What happened
On the afternoon of July 27, 2024, Faro Airport (LPFR) experienced a period of high workload following a Mayday declaration from an Airbus A319 (G-EZBT). The aircraft had suffered a birdstrike in its number one engine shortly after takeoff from runway 28. To preserve the runway for the emergency aircraft and subsequent inspections for debris, air traffic controllers had to suspend operations and redistribute several aircraft within the airspace.
During this reorganization, the approach controller (APP) coordinated several aircraft into holding patterns. While managing the transition, a discrepancy occurred regarding the assigned flight level for TAP1905. Although the aircraft label on the situation display was updated to FL100, the controller failed to instruct the crew to stop their descent at FL100, despite the aircraft having been previously cleared to FL070.
At approximately 16:17 UTC, the Short Term Conflict Alert (STCA) activated twice. The second activation occurred as TAP1905 was maneuvering through FL110. At 16:17:10, the two aircraft, TAP1905 and TRA505E, lost vertical separation, with the distance between them dropping to 600ft, well below the required 1000ft separation standard. The conflict was resolved after the controller instructed TAP1905 to climb to FL100 and provided diverging headings to separate the two aircraft.
The investigation
The GPIAAF investigation examined the performance of the air traffic controllers and the management of the situation by the supervisor. The investigation noted that the approach controller was struggling with routine tasks, such as updating aircraft labels, which led to a buildup of tasks and delayed decision-making. Furthermore, the transfer of traffic from the tower to the approach controller to clear the frequency increased the controller's workload.
The investigation also scrutinized the role of the supervisor. It was found that instead of calling on controllers rostered for the afternoon shift, the supervisor called a backup controller who had finished their duty at 16:00. This backup controller positioned themselves between the tower and approach positions without a standard view of the situation display and without proper training for that specific placement.
Findings
- The loss of vertical separation was driven by the controller's inability to manage the high workload and the accumulation of tasks during the emergency redistribution.
- An automated alert (DAP/CFL) regarding a flight level discrepancy was visible to the controller but went unnoticed during the period of high workload.
- The use of non-standard phraseology by the approach controller was noted.
- The supervisor's decision to utilize a controller who had recently finished their shift, rather than available rostered staff, contributed to the lack of effective support.
- A technical limitation in the TopSky-ATC system prevented an audible STCA alarm from sounding in the tower.