Airworthiness Directives; Viking Air Limited (Type Certificate Previously Held by Bombardier Inc. and de Havilland, Inc.) Airplanes

[Federal Register Volume 90, Number 162 (Monday, August 25, 2025)]
[Rules and Regulations]
[Pages 41290-41293]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-16190]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2025-1107; Project Identifier MCAI-2024-00784-A; 
Amendment 39-23118; AD 2025-17-08]
RIN 2120-AA64


Airworthiness Directives; Viking Air Limited (Type Certificate 
Previously Held by Bombardier Inc. and de Havilland, Inc.) Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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[[Page 41291]]

SUMMARY: The FAA is superseding Airworthiness Directive (AD) 2022-23-
08, which applied to all Viking Air Limited (Viking) Model DHC-3 
airplanes. AD 2022-23-08 required a visual inspection of the stabilizer 
actuator to confirm that the stabilizer actuator lock ring is present, 
correctly seated in the groove in the upper housing, and engaged in the 
clamp nut, applicable corrective actions, application of a torque seal, 
and sending the inspection results to the FAA. Since the FAA issued AD 
2022-23-08, Transport Canada, which is the aviation authority for 
Canada, issued mandatory continuing airworthiness information (MCAI) to 
address the unsafe condition identified as a missing stabilizer 
actuator lock ring. This AD requires repetitively inspecting the 
stabilizer actuator to confirm that the stabilizer actuator lock ring 
is present, correctly seated in the groove in the upper housing, and 
engaged in the clamp nut; taking applicable corrective actions; 
applying a witness mark (torque seal); and installing a secondary 
retention feature as terminating action for the repetitive inspections. 
This AD also prohibits installing any stabilizer actuator unless it is 
a serviceable part. The FAA is issuing this AD to address the unsafe 
condition on these products.

DATES: This AD is effective September 29, 2025.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of September 
29, 2025.

ADDRESSES: 
    AD Docket: You may examine the AD docket at regulations.gov under 
Docket No. FAA-2025-1107; 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 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; 
phone: (888) 663-3639; email: [email protected]; website: tc.canada.ca/en/aviation.
    <bullet> You may view this material at the FAA, Airworthiness 
Products Section, Operational Safety Branch, 901 Locust, Kansas City, 
MO 64106. 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-2025-1107.

FOR FURTHER INFORMATION CONTACT: Brenda Buitrago, Aviation Safety 
Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; 
phone: (516) 228-7368; email: [email protected].

SUPPLEMENTARY INFORMATION: 

Background

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 to supersede AD 2022-23-08, Amendment 39-22235 (87 FR 
66084, November 2, 2022) (AD 2022-23-08). AD 2022-23-08 applied to 
Viking Model DHC-3 airplanes, all serial numbers.
    AD 2022-23-08 required a visual inspection of the stabilizer 
actuator to confirm that the stabilizer actuator lock ring is present, 
correctly seated in the groove in the upper housing, and engaged in the 
clamp nut, applicable corrective actions, application of a torque seal, 
and sending the inspection results to the FAA. The FAA issued AD 2022-
23-08 to correct an unsafe condition identified as a missing stabilizer 
actuator lock ring.
    The NPRM was published in the Federal Register on June 20, 2025 (90 
FR 26228). The NPRM was prompted by Transport Canada AD CF-2024-46, 
dated December 23, 2024 (Transport Canada AD CF-2024-46) (also referred 
to as the MCAI).
    The MCAI states that a fatal DHC-3 airplane accident occurred on 
September 4, 2022, at Mutiny Bay, near Freeland, WA. Witnesses reported 
that the airplane was in level flight before it entered a slight climb, 
then pitched down in a near-vertical descent until it impacted water 
resulting in fatal injuries to the pilot and the nine passengers.
    The MCAI also states that the National Transportation Safety Board 
(NTSB) carried out the accident investigation and released a final 
investigation report on September 29, 2023. The NTSB noted in the 
report that the stabilizer actuator clamp nut on the accident airplane 
separated from the stabilizer barrel by unthreading and the lock ring 
securing the clamp nut to the barrel was missing. The NTSB also found 
an unapproved moisture seal had been installed on the stabilizer 
actuator, which is not part of the airplane's type design, leading to 
increased rotational friction between the clamp nut and eye bolt, which 
has the potential to increase the rate of separation between the clamp 
nut and barrel in the absence of the lock ring.
    To address the unsafe condition, Transport Canada AD CF-2024-46 
requires initial and repetitive inspections of the stabilizer actuator 
to confirm that the stabilizer actuator lock ring is present, correctly 
seated in the groove in the upper housing, and fully engaged in the 
clamp nut. Transport Canada AD CF-2024-46 also requires application of 
a witness mark (torque seal) and prohibits the installation of a 
stabilizer actuator that has not been inspected in accordance with 
Transport Canada AD CF-2024-46 or has not been marked. If the lock ring 
is missing or incorrectly installed, Transport Canada AD CF-2024-46 
requires the rectification of the actuator in accordance with Viking 
Service Letter DHC3-SL-27-001, dated October 25, 2022, or replacement 
with a serviceable actuator, and prohibits the installation of affected 
parts.
    In the NPRM, the FAA proposed to retain none of the requirements of 
AD 2022-23-08. Instead, the FAA proposed to require accomplishing the 
actions specified in Transport Canada AD CF-2024-46 except for any 
differences identified as exceptions in the regulatory text of this AD. 
See ``Differences Between this AD and the MCAI'' for a general 
discussion of these differences.
    The FAA is issuing this AD to ensure that the stabilizer actuator 
clamp nut does not separate from the stabilizer barrel by unthreading 
and to ensure that the lock ring securing the clamp nut to the 
stabilizer barrel does not separate. This condition, if not detected 
and corrected, could result in a reduction or loss of pitch control 
during flight with consequent loss of control of the airplane.
    You may examine the MCAI in the AD docket at regulations.gov under 
Docket No. FAA-2025-1107.

Discussion of Final Airworthiness Directive

Comments

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

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

[[Page 41292]]

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. This AD is adopted as proposed 
in the NPRM.

Material Incorporated by Reference Under 1 CFR Part 51

    The FAA reviewed Transport Canada AD CF-2024-46, which specifies 
procedures for initial and repetitive inspections of the stabilizer 
actuator, applicable corrective actions, and torque seal (witness mark) 
application. Transport Canada AD CF-2024-46 also prohibits the 
installation of any stabilizer actuator unless it is a serviceable 
part.
    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

    Where Part V of Transport Canada AD CF-2024-46 specifies installing 
a new clamp nut and safety wire on the horizontal stabilizer as an 
optional terminating action, this AD requires installing a secondary 
retention feature using a method approved by the FAA within 330 hours 
time-in-service after the effective date of this AD.
    Where Transport Canada AD CF-2024-46 requires reporting any 
movement of the lock ring or witness mark to the Transport Canada Web 
Service Difficulty Reporting System (WSDRS), this AD does not require 
that action.

Costs of Compliance

    The FAA estimates that this AD affects 64 airplanes of U.S. 
registry.
    The FAA estimates the following costs to comply with this AD.

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                Cost on U.S.
              Action                    Labor cost        Parts cost    Cost per product          operators
----------------------------------------------------------------------------------------------------------------
Inspect lock ring................  1 work-hour x $85              $0  $85 per inspection    $5,440 per
                                    per hour = $85 per                 cycle.                inspection cycle.
                                    inspection cycle.
Apply witness mark (torque seal).  1 work-hour x $85               0  $85.................  $5,440.
                                    per hour = $85.
Install secondary retention        17 work-hours x $85           795  $2,240..............  $143,360.
 feature.                           per hour = $1,445.
----------------------------------------------------------------------------------------------------------------

    The FAA estimates the following costs to do any necessary actions 
that are required based on the results of the inspection. The agency 
has no way of determining the number of airplanes that might need these 
actions:

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
                    Action                                Labor cost              Parts cost   Cost per product
----------------------------------------------------------------------------------------------------------------
Install lock ring if missing or incorrectly    15 work-hours x $85 per hour =            $50              $1,325
 installed.                                     $1,275.
----------------------------------------------------------------------------------------------------------------

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 has determined that 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:
0
a. Removing Airworthiness Directive 2022-23-08, Amendment 39-22235 (87 
FR 66084, November 2, 2022); and
0
b. Adding the following new airworthiness directive:

2025-17-08 Viking Air Limited (type certificate previously held by 
Bombardier Inc. and de Havilland, Inc.): Amendment 39-23118; Docket 
No. FAA-2025-1107; Project Identifier MCAI-2024-00784-A.

(a) Effective Date

    This airworthiness directive (AD) is effective September 29, 
2025.

(b) Affected ADs

    This AD replaces AD 2022-23-08, Amendment 39-22235 (87 FR 66084, 
November 2, 2022).

[[Page 41293]]

(c) Applicability

    This AD applies to Viking Air Limited (Viking) (type certificate 
previously held by Bombardier Inc. and de Havilland, Inc.) Model 
DHC-3 airplanes, certificated in any category, as identified in 
Transport Canada AD CF-2024-46, dated December 23, 2024 (Transport 
Canada AD CF-2024-46).

(d) Subject

    Joint Aircraft System Component (JASC) Code 5520, Elevator 
Structure.

(e) Unsafe Condition

    This AD was prompted by an investigation of a Viking Model DHC-3 
airplane where the lock ring of the stabilizer actuator was found to 
be missing. The FAA is issuing this AD to ensure that the stabilizer 
actuator clamp nut does not separate from the stabilizer barrel by 
unthreading and to ensure that the lock ring securing the clamp nut 
to the stabilizer barrel does not separate. This condition, if not 
detected and corrected, could result in a reduction or loss of pitch 
control during flight with consequent loss of control of the 
airplane.

(f) Compliance

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

(g) Required Actions

    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-2024-46.

(h) Exceptions to Transport Canada AD CF-2024-46

    (1) Where Transport Canada AD CF-2024-46 refers to its effective 
date, this AD requires using the effective date of this AD.
    (2) Where Transport Canada AD CF-2024-46 requires compliance in 
terms of hours air time, this AD requires using hours time-in-
service (TIS).
    (3) Where Part V of Transport Canada AD CF-2024-46 specifies 
installing a new clamp nut and safety wire on the horizontal 
stabilizer as an optional terminating action using FAA Supplemental 
Type Certificate SA02761SE, this AD requires installing a secondary 
retention feature using a method approved by the FAA within 330 
hours time-in-service after the effective date of this AD.
    (4) Where Transport Canada AD CF-2024-46 requires reporting any 
movement of the lock ring or witness mark to the Transport Canada 
Web Service Difficulty Reporting System (WSDRS), this AD does not 
require that action.

(i) 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, mail 
it to the address identified in paragraph (j) 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.

(j) Additional Information

    For more information about this AD, contact Brenda Buitrago, 
Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, 
Westbury, NY 11590; phone: (516) 228-7368; email: 
[email protected].

(k) Material Incorporated by Reference

    (1) The Director of the Federal Register approved the 
incorporation by reference (IBR) 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) Transport Canada AD CF-2024-46, dated December 23, 2024.
    (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; phone: (888) 
663-3639; email: [email protected]; website: tc.canada.ca/en/
aviation.
    (4) You may view this material at FAA, Airworthiness Products 
Section, Operational Safety Branch, 901 Locust, Kansas City, MO 
64106. 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 August 20, 2025.
Steven W. Thompson,
Acting Deputy Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2025-16190 Filed 8-22-25; 8:45 am]
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