What happened
On the final flight of its daily operations, a Douglas DC-3C, registered as C-FADD, was traveling from Big Trout Lake to Pickle Lake after completing a fuel delivery mission. Before arriving at the destination, the pilot notified dispatch that they would perform local training maneuvers to prepare the co-pilot for an upcoming promotion to captain. During this flight, the captain occupied the right seat of the aircraft.
The crew entered a holding pattern at the airport's NDB, moving from west to east while descending from 8,500 feet to 2,700 feet. The pilot communicated their intention to perform an NDB approach and later reported being inbound during the procedure turn. During this descent, witnesses in nearby aircraft observed the plane's left wing folding upward. The aircraft subsequently entered an inverted descent before impacting the ground.
Findings
Investigations into the accident revealed that the left wing failed while the aircraft was under normal flight loads. This structural failure was triggered by a fatigue crack located in the lower skin of the center wing section. It was further determined that previous non-destructive testing inspections had identified anomalies via radiographs, but these findings were not properly interpreted by inspectors.