What happened
A charter flight departing from a logging camp at Fish Egg Inlet, British Columbia, ended in tragedy when a de Havilland DHC-6-100 lost control shortly after takeoff. The aircraft, operated by Pacific Coastal Airlines, was performing a 16-nautical-mile VFR flight to Pruth Bay with a crew of two and two passengers.
During the initial climb, as the aircraft reached approximately 100 feet above the surface and the flaps were being retracted, the aircraft experienced a violent nose-up pitch and entered a stall. The aircraft struck the water near the shoreline and sank immediately. While the captain sustained serious injuries and managed to swim to shore, the first officer and both passengers drowned within the submerged wreckage.
The investigation
The investigation focused on the mechanical failure of the elevator control system. Investigators determined that the down elevator control cable at station 376 had failed. Microscopic analysis of the broken cable revealed that several strands had significantly thinned due to long-term degradation.
Maintenance records were examined, noting that the aircraft had undergone a recent inspection. However, the engineer performing the inspection did not remove the baggage compartment floor panel, which is necessary to view the forward side of the pulley cluster at station 376. While the controls were cycled, the specific area of the cable prone to failure remained difficult to inspect. Additionally, investigators noted that the pilot had selected a 30-degree flap setting for takeoff, whereas the aircraft flight manual specifies 20 degrees for float-equipped operations.
Findings
- The primary cause of the accident was the failure of the down elevator control cable due to corrosion.
- The corrosion on the cable was not identified during the most recent maintenance inspection.
- The aircraft was destroyed by the impact and subsequently submerged in salt water.
- The crew and passengers were not wearing shoulder harnesses or available flotation devices at the time of the crash.