What happened
A Piper PA-31-350 Navajo, registration C-GHMK, was conducting a visual flight rules charter service from St. Andrews, Manitoba, toward Berens River when the incident occurred. The aircraft was carrying one pilot and ten passengers, including an infant, along with a dog in the baggage area.
At roughly 15:30 CDT, while flying at approximately 2,500 feet and located 30 nautical miles south of the destination, the pilot experienced a loud noise from the left engine. This was accompanied by smoke and visible deformation of the engine cowling, which partially detached during flight. The aircraft experienced a significant yaw to the left. The pilot attempted to feather the left propeller but found the control lever stuck at the halfway position. Despite applying maximum power to the right engine, the aircraft was unable to maintain its altitude.
The pilot notified dispatch of his intention to perform an emergency landing and successfully touchdown in a mossy marsh. All eleven people on board and the animal evacuated without life-threatening injuries, though five passengers suffered minor injuries during the process. Following the landing, a fire broke out that consumed the entire aircraft, leaving only the empennage behind the horizontal stabilizers intact.
Findings
Investigation into the engine failure revealed that a base nut was missing from a through stud on the third cylinder. This deficiency caused the lower rear base nut of the second cylinder to loosen. Consequently, the studs for the number two cylinder failed due to fatigue, leading to the separation of that cylinder from the crankcase.
The separation of the engine cylinder prevented the propeller governor control from moving, making it impossible to feather the left propeller. The resulting aerodynamic drag from the unfeathered propeller and the damaged cowling made it impossible for the aircraft to stay airborne. Additionally, investigators noted that the emergency locator transmitter was not easily accessible without tools.