ACAS RA Climb During Descent at Paris Charles de Gaulle

Incident Overview On 6 October 2019, an Enter Air Boeing 737-800, registration SP-ENV, was descending to land at Paris Charles de Gaulle (LFPG). While descending from flight level 150 to flight level 130, the aircraft's Airborne Collision Avoidance System (ACAS) issued a “TRAFFIC” alert shortly before the aircraft reached FL130. ## ACAS Response The ACAS then issued a mandatory Resolution Advisory (RA) “CLIMB,” instructing the crew to stop the descent and climb to avoid a potential mid-air collision. The pilot flying complied, arresting the descent and climbing until the system displayed “DON’T DESCENT” and later “CLEAR OF CONFLICT.” The crew then reported the ACAS RA event to air traffic control. ## Separation and Contributing Factors According to information provided by the French side, the separation minima between the two aircraft were 2.25 nautical miles horizontally and 1,700 feet vertically, and these minima were not breached by SP-ENV. The investigating authority identified the cause as the excessive climb rate of the aircraft below SP-ENV. No contributing circumstances were indicated. ## Safety Actions The State Commission for Investigation of Aviation Accidents accepted the operator’s proposed preventive action to publish information about the incident in the next Flight Safety Bulletin. No additional safety recommendations were issued.