What happened
During a scheduled maintenance check in Toronto, the right off-wing slide deployment system on a Boeing 767-233, registration C-GAUH, was inadvertently activated. This event triggered several actuators and caused the secondary lock shear-pin to break. While restoring the system to service, the inflation trigger was left disconnected, and the broken shear-pin was not replaced as required by the job ticket.
On the day of the flight, the aircraft was undergoing de-icing in Toronto when a slide door alert message illuminated. Although maintenance personnel inspected the door and verbally released the aircraft under the Minimum Equipment List (MEL), the required detailed inspection steps were not performed. The aircraft departed for Vancouver with the warning light active.
During the approach to Vancouver International Airport, a loud bang was heard in the cabin. Upon landing, ground crews discovered that the right off-wing slide compartment door had opened in flight, causing the slide to separate from the aircraft. The slide was believed to have fallen into the Georgia Strait. There were no injuries among the 103 people on board.
The investigation
The investigation focused on the maintenance actions taken during the "A" check and the subsequent inspection on the ramp. Investigators found that the technician responsible for the restoration failed to replace the sheared pin because a replacement was not immediately available, and a visual inspection was insufficient to detect the damage. Furthermore, the technician who performed the ramp inspection lacked recent experience with the specific system and was hesitant to manipulate the hardware due to fears of accidental deployment.
Findings
- The secondary lock shear-pin had been broken during the initial maintenance error.
- The maintenance error remained undetected because the mandatory MEL inspection procedures were bypassed.
- The aircraft was released for flight despite the inflation trigger being left disconnected and the warning light remaining active.
- Maintenance personnel involved had inadequate familiarity with the off-wing slide system.
- The flight crew accepted the aircraft based on a verbal release rather than following formal documentation procedures.