History of the Flight
The Canadian Air Charters Piper PA-31-350 Chieftain (registration C-GNAF) was operating under visual flight rules as APEX 511 on the final leg of a multi-leg cargo flight from Vancouver to Nanaimo and Victoria, British Columbia, with a return to Vancouver. The weather was visual meteorological conditions, and the last 9 minutes of the flight took place during official darkness. The flight was third for landing and turned onto the final approach course 1.5 nautical miles behind and 700 feet below the flight path of a heavier Airbus A321, approaching Runway 26 Right at Vancouver International Airport. At 2208 Pacific Daylight Time, the target for APEX 511 disappeared from tower radar. The aircraft impacted the ground in an industrial area of Richmond, British Columbia, 3 nautical miles short of the runway. There was a post-impact explosion and fire. The 2 crew members on board were fatally injured. There was property damage but no injuries on the ground. The onboard emergency locator transmitter was destroyed in the accident, and no signal was detected.
Technical Examination
The wreckage distribution pattern indicated that the aircraft was upright with wings approximately level. The change in the angle of descent likely commenced before the aircraft tail contacted a chimney, suggesting that flight controls were functional and that recovery from the upset was in progress, but altitude remaining precluded complete recovery. Technical examination of the aircraft and associated records identified a risk to safety but did not identify any aircraft defects contributory to this accident.
Maintenance - Engine Components
The condition of the right-hand engine-driven fuel pump drive splines indicated that it was not replaced or overhauled at the engine TBO of 1800 hours and was not subject to any repetitive periodic inspections. The operator did not have a reliability program in place as required under its approved maintenance program to track wear and deterioration of such components. Therefore, the risk continues that components like fuel pumps will remain in service until they fail. The company's SOP for the Piper Chieftain directs flight crews to turn off backup emergency electric fuel pumps for the cruise portion of flight.
Visual Separation and Wake Turbulence
Controllers frequently plan IFR traffic flows based on visual approaches when VMC exist. According to AIM RAC 9.6.2, acceptance of a visual approach clearance acknowledges that the pilot is responsible for maintaining adequate wake turbulence separation. Once visual separation is established, ATC is not responsible for flight crew actions, which may result in more or less than recommended wake turbulence spacing. Research shows humans are poor judges of distance, especially in darkness. At the time, AIC 12/08 was in effect on a trial basis at Vancouver, stating that controller-applied visual separation could not be used if wake turbulence separation was required for IFR departures. In July 2010, AIC 15/10 changed the pilot-applied visual separation procedure for departures but not for arrivals. Transport Canada's study indicated wake turbulence events average about 15 per year with an increasing trend. The accident demonstrates that encounters with wake turbulence, especially at low altitude, can produce catastrophic results with little warning. Visual separation may not ensure adequate spacing for wake turbulence, particularly in darkness.
Flight Duty Regulations
Company policy, regulations, and pilot personal responsibility are primary defences against fatigue. Both pilots worked part-time for CAC and had other non-aviation jobs. The captain had been awake for an extended period and had a work-related sleep deficit, having woken 3.5 hours earlier than normal on the accident day with no subsequent sleep. Under CARs, some work time was not considered for fatigue management because it was not defined as flight duty time, creating conditions that could lead to fatigue. Without a mechanism requiring pilots to report duty time from all sources of employment, unsafe conditions persist.
Flight Crew Actions
APEX 511 joined the downwind leg as instructed. The controller's plan placed APEX 511 between two Airbus aircraft. The crew was responsible for avoiding the preceding aircraft's wake turbulence. Until turning base leg, the flight appeared normal. The crew had to use unaided eyesight in darkness to judge distance from preceding traffic. APEX 511 turned onto final within the wake turbulence area—1.5 nm behind and 700 feet below the heavier aircraft. About 2 nm after turning final, a wake turbulence encounter caused an upset and loss of control at an altitude from which recovery was impossible. Two hypotheses could explain the crew's actions: either they intended to follow closely (possibly underestimating wake turbulence risk due to previous uneventful experiences and fatigue) or they misjudged the distance due to reliance on visual estimates in darkness, compounded by fatigue.
Airport Controller Actions
The airport controller considered the downwind method the most efficient arrival option for APEX 511. The controller arranged spacing between traffic to accommodate APEX 511, but the spacing was insufficient to avoid the wake turbulence encounter.