What happened
On June 1, 2015, at approximately 16:27 local time, a Cessna 172 R operating an IFR training flight from Cologne-Bonn to Mönchengladbach experienced a serious loss of separation with an unidentified glider near Bergheim. The Cessna was being operated by a flight instructor and a student pilot.
During the flight, the pilot had received instructions from Langen Radar to descend from 4,000 ft to 3,000 ft AMSL. While the aircraft was in a descent and the crew was in the process of switching radio frequencies, the student pilot noticed movement through the cloud layer and haze. The student identified a glider approaching from the left, appearing to be on a collision course with the descending Cessna. The student immediately alerted the instructor.
The instructor, who was focused on flying the aircraft under instrument conditions while the student managed approach preparations, also observed the glider through the haze. The instructor noted red tape on the nose of the glider and subsequently saw similar red tape on the wingtips of the Cessna after initiating an evasive maneuver. To avoid the conflict, the instructor ended the descent, climbed to approximately 3,900 ft AMSL, and initiated a right turn, eventually leveling off at 4,200 ft AMSL once the threat had passed.
The investigation
The BFU investigation examined radar data from both the air traffic control organization and the German military (Bundeswehr). While the air traffic control radar did not show any targets in the flight path of the Cessna at the time of the event, military primary radar documented a target approximately 0.4 nautical miles southeast of the Cessna, moving in a northeasterly direction.
The investigation could not identify the specific model or registration of the glider, nor its departure or arrival points. The glider was flying without an active transponder, which meant it was not visible on the air traffic control radar system. The investigation also noted that the weather conditions involved a cloud ceiling and haze, which limited visibility.
Findings
- The Cessna 172 R was operating under IFR, while the glider was flying under VFR conditions.
- The glider was not transmitting a transponder signal, rendering it invisible to the air traffic control radar and collision warning systems.
- The proximity of the two aircraft was estimated by the pilot to be between 40 and 60 meters.
- The presence of haze and a cloud layer contributed to the difficulty in detecting the glider before the near-collision occurred.