What happened
On June 3, 2013, a Cessna 172 was conducting a VFR flight from Bagicz (EPKG) to Leszno (EPLS). Approximately 20 nautical miles from the destination, the pilot experienced a strong signal in the onboard radio headset that completely prevented the reception of communications from the Flight Information Service (FIS) controller.
In response to the loss of communication capability, the pilot transmitted a blind message to inform air traffic services of the radio malfunction, set the transponder code to 7600, and continued the flight to the planned destination. The landing at Leszno was completed without further incident.
The investigation
Following the flight, an experiment was conducted at the aircraft's home base to identify the source of the interference. The crew performed a total shutdown of the aircraft's electrical power supply. This procedure did not stop the interfering signal, which allowed investigators to pinpoint the source as the aircraft's Emergency Locator Transmitter (ELT).
Because the pilot could not be certain if the ELT had been transmitting an emergency signal during the flight, the nearest air traffic control authority was notified via telephone to prevent the unnecessary activation of search and rescue operations.