What happened
On September 30, 2020, at 17:26 UTC, a serious air traffic incident occurred within the Fortaleza Terminal Area (TMA-FZ). The incident involved a Brazilian Air Force A-29 (registration FAB 5724) on final approach and a Piper PA-31T (registration PR-HRM) operating a passenger flight.
The aircraft PR-HRM was flying from Sobral to Fortaleza. During the flight, the pilot requested and received authorization to change flight rules from IFR to VFR. While descending, the air traffic controller (ATC) at Fortaleza Approach (APP-FZ) instructed the pilot to descend for the traffic pattern, simultaneously alerting the crew to the presence of "essential traffic" (the A-2NM FAB 5724) located 4 nautical miles away.
Despite the warning, the horizontal distance between the two aircraft rapidly decreased. At the moment of closest approach, the aircraft were separated by only 400 feet vertically and 0.1 nautical miles horizontally. Neither crew established visual contact with the other. The conflict was only resolved when the Tower controller (TWR-FZ) intervened, instructing the A-29 to perform an immediate right turn, while the APP-FZ instructed PR-HRM to turn left toward the coastline. Both aircraft landed safely without damage, and all occupants were uninjured.
The investigation
CENIPA's investigation focused on the sequence of communications and the operational environment at the time of the incident. The investigation confirmed that the PR-HRM pilot was fully qualified and that the aircraft was operating within its weight and balance limits. The A-29 was also found to be in good maintenance standing.
Investigators examined the ATC environment, noting that due to reduced traffic density during the COVID-19 pandemic, the Assistant Controller (ASST APP) position had been grouped with the Controller (APP) position. Communication transcripts revealed that while the controller had provided traffic information, the subsequent interaction with three other aircraft on the frequency may have divided the controller's attention. The investigation also looked into the application of flight rule changes and the use of specific air traffic procedures (AIC-N 16/20) regarding traffic sequencing.
Findings
- Lack of effective planning by the APP-FZ controller, specifically the failure to adopt measures to ensure separation after authorizing the change to VFR rules.
- Complacent attitude regarding the maintenance of required separation standards.
- Delayed perception and a breakdown in the controller's mental representation of the airspace, characterized by a failure to anticipate the conflict.
- Divided attention caused by simultaneous communications from multiple aircraft on the VHF channel.
- Inadequate decision-making regarding the authorization of the flight rule change, which allowed the PR-HRM to descend into the path of the approaching A-29.