DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0839; Project Identifier MCAI-2020-01697-R;
Amendment 39-21877; AD 2021-26-18]
RIN 2120-AA64

Airworthiness Directives; Airbus Helicopters

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is superseding Airworthiness Directive (AD) 2020-21-01
for certain Airbus Helicopters Model AS-365N2, AS 365N3, EC 155B,
EC155B1, and SA-365N1 helicopters. AD 2020-21-01 required modifying the
main gearbox (MGB) tail rotor (T/R) drive flange installation. This AD
was prompted by several reported occurrences of loss of tightening
torque of the Shur-Lok nut, which serves as a retainer of the MGB T/R
drive flange. This AD continues to require modifying the MGB T/R drive
flange installation, and includes additional helicopters in the
applicability for the required actions. The FAA is issuing this AD to
address the unsafe condition on these products.

DATES: This AD is effective February 9, 2022.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of February 9,
2022.
The Director of the Federal Register approved the incorporation by
reference of certain other publications listed in this AD as of
November 12, 2020 (85 FR 63440, October 8, 2020).

ADDRESSES: For service information identified in this final rule,
contact Airbus Helicopters, 2701 North Forum Drive, Grand Prairie, TX
75052; phone: (972) 641-0000 or (800) 232-0323; fax: (972) 641-3775; or
at https://www.airbus.com/helicopters/services/support.html. You may
view this service information at the FAA, Office of the Regional
Counsel, Southwest Region, 10101 Hillwood Pkwy, Room 6N-321, Fort
Worth, TX 76177. For information on the availability of this material
at the FAA, call (817) 222-5110. It is also available at https://www.regulations.gov
by searching for and locating Docket No. FAA-2021-0839.

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0839; 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 Union Aviation Safety Agency (EASA) AD, any comments received,
and other information. The address for Docket Operations is U.S.
Department of Transportation, Docket Operations, M-30, West Building
Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC
20590.

FOR FURTHER INFORMATION CONTACT: Andrea Jimenez, Aerospace Engineer,
COS Program Management Section, Operational Safety Branch, Compliance &
Airworthiness Division, FAA, 1600 Stewart Ave., Suite 410, Westbury, NY
11590; phone: (516) 228-7330; email: andrea.jimenez@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 to supersede AD 2020-21-01,
Amendment 39-21274 (85 FR 63440, October 8, 2020) (AD 2020-21-01). AD
2020-21-01 applied to certain Airbus Helicopters Model AS-365N2, AS
365N3, EC 155B, EC155B1, and SA-365N1 helicopters. The NPRM published
in the Federal Register on September 30, 2021 (86 FR 54139). In the
NPRM, the FAA proposed to continue to require modifying the MGB T/R
drive flange installation, and also proposed to include additional
helicopters in the applicability for the required actions. The NPRM was
prompted by several reported occurrences of loss of tightening torque
of the Shur-Lok nut, which serves as a retainer of the MGB T/R drive
flange.
EASA AD 2020-0287, dated December 21, 2020 (EASA AD 2020-0287), was
issued by EASA, which is the Technical Agent for the Member States of
the European Union, to correct an unsafe condition for certain AS 365
N2, AS 365 N3, SA 365 C1, SA 365 C2, SA 365 C3, SA 365 N and SA 365 N1
helicopters; and all EC 155 B and EC 155 B1 helicopters. Model SA 365
C3 helicopters 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 helicopters in the applicability. EASA AD 2020-0287
supersedes EASA AD 2020-0212, dated October 5, 2020, which required
modification of the MGB T/R drive flange installation. EASA advises of
reported occurrences of loss of tightening torque of the Shur-Lok nut,
which serves as a retainer of the T/R drive flange of the MGB. EASA
also advises of subsequent investigation that determined that these
occurrences were the result of failure of the Shur-Lok nut locking
function, which is normally ensured by two antirotation tabs engaged
into two slots at the end of the MGB output shaft pinion. EASA states
this condition could lead to the loosening of the Shur-Lok nut and
disengagement of the Shur-Lok nut threads, possibly resulting in
reduction of T/R drive control, rear transmission vibrations, and
subsequent reduced control of the helicopter.
Accordingly, EASA AD 2020-0287 retains the modification of the MGB
T/R drive flange installation. EASA AD 2020-0287 also includes
additional helicopters in the applicability for the required actions
(Model SA-365C1, SA-365C2, and SA-365N helicopters on which Airbus
Helicopters modification 0763B64 has been embodied; and Model EC 155B
and EC155B1 helicopters without modification 0763B64 embodied).

Discussion of Final Airworthiness Directive

Comments

The FAA received comments from three commenters. The commenters
were an individual who made a statement about the applicability; an
individual who expressed support and favor for the NPRM; and an
anonymous commenter, who had a question about the applicability. The
following presents the comments received on the NPRM and the FAA's
response to each comment.

Request for Clarification of Applicability

An individual stated the opinion that all helicopters should be
subject to the same rules, a preference for unity under the law, and
that it is unfair to have different rules for different helicopters. An
anonymous commenter asked why the NPRM is only applicable to Airbus
Helicopters and not other current and modern models of helicopters. The
FAA infers that the commenters may be suggesting that this AD should
apply to all helicopter models. No further justification was given.
The FAA agrees to clarify the applicability. Each FAA AD has a
specific applicability, and this FAA AD reflects the applicability of
EASA AD 2020-0287. This AD only addresses the models specified in the
EASA AD that are affected by the unsafe condition. Helicopters and the
systems that support the design are varied, and because of design
variances between manufacturers, may or may not be subject to an unsafe
condition. Therefore, in crafting a rule, the FAA specifically works to
apply rulemaking only to the models and systems that are affected.
Otherwise, the FAA may be creating arbitrary regulations, unnecessary
work, and burdensome costs for the operators of the unaffected
helicopters. There is no further need to expand the applicability of
this AD to other helicopter models due to the likelihood that the type
designs are different and therefore not subject to the unsafe
condition. If information is received indicating other models are
affected by the unsafe condition, the FAA will consider further
rulemaking. The FAA has made no changes to this AD.

Conclusion

These helicopters have been approved by EASA and are approved for
operation in the United States. Pursuant to the FAA's bilateral
agreement with the European Union, EASA has notified the FAA about the
unsafe condition described in its AD. The FAA reviewed the relevant
data, considered the comments received, and determined that air safety
requires adopting this AD as proposed. Accordingly, the FAA is issuing
this AD to address the unsafe condition on these helicopters. Except
for minor editorial changes, this AD is adopted as proposed in the
NPRM. None of the changes will increase the economic burden on any
operator.

Related Service Information Under 1 CFR Part 51

The FAA reviewed the following service information.
Airbus Helicopters Alert Service Bulletin (ASB) No. AS365-63.00.26,
Revision 0, dated July 22, 2020, for Model AS365N helicopters and non
FAA-type certificated military Model AS365Fs helicopters; and Airbus
Helicopters ASB No. SA365-65.52, Revision 1, dated July 22, 2020, for
Model SA-365C1 and SA-365C2 helicopters and non FAA-type certificated
Model SA-365C3 helicopters. This service information specifies
procedures for modifying the MGB T/R drive flange installation, which
include installing a rear (aft) output stop between the T/R drive
flange and T/R drive shaft. These documents are distinct since they
apply to different helicopter models.
This AD also requires Airbus Helicopters ASB No. AS365-63.00.19,
Revision 1, dated January 31, 2019; and Airbus Helicopters ASB No.
EC155-63A013, Revision 1, dated January 31, 2019; which the Director of
the Federal Register approved for incorporation by reference as of
November 12, 2020 (85 FR 63440, October 8, 2020).
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.

Differences Between This AD and the EASA AD

EASA AD 2020-0287 specifies compliance times of 600 flight hours or
a certain time frame (months). However, this AD only requires the
compliance time of 600 hours time-in-service.

Costs of Compliance

The FAA estimates that this AD affects 53 helicopters of U.S.
Registry. Labor rates are estimated at $85 per work-hour. Based on
these numbers, the FAA estimates the following costs to comply with
this AD.

Estimated Costs

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.

Regulatory Findings

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) 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
reference, Safety.

The Amendment

Accordingly, under the authority delegated to me by the
Administrator, the FAA amends 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:

a. Removing Airworthiness Directive 2020-21-01, Amendment 39-21274 (85
FR 63440, October 8, 2020); and
b. Adding the following new airworthiness directive: