What happened
A DHC-4A Caribou was performing a transport mission from Calgary to Ross River, carrying silver ore concentrate equipment and a crew consisting of two pilots and two maintenance engineers. The flight included a scheduled refueling stop at Fort Nelson before proceeding under an IFR flight plan toward the destination. Due to the mountainous terrain and lack of instrument approaches at Ross River, the flight profile required an NDB approach at Faro followed by a visual navigation segment along the river valley.
Upon reaching Faro around 16:15, the crew attempted to descend through a cloud base situated between 400 and 600 feet AGL. After failing to establish visual ground references, the pilot diverted to Watson Lake. During this period of cruise flight, the number two engine experienced a total loss of oil pressure. In response, the crew shut down the right engine and feathered the propeller.
The aircraft later returned toward Ross River for an approach to runway 26. During the landing sequence, the nose gear failed to lock into position upon its initial extension, necessitating a gear cycle. Because the aircraft was no longer capable of a safe landing, the captain initiated a go-around. During this maneuver, the plane lost altitude while passing the town, striking trees that tore away sections of the right wing. The aircraft rolled to the right and impacted the ground before cartwheeling down an embankment to the river shore.
Findings
Investigations revealed that the engine oil loss was caused by the installation of an improper gasket in the right engine, a result of communication failures at the company's maintenance facility. The accident occurred because a go-around was attempted under difficult conditions involving single-engine performance and high terrain while flying below the cloud base. Additionally, the crew retracted the flaps fully before the aircraft had reached the minimum required speed for single-engine flight in a zero-flap configuration.