Occurrence
On December 11, 2022, an Airbus A321 (registration HA-LVO) taxied via taxiway L to the threshold of runway 29 for departure from Warsaw Chopin Airport (EPWA). Weather conditions were unfavorable, with a METAR at 11:30 a.m. reporting visibility of 1,800 meters and light snowfall.
At 11:35:48 a.m., the tower controller cleared another aircraft (airplane B) to cross runway 29 from taxiway A4. At 11:36:18, the controller cleared the Airbus crew to occupy the runway 29 threshold and wait. The controller waited for airplane B to clear the runway before issuing further clearance.
At the same time, the airport duty officer (Duty Officer) requested to cross runway 29 from taxiway A4, communicating with the tower controller's assistant (Assistant). The Assistant was aware that airplane B had just been cleared to cross from the same taxiway. On the surface movement radar (SMR) display, the Assistant observed airplane B crossing and also observed the Airbus taxiing toward the threshold, but then lost focus due to increased traffic from adverse weather. The Assistant incorrectly assumed that the controller's clearance for airplane B meant no departures from runway 29 in the near term, and that the Duty Officer could cross behind airplane B. Without asking the controller's permission—as required by regulations—the Assistant authorized the Duty Officer to cross at 11:36:35.
Airplane B crossed and moved to a safe distance. The controller, unaware of the Assistant's authorization, issued takeoff clearance to the Airbus at 11:36:45. At that moment, the Duty Officer was still on taxiway A4 before the runway intersection, and the Airbus was already taxiing on runway 29 to its takeoff position.
The Assistant heard the takeoff clearance and informed the controller that he had already authorized the Duty Vehicle to cross. The Duty Vehicle had entered the intersection, and the Airbus was in takeoff position. The controller did not cancel the takeoff clearance but informed the crew about a vehicle crossing runway 29 at taxiway A4. The Airbus crew began takeoff after the Duty Vehicle left the runway.
Contributing Factors
The investigation identified four contributing factors: 1. Incorrect assumption by the tower controller's assistant that there would be no takeoffs from runway 29 in the short term. 2. Issuance of a takeoff clearance for the Airbus in the absence of knowledge of a previously issued clearance for a vehicle to occupy the runway. 3. Visibility limited to 1,500 meters in light snowfall. 4. Increased traffic on the airfield due to unfavorable weather conditions.
Probable Cause
The probable cause was the issuance of a runway crossing clearance to a vehicle without coordination with the tower controller.