What happened
On December 8, 2016, a Saab 340A was operating a scheduled flight from Katowice-Pyrzowice, Poland, to Bucharest, Romania. The flight was proceeding at FL 190 via a predefined route including several waypoints such as LENOV, KARIL, and REBLA.
After departing Slovak airspace, the crew was transferred from Bratislava ACC to Budapest Radar on frequency 120.375 MHz. Upon passing waypoint REBLA at 14:07 UTC, the First Officer noticed that while other aircraft communications were audible, there were no responses from air traffic controllers. Despite multiple attempts to establish contact on the assigned frequency, the crew remained unable to reach Budapest Radar.
Communication was eventually re-established through the assistance of another aircraft, BELAVIA 812, which provided an alternative frequency (124.1 MHz). This allowed the crew to contact Bucharest ACC. Following the loss of communication, Bucharest Radar initiated standard procedures, which included dispatching a military aircraft to escort the Saab 340A until it could begin its descent into Bucharest.
The investigation
The investigation, conducted by the operator, examined the radio communication sequence, the handover procedures between Budapest and Bucharest sectors, and the crew's monitoring of the flight progress and emergency frequencies.
Findings
- The primary cause was the failure of Budapest Radar to transfer the aircraft to the correct sector frequency (124.100 MHz) at the appropriate time.
- The flight crew did not adequately monitor their progress along the planned route.
- The crew failed to properly monitor the emergency frequency 121.500 MHz on the secondary radio set.