What happened
Between 2012 and 2013, two separate incidents occurred in the airspace near Eindhoven Airport involving close proximity between departing commercial aircraft and light propeller planes.
In the first incident on March 9, 2012, an Airbus A320, registration HA-LWA, was climbing after departing Eindhoven. Simultaneously, a Cessna 172, registration OO-WVS, was transiting the area at 3,500 feet. Due to a misunderstanding regarding the altitude of the Cessna 172, the air traffic controller instructed the Airbus A320 to limit its climb. The two aircraft eventually converged to a lateral distance of only 0.4 NM and a vertical separation of 1,500 feet.
In the second incident, an Airbus A320, registration HA-LWK, was climbing through 3,000 feet when it encountered a twin-engine propeller aircraft, registration D-IBGC. The controller, observing the D-IBGC on a crossing course, advised the pilot of the D-IBGC to turn to a heading of 360 degrees. This maneuver placed the propeller aircraft directly in the path of the departing airliner. The encounter resulted in a vertical separation of only 300 feet, triggering a TCAS Resolution Advisory for the Airbus A320 to descend.
The investigation
The Dutch Safety Board examined the airspace structure at the time, known as the BVG Eindhoven, which was a special airspace area designed to manage a mix of controlled and uncontrolled traffic. The investigation looked into the communication between Dutch Mil Info and the various aircraft, as well as the accuracy of radar data.
In the first case, investigators found that the controller lacked precise altitude information for the Cessna 172 because the transponder's Mode C data was not clearly transmitted. In the second case, the investigation focused on the controller's decision-making regarding heading instructions and the lack of simultaneous communication between the two aircraft, which were operating on different radio frequencies.
Findings
- In the first incident, the controller incorrectly assumed the Cessna 172 was at 2,500 feet, leading to an instruction that restricted the Airbus A320's climb.
- In the second incident, the primary cause was the controller's advice to the propeller aircraft to turn to heading 360, which directed the aircraft into the flight path of the departing airliner.
- The controller was not fully aware of the maneuverability of the light aircraft and the potential risk of the proposed turn.
- The two aircraft in the second incident were unable to communicate directly because they were on different radio frequencies.