DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2025-0629; Project Identifier MCAI-2023-01183-R]
RIN 2120-AA64

Airworthiness Directives; Airbus Helicopters Deutschland GmbH
(AHD) 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 all Airbus Helicopters Deutschland GmbH (AHD) Model EC135P1,
EC135P2, EC135P2+, EC135P3, EC135T1, EC135T2, EC135T2+, EC635T2+, and EC135T3
helicopters. This proposed AD was prompted by reports of ruptured and
deformed flexible couplings. This proposed AD would require inspecting
the axial displacement of the tail rotor driveshaft and, depending on
the results, taking corrective actions including inspecting the
flexible couplings. This proposed AD would also prohibit installing a
tail rotor drive shaft unless certain procedures are followed. These
actions are specified in a European Union Aviation Safety Agency (EASA)
AD, which is proposed for incorporation by reference. The FAA is
proposing this AD to address the unsafe condition on these products.

DATES: The FAA must receive comments on this NPRM by June 9, 2025.

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 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.

AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2025-0629; 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 mandatory continuing airworthiness
information (MCAI), any comments received, and other information. The
street address for Docket Operations is listed above.

Material Incorporated by Reference:

For EASA material identified in this proposed AD, contact
EASA, Konrad-Adenauer-Ufer 3, 50668 Cologne, Germany; phone: +49 221
8999 000; email: ADs@easa.europa.eu; website: easa.europa.eu. You may
find the EASA material on the EASA website at ad.easa.europa.eu.

You may view this material at the FAA, Office of the
Regional Counsel, Southwest Region, 10101 Hillwood Parkway, Room 6N-
321, Fort Worth, TX 76177. For information on the availability of this
material at the FAA, call (817) 222-5110. The EASA material is also
available at regulations.gov under Docket No. FAA-2025-0629.

FOR FURTHER INFORMATION CONTACT: Aaron Nguyen, Aviation Safety
Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590;
phone: (817) 222-5134; email: Aaron.T.Nguyen@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments to an address listed
under the ADDRESSES section. Include "Docket No. FAA-2025-0629;
Project Identifier MCAI-2023-01183-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
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 Aaron
Nguyen, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410,
Westbury, NY 11590; phone: (817) 222-5134; email:
Aaron.T.Nguyen@faa.gov. Any commentary that the FAA receives which is
not specifically designated as CBI will be placed in the public docket
for this rulemaking.

Background

EASA, which is the Technical Agent for the Member States of the
European Union, has issued EASA AD 2023-0197, dated November 10, 2023
(EASA AD 2023-0197) (also referred to as the MCAI), to correct an
unsafe condition on Airbus Helicopters Deutschland GmbH Model EC135 P1,
EC135 P2, EC135 P2+, EC135 P3, EC135 T1, EC135 T2, EC135 T2+, EC135 T3,
EC635 P2+, EC635 P3, EC635 T1, EC635 T2+, and EC635 T3 helicopters. The
MCAI advises of reports of ruptured and deformed flexible couplings,
and that investigations determined that a flexible coupling installed
with high axial displacement causes increased stresses and friction
between its sheets. The MCAI states that this unsafe condition, if not
detected and corrected, could lead to cracks and extensive deformation
of flexible couplings and consequent high vibration of the tail rotor
drive shaft, possibly resulting in reduced control of the helicopter.
The FAA is proposing this AD to address the unsafe condition on these
helicopters.

You may examine the MCAI in the AD docket at regulations.gov under
Docket No. FAA-2025-0629.

Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed EASA AD 2023-0197, which requires a one-time
inspection of the flexible coupling for axial displacement and,
depending on the results, replacing both flexible couplings and
correcting the axial displacement, or inspecting the flexible
couplings, replacing each flexible coupling having a discrepancy, and
correcting the axial displacement. For certain flexible couplings not
replaced based on the results of the flexible coupling inspection, EASA
AD 2023-0197 requires replacing the flexible couplings within a longer
compliance time. EASA AD 2023-0197 also prohibits installing a tail
rotor drive shaft on any helicopter unless certain procedures are
followed. This material 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.

FAA's Determination

These products have been approved by the aviation authority of
another country and are approved for operation in the United States.
Pursuant to the FAA's bilateral agreement with this State of Design
Authority, it has notified the FAA of the unsafe condition described in
the MCAI referenced above. The FAA is issuing this NPRM after
determining that the unsafe condition described previously is likely to
exist or develop on other products of these same type designs.

Proposed AD Requirements in This NPRM

This proposed AD would require accomplishing the actions specified
in EASA AD 2023-0197, described previously, as incorporated by
reference, except for any differences identified as exceptions in the
regulatory text of this proposed AD and except as discussed under
"Differences Between this Proposed AD and the MCAI."

Explanation of Required Compliance Information

In the FAA's ongoing efforts to improve the efficiency of the AD
process, the FAA developed a process to use some civil aviation
authority (CAA) ADs as the primary source of information for compliance
with requirements for corresponding FAA ADs. The FAA has been
coordinating this process with manufacturers and CAAs. As a result, the
FAA proposes to incorporate EASA AD 2023-0197 by reference in the FAA
final rule. This proposed AD would, therefore, require compliance with
EASA AD 2023-0197 in its entirety through that incorporation, except
for any differences identified as exceptions in the regulatory text of
this proposed AD. Using common terms that are the same as the heading
of a particular section in EASA AD 2023-0197 does not mean that
operators need comply only with that section. For example, where the AD
requirement refers to "all required actions and compliance times,"
compliance with this AD requirement is not limited to the section
titled "Required Action(s) and Compliance Time(s)" in EASA AD 2023-
0197. Material referenced in EASA AD 2023-0197 for compliance will be
available at regulations.gov by searching for and locating Docket No.
FAA-2025-0629 after the FAA final rule is published.

Differences Between This Proposed AD and the MCAI

The MCAI applies to Model EC635 P2+, EC635 P3, EC635 T1, and EC635
T3 helicopters, whereas this proposed AD would not because these model
helicopters are not FAA type-certificated.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 69 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.

Inspecting both flexible couplings for axial displacement would
take 8 work-hours for an estimated cost of $680 per helicopter and
$46,920 for the U.S. fleet.

If required, replacing both flexible couplings would take 2 work-
hours and parts would cost $4,100 for an estimated cost of $4,270 per
helicopter. Replacing one flexible coupling would take 1 work-hour and
parts would cost $2,050 for an estimated cost of $2,135 per flexible
coupling.

If required, correcting the axial displacement of the flexible
couplings would take 5 work-hours for an estimated cost of $425 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.

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 above, 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
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(f), 40113, 44701.

Sec. 39.13 [Amended]

2. The FAA amends Sec. 39.13 by adding the following new airworthiness
directive: