Austral Líneas Aéreas Flight 2553

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Austral Líneas Aéreas 2553, better known as Austral 2553 is the name of an Douglas DC-9 aircraft of Austral Líneas Aéreas, registered as LV WEG ^[1] which crashed in Fray Bentos, Uruguay, on October 10, 1997. All 74 passengers on the plane and the crew died on impact.

[edit] The Accident

The aircraft, which left from Posadas and was headed to Buenos Aires, was forced to divert towards Fray Bentos to avoid a storm. Examination of the aircraft's black box revealed that shortly after this diversion, the aircraft's airspeed began to fall to an alarmingly slow velocity. In response, the pilots repeatedly increased power to the turbines in order to maintain velocity. Seeing no improvement in the aircraft's airspeed, the pilots then contacted the control tower in Ezeiza Airport and requested clearance to descend to a lower altitude. After receiving no response, the pilots lowered the aircraft's wing slats to maintain their altitude and lower the plane's stall speed. When lowering the slats however, one of them ripped off, causing catastrophic asymmetry in the air flow over the wings. The plane immediately became uncontrollable and crashed.

According to an investigation by Argentine and Uruguayan Air Forces, the pitot tube - the primary instrument for measuring the aircraft's airspeed - froze when the aircraft passed through a cloud, blocking the instrument and causing it to give a false reading. Compounding this problem was the failure of the alarm designed to report such a malfunction (raising serious questions about inspection irregularities by the Argentine Air Force). Thinking that the aircraft was flying at dangerously low speeds, the pilots increased power to the engines. Far from flying at the low speed reported by the instruments however, the aircraft was actually flying well outside its safe cruising speed, and far above a safe speed for deploying slats. During the deployment of the slats, one was ripped off by the force of the high speed airflow travelling over the wing, which caused the plane to become unflyable and enter a steep descent.

During the descent, the black box recorded an increase in the plane's speed from 300 to 800 km/h in three seconds, which could only signify the sudden unfreezing of the pitot tube. Specialists predicted that the plane crashed perpendicularly to the ground at a speed of 1200 km/h, leaving a crater 70 metres wide and 10 deep. ^[2]

The film Fuerza Aérea Sociedad Anónima by former pilot Enrique Piñeyro briefly explains the crash's major causes.