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Federal Register / Vol. 86, No. 131 / Tuesday, July 13, 2021 / Rules and Regulations
European Union, has issued EASA AD
20180172, dated August 7, 2018 EASA
AD 20180172 also referred to as the Mandatory Continuing Airworthiness Information, or the MCAI, to correct an unsafe condition for all Airbus Helicopters Model AS332L2 and EC225LP helicopters. EASA AD 2018
0172 superseded EASA AD 20150016, dated January 30, 2015 which prompted FAA AD 20171701, Amendment 3918991 82 FR 39506, August 21, 2017 AD 20171701.
The FAA issued a notice of proposed rulemaking NPRM to amend 14 CFR
part 39 to supersede AD 20171701.
AD 20171701 applied to certain Airbus Helicopters Model AS332L2 and EC225LP helicopters. The NPRM
published in the Federal Register on November 24, 2020 85 FR 74931. The NPRM was prompted by the FAAs determination that it is necessary to measure the attachment pin chamfer after corrosion removal, that replacement of an attachment pin after four corrosion removals is no longer necessary, and that all Airbus Helicopters Model AS332L2 and EC225LP helicopters are affected by the unsafe condition. The NPRM proposed to continue to require the repetitive inspections of the MRB attachment pins, as specified in an EASA AD. The NPRM
also proposed to require repetitive measurement of the attachment pin chamfer at certain intervals after corrosion removal, as specified in an EASA AD.
The FAA is issuing this AD to address cracked MRB attachment pins which could result in loss of an MRB and subsequent loss of control of the helicopter. 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.
Request To Allow Rework of Corrosion Pits Air Center Helicopters, Inc. ACH
and Airbus Helicopters AH requested that the FAA allow rework of corrosion pits. ACH disagreed with the FAAs determination to disallow blade pin rework, and stated that scrapping blade pins due to disallowing rework is fiscally irresponsible, due to substantial replacement costs each main rotor hub has 10 blade pins. ACH pointed out that since the FAA issued AD 201717
01, ACH has removed and reworked numerous corrosion pitted EC225 blade
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pins from service in accordance with Airbus Helicopters Alert Service Bulletin EC22505A040. ACH discussed that in many cases the corrosion pitting was nearly undetectable using 10X
magnification, and that additional inspections were done using a 0.005
inch ball gauge. ACH also mentioned that visible corrosion pitting was often undetectable using the ball gauge, and pointed out that to ACH, the undetectable corrosion pitting indicated that the blade pin was salvageable with a minimum of rework.
ACH agreed with not allowing blade pin rework in FAA AD 20171701
because Revision 0 of Airbus Helicopters Alert Service Bulletin EC22505A040 did not specify a method to determine dimensional airworthiness after rework. ACH stated that Revision 1 of Airbus Helicopters Alert Service Bulletin EC22505A040, included post rework inspection procedures and dimensional criteria for post rework blade pin airworthiness, and that Revision 2 of Airbus Helicopters Alert Service Bulletin EC22505A040 introduced a maximum radius to the caliper points of 0.6 mm 0.0236 inch to ensure the point seats properly within the external blade pin blend radius ensuring accurate wall thickness measurements. ACH specified that Airbus Helicopters Alert Service Bulletin EC22505A040 provides a definitive procedure for inspection and verification of blade pin airworthiness after corrosion pitting rework, and that the procedure was approved by EASA.
ACH and AH argued that the term corrosion in Airbus Helicopters Alert Service Bulletin EC22505A040, is intended to include corrosion pitting.
AH pointed out that the service information is currently at Revision 2, that the revision was based on research and feedback from customer reports, and implemented detailed inspection procedures and measurements to determine airworthiness of the blade pins. AH then stated that the FAA did not reflect the intentions of the latest service information.
The FAA disagrees with the request.
Although the MCAI and service information specify rework in case corrosion is found, neither clearly address action in the case of corrosion pitting. Corrosion pitting is different than uniform corrosion and can be more dangerous. Additionally, the FAA does not agree with the inference that the intention of the service information is to allow rework of corrosion pits. The FAA
has not revised this AD in this regard.

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Conclusion The FAA reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this final rule as proposed, except for minor editorial changes. The FAA has 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.
Related Service Information Under 1
CFR Part 51
EASA AD 20180172 specifies procedures for repetitive inspections for corrosion and cracking of the attachment pins and corrective actions if necessary, and repetitive conditional measurement of the thickness of the chamfer of the attachment pins at certain intervals after corrosion removal.
Corrective actions include corrosion removal and replacement of the attachment pins. 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.
Differences Between This Proposed AD
and the MCAI
EASA AD 20180172 requires an inspection of the affected part in accordance with the applicable service information. The service information for Model AS332L2 helicopters and the service information for Model EC225LP
helicopters both describe procedures for an inspection for corrosion and cracking of the attachment pins. However, the service information for Model AS332L2
helicopters also describes an inspection of the protective coating of each attachment pin for scratches and missing protective coating and sanding if necessary; the service information for Model EC225LP helicopters does not describe those actions.
Although EASA AD 20180172
requires corrective actions if there is corrosion or cracking of the attachment pins, EASA AD 20180172 does not require any corrective actions if there is any scratch or any missing protective coating.
This AD requires inspecting the protective coating of each attachment pin for scratches and missing protective coating, and sanding if there is any scratch or any missing protective coating, for all affected helicopters.
EASA AD 20180172 requires removing corrosion but does not
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