What happened
On 12 May 2019, a Boeing 737-86N, registration G-GDFS, was performing a missed approach at Reus Airport. While executing the outbound leg of an ILS Y approach to runway 25, the aircraft was flying at approximately 3800 ft. Simultaneously, a Diamond DA20-C1, registration EC-KMH, was entering the Reus CTR via point E, flying at 3600 ft.
The flight paths of the two aircraft converged, leading to a near-miss. The crew of the Boeing 73 and-86N reported seeing the other aircraft 200 ft below them. The conflict was resolved only after the Boeing 737-86N received a TCAS RA, which prompted the crew to execute an avoidance maneuver. The minimum separation between the aircraft was recorded at 0.6 NM horizontally and 200 ft vertically. There were no injuries and no damage to either aircraft.
The investigation
The CIAIAC investigation focused on the actions of the air traffic controllers in the Reus tower. At the time, the controller was receiving on-the-job instruction under the supervision of an instructor. The investigation examined the use of radar, the management of the aerobatic air show occurring nearby, and the controllers' situational awareness.
Investigators found that the radar system was configured to monitor only the Reus ATZ airspace, meaning the approach control service was being provided procedurally. The investigation also reviewed the instructions given to the Diamond DA20-C1, which had been cleared to maintain 3500 ft or higher to avoid the aerobatic display, a clearance that placed it directly in the path of the arriving Boeing 737.
Findings
The investigation concluded that the lack of situational awareness contributed to the incident. The controller had cleared the light aircraft to an altitude that conflicted with the arrival path of the airliner. Furthermore, the investigation noted that the use of a flight strip system and the lack of coordination between the aerobatic flight area and the arrival procedures created a hazardous environment. The investigation also highlighted that the controller failed to identify the potential conflict between the two aircraft during the approach phase.