Overview
On arrival of Air Canada Flight 861 from London, England, at St. John's Airport, passengers deplaned via a passenger stand positioned at door L1. After approximately 10 to 12 passengers had exited, a flight attendant carrying an infant in a car seat stepped onto the stand and noticed it descending slowly. As he turned to alert the in-charge flight attendant, the infant's five-year-old brother, following with his mother, stepped out and fell between the aircraft and the stairs to the apron. The child suffered a broken arm and lacerations to the head and was taken to the hospital for treatment.
Details
The passenger stand used was a Trailbec BMH series unit No.15. Its upper stair portion is adjustable by a hydraulic cylinder and held in place by a mechanical pawl and dog locking system. The pawl is engaged by a spring and disengaged by an electric solenoid controlled by a deadman button in the vehicle cab. During this occurrence, the pawl had only partially engaged the dog rail. After several passengers traversed the stairs, the pawl slipped off, allowing the upper stairs to descend away from the aircraft. The proper functioning of the locking mechanism was impeded, whether due to spring weakness, mechanical resistance, or a combination of both.
Investigation Findings
The investigation revealed that the locking mechanism was not functioning properly, which allowed the stairs to descend. Contributing factors included the failure to adhere to the company's maintenance schedule for ground support equipment; the passenger stand was 130 hours overdue for a service check. Additionally, there was no policy requiring the operator to perform a close visual inspection of the locking mechanism. Operators typically gave only a cursory look when leaving the vehicle. Visual inspection was further hindered because the pawl, dog rail, and background were all painted the same dark green color, and a support brace obstructed the operator's view on this particular vehicle.
Safety Actions Taken
Air Canada conducted a comprehensive inspection of all its passenger stands within 48 hours. All pawl mechanisms were painted in contrasting colors to facilitate position checks, and support braces were relocated to improve visibility. All airstairs units were placed on a weekly follow-up schedule to ensure timely checks. The company disseminated details of the occurrence to the Air Transportation Association of Canada, the International Air Transportation Association, and the Air Transportation Association of America. The Transportation Safety Board issued an Occurrence Bulletin to Transport Canada for dissemination. Transport Canada is distributing a Commercial and Business Aviation Advisory Circular to advise other operators of similar equipment.