This Commercial and Business Aviation Advisory Circular (CBAAC) is intended to inform air operators of hazards associated with the use of mobile aircraft passenger stands and to remind all air operators of their responsibilties regarding the safe movement of passengers to and from the aircraft.
On March 31, 1999, a B767 aircraft arrived in St. John’s, Newfoundland, from London, England. The aircraft was marshalled to a gate on the open ramp and a passenger stand was positioned at the main passenger door of the aircraft. Two employees ascended the stairs to open the aircraft door and position the side gates of the passenger stand. After approximately 10 to 12 passengers had exited the aircraft, a flight attendant carrying an infant in a car seat deplaned. When the flight attendant stepped on the passenger stand, he noticed that it was descending slowly away from the aircraft. As he turned to tell the in-charge flight attendant, the infant’s five-year old brother stepped out and fell between the aircraft and the passenger stand to the apron below. The child suffered a broken arm and lacerations to the head in the fall.
The passenger stand (Trailbec BMH series unit No.15) used for the deplaning is designed for use with various aircraft and at different door sill heights. The stair height is adjusted by means of a moveable upper stair portion which is raised and lowered by a hydraulic cylinder. The upper stair portion is held in the raised position by a mechanical pawl and dog locking system.
Following the occurrence, the Transportation Safety Board (TSB) conducted an investigation which, together with subsequent tests, revealed that the pawls would fail to engage or only partially engage. Where the pawl partially engaged the dog, the upper stairs remained in place for a short period, then, as the pawl slipped off the dog, the stair descended. In tests where the pawl failed to engage the dog, the stairs began to descend immediately.
The locking mechanism used to hold the upper stairs in position is a fairly simple mechanical device. The pawl that prevents the stairs from descending is held in place against the dog rail by a spring and released by energizing a solenoid. In this occurrence, the pawl had only partially engaged the dog rail and, after several passengers had travelled over the stairs, it slipped off, allowing the stairs to descend away from the aircraft.
The company had procedures in place whereby periodic service checks and periodic operational/safety checks were to be carried out on all ground support equipment to ensure proper mechanical functioning. However, these procedures were not being followed and the passenger stand was overdue for a service check.
There was no policy in place requiring the passenger stand operator to do a close visual inspection of the locking mechanism to ensure full engagement. Other passenger stand operators reported that they would take only a cursory look at the locking mechanism when leaving the vehicle. Any visual inspection would have been impeded because the pawl, the dog rail and the background were all painted the same dark colour and, on this particular vehicle, a support brace impeded the operator’s view.
Air operators are reminded of the regulatory requirements to ensure the safe movement of passengers to and from the aircraft. In addition, air operators using mobile aircraft passenger stands are urged to ensure that their operational and safety checks are adequate to confirm equipment serviceability and that their training and operational procedures are reviewed to ensure that personnel are correctly trained in the use of the equipment and associated hazards.
Commercial & Business Aviation
Commercial & Business Aviation Advisory Circulars (CBAAC) are intended to provide information and guidance regarding operational matters. A CBAAC may describe an acceptable, but not the only, means of demonstrating compliance with existing regulations. CBAACs in and of themselves do not change, create any additional, authorize changes in, or permit deviations from regulatory requirements.