Safety Recommendation A-22-023

We note that, on November 2, 2022, you issued emergency Airworthiness Directive (AD) 2022-23-08, “Viking Air Limited (Type Certificate Previously Held by Bombardier Inc. and de Havilland, Inc.),” which requires operators to, within 10 hours of time-in-service after the effective date of the AD, visually inspect 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. The AD also requires operators to repair the stabilizer actuator if the lock ring is missing or incorrectly installed, apply a torque seal, and send the inspection results to the FAA for review.

We believe AD 2022-23-08 satisfies the intent of Safety Recommendation A-22-23. Accordingly, this recommendation is classified CLOSED-- ACCEPTABLE ACTION.

Thank you for promptly taking this step to improve aviation safety.

-From Billy Nolen, Acting Administrator: In direct response to this urgent safety recommendation, the Federal Aviation Administration (FAA) issued Airworthiness Directive (AD) 2022-23-08, Viking Air Limited (Type Certificate Previously Held by Bombardier Inc. and de Havilland, Inc.), as an emergency AD effective on November 2, 2022 (87 FR 66084).

The FAA issued this AD because we determined that the unsafe condition described above is likely to exist in all airplane models of the same type design. The AD 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, and application of a torque seal. It also requires sending the inspection results to the FAA for review.

I believe that the FAA has effectively addressed Safety Recommendation A-22-23 and consider our actions complete.

This letter provides information about the National Transportation Safety Board’s (NTSB) 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 the Federal Aviation Administration (FAA):

• 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 the Federal Aviation Administration. (A 22 23) (Urgent)

The NTSB is vitally interested in this urgent recommendation because it is 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 this urgent recommendation. When replying, please refer to the safety recommendation by number (Safety Recommendation A-22-23). 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.

Justification for Safety Recommendation A-22-23 from Urgent Safety Recommendation Report "Require Immediate One-Time Inspection of De Havilland Canada DHC-3 Horizontal Stabilizer Actuator:" The NTSB concludes that a missing or an improperly installed horizontal stabilizer actuator lock ring is an immediate safety hazard because it could result in a reduction or loss of pitch control during flight in De Havilland Canada DHC-3 airplanes. Further, a requirement for operators to report the findings of their inspections could help identify the scope of the problem.