Investigation Summary
The investigation focused on the lack of a pitot heat warning system on the DC-9-32, which allowed the pitot tubes to freeze without the crew's knowledge. As the tubes iced over, the trapped pressure caused the airspeed indicators to drop toward zero while the aircraft was actually at cruise speed. Believing they were losing speed, the crew requested a descent from FL350 to FL300. During this descent, the crew increased thrust to maximum. When the airspeed continued to drop on their instruments despite the descent and increased power, they attempted to extend the slats to increase lift. However, because the aircraft was actually traveling at a very high speed (well above the slat extension limit), the slats were torn away or failed to deploy correctly, causing an uncontrollable roll and dive. The aircraft struck the ground at a speed exceeding 1,000 km/h, creating a large crater and leaving no survivors.
Final Conclusions
The primary cause was the icing of the pitot tubes due to the crew's failure to activate the anti-ice system or the system's failure to operate, combined with the lack of a 'pitot heat off' warning light. This led to erroneous airspeed readings. The crew's subsequent decision to extend slats at high speed, based on these false readings, resulted in structural failure and loss of control.
Video Analysis
No video analysis linked for this case file yet.
Crew Experience
Captain
Jorge Ceballos
First Officer
Horacio Cecere
Systems & Failure Modes
Pitot-Static System
The system responsible for measuring airspeed; its failure due to icing provided the crew with false data.
Leading Edge Slats
High-lift devices on the wings that were extended at excessive speed, leading to structural failure and loss of control.
Pitot Anti-Ice
Heating elements designed to prevent ice buildup on the pitot tubes, which were either not activated or failed.
Interesting Facts
- 01The accident is the deadliest aviation disaster in Uruguayan history.
- 02The aircraft impacted the ground at a very high speed, estimated to be near the speed of sound.
- 03The impact created a large crater at Estancia Magallanes.
- 04The DC-9-32 involved did not have a warning light to indicate that pitot heat was not functioning.
- 05The crew extended the slats at a speed significantly higher than their maximum operating limit.
Safety Actions & Advisories
Pitot Heat Warning Modification
Recommendations were made to mandate the installation of 'Pitot Heat Off' warning lights on older DC-9 models to prevent crews from flying into icing conditions without probe heating.
Known Controversies & Unanswered Questions
Dispute over Investigation Findings
Reference ↗There were documented disagreements between Uruguayan and Argentine investigators regarding the specific sequence of pilot actions and the exact state of the aircraft's anti-ice systems prior to the crash.