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

<RULE> DEPARTMENT OF TRANSPORTATION <SUBAGY>Federal Aviation Administration</SUBAGY> <CFR>14 CFR Part 39</CFR> <DEPDOC>[Docket No. FAA-2025-1107; Project Identifier MCAI-2024-00784-A; Amendment 39-23118; AD 2025-17-08]</DEPDOC> <RIN>RIN 2120-AA64</RIN> <SUBJECT>Airworthiness Directives; Viking Air Limited (Type Certificate Previously Held by Bombardier Inc. and de Havilland, Inc.) Airplanes</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Federal Aviation Administration (FAA), DOT. <HD SOURCE="HED">ACTION:</HD> Final rule. <SUM> <HD SOURCE="HED">SUMMARY:</HD> 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. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> 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. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> <E T="03">AD Docket:</E> You may examine the AD docket at <E T="03">regulations.gov</E> 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. <E T="03">Material Incorporated by Reference:</E> • 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: <E T="03">TC.AirworthinessDirectives-Consignesdenavigabilite.TC@tc.gc.ca;</E> website: <E T="03">tc.canada.ca/en/aviation.</E> • 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 <E T="03">regulations.gov</E> under Docket No. FAA-2025-1107. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Brenda Buitrago, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (516) 228-7368; email: <E T="03">brenda.l.buitrago.perez@faa.gov</E> . </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">Background</HD> 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 <E T="04">Federal Register</E> 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 <E T="03">regulations.gov</E> under Docket No. FAA-2025-1107. <HD SOURCE="HD1">Discussion of Final Airworthiness Directive</HD> <HD SOURCE="HD1">Comments</HD> The FAA received no comments on the NPRM or on the determination of the costs. <HD SOURCE="HD1">Conclusion</HD> 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. This AD is adopted as proposed in the NPRM. <HD SOURCE="HD1">Material Incorporated by Reference Under 1 CFR Part 51</HD> 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 <E T="02">ADDRESSES</E> section. <HD SOURCE="HD1">Differences Between This AD and the MCAI</HD> 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. <HD SOURCE="HD1">Costs of Compliance</HD> The FAA estimates that this AD affects 64 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD. <GPOTABLE COLS="5" OPTS="L2,nj,i1" CDEF="s50,r50,10,r25,r25"> <TTITLE>Estimated Costs</TTITLE> <CHED H="1">Action</CHED> <CHED H="1">Labor cost</CHED> <CHED H="1">Parts cost</CHED> <CHED H="1">Cost per product</CHED> <CHED H="1"> Cost on U.S. operators </CHED> <RO ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 19k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━