What happened
On a scheduled night flight from Toronto/Lester B. Pearson International Airport to Windsor Locks, Connecticut, a de Havill and DHC8, registration C-FACF, experienced a structural failure during its takeoff roll. As the aircraft accelerated on Runway 06L, a three-foot section of the left wing leading edge, which included the attached de-ice boot, separated from the airframe.
Following the separation, the flight crew felt vibrations through the flight controls during the initial climb. The pilots elected to abort the departure and return to Toronto. Ground crews subsequently recovered the debris from the runway. The aircraft landed safely on Runway 06L with emergency responders on standby, and no injuries or fatalities were reported.
The investigation
An investigation into the maintenance history of the aircraft revealed that the 14 screws required to secure the leading-edge section to the bottom of the wing were missing. The investigation focused on the maintenance activities performed during a recent task involving the replacement of the leading-edge panel.
Several maintenance personnel were involved in the task, including an experienced technician, an apprentice, and a second technician. The investigation found that the technician responsible for the task had completed the top portion of the panel but had inadvertently failed to reinstall the bottom screws. This error was compounded by a lack of clear communication during shift changes and a failure to properly document the incomplete work.
Findings
- The primary cause of the component separation was the failure to install the screws securing the leading-edge section to the wing.
- Maintenance personnel failed to verify their own work or the work of their colleagues.
- There was a lack of formal procedures to ensure that incomplete or deferred maintenance tasks were accurately recorded and communicated between shifts.
- The presence of unauthorized personnel at the worksite created distractions and led to incorrect assumptions regarding task completion.
- The crew chief signed off on the maintenance task as complete despite knowing the leading-edge installation was unfinished.
- The company's maintenance task structure had removed the requirement for an independent inspector's signature, eliminating a critical layer of oversight.
- Visual inspection was hindered by the fact that the unpainted brass screws were difficult to distinguish from the aluminum structure in the absence of specific focus.