What happened
A scheduled flight departed Posadas-Libertador General José de San Martín Airport at 21:18 local time, bound for Buenos Aires. The flight was carrying 69 passengers and five crew members. While cruising at 35,000 feet, the aircraft encountered extreme weather, including heavy turbulence, winds of 80 km/h, and icing conditions. During this period, the crew entered the Montevideo FIR without notifying Montevideo ATC.
At approximately 22:04, the aircraft entered a zone of severe icing. Shortly after, the pilot-in-command began a descent without authorization. While the captain attempted to coordinate a descent with Ezeiza Control, they were instructed to contact Montevideo ATC. Montevideo controllers cleared the descent to FL257 at 22:09:17, and the aircraft reached this altitude at 22:10:25.
During the descent, the first officer noted a malfunction with the airspeed indicator. As the aircraft passed through FL300, the first officer deployed the slats. Because the aircraft's speed was higher than the permitted limit for this configuration, the deployment caused an asymmetry. The aircraft subsequently entered an uncontrolled descent, striking an open field approximately 21 km east of Nuevo Berlin in a near-vertical attitude. The impact caused the Boeing 737 to disintegrate, creating a crater 10 meters deep and 30 meters wide. There were 74 fatalities and no survivors.
Findings
Investigation into the accident suggests that the airspeed indicator may have malfunctioned after the Pitot tubes became iced, causing a sudden recorded increase in speed from 200 to 450 knots within four seconds. The extension of the slats at an excessive airspeed was the primary factor that led to the asymmetric configuration and the subsequent loss of control.