What happened
On the night of February 9, 2016, during a period of severe weather characterized by a cold front and heavy gusts, a sequence of seven interconnected baggage trolleys moved uncontrolled across the apron at Zurich Airport. The movement was driven by intense westerly winds, which were recorded at 38 knots.
The trolleys traveled across taxiways Alfa 4 and Juliet, eventually coming to rest on the grass verge on the north side of Runway 28. The incident occurred in the dark and under poor visibility due to rain. The timing of the incursion was critical; a Finnair Airbus A320 had landed on the runway approximately two minutes prior, and a Swiss Avro RJ100 landed roughly one minute after the trolleys had crossed the active surface. The pilots of both aircraft did not observe the equipment on the runway and exited via taxiway Echo.
The investigation
An investigation by the SUST established that ground personnel had previously attempted to secure baggage equipment against the storm. A line of seven trolleys had been positioned across a stand at position India 93 to act as a barrier to prevent other equipment from rolling away. While the lead trolley was secured with a brake and wheel chocks, the remaining connected units were not sufficiently anchored.
Investigators also examined the technical warning systems in place at the airport. They found that while stopbars and ground radar were operational, the existing technical alarm systems failed to function as a safety net in this specific instance. Furthermore, the investigation looked into the maintenance and management of the baggage trolley pool, noting a lack of clear oversight regarding the technical condition of the equipment.
Findings
- The primary cause of the serious incident was that a string of seven baggage trolleys was pushed onto Runway 28 by strong, gusty westerly winds, creating a significant hazard to landing aircraft.
- The trolleys were inadequately secured against movement due to a lack of both physical means and established procedures for such weather conditions.
- The technical warning systems designed to alert Air Traffic Control of unauthorized runway incursions failed to trigger because their design was unable to detect the movement of such small objects.
- Systemic risks were identified regarding the maintenance of the trolley pool, including insufficient regulation of responsibilities and a reactive maintenance concept that lacked a comprehensive overview of the equipment's technical state.