What happened
On 26 February 2004, an Iberia LAE Boeing 747-300, registration TF-ATJ, was operating a scheduled flight from Buenos Aires to Madrid. While cruising at flight level 340 over international waters near the equator, the aircraft encountered sudden, moderate-to-strong turbulence. The event lasted approximately three minutes and was characterized by a rapid descent of three to four thousand feet per minute, followed by a sharp climb.
At the time of the encounter, the cabin lights were dimmed and the fasten seat belt signs were not illuminated, as no turbulence had been forecast for that specific area. A passenger who was walking down the aisle toward the rear of the aircraft was violently thrown, resulting in serious injuries, including head contusions and internal injuries that caused hemiplegia. The aircraft diverted to Las Palmas de Gran Canaria, where the passenger was evacuated via helicopter for emergency medical treatment. Eleven other passengers and one flight attendant also experienced minor injuries or anxiety attacks.
The investigation
The CIAIAC investigation examined the flight records, meteorological data, and aircraft performance. Analysis of the Digital Flight Data Recorder (DFDR) confirmed the turbulence encounter and noted a drop in Total Air Temperature (TAT) from –9.5 °C to –14 °C, suggesting a change in the atmospheric environment.
Investigators reviewed weather charts and satellite imagery, noting that while the flight planning information did not forecast turbulence at the exact accident site, there was evidence of convective activity and embedded cumulonimbus clouds in the surrounding tropical regions. The investigation also looked into the use of onboard weather radar and the visibility of convective cells during the night flight.
Findings
- The aircraft was airworthy, and the crew was properly licensed and experienced.
- The turbulence was likely of a convectively-induced nature (CIT) and appeared suddenly without warning.
- The accident was caused by the aircraft penetrating an area of turbulence while passengers were not secured with seat belts.
- The lack of expected turbulence meant the crew had not activated the seat belt signs, leaving passengers walking in the aisle vulnerable to the sudden vertical accelerations.