What happened
On February 24, 2016, at 05:48 UTC, two large commercial aircraft experienced a loss of separation while operating in the Amazonian Flight Information Region (FIR). The first aircraft, a Boeing 777 with registration N752AN, was operating flight AAL929 from Miami to Guarulhos. While cruising at FL370 on airway UL304, the aircraft was instructed by the Amazonian Area Control Center (ACC-AZ) to climb to FL380 following a transfer from the Maiquetia ACC.
Upon reaching FL380, the Boeint 777 encountered the traffic of a Boeing 787, registration N26952, operating flight UAL128 in the opposite direction on the same airway. The pilots of both aircraft performed evasive maneuvers to the right to avoid a head-on collision. The minimum lateral separation between the two aircraft was recorded at 9.6 NM. There were no injuries to the occupants and no damage to either aircraft.
The investigation
CENIPA's investigation focused on the actions of the Amazonian Area Control Center (ACC-AZ). The investigation established that the air traffic controller (ATCO) in the control position was newly qualified, having been certified only a few days prior, and was working his first night shift.
The investigation found that the ATCO experienced significant anxiety and insecurity during the shift. This emotional state, combined with high workload, led the controller to confuse the transponder code of N752AN with that of another aircraft (AZU8707). Furthermore, the controller misidentified the callsign of flight AAL909 as AAL929, which resulted in the instruction to climb to FL380, placing the aircraft on a collision course with the oncoming N26952.
Technical analysis confirmed that all radar and radio communication equipment were functioning correctly. However, the investigation noted that the controller failed to establish radar identification for N752AN as required by regulations. Additionally, the investigation found that the supervisors on duty failed to notice the automated conflict alerts (AR-AR) or the unauthorized climb of the aircraft.
Findings
- Controller error: The ATCO failed to follow standard procedures, specifically regarding the identification of aircraft and the monitoring of flight trajectories.
- Human factors: The ATCO's anxiety and insecurity, alongside the high workload of managing grouped sectors, degraded operational performance.
- Organizational failures: The assignment of a newly qualified controller on his first night shift, assisted by an intern, contributed to the loss of separation.
- Communication breakdown: Inadequate coordination between the assistant and control positions led to the loss of critical transponder data during the aircraft transfer.
- Supervisory oversight: Supervisors failed to monitor the traffic evolution effectively and did not react to system-generated alerts.
- Informal procedures: A culture of using informal paper-based notes for transponder codes instead of standardized digital or integrated methods compromised safety.