What happened
On the evening of the accident, a twin engine airplane, registration C-FCAS, departed from Montreal-Dorval Airport at 17:41 local time. The aircraft was conducting a specialized calibration mission for a radar antenna on behalf of Transport Canada. After communicating with air traffic control, the crew began an orbiting pattern approximately 20 nautical miles from the target antenna while maintaining an altitude of 1,700 feet.
While crossing the 165 radial, the aircraft experienced an uncontrolled descent and impacted a field in the vicinity of Sherrington. The impact resulted in the total destruction of the airframe and two fatalities. During the investigation, wreckage from the outer section of the right wing, located outboard of the engine nacelle, was recovered 640 meters away from the primary crash site.
Findings
Investigators determined that a structural failure occurred when the forward outboard wing attachment fitting on the right side of the aircraft fractured. This progressive cracking caused the outer section of the wing to separate from the aircraft under normal flight loads.
Laboratory examinations of the failed component revealed that the crack development was driven by fatigue from cyclic flight stresses. The root cause was traced to a manufacturing defect consisting of gas bubbles located on the grain boundaries of the fitting. These bubbles facilitated the initial stages of the crack. While the part met all standard specifications and passed previous inspections, it was noted that the specific batch of fittings contained this hidden deficiency.
Furthermore, the investigation highlighted that a required dye penetrant inspection, which should have occurred at 5,407 hours, had not been performed due to ambiguities in existing airworthiness directives regarding inspection intervals.