What happened
On the morning of February 17, 1997, a ski-equipped Cessna A185F, registration C-GCTI, departed Sept-Îles Airport, Quebec, for a flight to Wabush, Newfoundland. The flight was being conducted under visual flight rules in favorable weather conditions. While cruising at 4,5/00 feet above sea level at approximately 145 mph, the aircraft experienced a sudden, sharp pitch-down motion. The pilot attempted to stabilize the aircraft by reducing power and adjusting the elevator, but the aircraft disintegrated in flight.
The aircraft's wreckage was located 14 nautical miles north of the departure airport. The impact resulted in two fatalities, involving the pilot and the aircraft owner, while two passengers in the rear of the aircraft survived the fall from approximately 3,500 feet. The wreckage was found scattered, with the fuselage having separated into multiple sections.
The investigation
Investigators examined the wreckage and conducted laboratory analyses of the engine, propeller, and structural components. The investigation established that the aircraft's right wing, engine, and fuselage had all suffered failures due to instantaneous overload. Examination of the engine revealed that the propeller had struck a metal plate and a cable that had been thrown from the ski tip.
Technical analysis of the landing gear revealed that the AN-7 bolt, which secures the landing gear leg, had been incorrectly tightened during the installation of the skis. Furthermore, the investigation looked into the maintenance history of the Airglas skis installed on the aircraft. It was determined that a mandatory Airworthiness Directive (AD) regarding the modification of the bungee and cable attachment points had not been implemented.
Findings
- The right ski rotated downward during flight, which increased aerodynamic resistance and caused the initial pitch-down.
- The bungee on the right ski failed, allowing the ski to rotate further and causing the metal plate and cable to detach.
- The detached cable and plate struck the propeller, leading to the failure of the engine mount brackets and the separation of the engine.
- Non-compliance with Airworthiness Directive CF-80-18 meant the necessary modifications to the ski assembly were not in place.
- An incorrectly tightened bolt (AN-7) contributed to the failure of the landing gear leg.
- The separation of the ski and landing gear caused them to strike the right wing, triggering the structural failure of the wing and the subsequent breakup of the fuselage.