What happened
On 17 July 2014, an Airbus A340-300E, registration ZS-SXA, was operating a scheduled commercial flight from O.R. Tambo International Airport to Hong Kong International Airport. While cruising at 37,000 feet through Malaysian airspace over the Andaman Sea, the aircraft encountered sudden and severe clear air turbulence. The event, which lasted approximately six to eight seconds, included significant negative G-forces.
At the time of the encounter, the 'Fasten Seat Belt' sign was not illuminated. Because several passengers and cabin crew members were not seated or restrained, the turbulence caused them to be thrown violently. Some occupants struck overhead panels with their heads, leading to damage to the cabin's interior stowage. The force of the movement also caused oxygen masks near door 3R to drop from their panels. The aircraft eventually landed safely at Hong Kong International Airport, where medical services were waiting to treat the injured.
The investigation
An investigation by the SACAA AIID examined flight data recorder (FDR) and cockpit voice recorder (CVR) information to reconstruct the event. The analysis of the FDR confirmed that the aircraft experienced vertical accelerations reaching peaks of +1.6g and -0.5g. While the flight crew reported an overspeed warning, investigators determined this was likely an altitude deviation alert rather than a speed violation, as the flight data showed no master warnings or overspeed conditions.
Meteorological analysis of satellite imagery and Malaysian weather reports indicated that the sky was clear, with no significant convective activity or cumulonimbus clouds present in the area. This confirmed the occurrence was indeed clear air turbulence (CAT), which is notoriously difficult to detect via radar. The investigation also reviewed the aircraft's maintenance records, finding the Airbus A340-300E was airworthy and maintained according to all regulations.
Findings
- The primary cause of the injuries was the sudden encounter with severe clear air turbulence and negative G-forces while passengers and crew were unrestrained.
- 21 people were injured in total, including 3 cabin crew and 18 passengers (comprising 7 South Africans and 14 Chinese nationals).
- The 'Fasten Seat Belt' sign was switched off during the cruise phase, and the turbulence was not preceded by any detectable weather radar warnings or pilot reports.
- Some cabin crew members were actively moving through the cabin to secure galleys and toilets when the impact occurred.
- The aircraft sustained no structural damage, though overhead panels were damaged by the impact of passengers' heads.