What happened
On 22 October 2020, two gliders were flying near the circuit starting point at Venlo glider airfield, intending to join the left-hand circuit for runway 29. The first aircraft, a PZL-Bielsko SZD-51-1 “Junior”, was cruising at an altitude of 220 meters when the pilot spotted an Alexander Schleicher ASK 21 approaching from the right at a nearly identical altitude. To prevent a collision, the pilot of the PZL-Bielsko SZD-51-1 “Junior” performed a 360-degree left turn.
As the Alexander Schleicher ASK 21 turned right toward the downwind leg, the pilot of the PZL-Bielsko SZD-51-1 “Junior” followed the aircraft and attempted to communicate via radio, notifying the crew of the Alexander Schleicher ASK 21 that he was flying behind and below them and requesting they take the outside bend. Due to a malfunction, the crew of the Alexander Schleicher ASK 21 did not receive this transmission. Consequently, the pilot of the PZL-Bielsko SZD-51-1 “Junior” flew in front of the Alexander Schleicher ASK 21 during the base leg. Both aircraft eventually completed safe landings.
The investigation
The investigation established that the pilot of the PZL-Bielskio SZD-51-1 “Junior” only observed the other aircraft at the last moment because it was approaching head-on, and its visible profile was minimal. The crew of the Alexander Schleicher ASK 21 reported they did not see the PZL-Bielsko SZD-51-1 “Junior” near the circuit start.
Technical inspections revealed that the FLARM system in the Alexander Schleicher ASK 21 was defective, which prevented a collision warning from being issued. Additionally, the radio transmitter in the PZL-Bielsko SZD-51-1 “Junior” was not functioning correctly, which prevented the pilot from successfully alerting the other aircraft. Both sets of equipment defects were known prior to the flight.