What happened
On 17 January 2021, an Emirates Boeing 777-31HER, registration A6-EPN, was operating a scheduled passenger service from Dubai to Beirut. While descending through the Nicosia Flight Information Region (FIR) in Cyprus, the aircraft encountered moderate to severe air turbulence for approximately three minutes. The turbulence occurred at a pressure altitude of roughly 29,200 feet. Because the aircraft's weather radar showed no precipitation, the flight crew initially believed they were experiencing clear air turbulence. The sudden vertical g-forces caused several passengers and cabin crew members to be jolted from their seats, impacting the cabin interior. The event resulted in seven injuries, including one passenger who sustained a serious foot fracture.
The investigation
The UAE Air Accident Investigation Sector (AAIS) conducted the inquiry, examining flight data, cockpit voice recordings, and meteorological reports. Investigators focused on the flight crew's awareness of weather hazards and the effectiveness of the aircraft's automated weather alert systems. The investigation also reviewed the meteorological watch services provided by the Larnaca International Airport Meteorological Watch Office (MWO) and the compatibility of their reporting format with the airline's dispatch software.
Findings
- The primary cause of the injuries was the significant vertical g-forces produced by severe clear air turbulence.
- A critical failure in the communication chain occurred because the airline's weather application failed to generate a timely alert for a specific SIGMET (Significant Meteorological Information) report.
- The Larnaca MWO used non-standard free text (the word 'AND' instead of the standard '/') when describing affected flight levels, which caused the airline's WSI Fusion software to stop analyzing the data at FL260.
- Consequently, the flight crew was unaware of the severe turbulence forecast for their descent altitude until the aircraft had already entered the turbulent area.
- The turbulence was driven by the influence of the jet stream and thunderstorms in the flight path.