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 Model A318-111, and -112 airplanes, Model A319-111, -112, -113, -114, and -115 airplanes, Model A320-211, -212 and -214 airplanes, and Model A321-111, -112, -211, -212, and -213 airplanes. The NPRM published in the Federal Register on May 31, 2016 (81 FR 34287) (``the NPRM''). The NPRM was prompted by a report of a production quality deficiency on the inner retainer installed on link assemblies of the aft engine mount, which could result in failure of the retainer. The NPRM proposed to require an inspection for, and replacement of, all non-conforming aft engine mount retainers. We are issuing this AD to detect and correct non- conforming retainers of the aft engine mount. This condition could result in the loss of the locking feature of the nuts of the inner and outer pins; loss of the pins will result in the aft mountengine link no longer being secured to the aft engine mount, possibly resulting in damage to 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 2016-0010R1, dated February 16, 2016 (referred to after this as the Mandatory Continuing Airworthiness Information, or ``the MCAI''), to correct an unsafe condition for all Airbus Model A318-111, and -112 airplanes; Model A319-111, -112, -113, -114, and - 115 airplanes; Model A320-211, -212, and -214 airplanes; and Model A321-111, -112, -211, -212, and -213 airplanes. The MCAI states:
During in-service inspections, several aft engine mount inner retainers, fitted on aeroplanes equipped with CFM56-5A/5B engines, have been found broken. The results of the initial investigations highlighted that two different types of surface finish had been applied (respectively bright and dull material finishes), and that dull finishaffects the strength of the retainer with regard to fatigue properties of the part. The pins which attach the engine link to the aft mount are secured by two nuts, which do not have a self-locking feature; this function is provided by the retainer brackets. In case of failure of the retainer bracket, the locking feature of the nuts of the inner and outer pins is lost; as a result, these nuts could subsequently become loose.
In case of full loss of the nuts, there is the potential to also lose the pins, in which case the aft mount link will no longer be secured to the aft engine mount. The same locking feature is used for the three link assemblies of the aft mount.
This condition, if not detected and corrected, could lead to in- flight loss of an aft mount link, possibly resulting in damage to the aeroplane and/or injury to persons on the ground.
To address this potential unsafe condition, EASA issued AD 2013- 0050 [which corresponds to FAA AD 2014-14-06, Amendment 39-17901 (79 FR 42655, July 23, 2014)] to require a detailed inspection (DET) of the aft engine mount inner retainers and the replacement of all retainers with dull finish with retainers having a bright finish. Since that [EASA] AD was issued, inspection results showed that the main cause of crack initiation remains the vibration dynamic effect that affects both retainers, either with ``dull'' or ``bright'' surface finishes. The non-conforming ``dull'' surface's pitting is an aggravating factor. Consequently, EASA issued AD 2015-0021 [which corresponds to FAA NPRM Docket No. FAA-2015-3632; Directorate Identifier 2015-NM-023-AD (80 FR 55798, September 7, 2015)], retaining the requirements of EASA AD 2013-0050, which was superseded, and requiring repetitive DET of all aft engine mount inner retainers and, depending on findings, their replacement.
Since that [EASA] AD was issued, a production quality deficiency was identified by Airbus and UTAS (formerly Goodrich Aerostructures, the engine mountretainer manufacturer) on the delivery of the inner retainer, Part Number (P/N) 238-0252-505, installed in the three Link assemblies of the engine mount fitted on CFM56-5A/5B engines. Airbus issued AOT A71N011-15 and SB A320-71-1070 providing a list of affected parts and applicable corrective actions.
Consequently, EASA issued AD 2016-0010, retaining the requirements of EASA AD 2015-0021, which was superseded, and in addition requiring the identification and replacement of all non- conforming aft engine mount inner retainers.
Since that [EASA] AD was issued, AOT A71N011-15 was revised, removing errors and reducing the list of affected parts.
For the reason described above, this [EASA] AD is revised, adding reference to the revised AOT, and removing [EASA] AD appendixes, which content is included in the referenced Airbus documentation.
This [EASA] AD is still considered to be an interim action, pending development and availability of a final solution.
This AD requiresan inspection for, and replacement of, all non- conforming aft engine mount retainers. 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-2016-6896.
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.
Request To Remove Part Identification Requirement
Delta Airlines (DAL) requested that we remove the requirement to do an inspection to determine the part number of each engine mount inner retainer specified in paragraph (g) of the proposed AD. DAL stated that Airbus Service Bulletin A320-71-1070, dated November 23, 2015, does not specify identifying the part number. DAL stated that identifying the part number has no value in determining the affected population of non- conforming retainers. DAL also requested that we revise the records review language in paragraph (g) of the proposed AD to reference the criteria in paragraphs (g)(1), and (g)(2), and (g)(3) of the proposed AD instead of referring to the part number.
We do not agree with DAL's request to remove the inspection required by paragraph (g) of this AD. However, we do agree that the inspection language should be clarified. Paragraph (g) of this AD, which corresponds with the MCAI, requires doing actions in accordance with Airbus Service Bulletin A320-71-1070, dated November 23, 2015, which specifies to determine if there is a non-compliant engine mount inner retainer. We have revised paragraph (g) of this AD accordingly.
Request To Clarify Engine Mount Retainer
DAL requested that we clarify in paragraph (g) of the proposed AD which engine mount retainer (forward or aft) is to be inspected.
We agree to clarify. We have revised paragraph (g) of this AD to specify the aft engine mount inner retainer.
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Requests To Use the Airplane Maintenance Manual(AMM)
DAL requested that we include an option for using the AMM to accomplish the required actions. DAL stated that paragraph (g) of the proposed AD specifies that the replacement must be done in accordance with the service information specified in paragraph (h)(1), (h)(2), or (h)(3) of the proposed AD. DAL recommended that operators be allowed to take credit for the replacement through other means such as the AMM.
We do not agree with DAL's request. An AMM is a customized document that varies for each operator and depends on the airplane configuration. In addition, the AMM might not include all required compliance steps to mitigate the risk addressed in this AD. We have not changed this AD in this regard. However, under the provisions of paragraph (l) of this AD, we will consider requests for approval of alternative methods of compliance if sufficient data are submitted to substantiate that the new methods would provide an acceptable level of safety.
Requests To Revise Part Installation Prohibition
DAL requested that we revise paragraph (j) of the proposed AD to prohibit installation of an engine mount inner retainer in lieu of ``any part.'' DAL asserted that if not changed, paragraph (j)(l) of the proposed AD will prohibit the installation of all aft mounts identified in table 1 of Airbus Alert Operators Transmission (AOT) A71N011-15, Revision 01, dated February 1, 2016.
We agree with DAL's request. We have revised paragraph (j) of this AD to prohibit installation of certain engine mount inner retainers.
DAL requested that we revise paragraph (j)(3) of the proposed AD, which prohibits installation of parts delivered through an unidentified Purchase Order (PO) to provide more specific information for the identification of non-conforming aft engine mount inner retainers. DAL suggested that the proposed AD specify using the original equipment manufacturer (OEM) new part release certificate as a mean of verifying conformity for each aft engine mount inner retainer. DAL explained that it is suggesting this action because non-conforming field parts could be sold on the surplus market prior to the release of the AD under a non-OEM purchase order number.
We do not agree with DAL's request to revise paragraph (j)(3) of the proposed AD. We have determined that paragraph (j)(3) of this AD clearly prohibits installation of parts delivered through an unidentified PO and corresponds with the MCAI. We are unaware of any non-conforming parts delivered through an unidentified PO that have been sold on the surplus market. However, if those parts exist, then they are prohibited from installation as of the effective date of this AD. 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 AD with the changes described previously and minor editorial changes. We have determined that theseminor 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
We reviewed the following service information. This service information describes procedures for replacement of all non-conforming aft engine mount retainers.
Airbus Service Bulletin A320-71-1070, dated November 23, 2015. This document also describes procedures for an inspection for non-conforming aft engine mount retainers.
Airbus Alert Operators Transmission (AOT) A71N011-15, Revision 01, dated February 1, 2016. This document also contains the affected purchase order numbers used in identifying the affected parts.
Goodrich Service Bulletin RA32071-165, dated October 9, 2015. This document also contains the affected part numbers.
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 959 airplanes of U.S. registry.
We estimate the following costs to comply with this AD:
Estimated Costs ----------------------------------------------------------------------------------------------------------------
Action Labor cost Parts cost Cost per product Cost on U.S. operators ---------------------------------------------------------------------------------------------------------------- Inspection................... Up to 4 work-hours x $0 Up to $340...... Up to $326,060.
$85 per hour = $340. ----------------------------------------------------------------------------------------------------------------
Weestimate the following costs to do any necessary replacements that would be required based on the results of the inspection. We have no way of determining the number of aircraft that might need these replacements:
On-Condition Costs ----------------------------------------------------------------------------------------------------------------
Action Labor cost Parts cost Cost per product ---------------------------------------------------------------------------------------------------------------- Replacement........................ Up to 36 work-hours x $85 $10,000 Up to $13,060.
per hour = $3,060. ----------------------------------------------------------------------------------------------------------------
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,
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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.
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, 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.