What happened
On 14 November 2006, a serious traffic conflict occurred within the Rotterdam Terminal Control Area (TMA) involving two aircraft. A Cessna 560 XL Citation, registration N666MX, was departing Rotterdam Airport on a charter flight to Cannes. Simultaneously, a Boeing 737-700, registration PH-XRV, was on a scheduled passenger flight approaching the same area.
Following takeoff from runway 24, the N666MX was cleared for a "Woody1B" departure. However, the air traffic controller at the Schiphol-based approach center operated under the mistaken assumption that the aircraft was following a "Refso1B" departure, which would have directed it westward. Meanwhile, the PH-XRX was descending from the west. Because the controller believed the aircraft were on opposite courses, they instructed the N666MX to climb to FL50 and the PH-XRV to descend to 3000 feet.
As the N666MX executed its actual left turn for the "Woody1B" procedure, it intersected the flight path of the PH-XRV, which had leveled off at approximately 5100 feet instead of the requested 3000 feet. The separation between the two aircraft rapidly diminished to a horizontal distance of 0.4 nm and a vertical distance of 900 feet. The conflict was resolved when both crews received TCAS2 resolution advisories—instructing the N666MX to descend and the PH-XRV to climb—and the controller subsequently directed the N666MX to a new heading.
The investigation
An investigation by the OVV examined the operational environment and the actions of the air traffic control (ATC) personnel. It was established that the approach controller was working from a remote facility at Schiphol Oost rather than at Rotterdam Airport. This relocation had introduced several challenges, including differences in radar monitor layouts and the use of electronic data displays that differed from the controller's accustomed paper-strip system.
The investigation also looked into the controller's performance, noting that several critical clues regarding the N666MX departure were missed. These included an intercom notification from the tower, a direct radio call from the N666MX crew, and information displayed on the electronic flight labels. The controller's physical state was also scrutinized, as he had reported only five hours of sleep the previous night.
Findings
- The primary cause of the incident was the approach controller's misconception regarding the standard instrument departure procedure being flown by the N666MX.
- The PH-XRV crew did not follow the instruction to descend to 3000 feet, likely due to the need to reduce speed for the Rotterdam TMA, which contributed to the loss of vertical separation.
- The controller's mental and physical condition may have been suboptimal due to fatigue resulting from sleep restriction.
- The working environment at the Schiphol-based approach center was identified as suboptimal for Rotterdam-based controllers due to unfamiliar monitor layouts and a lack of integration with the local Rotterdam systems.