What happened
On March 1, 2018, an incident occurred within the Warsaw TMA (EPWA) involving two aircraft: an E170 (LOT7005) departing Warsaw Chopin Airport and a B737-800 (LOT268) arriving from Amsterdam.
During the departure of LOT7005, the crew was initially cleared to climb to FL80 due to conflicting arrival traffic. As the aircraft climbed, the Air Traffic Controller (ATC) issued instructions to establish radar separation. However, a series of Short Term Conflict Alerts (STCA) were triggered. A prediction alert appeared when the vertical separation between the two aircraft was approximately 2,000 feet, followed by a violation alert (red) when the vertical distance decreased to 60/700 feet.
In an attempt to resolve the conflict, the controller instructed LOT7005 to fly straight to waypoint KUKAM. A second conflict subsequently developed with a third aircraft, an E170 (LOT3936) arriving from Pyrzowice. To maintain separation with this third aircraft, the controller instructed LOT7005 to level off at FL90. The crew reported that it was too late to level off at that altitude, prompting the controller to issue an alternative instruction to level off at FL100.
The investigation
The investigation, conducted by the operator's commission, examined the sequence of radar data, STCA alerts, and radio communications. The investigation focused on the timeline between the issuance of ATC instructions and the actual execution of maneuvers by the flight crews. The investigation also reviewed the impact of simultaneous transmissions on the clarity of instructions and readbacks.
Findings
- The primary cause of the incident was a delay in the execution of ATC instructions by the flight crew.
- The delay was exacerbated by the fact that the pilot monitoring (PM) performed the readback, while the pilot flying (PF) did not hear the transmission, necessitating a repetition of the instruction.
- Communication difficulties were caused by the repeated overlapping of transmissions from two different transmitting stations.
- The controller managed the workload effectively and maintained the safety of other traffic, despite the temporary increase in workload caused by the conflict.
- Atmospheric conditions had no impact on the occurrence.