What happened
On May 20, 2019, at Warsaw Chopin Airport (EPWA), a runway incursion occurred on Runway 15 involving two aircraft. A Bombardier DHC8 (SP-EQH) was holding on taxiway D2, while an Embraer ERJ190-200 (SP-LNM) was holding at taxiway A0. At 11:56 UTC, the tower controller issued a conditional clearance to the crew of the DHC8 to enter Runway 15 behind a landing Boeing 787. However, the crew of the Embraer ERJ190-200 mistakenly believed the clearance applied to their aircraft. Due to a double transmission on the frequency, the controller did not realize the error. Both aircraft subsequently entered Runway 15.
As the aircraft were occupying the runway, a Boeing 737-800 (SP-ENN) was on approach for landing. While the DHC8 began its takeoff, the controller issued instructions to the Boeing 737-800 to execute a missed approach procedure. During this maneuver, the Boeing 737-800 and the departing DHC8 experienced a loss of separation. The aircraft came within 2.18 NM of each other, failing to meet the required radar separation of at least 3 NM, with a vertical separation of approximately 900 ft, falling short of the 1000 ft requirement.
The investigation
The PKBWL examined radio frequency recordings and audio from the tower operations room, which revealed an unreadable double transmission. The investigation also reviewed Surface Movement Radar (SMR) data, which showed both aircraft on the runway. The investigators examined the tower's line of sight, noting that a structural pillar in the control tower obstructed the controller's view of the beginning of Runway 15. The investigation also assessed the controller's use of SMR to monitor surface traffic.
Findings
- The primary cause of the runway incursion was the crew's misunderstanding of a clearance issued to another aircraft.
- The tower controller failed to react to the unreadable double transmission between the two aircraft crews.
- High traffic intensity on a single runway contributed to the complexity of the situation.
- Visual monitoring of Runway 15 was ineffective due to the physical obstruction caused by a pillar in the tower.
- The controller did not utilize the Surface Movement Radar (SMR) to monitor compliance with instructions.
- The crew of the Embraer ERJ190-200 may have been influenced by expectation bias, as they were approaching the runway for departure.