What happened
On February 27, 2016, a Cessna 152 was conducting a VFR flight, departing from EPBC with plans for a low-level pass over Warsaw Chopin Airport (EPWA). While operating between VFR points Z and N at approximately 1,400 ft, the pilot established contact with Warsaw Tower. The controller instructed the pilot to proceed to VFR point E, maintaining 1,000 ft.
At approximately 18:47, the aircraft disappeared from the radar display while approaching point N. Although the crew confirmed that the transponder was set to the ON position and that they were maintaining 1,000 ft, the aircraft's track became intermittent. The tower controller issued several instructions to fly parallel to Runway 15 and then proceed toward the city. By 18:54, the aircraft reappeared on radar 3 NM northwest of point E at 1,000 ft, heading back toward EPBC.
The intermittent tracking continued as the aircraft requested a flight path toward VFR point J and a low-level pass over EPMO. While inside the EPMO control zone, the aircraft's track disappeared again while the pilot was below 1,000 ft. After exiting the EPMO control zone, the Flight Information Service (FIS) requested the pilot descend from 1,400 ft to below 100 ft. At approximately 900 ft, the aircraft disappeared from radar for a third time, at which point the crew confirmed they were experiencing transponder failure.