Flight History
The incident involved two aircraft, Z3DCL and HALYS, operating in the airspace of the Republic of North Macedonia. According to the investigation, Z3DCL was conducting a flight with its transponder switched off. The flight was approved without an instruction for a transponder code. A handover of air traffic control duties took place prior to the critical event.
Trajectories
During the critical period, the trajectories of Z3DCL and HALYS converged. The closest point of approach involved a small horizontal and vertical separation. The aircraft were on conflicting paths, with Z3DCL flying a route related to rabies vaccination of foxes and HALYS following a standard instrument departure procedure.
Findings
The investigation committee (KINSIV) documented several findings:
- Z3DCL operated with a switched-off transponder.
- ATC approved the flight without assigning a transponder code.
- There was a handover of duties among controllers.
- Flight charts for fox rabies vaccination were distributed.
- Errors and omissions were found in the Aeronautical Information Publication (AIP).
- Discrepancies existed between the AIP and the Air Traffic Services Manual.
Direct and Indirect Causes
The investigation identified a direct cause for the event, as well as indirect causes related to procedural errors and documentation inconsistencies. Safety recommendations were issued to address these issues.