What happened
On September 13, 2000, a Skyservice Airlines Airbus A320 (registration C-GTDC) was departing runway 2lar 23 at Toronto/Lester B. Pearson International Airport for a domestic charter to Edmonton. During the takeoff roll, the aircraft reached rotation when a loud bang and a significant shudder were felt by the crew. While the master caution light activated, no specific electronic monitoring messages were initially displayed.
As the aircraft climbed to 1,500 feet, the electronic centralized aircraft monitoring system began reporting multiple faults related to the left engine. The flight crew declared an emergency and initiated an immediate return to Toronto. The aircraft performed an overweight landing on the same runway from which it had departed. During the landing roll, the captain had to maneuver the aircraft to avoid debris on the runway, which was later identified as the detached fan cowlings from the left engine. Following an inspection by emergency responders, the aircraft returned to the gate, and all passengers deplaned without injury.
The investigation
The investigation focused on the maintenance activities performed on the aircraft prior to the flight. During the previous night shift, a maintenance crew had been replacing an oil-scavenge line on the left engine. Due to the complexity of the task and a lack of available parts, the crew completed the line replacement but did not install all required clamps. Crucially, as the shift was ending, the crew closed the engine fan cowlings but intentionally left the latches unsecured.
Subsequent reviews of the maintenance handover process revealed that the verbal and written communications between the night and day shifts were inadequate. The incoming crew chief was not effectively notified that the fan cowlings remained unlatched. Furthermore, while several walkaround inspections were performed by maintenance personnel and the flight crew prior to departure, the unlatched state of the cowlings was not detected. The investigation also noted that the aircraft lacked certain modifications that could have provided a visual cue for an unlatched condition.
Findings
- The left-engine fan cowlings were closed but the latches were intentionally left unlocked.
- Maintenance and standard operating procedures were not followed, leading the crew to believe the engine was secure.
- The verbal handover between maintenance shifts failed to communicate the unlatched status of the cowlings.
- Pre-flight walkaround inspections by both ground and flight crews failed to identify the unsecured latches.
- The placement of the caution placard regarding the cowlings was not easily visible when the cowlings were closed.