What happened
On August 7, 2015, at approximately 16:05 local time, a near mid-air collision occurred at flight level 100 near Heilbronn, Germany. An Airbus A319-112, operating an IFR flight from Berlin-Tegel to Stuttgart with 131 passengers and five crew members, encountered a Ventus-2cM motor glider flying under VFR.
During the descent to flight level 100, the copilot of the Airbus identified the motor glider ahead on a similar course. To prevent a collision, the copilot deactivated the autopilot and initiated a left turn. Flight recorder data confirmed the maneuver, showing a turn from approximately 213° to 200°. The pilot in command of the Airbus noted that the avoidance maneuver was already underway by the time visual contact was established by the commander. The motor glider pilot also observed the large aircraft at a distance of approximately 300 to 500 meters and initiated a right turn, which resulted in the two aircraft moving apart. The minimum separation between the aircraft was reported by the Airbus crew to be approximately 0.5 nautical miles.
The investigation
The BFU investigation examined radar data from both the air traffic control service and the German military, as well as flight recorder data from the Airbus. The investigation also reviewed radio communications between the Airbus crew and Langen Radar. Investigators analyzed the visibility of the aircraft on radar and the functionality of the onboard collision avoidance systems.
Findings
- The motor glider was flying with its engine folded.
- The motor glider was not transmitting a transponder signal, which rendered it invisible to air traffic control radar.
- Because the motor glider lacked active transponder information, the TCAS (Traffic Alert and Collision Avoidance System) on the Airbus failed to detect the aircraft.
- The pilot of the motor glider did not perceive the encounter as a significant danger at the time.