Airworthiness Directives; Airbus Helicopters Deutschland GmbH Helicopters

[Federal Register Volume 91, Number 14 (Thursday, January 22, 2026)]
[Rules and Regulations]
[Pages 2681-2683]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2026-01180]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2025-0629; Project Identifier MCAI-2023-01183-R; 
Amendment 39-23237; AD 2026-02-01]
RIN 2120-AA64


Airworthiness Directives; Airbus Helicopters Deutschland GmbH 
Helicopters

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting 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 AD was prompted by reports of ruptured and deformed 
flexible couplings. This AD requires inspecting the axial displacement 
of the tail rotor drive shaft and, depending on the results, taking 
corrective actions including inspecting the flexible couplings. This AD 
also prohibits installing a tail rotor drive shaft unless certain 
procedures are followed. The FAA is issuing this AD to address the 
unsafe condition on these products.

DATES: This AD is effective February 26, 2026.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of February 26, 
2026.

ADDRESSES: 
    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 final rule, the mandatory continuing airworthiness 
information (MCAI), any comments received, and

[[Page 2682]]

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.
    Material Incorporated by Reference:
    <bullet> For European Union Aviation Safety Agency (EASA) material 
identified in this AD, contact EASA, Konrad-Adenauer-Ufer 3, 50668 
Cologne, Germany; phone: +49 221 8999 000; email: [email protected]; 
website: easa.europa.eu. You may find the EASA material on the EASA 
website at ad.easa.europa.eu.
    <bullet> 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. It 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: [email protected].

SUPPLEMENTARY INFORMATION:

Background

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 by adding an AD that would apply to all AHD Model EC135P1, 
EC135P2, EC135P2+, EC135P3, EC135T1, EC135T2, EC135T2+, EC635T2+, and 
EC135T3 helicopters. The NPRM was published in the Federal Register on 
April 25, 2025 (90 FR 17352). The NPRM was prompted by AD 2023-0197, 
dated November 10, 2023 (EASA AD 2023-0197) (also referred to as the 
MCAI), issued by EASA, which is the Technical Agent for the Member 
States of the European Union. 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.
    In the NPRM, the FAA proposed to require inspecting the axial 
displacement of the tail rotor drive shaft and, depending on the 
results, taking corrective actions including inspecting the flexible 
couplings. The NPRM also proposed to prohibit installing a tail rotor 
drive shaft unless certain procedures are followed. The FAA is issuing 
this AD to address the unsafe condition on these products.
    You may examine the MCAI in the AD docket at regulations.gov under 
Docket No. FAA-2025-0629.

Discussion of Final Airworthiness Directive

Comments

    The FAA received no comments on the NPRM or on the determination of 
the costs.

Additional Changes Made to This AD

    The FAA has revised paragraph (h) of this AD to clarify that where 
paragraphs (4) and (6) of EASA AD 2023-0197 specify replacing the 
flexible couplings in accordance with the instructions of section 4.1 
of the service information referenced, this AD requires replacing the 
flexible couplings in accordance with the instructions of sections 4.1 
and 4.2 of the service information referenced in EASA AD 2023-0197.
    The FAA has also revised paragraph (h) of this AD to clarify that 
this AD prohibits installing a tail rotor drive shaft unless certain 
procedures are followed, as stated in the Preamble of the NPRM.

Conclusion

    These products have been approved by the civil 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, that authority has notified the FAA of the unsafe condition 
described in the MCAI referenced above. The FAA reviewed the relevant 
data, considered any 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 products. Except for 
minor editorial changes and any other changes described previously, 
this AD is adopted as proposed in the NPRM. None of the changes will 
increase the economic burden on any operator.

Material Incorporated by Reference Under 1 CFR Part 51

    The FAA reviewed EASA AD 2023-0197, which specifies a one-time 
inspection of the flexible coupling for axial displacement and, 
depending on the results, corrective actions. Corrective actions 
include 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.

Differences Between This AD and the MCAI

    The MCAI applies to Model EC635 P2+, EC635 P3, EC635 T1, and EC635 
T3 helicopters, whereas this AD does not because these models do not 
have an FAA type certificate.

Costs of Compliance

    The FAA estimates that this AD affects 69 helicopters of U.S. 
registry. Labor rates are estimated at $85 per hour. Based on these 
numbers, the FAA estimates the following costs to comply with this AD.
    Inspecting both flexible couplings for axial displacement will 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 will take 2 work-
hours, and parts will cost $4,100 for an estimated cost of $4,270 per 
helicopter. Replacing one flexible coupling will take 1 work-hour and 
parts will cost $2,050 for an estimated cost of $2,135 per flexible 
coupling.
    If required, correcting the axial displacement of the flexible 
couplings will 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

[[Page 2683]]

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

0
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]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive:

2026-02-01 Airbus Helicopters Deutschland GmbH: Amendment 39-23237; 
Docket No. FAA-2025-0629; Project Identifier MCAI-2023-01183-R.

(a) Effective Date

    This airworthiness directive (AD) is effective February 26, 
2026.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to Airbus Helicopters Deutschland GmbH (AHD) 
Model EC135P1, EC135P2, EC135P2+, EC135P3, EC135T1, EC135T2, 
EC135T2+, EC635T2+, and EC135T3 helicopters, certificated in any 
category.
    Note 1 to paragraph (c): Helicopters with an EC135P3H 
designation are Model EC135P3 helicopters and helicopters with an 
EC135T3H designation are Model EC135T3 helicopters.

(d) Subject

    Joint Aircraft System Component (JASC) Code 6510, Tail Rotor 
Drive Shaft.

(e) Unsafe Condition

    This AD was prompted by reports of ruptured and deformed 
flexible couplings. The FAA is issuing this AD to detect axial 
displacement of the tail rotor drive shaft that exceeds allowable 
limits. The unsafe condition, if not addressed, could result in 
cracks and extensive deformation of flexible couplings, high 
vibration of the tail rotor drive shaft, and consequent reduced 
control of the helicopter.

(f) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.

(g) Requirements

    Except as specified in paragraphs (h) and (i) of this AD: Comply 
with all required actions and compliance times specified in, and in 
accordance with, European Union Aviation Safety Agency AD 2023-0197, 
dated November 10, 2023 (EASA AD 2023-0197).

(h) Exceptions to EASA AD 2023-0197

    (1) Where EASA AD 2023-0197 requires compliance in terms of 
flight hours, this AD requires using hours time-in-service.
    (2) Where EASA AD 2023-0197 refers to its effective date, this 
AD requires using the effective date of this AD.
    (3) Where paragraphs (2) and (6) of EASA AD 2023-0197 state 
``new'', this AD requires replacing that text with ``new (zero hours 
time-in-service)''.
    (4) Where paragraph (4) of EASA AD 2023-0197 states ``any 
discrepancy'', for the purpose of this AD, discrepancy may be 
indicated by cracks, mechanical damage, deformation, delamination, 
corrosion, loose rivets, or damaged surface protection, where these 
discrepancies exceed the allowable limits as defined in the material 
referenced in EASA AD 2023-0197.
    (5) Where paragraph (4) of EASA AD 2023-0197 states ``replace 
that flexible coupling'', this AD requires replacing that text with 
``replace that flexible coupling with a new (zero hours time-in-
service) flexible coupling''.
    (6) Where paragraphs (4) and (6) of EASA AD 2023-0197 state ``in 
accordance with the instructions of section 4.1 of the 
Accomplishment Procedure of the ASB'', this AD requires replacing 
that text with ``in accordance with the instructions of sections 4.1 
and 4.2 of the Accomplishment Procedure of the material, referenced 
in EASA AD 2023-0197''.
    (7) This AD does not adopt the ``Remarks'' section of EASA AD 
2023-0197.

(i) No Reporting or Returning of Parts Requirement

    Although the material referenced in EASA AD 2023-0197 specifies 
to submit certain information and to send parts to the manufacturer, 
this AD does not require those actions.

(j) Special Flight Permits

    Special flight permits are prohibited.

(k) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, International Validation Branch, FAA, has the 
authority to approve AMOCs for this AD, if requested using the 
procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, 
send your request to your principal inspector or local Flight 
Standards District Office, as appropriate. If sending information 
directly to the manager of the International Validation Branch, send 
it to the attention of the person identified in paragraph (l) of 
this AD and email to: [email protected].
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the local Flight Standards District Office/certificate holding 
district office.

(l) Additional Information

    For more information about this AD, contact Aaron Nguyen, 
Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, 
Westbury, NY 11590; phone: (817) 222-5134; email: 
[email protected].

(m) Material Incorporated by Reference

    (1) The Director of the Federal Register approved the 
incorporation by reference of the material listed in this paragraph 
under 5 U.S.C. 552(a) and 1 CFR part 51.
    (2) You must use this material as applicable to do the actions 
required by this AD, unless the AD specifies otherwise.
    (i) European Union Aviation Safety Agency (EASA) AD 2023-0197, 
dated November 10, 2023.
    (ii) [Reserved]
    (3) For EASA material identified in this AD, contact EASA, 
Konrad-Adenauer-Ufer 3, 50668 Cologne, Germany; phone: +49 221 8999 
000; email: [email protected]; website: easa.europa.eu. You may 
find the EASA material on the EASA website at ad.easa.europa.eu.
    (4) 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.
    (5) You may view this material at the National Archives and 
Records Administration (NARA). For information on the availability 
of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations or email [email protected].

    Issued on January 14, 2026.
Steven W. Thompson,
Acting Deputy Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2026-01180 Filed 1-21-26; 8:45 am]
BILLING CODE 4910-13-P

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