Accident Sequence
The aircraft, a Convair 340 (580) registered C-GFHH, was on an instrument flight rules flight from La Grande 3 to La Grande 4, Quebec, with 18 passengers and 4 crew members. The aircraft touched down on the snow-covered runway approximately 800 feet beyond the threshold. Shortly after nose wheel touchdown and propeller reverse pitch selection, the aircraft drifted right. Despite the captain's corrective attempts, the aircraft exited the south side of Runway 09 at about 50 knots. It travelled 350 feet over soft, rocky ground and came to rest approximately 120 feet outside the runway edge, about 2,500 feet from the threshold.
After stopping, the crew attempted to shut down the engines, but the left engine could not be stopped. On the captain's order, the first officer initiated an evacuation through the right wing emergency exits. The left engine eventually shut down after about 15 minutes. Five persons sustained minor injuries. The aircraft sustained substantial damage but did not catch fire.
Probable Cause
The investigation identified the following causes and contributing factors: 1. The steering control valve lever was not reassembled in accordance with specifications: it had two washers instead of one, and the bushing circumference was 0.0005 inch larger than the hole in the lever, creating additional resistance that impeded steering wheel movement. 2. Nylon locknuts were reused during repair, contrary to single-use recommendations; they came loose in service, introducing play in the valve. 3. The crew incorrectly interpreted the problem and were influenced by previous experience with the nose-gear steering wheel, leading them to make the flight despite concerns about the steering system.
Other Findings
- Maintenance personnel at Precision Aero Components Inc. used the incomplete maintenance manual instead of the overhaul manual, contributing to incorrect reassembly.
- The steering control valve lever lacked a grease fitting, and the bushing exterior was not grooved for lubrication, risking corrosion and seizure.
- Limited experience and lack of formal training of maintenance personnel may have contributed to the incorrect reassembly.
- The pilot flying cut electrical power as per hard landing procedure, disabling the left engine shutdown and public address systems, delaying evacuation orders.
- The evacuation slide automatic deployment system was inadvertently deactivated, potentially delaying evacuation.
- After separating from the engine, the left propeller blades entered the fuselage and damaged an unoccupied seat.
- The numerous changes in Convair type certificate ownership and lack of technical support caused maintenance problems for operators and approved maintenance organizations.