Discussion
We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2016-01-11, Amendment 39-18370 (81 FR 3316, January 21, 2016) (``AD 2016-01-11''). AD 2016-01-11 applied to certain Airbus Model A320-211, -212, and -231 airplanes. The NPRM published in the Federal Register on December 13, 2017 (82 FR 58566). The NPRM was prompted by a report that, during a center fuselage certification full- scale fatigue test, cracks were found on the front spar vertical stringer at a certain frame. The NPRM proposed to continue to require repetitive inspections for cracking of the radius of the front spar vertical stringers and the horizontal floor beam on FR 36, repetitive inspections for cracking of the fastener holes of the front spar vertical stringers on FR 36, and repair if necessary. The NPRM also proposed to add new thresholds and intervals for the repetitive inspections; require, for certain airplanes, a potential terminating action modification of the center wing box area; and expand the applicability. We are issuing this AD to address fatigue cracking of the front spar vertical stringers on the wings, which
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could result in the reduced structural integrity 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 AD 2017-0099, dated June 8, 2017 (referred to after this as the Mandatory Continuing Airworthiness Information, or ``the MCAI''), to correct an unsafe condition for certain Airbus Model A318 series airplanes; Model A319 series airplanes; Model A320-211, -212, -214, -216, -231, -232, and -233 airplanes; and Model A321 series airplanes. The MCAI states:
During centre fuselage certification full-scale fatigue test, cracks were found on the front vertical stringer at frame (FR) 36. Analysis of these findings indicated that a number of in-service aeroplanes could be similarly affected.
This condition, if not detected and corrected, could lead to crack propagation and consequent deterioration of the structural integrity of the aeroplane.
To address this potential unsafe condition, Airbus issued Airbus Service Bulletin (SB) A320-57-1016 to provide inspection instructions, and, consequently, [Direction G[eacute]n[eacute]rale de l'Aviation Civile] DGAC France issued AD 97-311-105 [which corresponded to FAA AD 98-18-26, Amendment 39-10742 (63 FR 47423, September 8, 1998)] to require those repetitive [high frequency eddy current (HFEC)] inspections [for cracking]. At the same time, modification in accordance with Airbus SB A320-57-1017 was introduced as (optional) terminating action for the repetitive inspections * * *.
After that [French] AD was issued, and following new analysis, modification per Airbus SB A320-57-1017 was no longer considered to be terminating action for the repetitive inspections as required by DGAC France AD 97-311-105. Aeroplanes with [manufacturer serial number] MSN 0080 up to MSN 0155 inclusive were delivered with the addition of a 5 [millimeter] mm thick light alloy shim under the heads of 2 fasteners at the top end of the front spar vertical stringers (Airbus mod 21290P1546, which is the production line equivalent to in-service modification through Airbus SB A320-57- 1017). Aeroplanes with MSN 0156 or higher are delivered with vertical stiffeners of the forward wing spar upper end with stiffener cap thickness increased from 4 to 6 mm (Airbus mod 21290P1547).
Prompted by these findings, Airbus issued SB A320-57-1178 Revision 01 to introduce new repetitive inspections and, consequently, EASA issued AD 2014-0069 [which corresponds to FAA AD 2016-01-11], superseding DGAC France AD 97-311-105 to require the new repetitive inspections, and, depending on findings, accomplishment of applicable corrective action(s).
Since [EASA] AD 2014-0069 was issued, further investigations in the frame of the WidespreadFatigue Damage (WFD) campaign identified that some repetitive inspection thresholds and intervals have to be revised or introduced, and a new [potential] terminating action modification has been designed.
For the reasons described above, this [EASA] AD retains the requirements of EASA AD 2014-0069, which is superseded, revises and introduces thresholds and intervals for the repetitive inspections, [introduces a potential terminating action modification,] and expands the Applicability.
Required actions also include reporting. Although this AD does not explicitly restate the requirements of AD 2016-01-11, it retains certain requirements of AD 2016-01-11. Those requirements are referenced in Airbus Service Bulletin A320-57-1178, Revision 03, including only Appendix 03, both dated November 29, 2016.
This service information is identified in ``Related Service Information under 1 CFR part 51,'' in this preamble and in paragraph (i)(1) of this AD. You may examine the MCAI in theAD docket on the internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2017-1102.
Comments
We gave the public the opportunity to participate in developing this AD. The following presents the comments received on the NPRM and the FAA's response to each comment.
Support for the NPRM
United Airlines (UAL) stated that it agrees with the intent of the NPRM.
Request To Change Costs of Compliance Section
Delta Airlines (DAL) requested that the Costs of Compliance section of the proposed AD be revised to include the costs for reporting inspection findings and for modifying the airplane as specified in Airbus Service Bulletin A320-57-1200. DAL stated that the cost of reporting, in addition to the cost for the modification has been significantly underestimated in the cost section of the proposed AD. DAL noted that it takes 2 work-hours per airplane to do the steps for reporting, in addition to numerous work-hours for setup time. DALpointed out that the proposed AD mandates two service bulletins, and the cost of both should be included in the proposed AD. DAL explained that the kit cost for the modification is $55,360 (depending on configuration), and the labor is approximately 137 work-hours. DAL stated that the cost does not reflect lost revenue due to removing the airplane from service outside of the normal maintenance schedule. Given all of these factors, DAL asserted that the true cost of the proposed AD on operators should be as follows.
For the inspection provided in Airbus Service Bulletin A320-57-1178: $1,947,850 + $232,275 for reporting.
For the modification provided in Airbus Service bulletin A320-57-1200: $54,609,075 + $232,275 for reporting.
Total cost to industry is: $57,021,475.
We partially agree. We do not agree to increase the work-hours for reporting; however. We estimate only the time necessary to submit a report (per each response), since the reporting information would be obtainedwhen accomplishing the inspection(s) in the service bulletin(s). However, we do agree to include the costs for the modification for certain airplanes specified in Airbus Service Bulletin A320-57-1200, dated November 20, 2015, which will result in a total fleet cost of $1,107,050 or $110,705 per product, for the basic requirement of this AD. We have changed the ``Costs of Compliance'' section of this final rule accordingly.
Request To Clarify Certain Requirements in Table 1 to Paragraphs (g), (h), (i)(1), and (j) of the Proposed AD
UAL asked that we revise table 1 to paragraphs (g), (h), (i)(1), and (j) of the proposed AD to clarify that Airbus modification (Mod) 21290P1546 is limited to airplanes with manufacturer serial numbers (MSN) 0080 up to MSN 0155 inclusive. UAL also asked that another clarification be added to table 1 to specify that Mod 21290P1547 is effective for airplanes with MSN 0156 or higher, which were delivered with vertical stiffeners of the forward wing spar upper end with stiffener cap thickness increased from 4 to 6 mm. UAL stated that those airplanes were delivered with the addition of a 5 millimeter (mm) thick light alloy shim under the heads of two fasteners at the top end of the front spar vertical stringers. UAL added that Mod 21290P1546 is the production line equivalent to in-service modifications through Airbus Service Bulletin A320-57-1017.
We do not agree with the commenter's requests. Figure 1 to paragraphs (g), (h), (i)(1), and (j) of this AD (table 1 to paragraphs (g), (h), (i)(1), and (j) of the proposed AD) defines configurations by whether or not certain modifications were done and certain service bulletins were embodied. Airbus Service Bulletin A320-57-1017 provides information regarding Mod 21290P1546 and Mod 21290P1547 that identifies the specific configuration of the airplanes. The definitions in figure 1 to paragraphs (g), (h), (i)(1), and (j) of this AD and figure 2 to paragraphs (g) and (i)(1) of this AD[[Page 33811]]
correspond to the airplane configuration definitions provided in Appendix 1 of EASA AD 2017-0099, dated June 8, 2017. Therefore, we have not changed this AD in this regard.
Request To Extend Compliance Times for Configuration 003 Airplanes
DAL asked that we extend the proposed initial compliance time for Configuration 003 airplanes identified in figure 3 to paragraph (i)(1) of the proposed AD. DAL asked that the initial inspection be extended to 24 months, or at a minimum, that the flight-hour limit be increased to 1,500 flight hours, since the initial inspection is dependent on flight cycles, not flight hours. DAL provided the following options for the proposed compliance time: (1) Next scheduled . . ., (2) 12-month . . ., or (3) 4-months. . . . DAL stated that it currently operates five airplanes, which are Configuration 003 on which the threshold of ``Before exceeding 32,000 flight cycles or 64,000 flight hours since airplane first flight'' for the initial inspection has been exceeded. DAL added that, at current fleet utilization rates, it will require the inspections be done within approximately 85 days after the effective date of the AD, due to the flight-hour limit. DAL noted that this will necessitate a special maintenance visit. DAL also stated that its maintenance program requires a maintenance visit every 24 months, and added that most, if not all, of the airplanes will not visit a hangar within the next 3 months.
DAL asked that the compliance time be extended to 6 years after the effective date of the AD, with supplemental inspections for accomplishing the modification required by paragraph (j) of the proposed AD. At a minimum, DAL requested relief by allowing for an inspection, as specified in Airbus Service Bulletin A320-57-1178, Revision 03, dated November 29, 2016, at 2-year intervals until the heavy ``H'' check can be reached. DAL stated that modifications to Configuration 003 airplanes require incorporation of AirbusService Bulletin A320-57-1200, dated November 20, 2015, prior to reaching 48,000 flight cycles or 96,000 flight hours, whichever occurs first. DAL stated that, at its current utilization rate, this modification would be required in approximately 4 years; however, its current heavy maintenance ``H'' checks are scheduled at 6-year intervals. DAL noted that this is a minimal risk, since Configuration 003 airplanes will receive supplemental inspections within a short time after the effective date specified in paragraph (i)(1) of the proposed AD.
We do not agree with the commenter's requests to extend the specified compliance times. The compliance times for the actions specified in this AD for addressing widespread fatigue damage (WFD) were established to ensure that affected structure is replaced before WFD develops. Standard inspection techniques cannot be relied on to detect WFD before it becomes a hazard to flight. We will not grant any extensions of the compliance time to completeany AD-mandated service bulletin related to WFD without extensive new data that would substantiate and clearly warrant such an extension. Therefore, we have not changed this AD in this regard.
Request To Allow Alternative Method of Compliance (AMOC) in Lieu of Contacting the Manufacturer for Repair Instructions
DAL asked that an allowance be made under the provisions of paragraph (o)(2) of the proposed AD (and future ADs) for contacting Airbus for any deviations to the instructions contained within the service bulletins required in paragraphs (i) and (j) of the proposed AD, and to be able to use their EASA Design Organization Approval (DOA) approvals without seeking separate and redundant FAA AMOCs. DAL stated that as airplanes are scheduled for maintenance to comply with the proposed AD, the operator may discover that the Airbus service information contains errors that can affect compliance with the actions in the proposed AD. DAL did not state there are any known errors inthe service information required in paragraphs (i) and (j) of the proposed AD. DAL added that, although the proposed AD provides an option to receive approval from the Manager, International Section, Transport Standards Branch, FAA; or EASA, or Airbus's EASA DOA; as specified in paragraph (o)(2) of the proposed AD, no such allowance is provided for receiving approval for deviations from the service information. DAL noted that past experience has shown that the FAA is unable to provide AMOC approvals within 2 days after receiving the request, which could result in grounding of airplanes. DAL suggested using the language in paragraph (6) of the MCAI.
We do not agree with the commenter's request. Paragraph (o)(2) of this AD, ``Contacting the Manufacturer,'' only addresses the requirement to contact the manufacturer for corrective actions for the identified unsafe condition and does not cover deviations from the requirements of AD-mandated actions. We do not agree to expand paragraph (o)(2) of this AD to include such deviations because we need to ensure that any deviations from the requirements of AD-mandated actions are properly reviewed to adequately address the unsafe condition. Regarding paragraph (6) of the MCAI, if an operator is not able to comply with service information that is required by an AD, then the operator must request an AMOC in accordance with the procedures specified in paragraph (o)(1) of this AD.
We also note that, although we cannot guarantee AMOC approvals within 2 business days, we have provided AMOC approvals to U.S. operators, including DAL, within 24 hours of receiving the request, provided operators submit a complete AMOC package with substantiation and explanation of the urgency, such as, but not limited to, a disruption in operation. Guidance for submitting AMOCs is available in FAA Advisory Circular (AC) 39-10. We also recommend that operators work with the original equipment manufacturers to address errors in service information as part of AD planning, in addition to submitting comments to the NPRM denoting any errors in the service information, so that corrections to methods of compliance (MOC) can be addressed in the FAA final rule. Additional guidance for operators on AD management can be found in FAA AC 39-9. We have not changed this AD in this regard.
Requests To Change or Delete Reporting Requirement
DAL and UAL asked that the reporting of findings (positive or negative), as specified in the reporting requirement in paragraphs (n) and (o)(4) of the proposed AD, be limited to positive findings only, or be removed entirely. DAL stated that it will require a significant amount of work to collect, collate, and disseminate the requested data to Airbus, resulting in little or no benefit to the airworthiness of the airplane. DAL added that any findings will require transmission of findings to engineering from maintenance prior to submission to Airbus, which could result in a time lag and opportunitiesfor error. DAL and UAL asserted that all positive findings are already reported to Airbus as part of the repair process and Airbus has the means to determine negative findings, so reporting is a duplicative burden on operators. Further, DAL argued that the Paperwork Reduction Act (https://www.gpo.gov/fdsys/pkg/PLAW-104publ13/html/PLAW-104publ13.htm) is meant to reduce the burden placed on public entities from government agencies when
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the information is obtainable from other sources, especially for the convenience of a foreign business. Additionally, DAL notes that only individuals that have the required access--controlled by Airbus--may submit reports, and provided data about what is required in order to submit a report (i.e., work-hours for the various steps in the process). DAL asserted that the cost of reporting on its operation would be $518,710, and that Airbus, EASA, nor the FAA have demonstrated in any of the service documents why the reporting requirement in this AD is necessary.
We agree to limit the reporting requirement to positive findings only for the reasons provided by the commenters. We have changed paragraph (n) of this AD accordingly.
We do not agree to remove the reporting requirement in this AD because the inspection reports will enable the manufacturer to obtain better insight into the nature, cause, and extent of the cracking, and eventually to develop final corrective action to address the unsafe condition. Once final corrective action has been identified, we might consider further rulemaking.
Clarification of Actions That Prompted This AD
We have revised the SUMMARY section of this final rule and paragraph (e) of this AD to clarify what prompted this AD. In addition to the report of cracks on the front spar vertical stringer at a certain frame, this AD was prompted by a determination that, during further investigations of the frame as part of the WFD campaign, certain inspection compliance times have to be revised and new inspections and a new potential terminating action modification have to be introduced.
Conclusion
We reviewed the available data, including the comments received, and determined that air safety and the public interest require adopting this AD with the changes described previously and minor editorial changes. We have determined that these changes:
Are consistent with the intent that was proposed in the NPRM for correcting 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 AD.
Related Service Information Under 1 CFR Part 51
Airbus has issued the following service information.
Service Bulletin A320-57-1178, Revision 03, including only Appendix 03, both dated November 29, 2016. The service information describes procedures for a rototest inspection for cracking of the radius of the front spar vertical stringers on FR 36, a HFEC for cracking of the horizontal floor beam on FR 36, and an HFEC inspection for cracking of the fastener holes of the front spar vertical stringers on FR 36.
Service Bulletin A320-57-1200, dated November 20, 2015. The service information describes procedures for modifying the center wing box area, which includes related investigative and corrective actions. Related investigative actions include an HFEC inspection on the radius of the rib flanges, a rototest inspection of the fastener holes, detailed and HFEC inspections for cracking on the cut edges, detailed and rototest inspections on all open fastener holes, and an inspection to determine if secondary structure brackets are installed. Corrective action includes reworking the secondary structure bracket and repair.
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 815 airplanes of U.S. registry.
The actions required by AD 2016-01-11, take about 24 work-hours per inspection cycle per product, at an average labor rate of $85 per work- hour. Based on these figures, the estimated cost of the actions that are required by AD 2016-01-11 is $2,040 per inspection cycle per product.
We also estimate that it takes about 273 work-hours per product to comply with the basic requirements of this AD and 1 work-hour for reporting per response. The average labor rate is $85 per work-hour. Required parts cost about $87,500 per product. Based on these figures, we estimate the cost of this AD on affected U.S. operators of certain airplanes specified in the service information to be $1,107,050 or $110,705 per product.
We have received no definitive data that would enable us to provide cost estimates for the repair of cracking 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 for reducing 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 RulemakingTitle 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 identified in 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 to the Director of the System Oversight Division.
Regulatory Findings
We determined that 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,
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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 nothave 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.