The BAe146 and the SAAB 340B were on converging tracks. The air traffic controller responsible for their separation received an electronically generated Short Term Conflict Alert (STCA) on his display. The STCA was a warning to the controller that the predicted radar paths of the two aircraft may lead to a loss of separation standards. The required separation standard was 5 NM laterally or 1,000 ft vertically. By the time the controller took positive control and instructed the crew of the BAe146 to turn left for avoiding action, lateral separation had reduced to below the required standard. The crew of the SAAB received a Traffic Alert from their aircraft's traffic alert and collision avoidance system (TCAS).
Analysis of the radar data indicated that lateral separation between the two aircraft reduced to 2.4 NM and vertical separation to 500 ft. The controller did not use any separation assurance technique in his traffic management plan. He stated that he was used to working in a much busier air traffic environment: circumstances that would demand closer vigilance. At the time of the conflict, the controller was distracted from his primary task of providing a radar control service during a discussion with a TAAATS Flight Data Corrections (TFDC) officer over a minor administrative issue.
