Incident Overview
A Buffalo Airways Curtiss C-46A, operating as flight 525 from Yellowknife, Northwest Territories (YZF) to Norman Wells, Northwest Territories (YVQ), experienced a critical engine issue while en route. The crew noticed a drop in the right engine oil quantity indicator accompanied by a propeller overspeed.
Engine Failure
The crew adjusted the propeller pitch to control the overspeed, but the oil quantity continued to drop rapidly. Visual inspection confirmed oil escaping from the engine breather vent at an abnormally high rate. The right propeller speed became uncontrollable, prompting the crew to perform the propeller overspeed drill. Despite attempts, the propeller did not initially feather. After several more attempts, the propeller finally feathered. The crew then secured the engine and completed the shutdown checklist.
Descent and Diversion
The crew decided to divert to Tulita, Northwest Territories (ZFN), but quickly determined that the descent rate would not permit a landing there. The only remaining diversion option was Déline, Northwest Territories (YWJ), where weather was reported as half a mile visibility and 300 feet ceiling. The crew declared an emergency with Déline radio.
Landing and Aftermath
Upon arrival at Déline, the crew did not select the landing gear down to prevent further loss of airspeed. The aircraft performed a belly landing approximately at the midpoint of runway 08. It continued off the end of the runway, coming to a stop about 700 feet beyond the threshold. The crew evacuated without sustaining injuries. The aircraft was destroyed.
Probable Cause
Buffalo Airways’ initial investigation revealed that the engine oil scavenge pump had failed.