What happened
On October 2, 2020, a serious air traffic disturbance occurred in Class G airspace near the Worms airfield. An Aquila AT01, operating on a training flight with a flight instructor and a student pilot, was on approach to runway 06. At approximately 17:08 local time, the aircraft crossed paths with an Airbus EC 135 P2 helicopter, which was performing an emergency medical transport flight from Ludwigshafen.
Radar data indicates the AT01 was flying at approximately 1,000 ft AMSL with a ground speed of 80 knots. The EC 135 P2 was cruising at approximately 900 ft AMSL at 140 knots. The two aircraft crossed paths at an angle of roughly 100 degrees, with the helicopter passing behind the fixed-wing aircraft. The minimum separation reached was approximately 100 meters horizontally and 100 feet vertically. The helicopter pilot initiated a descent to avoid a collision after being alerted by a crew member.
The investigation
The BFU investigation examined radar data from Deutsche Flugsicherung and the Bundeswehr to reconstruct the flight paths. The investigation also analyzed the visual detectability of both aircraft based on their dimensions and the physics of human perception.
Investigators noted that while the AT01 was not required to follow a specific traffic pattern, it was flying below the published circuit height. The investigation also reviewed the equipment on both aircraft, noting that while the EC 135 P2 was equipped with a FLARM collision warning system, this system could not detect the AT01 because the fixed-wing aircraft lacked compatible equipment. Furthermore, neither crew was in contact with the Flight Information Service (FIS) at the time of the encounter.
Findings
- Failure of the "See and Avoid" principle: Both crews identified the impending collision too late to take effective evasive action.
- Lack of situational awareness: The pilot of the AT01 was responsible for yielding to the helicopter as it approached from the right, but the danger was not recognized until the distance was minimal.
- Absence of Flight Information Service (FIS) contact: Neither crew was communicating with the FIS, meaning no radar-based traffic information or collision warnings could have been provided.
- Incompatibility of collision warning systems: The AT01 was not equipped with a collision warning system, and its lack of FLARM-compatible technology prevented the helicopter's warning system from alerting the crew.