What happened
On February 18, 2018, a loss of separation occurred between two commercial aircraft operating out of Aeroparque Jorge Newbery in Buenos Aires. The first aircraft, a McDonnell Douglas MD-83 with registration LV-AYD, departed for Mendoza following the EL PALOMAR 8 standard instrument departure (SID), restricted to flight level 050. Approximately four minutes later, a Bombardier CRJ-200, registration CX-LVA, departed the same runway for Montevideo, following the DORVO 7 SID, also restricted to flight level 050.
During the climb, the MD-83 crew received a TCAS-RA (Resolution Advisory) commanding an ascent. The crew executed the maneuver and visually identified the CRJ-200 approximately 150 to 200 meters to their left, at an altitude roughly 300 to 400 feet below them. Simultaneously, the CRJ-200 crew received a TCAS-RA commanding a descent, which they executed, passing approximately 600 feet below the MD-83. Both aircraft continued their flights without further incident after reporting the event to Ezeiza Air Traffic Control.
The investigation
The investigation examined the flight paths of both aircraft and the communication between the crews and the Ezeiza Area Control Center. It was established that while the two SIDs (PALOMAR 8 and DORVO 7) lead to different transition points, their initial trajectories intersect.
The investigation found that the CRJ-200 followed a shorter flight path than the MD-83, despite departing later. This difference in path length, combined with the identical altitude restriction of FL 050, created a high risk of conflict. Furthermore, the MD-83 crew attempted to notify the control center of their position, but their communications were lost due to heavy frequency congestion. Consequently, the MD-83 remained at FL 050 longer than intended, reducing longitudinal separation.
Findings
- The two aircraft departed approximately four minutes apart.
- The intersection of the two SID trajectories created a latent conflict point.
- Both aircraft were subject to the same altitude restriction (FL 050).
- Communication difficulties caused by frequency congestion prevented the MD-83 from receiving updated instructions, prolonging its time at the restricted altitude.
- Air Traffic Control did not issue instructions to prevent the loss of separation, only providing traffic information upon request.
- The separation was successfully maintained through the effective execution of TCAS-RA maneuvers by both crews.
Safety action
- Evaluation of the current SID designs to determine if new departure routes are necessary.
- Implementation of case studies in air traffic controller training, using simulators to replicate similar loss-of-separation events.
- Use of simulator training to help controllers identify system vulnerabilities during TCAS resolution scenarios.