Safety Recommendation A-22-024

We note that, as of January, you have contacted the owners of approximately 82 percent of Canada’s DHC-3 fleet and learned that they have either completed Viking Air’s SL or plan to do so before returning their aircraft to service. We also note that you are working with the type certificate holder to contact the remaining 18 percent of the fleet. Mr. Meunier reported that TCCA is still investigating this safety issue; however, the findings of the completed inspections do not indicate a systemic issue.

We also note that you maintain records of foreign-registered Canadian products and, on November 2, 2022, you distributed copies of Civil Aviation Safety Alert 2022-04 which notifies owners, operators, and maintainers of DHC-3 airplanes of this accident and recommends that they complete the inspection and corrective actions described in SL DHC3-SL-27-001 and report the findings to Viking Air Limited, to countries with registered DHC-3 aircraft.

We believe the actions that you reported are responsive to this recommendation and, if you can confirm that all DHC-3 airplanes registered in Canada have completed Viking Air’s SL, represent an acceptable alternative solution. Pending completion of the recommended actions, Safety Recommendation A-22-24 remains classified OPEN-- ACCEPTABLE ALTERNATE RESPONSE.

-From Felix Meunier, Director General, Civil Aviation Transport Canada: Transport Canada (TC), National Aircraft Certification (NAC), Continuing Airworthiness Division (CAW) has reviewed the letter requesting additional information related to NTSB report AIR-22-08 which contains the above safety recommendation addressed to Transport Canada Civil Aviation (TCCA).

Specifically, the NTSB is asking for the following additional information:

1. "Since 24 % of all DHC-3 airplanes registered in Canada have not been contacted yet by TC, NTSB would like to know how TC plans to address these aircraft", and

2. "NTSB would also like to know if TC, as the regulator for the State of Design and Manufacture of DHC-3 airplanes has a process for notifying its counterparts in other countries where these airplanes are registered about this safety issue and the actions recommended in CASA 2022-04."

As of January 5th, 2023, 18% of DHC-3 aircraft owners have not been directly contacted. The type certificate holder continues to actively pursue contact with these remaining aircraft owners under the oversight of TC. The findings of the investigation to-date do not indicate an immediate, systemic safety concern; however, the investigation remains open in anticipation of future reports from DHC-3 aircraft, which are currently out of service and awaiting completion of winter maintenance activities.

TCCA respects the International Civil Aviation Organization's (ICAO) Annex 8 guidance and therefore does have a process to notify all states of registry of continuing airworthiness information. Within NAC, the Program Integration and Publications group maintains Special Interest Group (SIG) mailing lists based on the information within ICAO Doc 95 and any non-ICAO states that have self-identified as having a Canadian product on their registry. SIGs are used to disseminate continuing airworthiness information to all listed contracting states and known states of registry primarily via email.

In the case of Civil Aviation Safety Alert (CASA) 2022-04, TCCA can confirm that a copy was sent to all contracting states and known states of registry on Wednesday, November 2nd at 12:21 pm EDT. Additionally, all CASAs are published on TCCA's public website and are distributed via Transport Canada E-Bulletin to any subscribers.

National Aircraft Certification, Continuing Airworthiness Division continues to investigate this accident with cooperation from the type certificate holder. Although mandatory corrective action is not indicated at this time, the investigation continues, and CAW will not hesitate to take any actions necessary to ensure an acceptable level of safety is maintained for the DHC-3 aircraft type if indicated.

We note that, on October 24, 2022, you issued Civil Aviation Safety Alert (CASA) 2022-04, which notifies owners, operators, and maintainers of DHC-3 airplanes in Canada of this accident and recommends that they complete the inspection and corrective actions described in Viking Air Limited Service Letter (SL) DHC3-SL-27-001 and report the findings to Viking Air Limited. We also note that you have contacted the owners of approximately 76 percent of Canada’s DHC-3 fleet and learned that they have either completed Viking Air’s SL or plan to do so before returning their aircraft to service.

You reported that the findings from those inspections do not indicate a systemic issue related to the actuator lock ring, but that you are still investigating this safety issue to determine if any mandatory corrective actions are needed for DHC-3 airplanes. We believe the actions that you reported are responsive to this recommendation and, if you can confirm that all DHC-3 airplanes registered in Canada have completed Viking Air’s SL, represent an acceptable alternative solution to the recommended requirement.

We understand, however, that approximately 24 percent of DHC-3 airplanes registered in Canada have not been contacted, and we would like to know how you plan to address these aircraft. We would also like to know if TC, as the regulator for the state of design and manufacture of DHC-3 airplanes, has a process for notifying its counterparts in other countries where these airplanes are registered about this safety issue and the actions recommended in CASA 2022-04. Pending our review of the requested information and completion of the recommended actions, Safety Recommendation A-22-24 is classified OPEN--ACCEPTABLE ALTERNATE RESPONSE.

-From Félix Meunier, Director General, Civil Aviation, Transport Canada: Transport Canada - TC has opened an investigation into this accident which is ongoing with cooperation from the type certificate holder. The objective of the investigation is to determine what, if any, mandatory corrective actions are required to ensure an acceptable level of safety is maintained for the DHC-3 aircraft type.

Upon review of the October 24th, 2022 update for NTSB investigation DCA22MA193, the National Aircraft Certification, Continuing Airworthiness Division - CAW issued Civil Aviation Safety Alert (CASA) 2022-04 to urgently raise awareness of the accident and the NTSB’s findings within the Canadian registered fleet. CASA 2022-04 also draws attention to Viking Air Limited Service Letter DHC3-SL-27-001, which provides instructions for a visual inspection to confirm the presence of the actuator lock ring and its correct engagement. Additionally, the service letter includes a method to expediently report the findings of those inspections to Viking Air Limited for further evaluation.

As part of this investigation, Transport Canada officials have directly contacted the owners of approximately 76% of the Canadian DHC-3 fleet and confirmed that affected aircraft have either been inspected as per the Viking Air Limited service letter, or that their aircraft are currently not operating and the inspection will take place during its seasonal maintenance prior to being returned to service. Inspection findings received up to November 10, 2022, do not indicate a systemic issue related to the actuator lock ring, however the CAW investigation continues.

The Continuing Airworthiness division of TC will continue to work with Viking Air, the FAA and the NTSB on this matter and will not hesitate to mandate any corrective actions determined necessary to maintain an acceptable level of aviation safety.

The National Transportation Safety Board (NTSB) is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant accidents in other modes of transportation—railroad, highway, marine, and pipeline. We determine the probable cause of the accidents and issue safety recommendations aimed at preventing future accidents. In addition, we carry out special studies concerning transportation safety and coordinate the resources of the federal government and other organizations to assist victims and their family members affected by major transportation disasters.

We are providing the following information to urge Transport Canada to act on the urgent safety recommendation in this letter because we believe your organization can help reduce the risk of future accidents. This letter includes information about our October 26, 2022, report Require Immediate One-Time Inspection of De Havilland Canada DHC-3 Horizontal Stabilizer Actuator (NTSB/AIR-22-08). The details of this ongoing accident investigation and the resulting urgent safety recommendations may be found in the attached report, which can also be accessed at http://www.ntsb.gov.

As a result of the NTSB’s preliminary findings in this investigation, we identified the following safety issue:

• Need to ensure that the lock ring in the horizontal stabilizer actuator is in place and properly installed to preclude a reduction or loss of pitch control.

Accordingly, the NTSB makes the following urgent safety recommendation to Transport Canada:

• Require all operators of De Havilland Canada DHC-3 airplanes to conduct an immediate one-time inspection of the horizontal stabilizer actuator lock ring in accordance with the instructions in Viking Air Limited Service Letter DHC3-SL-27-001 and report their findings to Transport Canada. (A-22-24) (Urgent) The NTSB is vitally interested in this urgent recommendation because it was designed to prevent accidents and save lives. We would appreciate a response within 30 days of the date of this letter, detailing the actions you have taken or intend to take to implement these recommendations. When replying, please refer to the safety recommendation by number (Safety Recommendation A-22-24).

We encourage you to submit your response to ExecutiveSecretariat@ntsb.gov. If your reply, including attachments, exceeds 20 megabytes, please e mail us at the same address for instructions on how to send larger documents. Please do not submit both an electronic copy and a hard copy of the same response.