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

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]</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> Notice of proposed rulemaking (NPRM). <SUM> <HD SOURCE="HED">SUMMARY:</HD> The FAA proposes to supersede Airworthiness Directive (AD) 2022-23-08, which applies to all Viking Air Limited (Viking) Model DHC-3 airplanes. AD 2022-23-08 requires 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. This proposed AD would require 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 proposed AD would also prohibit the installation of any stabilizer actuator unless it is a serviceable part. The FAA is proposing this AD to address the unsafe condition on these products. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> The FAA must receive comments on this NPRM by August 4, 2025. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> You may send comments, using the procedures found in 14 CFR 11.43 and 11.45, by any of the following methods: • <E T="03">Federal eRulemaking Portal:</E> Go to <E T="03">regulations.gov.</E> Follow the instructions for submitting comments. • <E T="03">Fax:</E> (202) 493-2251. • <E T="03">Mail:</E> 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">Hand Delivery:</E> Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. <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 NPRM, the mandatory continuing airworthiness information (MCAI), any comments received, and other information. The street address for Docket Operations is listed above. <E T="03">Material Incorporated by Reference:</E> • For Transport Canada material identified in this proposed 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. <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">Comments Invited</HD> The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under <E T="02">ADDRESSES</E> . Include “Docket No. FAA-2025-1107; Project Identifier MCAI-2024-00784-A” 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 the 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 <E T="03">regulations.gov,</E> including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this NPRM. <HD SOURCE="HD1">Confidential Business Information</HD> 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 Brenda Buitrago, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking. <HD SOURCE="HD1">Background</HD> The FAA issued AD 2022-23-08, Amendment 39-22235 (87 FR 66084, November 2, 2022) (AD 2022-23-08), for Viking Model DHC-3 airplanes, all serial numbers, certificated in any category. The FAA issued AD 2022-23-08 to correct an unsafe condition identified as a missing stabilizer actuator lock ring. AD 2022-23-08 requires 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 address the unsafe condition on these products. <HD SOURCE="HD1">Actions Since AD 2022-23-08 Was Issued</HD> Since the FAA issued AD 2022-23-08, Transport Canada, which is the aviation authority for Canada, issued 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 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. The FAA is proposing 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">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 <E T="02">ADDRESSES</E> . <HD SOURCE="HD1">FAA's Determination</HD> These products have been approved by the aviatio ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 22k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━