History of the Flight
The flight departed Lyon Saint-Exupéry at 12:01 UTC en route to Tel Aviv. The captain had briefed the crew on forecast slight to moderate turbulence. At 13:27:15, air traffic control advised of reported severe turbulence between FL380 and FL400; the aircraft was cruising at FL370. The captain warned the purser, who returned to the rear cabin. Fasten Seatbelt signs were illuminated. The first officer reduced speed from Mach 0.79 to Mach 0.77 at 13:29:06. Approximately one minute later, initial turbulence was felt.
At 13:30:20, moderate turbulence lasted ten seconds. The longitudinal wind component shifted from a 35 kt tailwind to an 11 kt headwind; left crosswind component decreased from 77 kt to 50 kt. Normal load factor varied between 0.52 g and 1.70 g. Indicated airspeed increased rapidly, triggering the overspeed warning. The first officer extended air brakes with auto-thrust engaged.
Turbulence then intensified for six seconds. Normal load factor ranged from -0.70 g to 1.71 g to -0.32 g, with a left roll up to 37° at 38°/s. The captain took control, engaging CWS mode, initiating a descent, and asking the first officer to inform ATC. After initial refusal, ATC cleared descent to FL350.
In the cabin, two cabin crew members who were standing were thrown against the ceiling; passengers without seatbelts struck overhead compartments. Some fastened passengers sustained minor injuries. The purser and another cabin crew member provided assistance. A doctor and student doctor among passengers helped. No diversion was required; the flight continued to Tel Aviv where medical assistance awaited.
Meteorological Information
Meteorological analysis indicated an anticyclone over Europe with a north-easterly jet stream perpendicular to the Dinaric Alps, causing clear air turbulence and mountain waves over the Adriatic. SIGWX charts for 12:00 UTC forecast moderate turbulence and severe local turbulence between FL300 and FL420. A SIGMET published at 11:49 UTC warned of severe turbulence observed in the southern Zagreb FIR between FL190 and FL400; the incident occurred within that area. The eWas PILOT application on the crew's EFB showed moderate turbulence below FL374 and moderate to severe turbulence above FL374, but the crew misidentified the color codes.
Crew Information
The captain held an ATPL with TRI and TRE qualifications, with approximately 15,000 total flight hours (11,200 as captain, 6,800 on type). The first officer held a CPL, with over 3,000 flight hours (about 900 on type).
Flight Preparation
The flight file was automatically compiled. The crew downloaded it at 07:29 and 08:04, obtaining the 09:00 SIGWX but not the updated 12:00 chart. They used eWas PILOT but did not notice severe turbulence due to unfamiliarity with color codes. The first officer re-downloaded the file at 11:22 but did not check for updated SIGWX or the SIGMET issued ten minutes before departure.
Event Management
The operator's safety manual addressed unforeseen severe turbulence. The crew followed procedures to reduce speed, extend air brakes, and descend. Cabin crew coordinated assistance after the event.