What happened
On May 28, 2021, at 13:32 local time, a conflict occurred in the southeast portion of the Barcelona TMA Area 1 between a KLM Boeing 73 3-800W, registration PH-BXF, and a training Tecnam P2006T, registration EC-MNG.
The Boeing 737-800W had departed from Josep Tarradellas Barcelona-El Prat Airport (LEBL) on runway 25L, climbing via the OKABI3Q standard instrument departure. Simultaneously, the Tecnam P2006T, operated by the European Aviation School of Barcelona, was conducting an instructional flight from Sabadell Airport (LELL) toward Castellón Airport (LECH) at flight level FL090.
As the Boeing 737-800W was climbing through 8,640 feet toward FL190, the aircraft's Traffic Collision Avoidance System (TCAS) issued a Traffic Advisory (TA) followed by a "DESCEND" Resolution Advisory (RA). At the moment of the RA, the vertical separation between the two aircraft had decreased to only 350 ft, with a horizontal separation of 1.52 NM. The crew of the Boeing 737-800W complied with the RA by halting its climb and descending to avoid the conflict. The crew of the Tecnam P2006T remained unaware of the proximity until the short-term conflict alert (STCA) was triggered.
The investigation
The investigation examined the coordination between two air traffic control sectors: LEBLT14W and LEBLT23FW. It was established that the LEBLT14W controller had transferred control of the Tecnam P2006T to the LEBLT23FW sector approximately nine minutes prior to the incident.
Investigators analyzed the performance of both controllers and the technical aspects of the radar displays. The LEBLT14W controller was managing multiple communications and various non-critical alarms at the time. The LEBLT23FW controller was focused on traffic within their own sector and did not anticipate the conflict with the departing aircraft. The investigation also noted that the radar color coding for transferred traffic (blue of interest) was visually similar to other traffic types on the screen, which could contribute to cognitive bias.
Findings
- The primary cause of the incident was a loss of situational awareness by the LEBLT23FW sector air traffic controller.
- The LEBLT14W controller transferred the Tecnam P2006T to the adjacent sector without anticipating a conflict with the departing Boeing 737-800W.
- The LEBLT23FW controller, focused on arrivals in their sector, did not anticipate the conflict with the departing aircraft.
- The Boeing 737-800W was required to perform an emergency descent due to the TCAS RA.
- No injuries were reported, and neither aircraft sustained damage.