What happened
On 14 June 1996, an Air China Boeing 747SP arrived at Stockholm/Arlanda airport for a scheduled flight. Although the ground handling staff had been notified via fax that the arriving aircraft was the shorter SP-version of the Boeing 747, the handler agent programmed the "Safedock" Docking Guidance System (DGS) for a standard B747.
As the aircraft taxied toward docking bridge 17, the information board on the terminal building displayed the incorrect aircraft version. The pilot did not notice this discrepancy. As the aircraft approached the bridge, the nosewheel passed the designated stop mark for the SP-version. Realizing a collision was imminent, the handler agent attempted to flee the bridge. During the impact, the aircraft's left wing struck the bridge's construction, causing substantial damage to the wing's upper surface. The aircraft's engines were subsequently stopped after a brief increase in power following the initial impact. All 108 passengers and 22 crew members were evacuated safely.
The investigation
The Swedish Board of Accident Investigation (SHK) examined the docking bridge, the DGS, and the ground equipment. The investigation confirmed that the docking bridge and the DGS were functioning correctly without mechanical malfunction. However, the investigation revealed that the DGS laser scanner was unable to distinguish between different versions of the same aircraft type, as it only measured the front contour of the aircraft.
Investigators also looked into the actions of ground personnel. While a technician on the ground attempted to stop the aircraft by shouting through an interphone, they were unaware of the function of an emergency stop button located on a nearby service building. Furthermore, the handler agent failed to activate the emergency stop button on the bridge panel when the error was first realized.
Findings
- The primary cause of the accident was the handler agent programming the wrong aircraft version into the docking system.
- The captain failed to notice that the terminal information board was displaying the incorrect aircraft type.
- Ground personnel lacked sufficient knowledge regarding the full range of functions within the docking and security systems, specifically the use of secondary emergency stop buttons.
- The DGS technology at the time lacked the capability to differentiate between various versions of the same aircraft model, preventing the system from triggering an automatic warning.