What happened
On September 26, 2015, at approximately 13:38 local time, a mid-air collision occurred near Hagen (OT Sandstedt), Germany, involving two aircraft operating under Visual Flight Rules (VFR). The first aircraft, a Cessna F 172M, was flying from Rotenburg (Wümme) to Juist with the pilot and two passengers on board. The second aircraft, a Piper PA-28-161, was flying from Bremen to Bremerhaven, operated by a single pilot.
Radar data indicates that the aircraft were flying at altitudes of 2,300 ft AMSL and 2,100 ft AMSL, respectively. As the aircraft approached each other, the Piper pilot initiated a right turn to avoid a restricted area. The collision occurred when the aircraft intersected, causing the Cessna F 172M to crash, resulting in three fatalities (the pilot and both passengers). The Piper PA-28-161 was able to perform an emergency landing at Bremerhaven airport, though the aircraft sustained significant damage.
The investigation
The BFU investigation examined radar data, aircraft wreckage, and pilot statements. Physical evidence from the wreckage showed that the vertical stabilizer of the Cessna struck the right wing root of the Piper, and the Cessna's left horizontal stabilizer struck the Piper's right main landing gear. This damage pattern suggested the Piper was flying approximately one meter higher than the Cessna.
The investigation also analyzed the visual detectability of the aircraft. Based on the approach angle and the size of the aircraft, the BFU calculated that the Cessna would have been visible to the Piper pilot for approximately 18 seconds before impact, while the Piper would have been visible to the Cessna pilot for only about 12 seconds. The investigation noted that the pilots were not in contact with Bremen Flight Information Service (FIS) and were not using collision warning systems.
Findings
- The primary cause of the accident was that neither pilot could detect the approaching aircraft in time to take effective evasive action.
- The high closure speed of approximately 180 knots and the acute angle of approach resulted in very small visible silhouettes and a limited window for recognition.
- The use of the "See and Avoid" principle was severely compromised by the high approach speed and the fact that the aircraft were only visible for a very short duration.
- The lack of active monitoring via Flight Information Service (FIS) or the use of collision warning systems (such as ADS-B or FLARM) meant there was no external assistance to alert the pilots to the conflict.