What happened
On 5 December 2021, an Airbus A350-900, registered F-HNET, operated by Air Caraïbes Atlantique, was performing a scheduled commercial flight from Paris-Orly to Cayenne-Félix Éboué. During the descent, the aircraft encountered two distinct periods of turbulence.
Shortly after 21:00 UTC, while cruising at FL 400, the aircraft entered a zone of turbulence lasting approximately 30 seconds. The flight crew had previously identified the risk and instructed all passengers to remain seated with seatbelts fastened. Following this first encounter, the captain notified the cabin crew that they could resume their duties, including clearing meal trays.
As the aircraft descended through FL 100, the captain communicated with the purser via interphone. Believing the turbulence had passed, the captain authorized the rear cabin crew to leave their seats to prepare the cabin for landing. However, at approximately 21:25 UTC, at an altitude of roughly 7,000 ft, the aircraft encountered a second, brief period of turbulence. The sudden vertical acceleration caused the purser to lose balance and fall, resulting in a double ankle fracture. Two other cabin crew members also sustained injuries to their heads and backs.
The investigation
The BEA examined flight data from the Quick Access Recorder (QAR), radio communications, and radar data. The investigation focused on the meteorological conditions and the effectiveness of the onboard detection systems.
Investigators noted discrepancies between the onboard weather radar and visual observations. While the crew attempted to fly between cloud layers to avoid convective cells, the radar did not display all visible convective activity. Furthermore, the crew utilized the eWAS application on their Electronic Flight Bag (EFB), which showed convective zones in forecast mode but not in observation mode during the critical minutes preceding the event.
Findings
- The second turbulence event was likely generated by a nearby convective cell.
- The crew may have been unable to detect or may have underestimated the extent of the turbulence zone's influence.
- The aircraft was flying at the edge of a rainfall line where convection was at its strongest.
- The weather radar, while advanced, may not detect all convective activity, particularly if the water concentration is low or if the turbulence is occurring in clear air.
- The decision to allow cabin crew to unfasten their seatbelts contributed to the injuries sustained during the second encounter.