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Federal Register / Vol. 86, No. 50 / Wednesday, March 17, 2021 / Rules and Regulations Mandatory Continuing Airworthiness Information, or the MCAI, to correct an unsafe condition for all Airbus SAS
Model A318111 and 112 airplanes;
Model A319111, 112, 113, 114, and 115 airplanes; Model A320211, 212, 214, 215, and 216 airplanes; and Model A321111, 112, 211, 212, and 213 airplanes. Model A320215
airplanes are not certificated by the FAA
and are not included on the U.S. type certificate data sheet; this AD therefore does not include those airplanes in the applicability.
The FAA issued a notice of proposed rulemaking NPRM to amend 14 CFR
part 39 to supersede AD 20181602, Amendment 3919342 83 FR 39326, August 9, 2018 AD 20181602. AD
20181602 applied to all Airbus SAS
Model A318111 and 112 airplanes, Model A319111, 112, 113, 114, and 115 airplanes, Model A320211, 212, 214, and 216 airplanes, and Model A321111, 112, 211, 212, and 213
airplanes. The NPRM published in the Federal Register on October 14, 2020
85 FR 64984. 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 continue to require modifying and re-identifying the 3-lug aft engine mount assemblies, as specified in an EASA AD. The NPRM
also proposed to require modifying and re-identifying the 4-lug aft engine mount assemblies, as specified in an EASA AD.
The FAA is issuing this AD to address non-conforming retainers of the aft engine mount. This condition could result in loss of the locking feature of the nuts of the inner and outer pins; loss of the pins will result in the aft mount engine link no longer being secured to the aft engine mount, possibly resulting in damage to the airplane. See the MCAI
for additional background information.

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Comments The FAA gave the public the opportunity to participate in developing this final rule. The following presents the comments received on the NPRM
and the FAAs response to each comment.
Support for the NPRM
The Air Line Pilots Association, International ALPA expressed support for the NPRM.
Request for Consistency in Used Terms Delta Air Lines DAL requested that, for consistency, the FAA remove the parenthesis around the terms 3-lug and 4-lug under the Actions Since AD 2018

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1602 Was Issued heading in the NPRM.
No further justification was provided.
The FAA agrees that the change would have provided consistency in terminology. However, that portion of the NPRM is not restated in this final rule; therefore, no change has been made to this final rule in this regard.
Request To Remove Duplicate Wording DAL requested that the FAA revise the NPRM to remove duplicate wording procedures for under the Related IBR
Material Under 1 CFR part 51 heading.
DAL pointed out that the duplicate wording is a typographical error.
The FAA agrees for the reasons provided and has updated this final rule accordingly.
Request To Clarify Whether Model CFM565B and 5C Engines are Affected United Airlines UAL requested that the FAA clarify whether the NPRM
affects airplanes equipped with CFM
International, S.A. Model CFM565B
and 5C engines that are fitted with a turbine rear frame TRF with a 4-lug configuration.
The FAA agrees to clarify. EASA AD
20200085 defines a 4-lug engine as a CFM565A1, CFM565A3, CFM56
5A4, CFM565A4/F, CFM565A5 or CFM565A5/F engines, fitted with a turbine rear frame TRF having a P/N
part number as identified in Appendix 1 of EASA AD 20200085. The FAA
has not received any information regarding Model CFM565B and 5C
engines that would cause the FAA to determine that those engine models are subject to the identified unsafe condition; therefore, those engines are not included in the applicability of this AD. However, should the FAA receive information that the Model CFM565B
and 5C engines are subject to the identified unsafe condition, the FAA
may consider additional rulemaking at that time. This final rule has not been changed in this regard.
Request To Extend Compliance Time for Parked Airplanes DAL requested that the FAA extend the compliance time specified in the NPRM for airplanes that are parked due to the ongoing COVID19 pandemic.
DAL pointed out that many operators have had to park airplanes, and that there is uncertainty regarding any return to service schedule. DAL mentioned that parked aircraft/engines are not operating and, therefore, do not accrue time/cycles. DAL then specified the belief that any deadline for modification and re-identification should be
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extended by adding the duration of parking.
The FAA disagrees with the request.
DAL indicated concern related to the retained requirements of the AD 2018
1602. The unsafe condition is the result of a production deficiency that can cause pitting corrosion, which is not directly related to the accumulation of flight cycles or flight hours. Corrosion growth is normally related to calendar time and it is unknown if pitting corrosion is arrested while the airplane is in long term storage/parking and therefore the FAA does not agree with the request to provide a compliance time extension for parked airplanes.
However, under the provisions of paragraph k1 of this AD, the FAA
may approve requests for adjustments to the compliance time if data are submitted to substantiate that such an adjustment would provide an acceptable level of safety. This AD has not been changed in this regard.
Request To Clarify Use of Production Quality Deficiency DAL requested that the FAA revise paragraph h5 of the NPRM to better define the production quality deficiency that prompted the NPRM. DAL pointed out that the NPRM does not define the production quality deficiency, and does not refer to any other document for a definition.
The FAA partially agrees. During inservice inspections, several aft engine mount inner retainers, fitted on airplanes equipped with Model CFM56
5A/5B engines, were found broken.
Investigation identified that the main cause of crack initiation was the vibration dynamic effect that affects the retainers, and that the dull surface finish pitting is an aggravating factor when compared with the bright surface finishing. The dull surface finish pitting is the production quality deficiency. The FAA has not revised paragraph h5 of this AD, but has instead added paragraph g of this AD
to include the definition of the production quality deficiency.
Subsequent paragraphs have been redesignated have accordingly.
Request To Correct Reference to AD
20181602
DAL requested that the FAA revise paragraph h7 of the proposed AD to correct the reference to AD 20181602.
The FAA agrees for the reasons provided and has updated paragraph i7 of this AD paragraph h7 of the proposed AD accordingly.

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