What happened
On July 9, 2021, at approximately 12:01 UTC, a Boeing 738 (registration SP-ESE, operating as GSW604 for Chair Airlines) was conducting an ILS approach to runway 17 at Pristina "Adem Jashari" International Airport. During the approach, the aircraft's TCAS II version 7.1 system issued a Traffic Advisory (TA) followed by a Resolution Advisory (RA) at approximately 3,500 feet. The RA commanded a climb to avoid a conflict with a UH-60 Black Hawk helicopter (callsign ABLE52) operating under VFR.
The helicopter, operated by KFOR, was transiting the airspace from north to south. The crew of the Boeing 738 maintained visual contact with the helicopter and followed the TCAS RA procedures, executing a missed approach. The minimum vertical separation between the two aircraft reached approximately 600 feet.
The investigation
The Aeronautical Accidents and Incidents Investigation Commission (KHAIA) examined the flight data, radar recordings, and air traffic control (ATC) communications. The investigation focused on the separation of the two aircraft and the effectiveness of the ATC services provided during the incident. The commission also reviewed the operational status of the tower's surveillance equipment and the quality of radio communications between the tower and the flight crews.
Findings
- The Boeing 738 was operating under IFR, while the UH-60 Black Hawk was operating under VFR.
- The UH-60 Black Hawk was not equipped with a TCAS system.
- The ATC tower's radar monitoring screen was non-functional at the time of the incident, preventing the controller from accurately tracking the helicopter's position.
- The controller relied on pilot reports for the helicopter's position rather than active radar surveillance.
- The controller failed to provide traffic information to the helicopter crew regarding the approaching commercial aircraft.
- Significant background noise was present during radio communications, which hindered clarity between the crew and the tower.
- The supervisor was located in the radar room rather than the tower room during the event.
Safety action
- The commission recommended that the Air Navigation Services Agency ensure the radar monitoring screen in the tower is fully functional.
- Recommendations were made to improve the quality of radio communications to reduce background noise.
- It was recommended that the supervisor be present in the tower room whenever possible.
- The agency was advised to ensure that traffic information, specifically regarding military aircraft, is consistently provided to all crews.