What happened
On October 18, 2018, an Aerolíneas Argentinas Airbus A330-223, registration LV-FNK, was operating a scheduled commercial flight from Miami, USA, to Ezeiza, Argentina. While cruising at flight level 390 over the Sena Madureira region in Amazonas, Brazil, the aircraft encountered severe turbulence and hail within an area of convective activity.
The encounter caused the aircraft to climb unexpectedly to flight level 410. During the event, the aircraft' and passengers experienced significant jolts. The impact of hail caused damage to the radome and lightning strikes were observed on the fuselage. Inside the cabin, the turbulence resulted in 25 injuries (17 passengers and 8 crew members). At the time of the encounter, the seatbelt sign was not illuminated, and cabin crew were performing meal services while several passengers were moving through the aisles.
The investigation
The investigation focused on the meteorological conditions, the aircraft's flight parameters, and the crew's response. Investigators examined the flight data and cockpit voice recordings, noting that the aircraft's flight parameters deviated significantly from normal operating limits. The investigation also looked into the effectiveness of the onboard weather radar and the availability of meteorological alerts in the region.
Findings
- The crew encountered an unexpected third convective cell that was developing rapidly with an estimated ascent rate of 100 knots.
- This specific cell was not detected by the aircraft's radar because it was positioned below the maximum antenna tilt angle.
- The aircraft experienced a near loss of control due to extreme flight parameter deviations, including an activation of the Alpha Floor protection due to excessive angle of attack.
- The autopilot disconnected unexpectedly due to high angle of attack conditions, forcing the crew to transition to manual flight.
- During the recovery, the crew provided conflicting sidestick inputs, sometimes in opposite directions, reaching maximum values.
- The seatbelt sign was not active during the encounter, and the crew had not been notified of severe turbulence by meteorological services prior to the event.
- The non-operational status of the Tabatinga radar prevented the early generation of a SIGMET to warn of the storm.
Safety action
Following the investigation, safety recommendations were issued to Aerolíneas Argentinas S.A. to include scenarios of unexpected severe turbulence and recovery from unusual parameters (such as excessive angle of attack and uncontrolled climbs) in simulator training. Additionally, the investigation recommended enhanced operational risk management through the monitoring of convective systems in the tropical/Amazonian region using flight data.