What happened
On 31 July 2021, a Boeing 737-8AS, registration EI-EPC, was performing a scheduled commercial flight from Fez, Morocco, to Barcelona, Spain. During the descent toward Barcelona Airport, the flight crew observed cumulonimbus clouds on the weather radar and requested a heading change to avoid them. Approximately 25 minutes before landing, the captain notified the cabin crew of potential turbulence and requested they begin securing the cabin.
Shortly after this notification, the aircraft entered an area of undetected turbulence. During the encounter, the aircraft's calibrated airspeed increased rapidly, approaching the maximum operating speed (VMO) of 340 kt. To prevent exceeding this limit, the pilot flying disengaged the autopilot and performed a nose-up maneuver, which resulted in a vertical acceleration of +3.09 g. One second later, the pilot applied a corrective nose-down input, causing vertical acceleration to drop to -0.18 g.
At the time of these maneuvers, the cabin crew were standing in the rear galley and aisle, having just begun their securing procedures. The sudden change in g-load caused the crew members to be thrown against the cabin interior and fall to the floor. Two cabin crew members were incapacitated by the impact. Additionally, one passenger sustained head wounds. The aircraft landed safely in Barcelona, where medical services attended to the injured.
The investigation
way The CIAIAC examined flight data from the Quick Access Recorder (QAR) and flight recorders, as well as meteorological reports and crew statements. The investigation analyzed the aircraft's flight path, the effectiveness of the autopilot, and the coordination between the flight and cabin crews. The investigators also reviewed the manufacturer's recommendations regarding overspeed recovery and turbulence operations.
Findings
- The aircraft entered an area of undetected turbulence while descending through FL180.
- The pilot flying disengaged the autopilot and performed abrupt pitch changes to prevent the aircraft from exceeding the VMO.
- These maneuvers caused a rapid fluctuation in vertical acceleration (a change of 3.2 g within one second).
- The cabin crew were not yet seated or secured when the severe turbulence and subsequent maneuvers occurred.
- The aircraft's speed increased to 334 kt, just below the VMO limit.
- Two cabin crew members and one passenger sustained injuries due to the vertical accelerations.