What happened
On the morning of 11 October 2013, a Boeing 737-400, registration TC-TLE, was taxiing at Zurich Airport following a routine landing. Under nighttime conditions and on wet pavement, the flight crew received taxi instructions from the apron ground movement manager to proceed via taxiways Foxtrot and Charlie.
As the aircraft progressed along taxiway Foxtrot, the pilot observed a mound of earth from a nearby construction site. Seeking to avoid this obstacle, the pilot executed a 55-degree turn to the right. This maneuver caused the aircraft to leave the paved surface and enter a grass area situated between de-icing lanes F2 and F3. The aircraft subsequently became immobilized on the soft ground, unable to move under its own power. Passengers were evacuated via the front right door using stairs, and no injuries were reported.
The investigation
An investigation by the Swiss Transportation Safety Investigation Board (STSB) examined the taxi instructions, the airport infrastructure, and the environmental conditions at the time of the incident. The inquiry focused on the clarity of the ground movement instructions and the visibility of the taxiway markings and boundaries during the night.