What happened
On 11 November 2018, two commercial aircraft experienced a loss of separation while departing from parallel runways 26R and 27L at Paris-Charles de Gaulle airport. The first aircraft, a Boeing B737-800 (registration UR-PSB) operated by Ukraine International Airlines, was cleared for departure from runway 27L using the RANUX 2A departure procedure. However, during flight preparation, the crew had pre-selected the RANUX 2B procedure, which is intended for runway 26R.
Shortly after the Boeing B7 and the Airbus A320-200 (registration F-HBNJ) operated by Air France took off from their respective parallel runways, the Boeing B737-800 began a left turn to follow the flight director instructions based on its incorrect FMC programming. This maneuver brought the aircraft toward the flight path of the Air France vessel. At approximately 13:54:28, the Short Term Conflict Alert (STCA) was activated on the controllers' radar. Air traffic controllers immediately intervened, ordering the Air France crew to stop their climb and instructing the Ukraine International Airlines crew to turn right, successfully restoring vertical separation.
The investigation
The BEA investigation focused on why the departure procedure was not updated in the flight management computer and why the deviation was not detected by the crew. Investigators examined the flight preparation phase, noting that the crew was interrupted by a ramp agent delivering load sheets at the moment they were meant to verify the departure data. Furthermore, the crew reported feeling time pressure due to a specific departure slot.
The investigation also reviewed the coordination between the various air traffic control positions (North and South LOC, and Departure controllers). While the controllers used the interphone to communicate the conflict, the investigation noted that the use of a general call function could have improved the speed of emergency notification to all controllers.
Findings
- The primary cause of the incident was the failure of the crew to update the departure procedure on the FMC after receiving a clearance that differed from their initial plan.
- The crew did not perform a cross-check of the FMC data against the official charts due to interruptions by ground personnel and time pressure from the assigned takeoff slot.
- The crew followed the flight director's lateral navigation commands without verifying if the programmed path was consistent with the assigned runway and SID.
- The loss of separation occurred in Instrument Meteorological Conditions (IMC), which prevented the crew from maintaining visual separation.
- The TCAS did not activate because the aircraft were still above the required time-to-approach (TAU) thresholds for a Traffic Advisory or Resolution Advisory.