What happened
On October 6, 2015, a mid-air separation loss occurred within the Szczecin–Goleniów (EPSC) TMA involving a Saab 340 (SF34) and a Dash 8 (DH8D). At approximately 18:08 UTC, the crew of the SF34 received clearance to depart runway 13, following a left turn toward the CHO waypoint and an initial climb to 6,000 ft.
Simultaneously, the DH8D was approaching the CHO NDB from the south, cleared to descend to 7,000 ft. Air traffic control informed the DH8D crew of the opposing traffic and instructed them to maintain visual contact. Both crews successfully established visual contact and were instructed to report passing each other.
During the climb, the SF3HD crew requested permission to deviate from their course to ensure a safe pass. The air traffic controller responded by instructing the crew to maintain 6,000 ft. However, the SF34 crew had already passed the transition altitude. As the aircraft climbed, the altitude alert signaled that 1,000 ft remained until the assigned altitude. Upon reaching the target, the crew disengaged the autopilot to transition to manual flight and level off. Due to aircraft inertia and a delay in response, the SF34 climbed to 6,500 ft. This altitude excursion brought the aircraft within 500 ft of the DH8D, which was descending through 7,000 ft on an opposing course. To avoid a collision, the DH8D crew initiated an independent course change.
The investigation
The PKBWL investigation examined radar data from the PEGASUS 21 system, which confirmed a vertical separation of only 500 ft during the event. The investigation also reviewed flight logs and crew statements. It was noted that the TCAS (Traffic Collision Avoidance System) did not generate any Resolution Advisories (RA) for either aircraft, and the ground-based surveillance system did not trigger a Short Term Conflict Alert (STCA). The investigation also looked into the flight management of the SF34, specifically the transition from autopilot to manual flight and the altitude preselector alert system.
Findings
- The primary cause of the incident was the violation of the air traffic control clearance by the SF34 crew, specifically the failure to arrest the climb at the assigned 6,000 ft altitude.
- The altitude excursion resulted in a loss of required separation minima between the two aircraft.
- The delay in manual flight intervention and aircraft inertia contributed to the aircraft overshooting the assigned altitude by 500 ft.
- No TCAS or ground-based conflict alerts were triggered during the encounter.