DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2017-1036; Product Identifier 2018-SW-015-AD]
Airworthiness Directives; Airbus Helicopters
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Supplemental notice of proposed rulemaking (SNPRM); reopening
of comment period.
SUMMARY: The FAA is revising a notice of proposed rulemaking (NPRM)
that applied to certain Airbus Helicopters Model AS-365N2, AS 365 N3,
SA-365N, and SA-365N1 helicopters. The NPRM proposed to require either
replacing the main gearbox (MGB) or as an alternative, replacing the
epicyclic reduction gear module for certain serial numbered planet gear
assemblies installed on the MGB. The NPRM also proposed to require
inspecting the MGB magnetic plugs and oil filter for particles and,
depending on the outcome of the inspection, further inspections and
replacing certain parts. The NPRM was prompted by the failure of an MGB
second stage planet gear. This action revises the NPRM by expanding the
applicability to include all Airbus Helicopters Model AS-365N2, AS 365
N3, SA-365N, and SA-365N1 helicopters. Since these actions impose an
additional burden over that proposed in the NPRM, the FAA is reopening
the comment period to allow the public the chance to comment on these
DATES: The FAA must receive comments on this SNPRM by May 6, 2021.
ADDRESSES: You may send comments by any of the following methods:
Federal eRulemaking Docket: Go to https://www.regulations.gov. Follow
online instructions for sending your comments electronically.
Mail: Send comments to the U.S. Department of
Transportation, Docket Operations, M-30, West Building Ground Floor,
Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590-0001.
Hand Delivery: Deliver to the "Mail" address between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
Examining the AD Docket
You may examine the AD docket on the internet at https://www.regulations.
gov by searching for and locating Docket No. FAA-2017-1036;
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 proposed AD, 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 listed
above. Comments will be available in the AD docket shortly after
FOR FURTHER INFORMATION CONTACT: Rao Edupuganti, Aviation Safety
Engineer, Dynamic Systems Section, Technical Innovation Policy Branch,
FAA, 10101 Hillwood Pkwy., Fort Worth, TX 76177; telephone 817-222-
5110; email firstname.lastname@example.org.
The FAA invites you to participate in this rulemaking by submitting
written comments, data, or views. The most helpful comments reference
specific portion of the proposal, explain the reason for any
recommended change, and include supporting data. To ensure the docket
does not contain duplicate comments, commenters should send only one
copy of written comments, or if comments are filed electronically,
commenters should submit only one time.
Except for Confidential Business Information (CBI) as described in
the following paragraph, and other information as described in 14 CFR
11.35, the FAA will post all comments received, without change, to
https://www.regulations.gov, including any personal information you
provide. The agency will also post a report summarizing each
substantive verbal contact received about this proposed AD.
Confidential Business Information
CBI is commercial or financial information that is both customarily
and actually treated as private by its owner. Under the Freedom of
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public
disclosure. If your comments responsive to this SNPRM contain
commercial or financial information that is customarily treated as
private, that you actually treat as private, and that is relevant or
responsive to this SNPRM, it is important that you clearly designate
the submitted comments as CBI. Please mark each page of your submission
containing CBI as "PROPIN." The FAA will treat such marked
submissions as confidential under the FOIA, and they will not be placed
in the public docket of this SNPRM. Submissions containing CBI should
be sent to Rao Edupuganti, Aviation Safety Engineer, Dynamic Systems
Section, Technical Innovation Policy Branch, FAA, 10101 Hillwood Pkwy.,
Fort Worth, TX 76177; telephone 817-222-5110; email
email@example.com. Any commentary that the FAA receives which is
not specifically designated as CBI will be placed in the public docket
for this rulemaking
The FAA issued an NPRM to amend 14 CFR part 39 to include an AD
that would apply to Airbus Helicopters Model AS-365N2, AS 365 N3, SA-
365N, and SA-365N1 helicopters with at least one Type X or Y planet
gear assembly with a serial number (S/N) listed in Appendices 4.A.
through 4.B of Airbus Helicopters Alert Service Bulletin No. AS365-
05.00.78, Revision 3, dated March 2, 2018 (ASB AS-365-05.00.78)
installed on the MGB. The NPRM published in the Federal Register on
August 7, 2020 (85 FR 47925). The NPRM proposed to require replacing
the MGB or as an alternative, replacing the epicyclic reduction gear
module for certain serial numbered planet gear assemblies installed on
the MGB. The NPRM also proposed to require inspecting the MGB magnetic
plugs and oil filter for particles. Depending on the outcome of those
inspections, the NPRM proposed to require further inspections and
replacing certain parts.
The NPRM was prompted by EASA AD No. 2017-0116, Revision 2, dated
March 2, 2018, (EASA AD 2017-01162R2), 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 AS 365 N2, AS 365 N3,
SA 365 N, and SA 365 N1 helicopters. EASA advises that after an
accident on a Model EC225 helicopter, an investigation revealed the
failure of a second stage planet gear of the MGB. EASA states that one
of the two types of planet gear assemblies used in the MGB epicyclic
module is subject to higher outer race contact pressures and therefore
is more susceptible to spalling and cracking. Airbus Helicopters
reviewed its range of helicopters with regard to this issue and
provided instructions to improve the reliability of the installed MGB.
Therefore, EASA AD 2017-01162R2 requires repetitive inspections of the
MGB magnetic plugs and corrective action if any particles are detected.
EASA AD 2017-01162R2 also requires, if certain MGB planet gear
assemblies are installed, replacing the planet gear assemblies.
Finally, the EASA AD prohibits installing an MGB with a Type X or Type
Y planet gear assembly on any helicopter.
Actions Since Previous NPRM Was Issued
Since the NPRM was issued, the FAA discovered that the proposed
applicability was limited to helicopters with at least one affected
assembly installed on the MGB, whereas all Airbus Helicopters Model AS-
365N2, AS 365 N3, SA-365N, and SA-365N1 helicopters, regardless of the
assembly, are subject to the unsafe condition and require repetitive
inspections of the MGB magnetic plugs for particles. Therefore, this
SNPRM corrects the applicability to include all helicopter models. The
FAA also determined that any special flight permits would be limited to
flights with no passengers on board.
The FAA gave the public the opportunity to comment on the original
NPRM (85 FR 47925, August 7, 2020). The FAA received no comments on
that NPRM or on the determination of the cost to the public.
The FAA is proposing this SNPRM after evaluating all known relevant
information and determining that an unsafe condition is likely to exist
or develop on other helicopters of these same type designs. Certain
changes described above expand the scope of the original NPRM. As a
result, the FAA has determined that it is necessary to reopen the
comment period to provide additional opportunity for the public to
comment on this SNPRM.
Related Service Information Under 1 CFR Part 51
Airbus Helicopters has issued ASB AS365-05.00.78 for Model SA-365N,
SA-365N1, AS-365N2, and AS 365 N3 helicopters. This service information
specifies performing periodic inspections of the MGB magnetic plugs for
particles. This service information also specifies identifying the type
of gear assembly installed in the MGB and replacing any Type X assembly
within 50 hours time-in-service (TIS). For Type Y gear assemblies, the
service information requires replacing the assembly within 50 hours TIS
or within 300 hours TIS, depending on the time since new. The service
information specifies Type Z gear assemblies should be left as is.
Airbus Helicopters has also issued Service Bulletin No. AS365-
63.00.21, Revision 3, dated July 26, 2018, for Model AS365 helicopters.
This service information contains procedures for replacing the MGB
epicyclic reduction gear as an option to replacing the MGB.
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.
Proposed Requirements of the SNPRM
This SNPRM would maintain the proposed corrective actions from the
NPRM as follows, but would no longer limit the applicability to only
Before further flight, for helicopters with a Type X planet gear assembly
with a certain S/N installed, replacing the MGB.
For helicopters with no Type X planet gear assembly installed but at
least one Type Y planet gear assembly with a certain S/N installed, re-
placing the MGB within 300 hours TIS or before any planet gear assembly
accumulates 1,300 hours TIS since new, whichever occurs first.
As an alternative to replacing the MGB, this SNPRM would
allow replacing the epicyclic reduction gear module in the affected
This proposed AD would also:
Prohibit installing a MGB with Type Y or Type X planet
gear assembly installed on any helicopter.
Require, within 10 hours TIS and thereafter before the
first flight of the day or at intervals not to exceed 10 hours TIS,
whichever occurs first, inspecting the lower MGB magnetic plugs for
particles and, if there are particles, replacing the MGB, depending on
the type and the size of those particles.
Differences Between This SNPRM and the EASA AD
The EASA AD requires a 50-hour or 300-hour TIS compliance time or
by June 30, 2019, whichever occurs first, to determine the type of
planet gear installed in the MGB, and depending on the outcome, to
replace the MGB. This proposed AD would set compliance deadlines based
only on hours TIS or before further flight. The EASA AD allows a pilot
to inspect the MGB magnetic plugs for particles, while this proposed AD
Costs of Compliance
The FAA estimates that this proposed AD would affect 34 helicopters
of U.S. Registry. Labor rates are estimated at $85 per work-hour. Based
on these numbers, the FAA estimates that operators may incur the
following costs in order to comply with this proposed AD.
Inspecting the magnetic plugs and oil filter for particle deposits
would take about 1 work-hour for an estimated cost of $85 per
Replacing an MGB would take about 42 work-hours for cost of $3,570
and parts cost about $295,000 (overhauled) for a total cost of $298,570
Replacing the epicyclic reduction gear would take about 56 work-
hours for an estimated cost of $4,760 and parts cost about $11,404 for
a total cost of $16,164 per helicopter.
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.
The FAA is 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.
The FAA determined that this proposed AD would not have federalism
implications under Executive Order 13132. This proposed AD would 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, I certify this proposed regulation:
1. Is not a "significant regulatory action" under Executive Order
2. Will not affect intrastate aviation in Alaska, and
3. 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
The Proposed Amendment
Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 14 CFR part 39 as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. The FAA amends Sec. 39.13 by adding the following new airworthiness