What happened
On July 11, 2003, a serious air traffic disturbance occurred within the Dresden control zone involving a Bombardier CL-600-2B19 and a HOAC-Austria Flugzeugwerke DV 20 Katana. The CL-600 had departed from runway 22 and was climbing toward Berlin radar coverage. Simultaneously, the Katana was conducting a VFR flight through the control zone, traveling from point WHISKEY toward point SIERRA.
As the CL-600 climbed, the crew received a TCAS traffic warning indicating another aircraft in close proximity. They observed the Katana performing a turn with an extreme bank angle at a short distance. The crew of the CL-600 executed a left avoidance maneuver to increase separation. Radar data confirmed that the minimum separation between the two aircraft reached only 0.3 NM horizontally and 400 ft vertically.
The investigation
The BFU investigation examined radar data, radio communications, and the actions of the air traffic controller (ATC). The investigation established that the controller was managing several aircraft, including a Dimona motor glider, at the time of the event. The controller had instructed the Katana to set a transponder code but provided no specific instructions or restrictions regarding its flight path.
While the controller was occupied with providing landing clearances to an arriving aircraft and managing the departure of the CL-600, the Katana approached the departure centerline. The investigation found that the controller's instruction for the Katana to perform a full right turn was issued too late to prevent the close approach, as the controller had underestimated the Katana's ground speed.
Findings
- The primary cause of the near-collision was inadequate control and monitoring of aircraft trajectories.
- The air traffic controller failed to utilize available radar equipment to the necessary extent to maintain situational awareness.
- The controller did not issue flight path restrictions to the Katana when its initial route was reported.
- The controller failed to provide traffic information to the departing CL-600 crew regarding the crossing VFR traffic.
- The controller was distracted by other tasks, including managing an arriving aircraft's landing clearance.
- The pilot of the Katana, while operating under VFR, assumed that the lack of specific instructions meant the flight path was permitted, failing to recognize the personal responsibility for collision avoidance in controlled airspace.