DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0410; Product Identifier 2019-SW-030-AD]
RIN 2120-AA64

Airworthiness Directives; Airbus Helicopters

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for certain Airbus Helicopters Model AS-365N2, AS 365N3, EC 155B,
EC155B1, and SA-365N1 helicopters. This proposed AD would require
modifying the main gearbox (MGB) tail rotor (T/R) drive flange
installation. This proposed AD was prompted by several reported
occurrences of loss of tightening torque of the Shur-Lok nut, which
serves as a retainer of the T/R drive flange. The actions of this
proposed AD are intended to address an unsafe condition on these
products.

DATES: The FAA must receive comments on this proposed AD by June 22,
2020.

ADDRESSES: You may send comments by any of the following methods:

Federal eRulemaking Docket: Go to https://www.regulations.gov. Follow the
online instructions for sending your comments electronically.

Fax: 202-493-2251.

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-2020-0410;
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 Union Aviation Safety Agency (previously
European 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
receipt.

For service information identified in this proposed rule, contact
Airbus Helicopters, 2701 N Forum Drive, Grand Prairie, TX 75052;
telephone 972-641-0000 or 800-232-0323; fax 972-641-3775; or at https://
www.airbus.com/helicopters/services/technical-support.html. You may
view the referenced service information at the FAA, Office of the
Regional Counsel, Southwest Region, 10101 Hillwood Pkwy., Room 6N-321,
Fort Worth, TX 76177.

FOR FURTHER INFORMATION CONTACT: Matt Fuller, Senior Aviation Safety
Engineer, Safety Management Section, Rotorcraft Standards Branch, FAA,
10101 Hillwood Pkwy., Fort Worth, TX 76177; telephone 817-222-5110;
email matthew.fuller@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to participate in this rulemaking by submitting
written comments, data, or views. The FAA also invites comments
relating to the economic, environmental, energy, or federalism impacts
that might result from adopting the proposals in this document. The
most helpful comments reference a 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.

The FAA will file in the docket all comments received, as well as a
report summarizing each substantive public contact with FAA personnel
concerning this proposed rulemaking. Before acting on this proposal,
the FAA will consider all comments received on or before the closing
date for comments. The FAA will consider comments filed after the
comment period has closed if it is possible to do so without incurring
expense or delay. The FAA may change this proposal in light of the
comments received.

Discussion

EASA, which is the Technical Agent for the Member States of the
European Union, has issued EASA AD No. 2019-0046, dated March 11, 2019
(EASA AD 2019-0046), to correct an unsafe condition for Airbus
Helicopters (formerly Eurocopter, Eurocopter France, Aerospatiale)
Model SA 365 N1, AS 365 N2, AS 365 N3, EC 155 B, and EC 155 B1
helicopters, all serial numbers, with modification 0763B64 installed,
except those with 0763C81 installed.

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 anti-
rotation tabs engaged into two slots at the end of the MGB output shaft
pinion. EASA states this condition could lead to the loosening and
disengagement of the Shur-Lok nut threads, possibly resulting in
reduction of T/R drive control, rear transmission vibrations, and
subsequent loss of control of the helicopter.

To address this unsafe condition, EASA issued a series of ADs,
initially with EASA AD No. 2014-0165, dated July 14, 2014 (EASA AD
2014-0165), which required a one-time inspection of the radial play
inside the T/R drive flange and the condition of the Shur-Lok nut.
Shortly after, EASA issued EASA AD No. 2014-0179, dated July 25, 2014
(EASA AD 2014-0179) to supersede EASA AD 2014-0165. EASA AD 2014-0179
retained the requirements of EASA AD 2014-0165 and expanded the
applicability of helicopters affected by the unsafe condition. EASA
later revised EASA AD 2014-0179 to Revision 1, dated July 29, 2014, to
revise the applicability and specify updated related service
information, and again to Revision 2, dated April 11, 2016 (EASA AD
2014-0179R2), to reduce the applicability and specify additional
updated related service information. Since EASA issued EASA AD 2014-
0179R2, another occurrence was reported that involved an on-ground loss
of T/R synchronization, resulting from disengagement of the Shur-Lok
nut. This additional occurrence prompted EASA to issue EASA AD 2019-
0046 to require installation of modification 07 63C81, which consists
of installing a rear output stop with 5 spigots on the T/R shaft
flexible coupling. According to Airbus Helicopters, the 5 spigots will
come into contact with the row of 5 bolt heads of the front T/R shaft
if the T/R drive flange moves backwards. This contact limits backward
displacement of the T/R drive flange and subsequently prevents T/R
drive flange disengagement.

FAA's Determination

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 of the
unsafe condition described in its AD. The FAA is proposing this AD
after evaluating all known relevant information and determining that an
unsafe condition is likely to exist or develop on other products of the
same type designs.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Airbus Helicopters Alert Service Bulletin (ASB)
No. AS365-63.00.19, for Model AS365N, N1, N2, and N3 helicopters and
non FAA-type certificated military Model AS365F, Fi, Fs, K, and K2
helicopters; and Airbus Helicopters ASB No. EC155-63A013 for Model
EC155B and B1 helicopters, both Revision 1 and dated January 31, 2019.
This service information specifies procedures for modification 0763C81
to install a rear (aft) output stop between the T/R drive flange and T/R
drive shaft.

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 AD Requirements

This proposed AD would require compliance with certain procedures
specified in the manufacturer's service information. This proposed AD
would require, within 600 hours time-in-service, modifying the MGB T/R
drive flange installation by removing the sliding flange from the
flexible coupling and installing the sliding flange with aft output
stop part number 365A32-7836-20 added, as per helicopter model and
configuration. This proposed AD would also require removing from
service certain washers, degreasing the bolt threads, applying a
sealant between the interlay mating surfaces, and applying torque to
the nuts.

Costs of Compliance

The FAA estimates that this proposed AD affects 46 helicopters of
U.S. Registry. The FAA estimates that operators may incur the following
costs in order to comply with this proposed AD. Labor costs are
estimated at $85 per work-hour.

Modifying the MGB T/R drive flange installation would take about 14
work-hours and parts would cost about $2,704 for an estimated cost of
$3,894 per helicopter and $179,124 for the U.S. fleet.

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

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
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 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
directive (AD):