What happened
On September 27, 2005, a Piper PA-28-161 and a Cessna 680 experienced a serious mid-air conflict within the Mönchengladbach control zone. The Piper, operating under Visual Flight Rules (VFR) toward Fritzlar, departed Mönchengladbach at 11:10 local time. The pilot was navigating via terrestrial landmarks, intending to use the A46 motorway junction for orientation. During the flight, the pilot initiated a left turn, eventually establishing a heading of approximately 055°.
Simultually, the Cessna 680 departed Mönchengladbach at 11:15 local time on an Instrument Flight Rules (IFR) flight to Berlin. Following the standard instrument departure (SID), the aircraft was under the direction of Düsseldorf RADAR. At 11:16, the aircraft was instructed to maintain 2,000 ft and its current heading.
At 11:16, the two aircraft converged at the same altitude with a horizontal separation of less than 0.1 NM. The pilot of the Cessna 680 reported a TCAS resolution advisory and executed evasive maneuvers. The pilot of the Piper PA-28-161 also visually identified the Cessna 680 and immediately initiated a descent to avoid the conflict. Both aircraft continued their flights and landed safely at their respective destinations with no injuries and no damage to either aircraft.
The investigation
The BFU investigation examined radar plots, radio communications, and pilot statements. The investigation established that the takeoff clearances for both aircraft were issued almost simultaneously, leaving a very narrow window for air traffic controllers to intervene.
The controller responsible for the control zone attempted to issue a traffic advisory to the Piper PA-24-161 via blind transmission, but the aircraft was no longer in contact with that specific frequency. Similarly, the Düsseldorf INFORMATION service could not provide timely information because the Piper PA-28-161 had only established contact five seconds before the encounter, which was insufficient for a definitive position assessment.
At Düsseldorf RADAR, the controller identified the Cessna 680 twenty seconds before the encounter. While no immediate danger was apparent at that moment, the controller issued a climb instruction and a traffic advisory as soon as the conflict became evident.
Findings
- The primary cause of the encounter was the loss of orientation by the pilot of the Piper PA-28-161, which resulted from the misidentification of terrestrial landmarks (specifically, confusing a motorway junction).
- The presence of altitude-encoding transponders in both aircraft and the TCAS installation in the Cessna 680 were critical factors in preventing a collision.
- The rapid succession of departures and the timing of frequency changes left air traffic controllers with insufficient time to coordinate a separation maneuver manually.