What happened
On August 12, 2016, a PZL-110 aircraft, registration SP-ARO, was conducting a cross-country navigation training flight. The crew, consisting of a student pilot training for a PPL(A) license and an instructor, was flying a route through several Polish aerodromes. Upon reaching the EPLB control zone (CTR) at an altitude of 500 meters, the student pilot established radio contact with the EPLB Tower and provided a position report. The tower controller subsequently cleared the aircraft to enter the control zone via points E and S.
During the flight, the instructor determined that the position reported by the student was incorrect. To verify the aircraft's actual location, the instructor unilaterally changed the radio frequency to contact FIS Warszawa. Because the aircraft was equipped with only a single radio set, this action resulted in a total loss of communication with the EPLB Tower. The tower controller noted the loss of contact and initiated procedures to determine the aircraft's position using other nearby aircraft, while also notifying the supervisor of the EPLB aerodrome.
Approximately twelve minutes later, at 12:16 LMT, the crew of SP-ARO re-established contact with the EPLB Tower, reported the visibility at the aerodrome, and received clearance to perform a low pass before continuing to the next leg of their flight.
The investigation
The investigation focused on the period during which the aircraft was out of contact with the tower and the reasons for the unauthorized frequency change. The inquiry examined the radio communications logs and the actions taken by both the flight crew and the air traffic controllers involved.