to combine as many THSA issues as possible into a single rulemaking action to simplify the THSA requirements. In response totheir efforts, we may consider additional rulemaking in the future to simplify the THSA requirements. However, at this time, we are issuing this final rule AD to address the specified unsafe condition. No change has been made to this AD in this regard.
Request To Refer to Revised Service Information
Airbus noted that two of the service bulletins referred to in the NPRM were revised and requested that the revised service bulletins be referred to in the final rule. The current revision levels are Airbus Service Bulletin A320-27-1164, Revision 14, dated January 16, 2018; and Airbus Service Bulletin A320-27-1248, Revision 01, dated April 16, 2018.
We agree with the commenter's request. In the NPRM we referred to Airbus Service Bulletin A320-27-1164, Revision 13, dated August 8, 2016; and Service Bulletin A320-27-1248, Revision 00, dated March 6, 2017. Airbus Service Bulletin A320-27-1164, Revision 14, dated January 16, 2018, includes clarifications regarding reporting inspection results but does not change the proposed reporting requirements of the NPRM and otherwise adds no substantive changes compared with the previous version. Airbus Service Bulletin A320-27-1248, Revision 01, dated April 16, 2018, clarifies the instructions, but adds no substantive changes compared with the previous version. We have therefore revised the ``Related Service Information under 1 CFR part 51'' paragraph in this final rule to refer to Airbus Service Bulletin A320-27-1164, Revision 14, dated January 16, 2018; and Airbus Service Bulletin A320-27-1248, Revision 01, dated April 16, 2018. We have also revised paragraphs (g), (h), (i), (j), and (o)(1) of this AD to refer to Airbus Service Bulletin A320-27-1164, Revision 14, dated January 16, 2018. In addition, we revised paragraph (m) of this AD to refer to Airbus Service Bulletin A320-27-1248, Revision 01, dated April 16, 2018.
Furthermore, we revised paragraph (s), ``Credit for Previous Actions,'' of this AD to include AirbusService Bulletin A320-27-1164, Revision 13, dated August 8, 2016; and Service Bulletin A320-27-1248, Revision 00, dated March 6, 2017. Specifically, we revised paragraph (s)(1) to provide credit for actions done before the effective date of this AD using Airbus Service Bulletin A320-27-1164, Revision 10, dated March 27, 2014; Revision 11, dated December 15, 2014; Revision 12, dated March 23, 2016; or Revision 13, dated August 8, 2016. We also added paragraph (s)(3) to this AD to provide credit for actions required by paragraph (m)(1) of this AD, if those actions were performed before the effective date of this AD using Airbus Service Bulletin A320-27-1248, Revision 00, dated March 6, 2017. We redesignated subsequent paragraphs of this AD accordingly.
Request To Supersede Affected ADs
Airbus requested that the FAA consider aligning with EASA's decision of superseding affected ADs instead of keeping the obsolete ADs active. We infer that Airbus is requesting that we supersedeAD 2007-06-02 and AD 2008-09-16 instead of issuing this stand-alone AD that terminates the requirements of AD 2007-06-02 and AD 2008-09-16.
We acknowledge the commenter's request. Although paragraph (u) of this AD states ``Accomplishing the initial actions required by paragraphs (g) and (h) of this AD, and accomplishing the applicable actions required by paragraphs (i) and (j) of this AD, terminates all requirements of AD 2007-06-02 and AD 2008-09-16,'' it does not supersede those ADs. The purpose of issuing stand-alone AD actions is to reduce the complexity involved with superseding certain ADs. After certain compliance times in this AD have passed, we may consider rescinding AD 2007-06-02 and AD 2008-09-16 since they are terminated by certain actions in this AD. In addition, if we converted this AD to a supersedure, we would need to issue another notice for public comment, which would further delay issuance of this final rule. Therefore, we have not changed this AD in this regard.
Conclusion
We reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this final rule with the changes described previously and minor editorial changes. We have determined that these minor changes:
Are consistent with the intent that was proposed in the NPRM for addressing the unsafe condition; and
Do not add any additional burden upon the public than was already proposed in the NPRM.
We also determined that these changes will not increase the economic burden on any operator or increase the scope of this final rule.
Related Service Information Under 1 CFR Part 51
Airbus has issued Alert Operators Transmission (AOT) A27N010-17, Revision 01, dated October 17, 2017, including AOT Appendix_A27N010-17. This service information describes the procedure for a one-time general visual inspection of the THSA lower attachment to measure the gap between the THSA lower attachment tab washer and attachment plates and replacement of the THSA lower attachment if the measured gap is less than 0.5 mm. The replacement includes doing an inspection of the THSA parts to confirm the bushing is missing and applicable corrective actions (i.e., repair).
Airbus has also issued Service Bulletin A320-27-1164, Revision 14, dated January 16, 2018. This service information describes procedures for a general visual inspection of the upper THSA attachment for correct installation, cracks, damage and metallic particles; a general visual inspection of the lower and upper THSA attachments for correct installation; a check of the clearance between secondary nut trunnions and junction plates and correct installation of the lower THSA attachment; a general visual inspection of the THSA ball screw to check for the absence of dents; and applicable related investigative and corrective actions.
In addition, Airbus has issued Service Bulletin A320-27-1245, Revision 00, dated March 6, 2017. This service information describes the procedure to modify the wiring provisions for the ELSD.
Airbus has also issued Service Bulletin A320-27-1246, Revision 01, dated November 4, 2016. This service information describes the procedures to adapt the wiring provision of the ELSD
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and THSA to accommodate the correct installation of the ELSD.
Airbus has issued Service Bulletin A320-27-1247, Revision 00, dated March 6, 2017. This service information describes the procedure to modify the upper attachment secondary load path of the THSA to accommodate the correct installation of the ELSD.
Airbus has issued Service Bulletin A320-27-1248, Revision 01, dated April 16, 2018. This service information describes the procedure to activate the ELSD.
UTAS has issued United Technologies Corporation (UTC) Aerospace Systems Repair Instructions RF-DSC-1361-17, Version 00, including Appendix A, dated May 24, 2017. This service information describes the repair instructions tofollow if the bushing is missing, as specified in AOT A27N010-17, Revision 01, dated October 17, 2017.
This service information 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
We estimate that this AD affects 1,180 airplanes of U.S. registry.
We estimate the following costs to comply with this AD:
Estimated Costs ----------------------------------------------------------------------------------------------------------------
Cost on U.S.
Action Labor cost Parts cost Cost per product operators ---------------------------------------------------------------------------------------------------------------- Inspections, check, activation, Up to 59 work- Up to $15,353..... Up to $20,368..... Up to $24,034,240.
and modifications. hours x $85 per
hour = $5,015. Reporting....................... 1 work-hour x $85 0................. 85................ 100,300.
per hour = $85. ----------------------------------------------------------------------------------------------------------------
We estimate the following costs to do any necessary replacements that would be required based on the results of the inspections. We have no way of determining the number of aircraft that might need this replacement:
On-Condition Costs ----------------------------------------------------------------------------------------------------------------
Cost per
Action Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- Replacement................................... 11 work-hours x $85 per hour = $240,000 $240,935
$935. ----------------------------------------------------------------------------------------------------------------
We have received no definitive data that would enable us to provide cost estimates for the on-condition repairs specified in this AD.
Paperwork Reduction Act
A federal agency may not conduct or sponsor, and a person is not required to respond to, nor shall a person be subject to penalty for failure to comply with a collection of information subject to the requirements of the Paperwork Reduction Act unless that collection of information displays a current valid OMB control number. The control number for the collection of information required by this AD is 2120- 0056. The paperwork cost associated with this AD has been detailed in the Costs of Compliance section of this document and includes time for reviewing instructions, as well as completing and reviewing the collection of information. Therefore, all reporting associated with this AD is mandatory. Comments concerning the accuracy of this burden and suggestions forreducing the burden should be directed to the FAA at 800 Independence Ave., SW, Washington, DC 20591, ATTN: Information Collection Clearance Officer, AES-200.
Authority for This Rulemaking
Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII: Aviation Programs, describes in more detail the scope of the Agency's authority.
We are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701: ``General requirements.'' Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identifiedin this rulemaking action.
This AD is issued in accordance with authority delegated by the Executive Director, Aircraft Certification Service, as authorized by FAA Order 8000.51C. In accordance with that order, issuance of ADs is normally a function of the Compliance and Airworthiness Division, but during this transition period, the Executive Director has delegated the authority to issue ADs applicable to transport category airplanes and associated appliances to the Director of the System Oversight Division.
Regulatory Findings
This AD will not have federalism implications under Executive Order 13132. This AD will not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government.
For the reasons discussed above, I certify that this AD:
(1) Is not a ``significant regulatory action'' under Executive Order 12866,
(2) Is not a ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979),
(3) Will not affect intrastate aviation in Alaska, and
(4) Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.