Introduction
A Buffalo Airways Limited Douglas C-54G-DC (DC-4), registration C-GXKN, departed Norman Wells, Northwest Territories, at 1749 mountain standard time on a visual flight rules flight to Yellowknife. The aircraft carried a crew of four and 2000 pounds of cargo.
In-Flight Engine Failure and Fire
While climbing through approximately 3500 feet above sea level, the crew experienced a failure of the number 2 engine and a nacelle fire. The crew executed the Engine Fire Checklist, which included discharging fire bottles and feathering the number 2 propeller. The fire continued unabated. During this period, an uncommanded feathering of the number 1 propeller and an uncommanded extension of the main landing gear occurred.
Emergency Response and Landing
The crew planned for an emergency off-field landing. During the descent to the landing area, the fuel selector was turned off as part of the Engine Securing Checklist, and the fire self-extinguished. A decision was made to return to the Norman Wells Airport, where a successful two-engine landing was completed at 1804 mountain standard time.
Damage and Injuries
The aircraft sustained substantial fire damage. There were no injuries to the four crew members on board.
Probable Cause
According to the official investigation, the probable cause includes three findings: (1) Airworthiness Directive AD 48-12-01 mandated replacement of a potentially hazardous fuel line, but the line had not been replaced on this aircraft. (2) A fuel leak from the main fuel inlet line in the engine compartment caused an in-flight fire that spread into the nacelle and wing. (3) The fuel-fed fire burned for an extended period because turning the fuel selector off was not required as part of the primary Engine Fire Checklist.