What happened
On a night-time cargo flight operating under visual flight rules, a Piper PA-31-3im-350 Chieftain, registered C-GNAF, was performing the final leg of a multi-stop route from Vancouver to Nanaimo and Victoria. While approaching Vancouver International Airport, the aircraft, operating as APEX 511, was positioned between two larger Airbus aircraft.
As the crew turned onto the final approach course for Runway 26 Right, the aircraft entered the wake turbulence area of a preceding heavy aircraft, positioned 1.5 nautical miles behind and 700 feet below that plane's flight path. The encounter caused an immediate upset and loss of control. The aircraft impacted the ground in an industrial area of Richmond, British Columbia, approximately 3 nautical miles short of the runway, resulting in a post-impact fire and explosion. The 2 fatalities involved were the two crew members on board. No injuries were reported on the ground, though property damage occurred.
The investigation
Investigators examined the wreckage and determined the aircraft was upright with wings nearly level at the time of impact, suggesting the crew may have been attempting a recovery before the altitude became insufficient. Technical inspections of the aircraft did not reveal any mechanical defects that contributed to the accident. However, the investigation noted that the right-hand engine-driven fuel pump drive splines had not been overhauled at the recommended interval, and the operator lacked a reliability program to track component wear.
The investigation also looked into the crew's workload and physiological state. The captain had experienced a significant sleep deficit due to non-aviation employment obligations that were not captured under flight duty regulations. Furthermore, the lack of cockpit recording devices prevented investigators from analyzing the specific decision-making processes or communications between the pilots during the approach.
Findings
- The aircraft encountered wake turbulence from a heavier preceding aircraft, leading to an unrecoverable loss of control.
- Limited spacing between arriving aircraft, caused by the proximity of faster trailing traffic, forced the crew to fly within the wake turbulence zone.
- The use of visual separation in darkness increased the difficulty of accurately judging distance and spacing from preceding traffic.
- Regulatory gaps meant the operator did not account for the crew's fatigue resulting from non-aviation work commitments.
- Maintenance practices regarding engine accessories did not align with manufacturer recommendations for life-limited components.