What happened
On 20 June 2002, a Boeing 747-286B, registration EP-IAH, was prepared for departure at London Heathrow Airport, positioned at Stand M30. Following the completion of boarding, an airbridge operator attempted to retract the equipment from the aircraft's 2L door.
While attempting to move the bridge away from the aircraft, the operator was particularly cautious of the proximity between the airbridge head and the aircraft's wing root. However, due to a lack of familiarity with this specific model of 'Apron-drive' airbridge, the operator applied an excessive steering command. When reverse drive was engaged, the bridgehead began moving laterally along the side of the fuselage.
An initial attempt to rectify the movement caused scratches to the aircraft's paintwork. Despite assistance from a training officer, a subsequent attempt to realign and retract the bridge resulted in the front of the airbridge puncturing the aircraft's pressure hull. The damage was significant enough that the aircraft had to be withdrawn from service.
The investigation
The AAIB investigation focused on the technical characteristics of the airbridge and the operator's ability to monitor the equipment's movement. It was established that the operator was qualified under airport requirements but lacked experience with this specific newer type of airbridge.
Investigators found that unlike older models, this airbridge lacked a drive axle position indicator on the control console. Operators must instead rely on a CCTV monitor to check the orientation of the drive axle. At the time of the incident, bright sunlight shining through the airbridge window made the monitor image extremely difficult to discern. Furthermore, the 'FRONT' and 'BACK' markings on the axle were not easily identifiable from the distance and low-quality video feed provided.
Findings
- The primary cause was the operator's inability to accurately assess the orientation of the drive axle due to the lack of a direct position indicator.
- High levels of sunlight glare through the airbridge window significantly hindered the visibility of the CCTV monitor.
- The operator's lack of familiarity with the specific movement geometry of this newer airbridge type contributed to the excessive steering command.
- The steering limit switches on the airbridge did not prevent the axle from being turned to an angle that allowed the bridgehead to move obliquely into the fuselage during reverse drive.
- The CCTV monitor lacked essential brightness, contrast, and zoom controls necessary for reliable monitoring in all lighting conditions.