What happened
On 21 October 2020, an Embraer ERJ170, registered F-HBXK, was on final approach to runway 26L at Paris-Charles de Gaulle under conditions of strong crosswinds and moderate to severe turbulence. At an altitude of 200 ft, the aircraft encountered windshear, triggering a warning. In accordance with the windshear procedure, the crew initiated a go-around, maintaining wings level to manage the atmospheric instability.
Simultaneously, an Airbus A320, registered OO-SNE, was cleared for takeoff from the parallel runway 26R. As the ERJ170 climbed, the combination of the windshear recovery procedure and heavy crosswinds caused the aircraft to deviate significantly to the right, drifting toward the path of the departing A320.
As the two aircraft approached each other, the Traffic Collision Avoidance System (TCAS) issued a Traffic Advisory (TA) to both crews. Shortly thereafter, the ERJ170 received a Resolution Advisory (RA) to climb, while the A320 received an RA to level off. The aircraft reached a minimum lateral separation of only 0.09 NM and a vertical separation of 460 ft. There were no fatalities or injuries and no damage to either aircraft.
The investigation
The BEA examined flight data from both aircraft, cockpit voice recordings, and air traffic controller statements. The investigation focused on the effectiveness of the simultaneous operations procedures at Paris-CDG, where the distance between runway centrelines is only 384 m. Investigators analyzed the interaction between the windshear recovery maneuvers and the air traffic controller's attempts to resolve the conflict. The investigation also reviewed the regulatory studies used to justify simultaneous operations on these parallel runways under high-wind conditions.
Findings
- The primary cause of the proximity was the flight path deviation of the ERJ170 caused by the necessity of complying with windshear procedures during strong crosswinds.
- The ERJ170 crew's adherence to the windshear procedure, which required maintaining wings level until 1,500 ft, restricted their ability to respond to lateral heading instructions from the controller.
- The air traffic controller's attempt to resolve the conflict was hindered by the rapid sequence of events and a delay in coordination with the adjacent Le Bourget sector.
- The investigation noted that the regulatory studies for simultaneous operations at this airport did not sufficiently account for the specific risks of a windshear-induced go-around combined with high crosswinds.
- Non-standard phraseology used by the crew during the TCAS event may have caused confusion regarding whether the resolution advisory was still active.