Flight Details
The aircraft, a Douglas DC-3C registered as C-FADD, was returning to Pickle Lake from Big Trout Lake after delivering a cargo of fuel. This was the third and final operation of the day. Prior to landing, the pilot informed the company dispatch office of an intention to conduct local training for the co-pilot, who was scheduled for an upgrade to captain status the following month. The captain, a company training pilot, occupied the right seat.
Sequence of Events
The aircraft entered a west-to-east holding pattern at the airport's Non-Directional Beacon (NDB), descending in stages from 8,500 feet above sea level (asl) to 2,700 feet asl, which was the appropriate altitude for an instrument approach. The pilot transmitted that they would execute an NDB approach and subsequently reported during the procedure turn inbound to the airfield. About three minutes later, two other pilots flying in the vicinity observed the aircraft in a descent with the left wing folded upward. The aircraft continued descending in an inverted attitude until it struck the ground.
Investigation Findings
The investigation determined that the left wing failed under normal flight loads as a result of a fatigue crack in the centre section lower wing skin. Anomalies in the radiographs taken during mandatory non-destructive testing inspections were not correctly interpreted.