What happened
On October 6, 2019, an Enter Air Boeing 737-800 (registration SP-ENV) was descending through Flight Level 150 toward Flight Level 130 while approaching Paris Charles de Gaulle Airport (LFPG). Shortly before reaching FL130, the aircraft's Airborne Collision Avoidance System (ACAS) issued a "TRAFFIC" advisory, alerting the crew to potential separation issues. This was quickly followed by a mandatory Resolution Advisory (RA) instructing the pilot to climb.
The flight crew immediately halted their descent and executed the climb maneuver as directed by the RA. They continued climbing until receiving subsequent ACAS messages indicating "DON'T DESCEND" and finally "CLEAR OF CONFLICT." The crew then reported the ACAS event to air traffic control. Controllers informed the crew that the conflicting aircraft had departed from Paris-Orly Airport (LFPO) and was cleared to climb to FL110. The Enter Air flight maintained a standard descent rate of 1,000 feet per minute prior to the event.
The investigation
The PKBWL reviewed the final report submitted by Enter Air's Safety Department. French authorities provided data confirming that vertical separation between the two aircraft was 1,700 feet and horizontal separation was 2.25 nautical miles at the closest point of approach. Both figures exceeded the required minima, meaning no regulatory separation standards were violated.
Findings
The primary cause of the incident was identified as the climbing aircraft below SP-ENV having an excessive climb rate, which triggered the ACAS RA despite adequate physical separation.
No contributing circumstances were identified. The PKBWL accepted Enter Air's proposal to publish details of the event in their next Flight Safety Bulletin. No additional safety recommendations were issued by the Commission.