What happened
On November 13, 2006, a near mid-air collision occurred within the control zone of Düsseldorf Airport involving a Boeing 73 and a Bell 430 helicopter. The Boeing 737 was operating an IFR scheduled flight from Berlin to Düsseldorf. As the aircraft was approximately one nautical mile from the runway on final approach, the Bell 430, which was operating a VFR factory flight from Stuttgart to Herne, approached from the south.
At 09:20 local time, the two aircraft reached a minimum separation of 0.8 NM at an altitude of 600 ft. During the encounter, the air traffic controller alerted the Boeing 737 crew to the helicopter and its flight path. The crew reported seeing the helicopter on their Traffic Collision Avoidance System (TCAS), though visual contact was not established. While the TCAS issued a warning, no resolution advisory (RA) was generated. The crew elected to continue the approach because the TCAS indicated the Bell 430 was briefly 100 ft above them. The Boeing 737 landed safely.
The helicopter's flight path had been altered due to weather. While flying north along the A 3 motorway under special VFR, the pilot encountered low-hanging cloud fragments near the Ratingen-Ost interchange. After deciding to turn back, the pilot initially intended to fly toward the airport but later changed course toward the Rhine as weather conditions improved. Following a query from the controller and personal doubts regarding the northern heading, the pilot executed a right turn to the south, leading to the close proximity with the airliner.