What happened
On 14 November 2013, a Boeing 747-443, registration G-VLIP, was operating a commercial passenger flight from Montego Bay, Jamaica, to London Gatwick. While cruising at FL370 in the North Atlantic airspace, approximately 350 nm south of Newfoundland, the flight crew observed weather radar returns indicating a line of weather across their planned route. To avoid this, the crew requested a track deviation; while a northward deviation was denied, they were permitted to deviate to the right.
As the aircraft flew abeam the weather, the radar returns disappeared, and the flight progressed through smooth air. However, the aircraft then encountered a period of increasing turbulence. The flight crew activated the cabin seat belt signs, and the commander noted a flash of light that appeared to be lightning from a thunderstorm cell beneath the aircraft. The turbulence rapidly intensified into a severe episode. During this period, the aircraft experienced significant vertical speed changes, and the stick shaker briefly activated, though the autopilot and autothube remained engaged.
In the cabin, the turbulence was significant enough to make it difficult for crew members to secure themselves in their harnesses. While most passengers were already seated with belts fastened following a recent meal service, the sudden jolts caused injuries to 9 passengers and 1 crew member. The most notable injury was a laceration to a passenger's knee. Following an assessment and consultation with medical specialists via radio, the flight continued to Gatwick, where medical personnel treated the injured.
The investigation
The investigation, supported by flight data and crew interviews, examined the aircraft's flight path and the meteorological conditions present at the time. Flight Data Recorder (FDR) analysis confirmed that the aircraft encountered light turbulence starting at 0349 hrs, which escalated into a short but severe period at 0400 hrs. The data recorded peak accelerations of -0.7g and +1.7g during the descent phase.
Findings
- The aircraft encountered severe turbulence while flying near the edge of a jetstream core with speeds of approximately 120 kt.
- Meteorological charts indicated that the area was subject to forecast moderate turbulence up to FL420.
- The turbulence occurred as the aircraft was transitioning through an area containing embedded cumulo-nimbus clouds.
- The injuries were concentrated in the rear right side of the aircraft, including one crew member in the crew rest area.