AD 2022-23-08 Requires A Visual Inspection Of The Stabilizer Actuator To Confirm That The Stabilizer Actuator Lock Ring Is Present

The FAA is adopting a new airworthiness directive (AD) for all Viking Air Limited (Viking) (type certificate previously held by Bombardier Inc. and de Havilland, Inc.) Model DHC-3 airplanes. 

This AD was prompted by a recent investigation of a Viking Model DHC-3 airplane where the lock ring of the stabilizer actuator was found missing. This 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. This AD also requires sending the inspection results to the FAA. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective November 2, 2022.

Supplementary Information: On September 4, 2022, a fatal accident of a Viking Model DHC-3 airplane in Mutiny Bay near Freeland, WA occurred. The National Transportation Safety Board investigation showed that the lock ring of the stabilizer actuator was found missing. The investigation revealed that the clamp nut that attaches the top eye end and bearing assembly of the horizontal stabilizer actuator to the actuator barrel had unscrewed from the barrel. The investigation also found that the circular wire lock ring, which was designed to prevent the clamp nut from unscrewing, was not present. 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. The FAA is issuing this AD to address the unsafe condition on these products.

FMI: www.regulations.gov