What happened
On February 27, 2012, an Air France Airbus A330-200, registration F-GZCG, was operating a scheduled international passenger flight from Antananarivo, Madagascar, to Paris Charles de Gaulle. While cruising at FL360 over Tanzania, the aircraft encountered a rapidly developing convective cell.
Prior to the event, the crew had received ACARS messages indicating that convective zones would be encountered, but the area was expected to clear after a specific waypoint. As the aircraft progressed, the crew noted clear skies and stars. However, the aircraft suddenly encountered intense lightning and severe turbulence. During the 40-second period of extreme turbulence, the aircraft experienced significant fluctuations in pitch (from -6° to +11°), roll (from -16° to +3 and 31°), and vertical speed, which peaked at approximately 8,500 ft/min. The turbulence was so violent that the autopilot and auto-thrust disengaged, and the crew experienced a temporary loss of control of the flight path. The aircraft's vertical load factor reached up to 2.28 g. During the event, one passenger and one cabin crew member sustained minor injuries.
The investigation
The BEA examined flight data from the FDR and DAR, as well as crew testimonies. The investigation focused on the meteorological evolution of the convective cell and the effectiveness of the onboard radar. Investigators found that the convective cell was developing extremely rapidly; satellite imagery showed the cell was virtually undetectable 15 minutes before the encounter and only became clearly visible on infrared imagery after the aircraft had passed the area.
The investigation also analyzed the aircraft's radar settings. The aircraft was equipped with a manual Rockwell Collins radar, where the tilt setting is shared between both Navigation Displays (ND). At the time of the incident, both NDs were set to a 160 NM scale. The investigation noted that while a 160 NM scale was being used, a 80 NM scale with an optimized tilt might have provided better detection, though the rapid growth of the cell made detection difficult regardless.
Findings
- The primary cause was the non-detection of a convective zone due to the extremely rapid development of a cumulonimbus cell.
- The aircraft's manual radar system and the crew's settings (160 NM scale) were not optimized for detecting such a rapidly evolving cell.
- The flight monitoring center (CCO) was unable to alert the crew in time because the cell's development outpaced the available satellite imagery updates.
- The crew's reliance on ACARS messages, which suggested clear weather ahead, may have reduced the level of active weather surveillance.