DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2020-0410; Product Identifier 2019-SW-030-AD; Amendment
39-21274; AD 2020-21-01]
Airworthiness Directives; Airbus Helicopters
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule.
SUMMARY: The FAA is adopting a new airworthiness directive (AD)
certain Airbus Helicopters Model AS-365N2, AS 365N3, EC 155B, EC155B1,
and SA-365N1 helicopters. This AD requires 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 T/R drive flange. The actions of this AD are intended to address an
unsafe condition on these products.
DATES: This AD is effective November 12, 2020.
The Director of the Federal Register approved the incorporation by
reference of certain documents listed in this AD as of November 12,
ADDRESSES: For service information identified in this final 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
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. It is also available on the internet at https://www.
regulations.gov by searching for and locating Docket No. FAA-2020-0410.
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 AD, the European Union Aviation Safety Agency (EASA) AD, any
service information that is incorporated by reference, 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 W12-140, 1200 New Jersey Avenue
SE, Washington, DC 20590.
FOR FURTHER INFORMATION CONTACT: Matt Fuller, AD Program Manager,
Airworthiness Products Section, General Aviation and Rotorcraft Unit,
10101 Hillwood Pkwy., Fort Worth, TX 76177; telephone 817-222-5110;
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 AS-365N2, AS 365N3, EC 155B, EC155B1, and SA-365N1 helicopters
with modification 0763B64 installed, except those with modification
0763C81. The NPRM published in the Federal Register on April 23, 2020,
(85 FR 22688). The NPRM proposed to 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. The NPRM also proposed to
require removing from service certain washers, degreasing the bolt
threads, applying a sealant between the interlay mating surfaces, and
applying torque to the nuts. The proposed requirements were intended to
prevent 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.
The NPRM was prompted by EASA AD No. 2019-0046, dated March 11,
2019 (EASA AD 2019-0046), issued by EASA, which is the Technical Agent
for the Member States of the European Union, 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 07 63C81 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.
The FAA gave the public the opportunity to participate in
developing this AD, but the FAA did not receive any comments on the
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 issuing this AD after
evaluating all information provided by EASA and determining the unsafe
condition exists and is likely to exist or develop on other products of
the same type designs and that air safety and the public interest
require adopting the AD requirements as proposed.
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.
Costs of Compliance
The FAA estimates that this AD affects 46 helicopters of U.S.
Registry. The FAA estimates that operators may incur the following
costs in order to comply with this AD. Labor costs are estimated at $85
per work-hour. Modifying the MGB T/R drive flange installation takes
about 14 work-hours and parts 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 helicopters identified in this rulemaking action.
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
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
Adoption of 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 adding the following new airworthiness