What happened
On July 18, 2018, at approximately 17:15 local time, an Embraer ERJ 190-100 LR operating an instrument flight rules (IFR) service from Frankfurt to Paderborn/Lippstadt experienced a serious flight disturbance near Meschede. The aircraft, carrying 20 passengers and a four-person crew, was cleared by air traffic control to descend to flight level 6000.
During the descent, the flying pilot (copilot) observed an Schleicher ASK 21 glider performing thermalling maneuvers directly in the flight path. The crew estimated that maintaining their original course would have resulted in a collision. To avoid the glider, the pilot deactivated the autopilot, applied full power to both engines, and initiated a climb. Flight recorder data confirmed that the engines increased from 33 to 93.9 percent N1 during the maneuver. At the closest point of approach, the aircraft was approximately 50 meters horizontally and 20 meters vertically from the glider.
The Schleicher ASK 21, operating under visual flight rules (VFR) from Brilon, was also involved in the encounter. The glider pilot, who was thermalling with two other unidentified gliders, spotted the airliner crossing from left to right. The pilot continued a left-hand turn to increase the separation distance.
The investigation
The BFU investigation examined radar data, flight recorder information, and interviews with the flight crew, the glider pilot, and the air traffic controller. The investigation confirmed that the airliner's flight recorder documented the sudden power increase and pitch-up maneuver.
Radar analysis showed that the air traffic controller at Langen Radar did not see the glider on their display. This was because the Schleicher ASK 21 was not equipped with a transponder, and at the time of the incident, a transponder was not mandatory for that aircraft type. Consequently, the glider was invisible to the controller's radar equipment.
Findings
- The primary cause of the near collision was the lack of transponder visibility for the glider, which prevented air traffic control from providing separation services or warnings.
- The airliner's crew performed an immediate and effective visual avoidance maneuver.
- The glider was not detectable on radar because it was not equipped with a transponder, a configuration that was permitted under the regulations at the time.
- There were no injuries and no damage to either aircraft.