Airworthiness Directives; Airbus Canada Limited Partnership (Type Certificate Previously Held by C Series Aircraft Limited Partnership (CSALP); Bombardier, Inc.) Airplanes

[Federal Register Volume 91, Number 101 (Wednesday, May 27, 2026)]
[Rules and Regulations]
[Pages 31341-31345]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2026-10486]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2025-2543; Project Identifier MCAI-2025-00215-T; 
Amendment 39-23347; AD 2026-10-07]
RIN 2120-AA64


Airworthiness Directives; Airbus Canada Limited Partnership (Type 
Certificate Previously Held by C Series Aircraft Limited Partnership 
(CSALP); Bombardier, Inc.) Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for 
certain Airbus Canada Limited Partnership Model BD-500-1A10 and BD-500-
1A11 airplanes. This AD was prompted by the discovery that titanium 
fasteners had been incorrectly installed in the butt strap at the outer 
wing box lower skin to center wing box interface in lieu of the correct 
nickel alloy fasteners. This AD requires the identification of 
fasteners installed in the butt strap at the outer wing box lower skin 
to center wing box interface, and applicable on-condition actions. The 
FAA is issuing this AD to address the unsafe condition on these 
products.

DATES: This AD is effective July 1, 2026.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of July 1, 
2026.

ADDRESSES: 
    AD Docket: You may examine the AD docket at regulations.gov under 
Docket No. FAA-2025-2543; 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 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 Transport Canada material identified in this AD, 
contact Transport Canada, Transport Canada National Aircraft 
Certification, 159 Cleopatra Drive, Nepean, Ontario K1A 0N5, Canada; 
telephone 888-663-3639; email [email protected]. You may find this material on the 
Transport Canada website at tc.canada.ca/en/aviation.
    <bullet> You may view this material at the FAA, Airworthiness 
Products Section, Operational Safety Branch, 2200 South 216th St., Des 
Moines, WA. For information on the availability of this material at the 
FAA, call 206-231-3195. It is also available at regulations.gov under 
Docket No. FAA-2025-2543.

FOR FURTHER INFORMATION CONTACT: Bill Ashforth, Aviation Safety 
Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 206-
231-3520; 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 certain Airbus Canada 
Limited Partnership Model BD-500-1A10 and BD-500-1A11 airplanes. The 
NPRM was published in the Federal Register on September 15, 2025 (90 FR 
44337). The NPRM was prompted by AD CF-2025-09, dated February 24, 2025 
(Transport Canada AD CF-2025-09) (also referred to as the MCAI), issued 
by Transport Canada, which is the aviation authority for Canada. The 
MCAI states that titanium fasteners (part number (P/N) B0206003GD) had 
been incorrectly installed in the butt strap at the outer wing box 
lower skin to center wing box interface in lieu of the correct nickel 
alloy fasteners (P/N B0206033GD). The use of titanium fasteners could 
result in a reduction in joint strength, and the risk of a fuel leak if 
the fastener fails and falls free from the joint. This condition, if 
not corrected, could cause damage to and loss of principal structure 
and fatigue critical structure.
    In the NPRM, the FAA proposed to require the identification of 
fasteners installed in the butt strap at the outer wing box lower skin 
to center wing box interface, and applicable on-condition actions, as 
specified in Transport Canada AD CF-2025-09. 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-2025-2543.

Discussion of Final Airworthiness Directive

Comments

    The FAA received a comment from an anonymous commenter who 
supported the NPRM without change.
    The FAA received additional comments from Delta Air Lines (Delta) 
and the Citizens Rulemaking Alliance. The following presents the 
comments

[[Page 31342]]

received on the NPRM and the FAA's response to each comment.

Request To Remove the Requirement To Contact the Manufacturer for 
Disposition

    Delta requested that the FAA add an exception to paragraph (h) of 
the proposed AD to allow use of an existing, approved Airbus Canada 
Limited Partnership (ACLP) disposition instead of contacting ACLP for 
an approved disposition via the instructions in the service information 
referenced in Transport Canada AD CF-2025-09. Delta noted that ACLP is 
changing the contact method specified in the service information, so 
operators may need to request an alternative method of compliance 
(AMOC) to use an alternative contact method. Delta also noted that ACLP 
has already issued two Generic Repair Engineering Orders (GREOs) to 
address discrepant fasteners found during the inspection, and that the 
GREOs meet the provisions of paragraph (j)(2) of the proposed AD for 
obtaining an approved disposition.
    The FAA agrees that operators may use existing repair instructions, 
including GREOs, for compliance with this AD provided the repair 
instructions were approved under the provisions of paragraph (j)(2) of 
this AD. No change to this AD is necessary in regard to that part of 
Delta's comment.
    The FAA also agrees with removing the requirement to obtain an 
approved disposition in accordance with the contact method specified in 
the service information referenced in Transport Canada AD CF-2025-09 
and has added a new exception in paragraph (h)(3) of this AD 
accordingly. The FAA notes that under paragraph (j)(2) of this AD 
operators must contact the Manager, AIR-520, Continued Operational 
Safety Branch, FAA; or Transport Canada; or ACLP's Transport Canada 
Design Approval Organization (DAO) to obtain an approved disposition 
for any requirement in this AD to obtain instructions from a 
manufacturer.

Request To Extend the Compliance Times

    Delta requested that the FAA revise paragraph (h)(2) of the 
proposed AD to allow the required inspection to be accomplished within 
11,400 total flight cycles, 22,800 total flight hours, or 500 flight 
cycles from the effective date of this AD, whichever occurs later, 
instead of performing the inspections within 500 flight cycles from the 
effective date of the AD or before accumulating 10,000 total flight 
cycles, whichever occurs later. Delta stated that ACLP has already 
issued two approved GREOs to address discrepant fasteners found during 
the inspection, and that one of the GREOs authorizes continued flight 
with the discrepant fasteners up to 11,400 total flight cycles or 
22,800 total flight hours, whichever occurs first. Delta asserted that 
if replacement of the discrepant fasteners can be deferred to those 
later thresholds, then deferring the inspection to the same thresholds 
provides an acceptable level of safety.
    The FAA disagrees with extending the compliance time for performing 
the inspection to determine if serviceable fasteners are installed. 
Transport Canada, as the state of design authority for these airplanes, 
analyzed the data, considered the recommendations of the manufacturers, 
and determined that the inspection must be accomplished before 
accumulating 10,000 total flight cycles or within 500 flight cycles 
from the effective date of the AD, whichever occurs later; and the FAA 
concurs with Transport Canada's determination. However, under the 
provisions of paragraph (j)(1) of this AD, the FAA will consider 
requests for approval of an extension of the compliance time if 
sufficient data are submitted to substantiate that the new compliance 
time would provide an acceptable level of safety. The FAA has not 
changed this AD as a result of this comment.

Request To Justify Forgoing Notice and Comment or Issue an NPRM

    The Citizens Rulemaking Alliance requested that the FAA either 
provide its justification for finding good cause to bypass notice and 
comment procedures and the 30-day delayed effective date, or convert 
this action to an NPRM with a 30-day comment period. The commenter 
asserted the FAA has not adequately justified use of the good cause 
exemption to bypass notice and comment and the 30-day delayed effective 
date.
    The FAA notes the comment was submitted in response to an NPRM for 
which the FAA provided a 45-day comment period. This final rule is 
effective 35 days after its publication in the Federal Register. 
Therefore, no change to this AD is necessary.

Request To Comply With the Paperwork Reduction Act (PRA)

    The Citizens Rulemaking Alliance requested that the FAA revise the 
AD to comply with the PRA if reporting is required or remove any 
reporting provisions until PRA requirements are satisfied. If reporting 
is not required, the commenter requested the FAA clarify that in the 
AD.
    The FAA notes paragraph (i) of this AD specifies that this AD does 
not require reporting. If an AD were to require reporting, the preamble 
of the AD would include a paragraph titled ``Paperwork Reduction Act'' 
that would provide the applicable OMB control number, required PRA 
statements, and the estimated time to collect the required information 
(burden). Any costs associated with the reporting requirement would be 
included in the Costs of Compliance section in the preamble of the AD. 
Therefore, the FAA did not change this AD as a result of this comment.

Request To Consider Impact on Small Entities

    The Citizens Rulemaking Alliance requested that the FAA either 
provide the factual basis for its certification under the Regulatory 
Flexibility Act (RFA) that the AD will not have a significant economic 
impact on a substantial number of small entities, or prepare an initial 
regulatory flexibility analysis that identifies potentially affected 
small entities and considers alternatives that minimize impact.
    The FAA provides the following clarification. The RFA of 1980 (5 
U.S.C. 601-612), as amended by the Small Business Regulatory 
Enforcement Fairness Act of 1996 (Pub. L. 104-121) and the Small 
Business Jobs Act of 2010 (Pub. L. 111-240), requires Federal agencies 
to consider the effects of the regulatory action on small business and 
other small entities and to minimize any significant economic impact. 
The term ``small entities'' comprises small businesses and not-for-
profit organizations that are independently owned and operated and are 
not dominant in their fields, and governmental jurisdictions with 
populations of less than 50,000.
    The FAA identified three air carriers that will be affected by this 
AD. Based on the Small Business Administration size standard, all three 
entities are large businesses:

[[Page 31343]]



                    Small Business Size Standards \1\
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         NAICS \2\ code               Description        Size standard
------------------------------------------------------------------------
481111..........................  Scheduled           1,500 employees.
                                   Passenger Air
                                   Transportation.
------------------------------------------------------------------------
\1\ Source: sba.gov: Table of Small Business Size Standards.
\2\ North American Industrial Classification System.

    If an agency determines that a rulemaking will not result in a 
significant economic impact on a substantial number of small entities, 
the head of the agency may so certify under section 605(b) of the RFA. 
Therefore, as provided in section 605(b) and based on the foregoing, 
the head of the FAA certifies that this AD will not result in a 
significant economic impact on a substantial number of small entities. 
The FAA did not change this AD as a result of this comment.

Request To Provide Additional Cost Information

    The Citizens Rulemaking Alliance requested that the FAA augment the 
economic analysis to include downtime and scheduled disruption costs, 
parts availability constraints, and cumulative fleet impacts, and 
adjust the compliance times to align with scheduled maintenance 
intervals and broaden AMOC pathways accordingly. The commenter stated 
that the FAA should also provide the per airplane and fleet costs, 
including labor hours, parts, engineering, software loads, and special 
tools.
    The FAA recognizes that, in doing the actions required by an AD, 
operators might incur indirect costs (such as engineering work or loss 
of revenue due to airplane downtime, scheduled disruptions, parts 
availability constraints, etc.) in addition to the direct costs. The 
cost analysis in an AD typically describes only the direct costs of the 
specific actions required by an AD, which does not include indirect 
costs since the FAA lacks data on those costs and they vary 
significantly among operators. Additionally, the FAA determined that 
there may be no downtime costs for some of the affected operators 
because the compliance times required by this AD would allow the 
required inspection to be performed during regularly scheduled 
maintenance. Further, special tools and software are not necessary to 
complete the actions required by this AD.
    In the Costs of Compliance section of the proposed AD, the FAA 
disclosed the number of affected airplanes on the U.S. registry, 
estimated number of work hours and parts costs provided by the 
manufacturer, and the fleet cost. Since the FAA has assessed and 
disclosed the total known costs of the AD requirements in the Costs of 
Compliance section of the proposed AD, and the commenter did not 
provide additional cost data for the FAA to consider in its cost 
analysis, it is not necessary to provide additional information in the 
AD docket.
    Further, in developing an appropriate compliance time for this AD, 
the FAA considered the compliance time in Transport Canada AD CF-2025-
09, the urgency associated with the subject unsafe condition, the 
availability of required parts, and the practical aspect of 
accomplishing the required actions within a period of time that 
corresponds to the normal scheduled maintenance for most affected 
operators. However, under the provisions of paragraph (j)(1) of this 
AD, the FAA will consider requests for approval of an extension of the 
compliance time if sufficient data are submitted to substantiate that 
the new compliance time would provide an acceptable level of safety. 
The FAA did not change this AD as a result of this comment.

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, 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 Transport Canada AD CF-2025-09, which specifies 
procedures for a detailed inspection to identify the part markings on 
the head of the fasteners, and applicable on-condition actions. On-
condition actions include replacing non-serviceable fasteners (those 
not identified as HST54, HST154, HST254, B0201074, B0201074 with 
oversize code X, or B0201074 with oversize code Y). For non-serviceable 
fasteners, the replacement includes a detailed inspection to make sure 
that the fastener heads are not damaged; the fastener heads are 
installed within requirements; and there are no signs of loose 
fasteners, fasteners that rotated, or fasteners that moved.
    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.

Costs of Compliance

    The FAA estimates that this AD affects 71 airplanes of U.S. 
registry. The FAA estimates the following costs to comply with this AD:

                                      Estimated Costs for Required Actions
----------------------------------------------------------------------------------------------------------------
                                                                                  Cost per       Cost on U.S.
                           Labor cost                              Parts cost      product         operators
----------------------------------------------------------------------------------------------------------------
29 work-hours x $85 per hour = $2,465...........................           $0        $2,465            $175,015
----------------------------------------------------------------------------------------------------------------

    The FAA estimates the following costs to do any necessary on-
condition actions that would be required based on the results of any 
required actions. The FAA has no way of determining the number of 
aircraft that might need this on-condition action:

[[Page 31344]]



                Estimated Costs of On-Condition Actions *
------------------------------------------------------------------------
           Labor cost                 Parts cost       Cost per product
------------------------------------------------------------------------
Up to 4 work-hours x $85 per      Up to $11,550.....  Up to $11,890.
 hour = $340.
------------------------------------------------------------------------
* For replacement of 11 fasteners.

    The FAA has included all known costs in its cost estimate. 
According to the manufacturer, however, some or all of the costs of 
this AD may be covered under warranty, thereby reducing the cost impact 
on affected operators.

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

    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:

2026-10-07 Airbus Canada Limited Partnership (Type Certificate 
Previously Held by C Series Aircraft Limited Partnership (CSALP); 
Bombardier, Inc.): Amendment 39-23347; Docket No. FAA-2025-2543; 
Project Identifier MCAI-2025-00215-T.

(a) Effective Date

    This airworthiness directive (AD) is effective July 1, 2026.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to Airbus Canada Limited Partnership (Type 
Certificate previously held by C Series Aircraft Limited Partnership 
(CSALP); Bombardier, Inc.) Model BD-500-1A10 and BD-500-1A11 
airplanes, certificated in any category, as identified in Transport 
Canada AD CF-2025-09, dated February 24, 2025 (Transport Canada AD 
CF-2025-09).

(d) Subject

    Air Transport Association (ATA) of America Code 57, Wings.

(e) Unsafe Condition

    This AD was prompted by the discovery that titanium fasteners 
had been incorrectly installed in the butt strap at the outer wing 
box lower skin to center wing box interface in lieu of the correct 
nickel alloy fasteners. The FAA is issuing this AD to address the 
use of titanium fasteners. The unsafe condition, if not addressed, 
could result in a reduction in joint strength, potential damage to 
and loss of principal structure and fatigue critical structure, and 
the risk of a fuel leak if the fastener fails and falls free from 
the joint.

(f) Compliance

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

(g) Requirements

    Except as specified in paragraph (h) of this AD: Comply with all 
required actions and compliance times specified in, and in 
accordance with, Transport Canada AD CF-2025-09.

(h) Exceptions to Transport Canada AD CF-2025-09

    (1) Where Transport Canada AD CF-2025-09 refers to its effective 
date, this AD requires using the effective date of this AD.
    (2) Where Transport Canada AD CF-2025-09 refers to ``10 000 
flight cycles'', this AD requires replacing that text with ``10,000 
total flight cycles''.
    (3) Where Transport Canada AD CF-2025-09 specifies to ``contact 
ACLP for an approved disposition in accordance with the ACLP SB 
procedure and perform the ACLP disposition instructions'', this AD 
requires replacing that text with ``contact ACLP for an approved 
disposition and perform the ACLP disposition instructions''.

(i) No Reporting Requirement

    Although the material referenced in Transport Canada AD CF-2025-
09 specifies to submit certain information to the manufacturer, this 
AD does not include that requirement.

(j) Additional AD Provisions

    The following provisions also apply to this AD:
    (1) Alternative Methods of Compliance (AMOCs): The Manager, AIR-
520, Continued Operational Safety 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 responsible Flight Standards Office, 
as appropriate. If sending information directly to the manager of 
the Continued Operational Safety Branch, send it to the attention of 
the person identified in paragraph (k) of this AD and email to: 
[email protected]. Before using any approved AMOC, notify your 
appropriate principal inspector, or lacking a principal inspector, 
the manager of the responsible Flight Standards Office.
    (2) Contacting the Manufacturer: For any requirement in this AD 
to obtain instructions from a manufacturer, the instructions must be 
accomplished using a method approved by the Manager, AIR-520, 
Continued Operational Safety Branch, FAA; or Transport Canada; or 
Airbus Canada Limited Partnership's Transport Canada Design Approval 
Organization (DAO). If approved by the DAO, the approval must 
include the DAO-authorized signature.

(k) Additional Information

    For more information about this AD, contact Bill Ashforth, 
Aviation Safety Engineer, FAA, 2200 South 216th St., Des

[[Page 31345]]

Moines, WA 98198; phone: 206-231-3520; email: [email protected].

(l) 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 this AD specifies otherwise.
    (i) Transport Canada AD CF-2025-09, dated February 24, 2025.
    (ii) [Reserved]
    (3) For Transport Canada material identified in this AD, contact 
Transport Canada, Transport Canada National Aircraft Certification, 
159 Cleopatra Drive, Nepean, Ontario K1A 0N5, Canada; telephone 888-
663-3639; email [email protected]. You may find this material on 
the Transport Canada website at tc.canada.ca/en/aviation.
    (4) You may view this material at the FAA, Airworthiness 
Products Section, Operational Safety Branch, 2200 South 216th St., 
Des Moines, WA. For information on the availability of this material 
at the FAA, call 206-231-3195.
    (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 May 11, 2026.
Brian Knaup,
Acting Deputy Director, Integrated Certificate Management Division, 
Aircraft Certification Service.
[FR Doc. 2026-10486 Filed 5-26-26; 8:45 am]
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