Incident
On a routine flight from Vancouver International Airport to Kelowna, British Columbia, a Northern Thunderbird Air Incorporated Beechcraft King Air 100 (serial number B-36, registration C-GXRX) experienced an oil leak about 15 minutes after takeoff. The flight diverted back to Vancouver without declaring an emergency. At 1611 Pacific Daylight Time, while on final approach approximately 300 feet above ground level and 0.5 statute miles from the runway, the aircraft suddenly banked left and pitched nose-down. It collided with the ground and caught fire, coming to rest on a roadway just outside the airport fence.
Rescue and Injuries
Passersby helped evacuate six passengers from the burning wreckage. Fire and rescue personnel rescued the remaining passenger and the two pilots. All seven passengers sustained serious injuries. Both pilots succumbed to their injuries in hospital. The aircraft was destroyed. Its emergency locator transmitter had been removed prior to the flight.
Probable Cause
The official investigation identified multiple causes and contributing factors. During routine maintenance, the left-engine oil-reservoir cap was likely left unsecured. A complete preflight inspection was not performed, so the unsecured cap went undetected, causing the left engine to vent significant oil during operation. A non-mandatory modification designed to limit oil loss when the cap is unsecured had not been installed. Oil leaking from the left engine during repositioning was pointed out to the crew, but they did not determine its source before departure. On final approach, the aircraft slowed below VREF speed. When power was applied—likely only to the right engine—the aircraft was below the speed required for directional control, yawed and rolled left, and pitched down. A partially effective recovery was initiated by reducing right-engine power, but insufficient altitude prevented full recovery. Impact damage compromised the fuel system. Ignition sources from metal friction and possibly the electrical system started fires. The damaged electrical system remained powered by the battery, causing arcing that may have ignited fires, including in the cockpit. Impact-related injuries limited the ability of the pilots and most passengers to extricate themselves.
Risk Findings
The investigation noted several risks. Multi-engine aircraft flight manuals and training programs do not include cautions and minimum control speeds for asymmetrical thrust when an engine is at low power or the propeller is not feathered. Pilots may not anticipate aircraft behavior when using asymmetrical thrust near or below unpublished critical speeds, risking loss of control. The company's standard operating procedures lacked clear directions for aircraft configuration in the last 500 feet or for handling unstable approaches in abnormal situations, demonstrating a risk of accidents from unstabilized approaches below 500 feet. Without battery isolation after damage, an energized battery may ignite fires via electrical arcing. Erroneous weight-and-balance data can cause crews to inadvertently fly outside the allowable center-of-gravity envelope.