What happened
On September 5, 1996, an Air France Boeing 747-400, registration F-GITF, was operating a scheduled flight from Johannesburg to Paris via Cape Town. Due to unfavorable weather forecasts for the direct route through Central Africa, the flight crew had established an alternative route over West Africa.
While cruising at flight level 350, the aircraft entered a region of intense thunderstorm activity near Ouagadougou. The aircraft encountered extreme turbulence, characterized by rapid vertical accelerations, heavy hail, and intense lightning strikes. During the event, the aircraft's load factor fluctuated violently between +2.09 and -1.15 within seconds, and the autopilot disconnected. The turbulence was so severe that it caused structural damage to the rear cabin interior, including the displacement of overhead bins and ceiling panels.
Following the encounter, the crew noted that the control column was partially jammed in the aft position. After the commander manually cleared a cable obstruction, the aircraft continued its flight toward Gao. Due to the medical condition of a critically injured passenger, who had fallen into a coma, the crew declared a MAYDAY and diverted the aircraft to Marseille Provence Airport.
The investigation
The investigation focused on the meteorological conditions, the aircraft's technical state, and the structural impact of the turbulence. Investigators examined the flight data recorder (FDR) and cockpit voice recorder (CVR) to reconstruct the extreme flight maneuvers. The BEA also analyzed the aircraft's onboard weather radar, which was noted to be inoperative at the time of departure under a technical tolerance (MEL).
Furthermore, the investigation scrutinized the cabin's interior configuration, specifically looking at how the overhead bins and ceiling panels were secured, as the turbulence caused significant damage to these components. The investigation also reviewed the meteorological preparation of the flight and the availability of real-time weather updates during the transit through African airspace.