DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2021-0839; Project Identifier MCAI-2020-01697-R]
Airworthiness Directives; Airbus Helicopters
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
SUMMARY: The FAA proposes to supersede Airworthiness Directive (AD)
2020-21-01, which applies to certain Airbus Helicopters Model AS-365N2,
AS 365N3, EC 155B, EC155B1, and SA-365N1 helicopters. AD 2020-21-01
requires modifying the main gearbox (MGB) tail rotor (T/R) drive flange
installation. Since the FAA issued AD 2020-21-01, the FAA has
determined that additional helicopters are affected by the unsafe
condition. This proposed AD would continue to require modifying the MGB
T/R drive flange installation, and would also include new helicopters
in the applicability for the required actions. The FAA is proposing
this AD to address the unsafe condition on these products.
DATES: The FAA must receive comments on this proposed AD by November 15, 2021.
ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:
Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow
the instructions for submitting comments.
Fax: (202) 493-2251.
Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590.
Hand Delivery: Deliver to Mail address above between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
For service information identified in this NPRM, 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.
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 NPRM, the European
Union Aviation Safety Agency (EASA) AD, any comments received, and
other information. The street address for Docket Operations is listed above.
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: email@example.com.
The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments to an address listed
under ADDRESSES. Include "Docket No. FAA-2021-0839; Project Identifier
MCAI-2020-01697-R" at the beginning of your comments. The most helpful
comments reference a specific portion of the proposal, explain the
reason for any recommended change, and include supporting data. The FAA
will consider all comments received by the closing date and may amend
this proposal because of those comments.
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 NPRM.
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 NPRM 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 NPRM, 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 NPRM. Submissions containing CBI should be sent to
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: firstname.lastname@example.org. 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 AD 2020-21-01, Amendment 39-21274 (85 FR 63440,
October 8, 2020), (AD 2020-21-01), for certain Airbus Helicopters Model
AS-365N2, AS 365N3, EC 155B, EC155B1, and SA-365N1 helicopters. AD
2020-21-01 requires modifying the MGB T/R drive flange installation. AD
2020-21-01 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.
EASA AD 2020-0287, dated December 21, 2020 (EASA AD 2020-0287),
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 airplanes are not certificated by the FAA and are not included on
the U.S. type certificate data sheet; this proposed AD therefore does
not include those airplanes in the applicability.
EASA advised 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 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.
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, dated March 11,
2019 (EASA AD 2019-0046) (which prompted FAA AD 2020-20-01), 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
Since EASA issued EASA AD 2019-0046, Airbus Helicopters reviewed
the applicability of modification 07 63C81 and developed an additional
4 spigot modification (07 63D01) that was applicable to an additional
subset of in-service helicopter models that were initially excluded
from the applicability of EASA AD 2014-0179R2, prompting EASA to issue
EASA AD 2020-0212, dated October 5, 2020 (EASA AD 2020-0212), to
require either a 4 spigot or 5 spigot modification for the originally
excluded helicopter models (which was dependent on the front shaft
configuration, on the T/R shaft flexible coupling).
Actions Since AD 2020-21-01 Was Issued
Since the FAA issued AD 2020-21-01, EASA issued EASA AD 2020-0287,
which supersedes EASA AD 2020-0212. EASA advises that modification of
the MGB T/R drive flange is necessary for additional helicopters that
were originally excluded from the previous EASA ADs due to date of
manufacture. This condition, if not addressed, could result in
loosening of the Shur-Lok nut, possibly resulting in disengagement of
the Shur-Loc nut threads, reduction of T/R drive control, rear
transmission vibrations, and subsequent reduced control of the
Accordingly, EASA AD 2020-0287 retains the modification of the MGB
T/R drive flange installation. EASA AD 2020-0287 also includes new
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).
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 is proposing this AD
after evaluating all known relevant information and determining that
the unsafe condition described previously is likely to exist or develop
on other helicopters of these same type designs.
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 and 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 proposed 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.
Proposed AD Requirements in This NPRM
This proposed AD would retain all of the requirements of AD 2020-
21-01. This proposed AD would require modifying the MGB T/R drive
flange installation, and would also include new helicopters in the
applicability for the required actions. This proposed AD would also
require accomplishing the actions specified in the service information
Differences Between This Proposed AD and the EASA AD
EASA AD 2020-0287 specifies compliance times of 600 flight hours or
a certain time frame (months). However, this proposed AD would only
require the compliance time of 600 hours time-in-service.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would
affect 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 proposed AD.
COST PER PRODUCT
COST ON U.S. OPERATORS
|Modification (46 helicopters) (retained actions from AD 2020-21-01).
|| 14 work-hours x $85 per hour = $1,190.
|Modification (new proposed action)
|| 14 work-hours x $85 per hour = $1,190.
Up to $18,474
Up to $19,664
Up to $1,042,192.
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 12866,
(2) Would not affect intrastate aviation in Alaska, and
(3) Would 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:
a. Removing Airworthiness Directive 2020-21-01, Amendment 39-21274 (85
FR 63440, October 8, 2020); and
b. Adding the following new airworthiness directive: