What happened
On 24 June 2002, a near-collision occurred in the airspace near Geneva during a period of heavy arrival traffic. The incident involved two commercial aircraft: an Embraer ERJ145 (flight CRX609) arriving from Paris-Roissy and a Boeing 737-300 (flight EZS974) arriving from London-Gatwick. Both aircraft were operating on the same standard arrival route toward runway 05.
While the Boeing 73 3-300 was being vectored for its final approach, the Embraer ERJ145 initiated a left turn toward waypoint INDIS. This maneuver caused the aircraft to cross the path of the Boeing 737-300 in the opposite direction. The pilot of the Boeing 737-300 experienced a TCAS proximity alert, which subsequently issued a resolution advisory (RA) commanding a descent. The closest point of approach between the two aircraft was recorded at 1.4 NM and 400ft.
The investigation
The investigation focused on the sequence of maneuvers and the performance of the radar system. Investigators established that the radar controller had failed to issue a specific instruction to the Embraer ERJ145 to maintain its previous heading, which would have prevented the conflicting turn. Additionally, the investigation examined the radar plots, which revealed several instances of lack of radar detection for the Boeing 737-300. These technical anomalies caused the aircraft's position to appear erroneous on the controller's screen, including a period where the track appeared to move backward.
Findings
- The radar controller experienced a lapse in memory, failing to stabilize the Embraer ERJ145 on its existing heading during a period of high traffic density.
- Radar plotting anomalies occurred, where the trajectory of the Boeing 737-300 was not accurately detected, leading to a loss of situational awareness for the controller.
- The pilot of the Embraer ERJ145 performed a turn that intersected the path of the other aircraft; while following the initial cleared route, the pilot did not alert the controller to his position before initiating the base leg turn.
- The pilot of the Embraer ERJ145 executed an evasive right turn after spotting other traffic, which inadvertently brought the aircraft into the path of the Boeing 737-300.