What happened
On the evening of October 27, 2002, a Boeing 737-80 and belonging to SAS landed at Stockholm/Arlanda airport after arriving from Luleå/Kallax. While following instructions to taxi to gate 35 via taxiways ZN and Z, the flight crew encountered a situation that led to a near-collision.
As the aircraft approached the intersection of taxiways ZN and ZP, the crew encountered a painted "roundabout" on the asphalt. Relying on a taxi chart from the SAS Route Manual, the pilots believed the area was a standard grass surface. They proceeded clockwise around this feature, inadvertently entering taxiway ZP. Simultaneously, a tow tractor was moving an MD-87 through the same area. The tractor driver, perceiving the incoming Boeing 737 as being on a high-speed collision course, performed an emergency maneuver by reversing the tractor and the attached aircraft approximately 50–75 meters to avoid impact.
The investigation
The Swedish Accident Investigation Board (SHK) examined the taxiway layout, the charts used by the crew, and the airport's information signage. The investigation focused on why the aircraft deviated from its assigned route despite the crew having a valid clearance. Investigators reviewed the SAS Route Manual and the Swedish Aeronautical Information Publication (AIP) to determine if the physical layout of the airport matched the documentation provided to pilots.
Findings
- The pilots were fully qualified and the aircraft held a valid certificate of airworthiness.
- The primary cause of the incident was that the taxi chart used by the pilots failed to depict the "roundabout" located between taxiways ZN and ZP.
- The physical area, which was not shown on the relevant charts, was mistaken by the crew for a known grass area.
- The design of certain combination information signs at the site was found to be ambiguous and prone to misinterpretation.
- The tractor driver's quick reaction prevented a physical collision between the two aircraft.
Safety action
The SHK recommended that the Swedish Civil Aviation Administration revise regulations regarding the design of taxi charts in the AIP and the implementation of information signs to reduce the risk of operational misinterpretation.