Incident Overview
On 9 July 2021 at 12:01 UTC, a serious incident occurred at Pristina International Airport "Adem Jashari" involving a Boeing 738 and a UH-60 Black Hawk helicopter. The Boeing 738, registration SP-ESE, call sign GSW604, was operated by Enter Air Ltd on behalf of Chair Airlines on a commercial flight from Zurich Airport (LSZH) to Pristina (BKPR). The helicopter, call sign ABLE52, was operated by the U.S. Army under NATO's Kosovo Force (KFOR). During the Boeing's ILS approach to runway 17, the minimum vertical separation between the two aircraft reduced to 600 feet, triggering a Traffic Collision Avoidance System Resolution Advisory (TCAS RA) on the Boeing. The Boeing crew executed a go-around and subsequently landed safely. The helicopter had no TCAS installed.
Flight History
The Boeing 738 departed Zurich and contacted Pristina Approach on 118.775 MHz at 11:47 UTC, requesting landing at flight level 130 and cleared via the XAXAN 17 A arrival. The crew was advised of unidentified traffic at 2,800 feet and instructed to perform an ILS approach to runway 17. At approximately 4,000 feet, a Traffic Advisory (TA) was generated as the helicopter approached the approach axis from the left. At around 3,500 feet, a TCAS RA (Climb) was issued. The crew informed the tower of the go-around due to TCAS RA at 12:00 UTC. The helicopter crew, flying under VFR, had not been advised of the traffic by tower controllers; they heard the go-around call on the radio. After the go-around, the Boeing crew performed a second approach and landed.
Aircraft Information
The Boeing 738 was equipped with TCAS II version 7.1. The UH-60 Black Hawk did not have a TCAS system installed. The Boeing operated under IFR; the helicopter operated under VFR.
Communication and Radar
According to radar recordings and communication transcripts, the Boeing crew maintained visual contact with the helicopter at approximately 2,500–3,000 feet. The helicopter crew, after passing Violet 072, crossed the extended centerline of runway 17. The pilot in the right seat of the helicopter observed the approaching Boeing. The helicopter crew stated they were unaware of the traffic until hearing the go-around call. The tower instructed the Boeing crew to contact approach frequency 118.775.
Conclusion
The Aeronautical Accidents and Incidents Investigation Commission of Kosovo (KHAIA) investigated the incident. The report noted that the minimum permissible distance between the two aircraft was not respected, leading to the activation of the TCAS RA. No injuries or damage were reported.