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Federal Register / Vol. 86, No. 225 / Friday, November 26, 2021 / Rules and Regulations
that is incorporated by reference is also available at https www.regulations.gov by searching for and locating Docket No.
FAA20210197.
Examining the AD Docket You may examine the AD docket at https www.regulations.gov by searching for and locating Docket No.
FAA20210197; or in person at Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this final rule, the European Aviation Safety Agency now European Union Aviation Safety Agency EASA AD, any comments received, and other information. The street address for Docket Operations is U.S. Department of Transportation, Docket Operations, M
30, West Building Ground Floor, Room W12140, 1200 New Jersey Avenue SE, Washington, DC 20590.
FOR FURTHER INFORMATION CONTACT: Rao Edupuganti, Aerospace Engineer, Dynamic Systems Section, Technical Innovation Policy Branch, Policy &
Innovation Division, FAA, 10101
Hillwood Pkwy., Fort Worth, TX 76177;
telephone 817 2225110; email rao.edupuganti@faa.gov.
SUPPLEMENTARY INFORMATION:

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Background The FAA issued a notice of proposed rulemaking NPRM to amend 14 CFR
part 39 by adding an AD that would apply to Airbus Helicopters Model EC
155B and EC155B1 helicopters. The NPRM published in the Federal Register on July 22, 2021 86 FR 38608.
In the NPRM, the FAA proposed to require for helicopters with at least one Type Y planet gear assembly with a certain serial number S/N installed, or at least one Type Z planet gear assembly with a certain S/N installed, within 10
hours time-in-service TIS after the effective date of the AD and thereafter at intervals not to exceed 10 hours TIS, inspecting the MGB magnetic plugs for particles. If there are particles, the NPRM proposed to require further inspections and analyses and replacing the MGB, depending on the type and the size of the particles.
The NPRM also proposed to require for helicopters with a Type Y planet gear assembly with a certain S/N
installed, within 25 hours TIS after the effective date of the AD, inspecting the MGB filter for particles. If there are particles, the NPRM proposed to require further inspections and analyses and replacing the MGB, depending on the type and the size of the particles. The NPRM proposed to require for helicopters with at least one Type Y

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planet gear assembly with a certain S/
N installed, within 50 hours TIS after the effective date of the AD, replacing the MGB. As an alternative to replacing the MGB, the NPRM would allow replacing the epicyclic reduction gear in the affected MGB.
Additionally, the NPRM proposed to require, for helicopters without any Type Y planet gear assembly but at least one Type Z planet gear assembly with a certain S/N installed, replacing the MGB within 50 hours TIS after the effective date of the AD or before any planet gear assembly accumulates 1,800
total hours TIS, whichever occurs later.
As an alternative to replacing the MGB, the NPRM would allow replacing the epicyclic reduction gear in the affected MGB.
The NPRM also proposed to require, for helicopters with at least one Type Z
planet gear with a certain S/N installed, within certain compliance times specified in the figures in this AD, inspecting the MGB filter and inspecting the oil sump for particles. If there are particles, the NPRM proposed to require further inspections and analyses, and replacing the MGB, depending on the type and the size of the particles.
The NPRM also proposed to prohibit installing an MGB with a certain serial numbered Type Y planet gear assembly and proposed to prohibit installing a Type Y planet gear assembly with a certain S/N on any helicopter.
Additionally, the NPRM proposed to prohibit installing certain serial numbered Type Z planet gear assemblies that have accumulated 1,800
or more total hours TIS and prohibit installing an MGB with certain serial numbered Type Z planet gear assemblies that have accumulated 1,800
or more total hours TIS.
Finally, the NPRM proposed to prohibit installing an MGB if the type of the planet gear assembly cannot be determined and also prohibit installing any planet gear assembly if the type cannot be determined.
The NPRM was prompted by EASA
AD 20180263, dated December 7, 2018
EASA AD 20180263, issued by EASA, which is the Technical Agent for the Member States of the European Union, to correct an unsafe condition for Airbus Helicopters Model EC 155 B
and EC 155 B1 helicopters. EASA
advises that after an accident on a Model EC225 helicopter, an investigation revealed the failure of an MGB second stage planet gear. EASA
states that one of the two types of planet gear used in the MGB epicyclic module is subject to higher outer race contact pressures and therefore is more susceptible to spalling and cracking.

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This condition, if not addressed, could result in failure of a MGB planet gear assembly, failure of the MGB, and subsequent loss of helicopter control.
Accordingly, EASA AD 20180263
requires repetitive inspections of the MGB magnetic plugs, the MGB filer, and the oil sump for particles, and depending on the results of those inspections, removing or replacing certain parts. EASA AD 20180263 also requires reducing the life limit of Type Z planet gear assemblies. EASA AD
20180263 also requires, if certain gear assemblies are installed, either replacing the MGB or replacing the epicyclic reduction gear. Finally, EASA AD 2018
0263 prohibits installing a Type Y
planet gear assembly or an MGB with a Type Y planet gear assembly on any helicopter.
Discussion of Final Airworthiness Directive Comments The FAA received comments from one commenter. The following presents the comments received on the NPRM
and the FAAs response.
Request to Revise the Required Actions Section of the NPRM
Airbus Helicopters Inc., requested that the FAA revise the Required Actions section of this AD dealing with the 25 hours TIS inspection for the oil sump also referred to as inspecting the bottom housing of the MGB by removing that repetitive inspection and explained that some of the proposed actions are unclear and not in line with the original equipment manufacturers OEM service information. The commenter also provided an example of a similar AD, AD 20211206, Amendment 3921593 86 FR 31612, June 15, 2021 AD 20211206, stating that AD 20211206 is clear in explaining both the required repetitive actions and the limits provided by the OEM for the MGB oil filter inspection after finding particles on the chip detector. The commenter stated that, as written, the proposed actions would create extra work, which could lead to an unwanted condition exposing the dynamic component to possible contamination and possibly foreign object debris.
The FAA agrees that the repetitive 25
hours TIS oil sump inspection for Type Y planet gears is not necessary and has revised paragraph g1 of the Required Actions section in this final rule by deleting this inspection.
Conclusion The FAA reviewed the relevant data, considered the comments received, and
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