What happened
On September 6, 2020, at approximately 15:33 local time, a Scheibe SF 25 C motor glider and a PZL-Bielsko SZD-50-3 “Puchacz” glider were involved in a mid-air collision near the Greiz-Obergrochlitz airfield in Germany. The motor glider was performing a series of glider tow flights to refresh the pilot's towing authorization. After the glider had released from the tow at approximately 450 m AGL, the motor glider proceeded to fly toward runway 23 to release the tow rope via a low pass.
Due to another aircraft landing, the air traffic controller instructed the motor glider pilot to delay the approach. Following the rope release, the motor glider entered a climb toward the west, turning approximately 20 degrees to the right of the runway centerline to comply with noise abatement procedures. Simultaneously, the glider was on a 90-degree right-hand base leg for runway 05. The pilot of the glider observed the motor glider approaching from the rear left at an angle of approximately 45 degrees. Despite attempting an evasive maneuver, the two aircraft collided. Both aircraft landed safely on runway 05 with no injuries to the occupants, though both aircraft sustained minor damage.
The investigation
The BFU investigation reconstructed the flight paths using GPS data from the glider's FLARM collision warning system, which confirmed the flight paths of both aircraft. The investigation examined the roles of the pilots, the air traffic controller, and the environmental conditions. The BFU noted that the motor glider lacked a collision warning system, whereas the glider was equipped with one. The investigation also reviewed the recent changes to airfield operations, specifically the transition to an asphalt runway and the implementation of a new tow-release procedure involving flying against the active runway direction.
Findings
The collision was caused by the fact that the motor glider pilot did not see the glider, and the glider pilot detected the motor glider too late to prevent the impact. Several contributing factors were identified:
- The release of the tow rope in the direction of the opposite runway.
- The motor glider's turn for noise abatement placed it on a collision course with the glider's approach path.
- Inadequate communication between the pilots and the air traffic controller prevented a complete shared understanding of the traffic situation.
- The pilots were significantly blinded by the position of the sun in the southwest.
- The motor glider was not equipped with a collision warning system.
Safety action
Following the accident, the local flying club ceased the practice of releasing tow ropes while flying against the active runway direction, opting instead to release the rope during the approach to the active runway. Additionally, the Scheibe SF 25 C was equipped with a collision warning system.