Incident Overview
On 29 October 2014, at approximately 06:55 UTC, a serious incident occurred in the Warsaw Terminal Control Area (TMA) involving two aircraft: a De Havilland Canada DHC-8 Dash 8 (registration SP-EQK, operating as LOT3957) and an Embraer 190 (registration DAEBS, operating as DLH8FN). The DHC-8 had just departed from Warsaw Chopin Airport (EPWA) and was climbing to a cleared flight level of FL90, while the Embraer 190 was inbound to the same airport at FL100. The incident resulted in the activation of the Airborne Collision Avoidance System (ACAS), which issued a Resolution Advisory (RA) to both aircraft. The closest recorded separation was 5 feet vertically and 1.8 nautical miles horizontally.
Flight History
The DHC-8 departed from runway 15 at EPWA under visual meteorological conditions (VMC). After departure, the pilot monitoring (PM) contacted Warsaw Approach (APP) and was cleared to climb to FL90. The autopilot was set to the selected altitude, and the crew performed the after-takeoff checklist. Between FL70 and FL80, the rate of climb was reduced to 1,000 feet per minute using the vertical speed mode. Just before reaching FL80, standard callouts were made. Shortly thereafter, an ACAS Traffic Advisory (TA) activated. The crew visually acquired the Embraer 190 at approximately the 10-11 o'clock position, slightly above. Seconds later, an RA commanded "MAINTAIN VERTICAL SPEED." The pilot flying (PF) disengaged the autopilot and increased the climb rate as indicated. The approach controller was informed of the RA. Subsequently, the RA changed to "DESCEND, DESCEND NOW," which was executed, and then "CLEAR OF CONFLICT" was announced. The crew returned to FL90 and contacted cabin crew to confirm normal conditions on board.
Findings and Causes
The investigation, conducted by the State Commission on Aircraft Accident Investigation (PKBWL), determined that the probable cause of the serious incident was improper configuration of the autopilot on the DHC-8 (LOT3957). This led to the aircraft exceeding the cleared flight level (a level bust) and infringing on the required separation minima. A contributing circumstance was a temporary loss of situational awareness by the DHC-8 flight crew regarding the ATC clearance, attributed to the occurrence of similar callsigns at a critical moment.
Safety Recommendations
As a result of the investigation, five safety recommendations were issued to the Polish Air Navigation Services Agency (PAŻP) and to LOT Polish Airlines (the operator of the DHC-8). The specific recommendations are detailed in the final report.