Accident
At 0741 Pacific daylight time, a Piper PA-31-350 (registration C-GVCP) crashed approximately 300 feet short of Runway 30 at the civilian terminal of the military airbase in Comox, British Columbia. The aircraft was on a scheduled cargo flight from Nanaimo, British Columbia. The crew had requested a practice back course/localizer approach to Runway 30, circling for landing on Runway 18. When the aircraft was about two miles from the threshold of Runway 30, the crew declared an emergency for an engine fire in the right engine. Less than 30 seconds later, the aircraft became engulfed in flames, rolled inverted, and struck the ground in a steep, nose-down, left-wing-low attitude. Both crew members were fatally injured.
Investigation
The wreckage was transported to the Transportation Safety Board (TSB) Regional Examination Facility. Examination revealed solidified droplets of molten aluminum and small structural components along the inbound course for Runway 30, as far back as 1000 feet before the initial impact point. The first ground contact was approximately 300 feet short of the threshold and slightly right of the extended centerline. The right engine separated from the wing and came to rest upright, remaining outside the post-crash fire area.
Fire patterns indicated an in-flight fire in the right engine compartment. The gill cowl inboard of the right engine showed burn patterns likely caused in flight. The leading edge of the right wing burned through, and the main fuel tank was penetrated by fire. Examination of the right engine revealed fire damage concentrated at the rear, with the origin near the center of the accessory section. The oil filter converter plate gasket was partially extruded and deteriorated, consistent with a failure that allowed pressurized engine oil to spray into the compartment. The oil ignited, likely on contact with hot turbocharger or exhaust components.
The failed gasket (part number LW-13388) was from a bad batch that entered the supply system in 1999. Airworthiness Directive 2002-12-07 required removal of such gaskets by 01 October 2003, but this was not accomplished on the accident engine. The aircraft had no engine-fire warning system, and the crew may not have been aware of the fire until shortly before declaring the emergency. The firewall shut-off valve remained open, and the engine-driven fuel pump casing melted, causing a pressurized fuel-fed fire that breached the main fuel tank.
Findings
The TSB determined that the improper oil filter converter plate gasket failed, allowing pressurized oil to spray and ignite. The firewall shut-off valve remained open, delivering fuel to the engine-driven fuel pump, whose casing melted, intensifying the fire. The flames then breached the main fuel tank, engulfing the aircraft. Compliance with Airworthiness Directive 2002-12-07 was not carried out on the accident engine. Transport Canada issued a Service Difficulty Alert (AL-2005-08) to ensure removal of all affected gaskets from service.