Austral Líneas Aéreas Flight 2553 was an

Argentine Argentines, Argentinians or Argentineans are people from Argentina. This connection may be residential, legal, historical, or cultural. For most Argentines, several (or all) of these connections exist and are collectively the source of their ...

domestic scheduled passenger flight from Posadas to

Buenos Aires Buenos Aires, controlled by the government of the Autonomous City of Buenos Aires, is the Capital city, capital and largest city of Argentina. It is located on the southwest of the Río de la Plata. Buenos Aires is classified as an Alpha− glob ...

. On October 10, 1997, the McDonnell Douglas DC-9-32 that was operating the flight crashed on the lands of Estancia Magallanes, Nuevo Berlín, away from Fray Bentos, Uruguay. All 74 passengers and crew died upon impact. The accident remains the deadliest in Uruguayan history.

Background

Aircraft

The aircraft involved was a McDonnell Douglas DC-9-32, registration LV-WEG. It had its maiden flight in 1969, and as of the time of the accident had flown a total of 56,854 hours and 54,800 takeoff and landing cycles.

Crew

The captain was 40-year-old Jorge Cécere, who had been with the airline since 1989 and logged 9,238 hours, including 223 hours on the DC-9. The first officer was Horacio Núñez, who was also 40. He had been with the airline since 1993 and had 2,910 flight hours. He was more experienced on the DC-9 than Captain Cécere, with 1,384 hours on that aircraft.

Accident

The aircraft, which left from Posadas and was due to land in Aeroparque Jorge Newbery, Buenos Aires, was forced to divert towards Fray Bentos to avoid a storm. Examination of the aircraft's flight data recorder (FDR) revealed that shortly after the diversion occurred, the aircraft

airspeed In aviation, airspeed is the speed of an aircraft relative to the air it is flying through (which itself is usually moving relative to the ground due to wind). In contrast, the ground speed is the speed of an aircraft with respect to the sur ...

indicator began to fall to an alarmingly low indicated airspeed. Unknown to the pilots, this was caused not directly, by a loss of power, but by ice formed inside the pitot tube, which reads the airspeed for the indicator by measuring the pressure of inflow air. The ice obstructing the pitot tube reduced the air inflow, thus giving an erroneously low indicated airspeed. In response to what they interpreted as a loss of engine power, the pilots disconnected the autopilot and gradually increased power from the engines in order to maintain airspeed. Seeing no improvement, they contacted the control tower in Ezeiza Airport and requested clearance to descend to a lower altitude. After receiving no response, the Captain decided to descend to a lower altitude to increase speed even with no clearance received from the Air Traffic Control. While descending from their assigned altitude of and reaching , the Captain identified the faulty airspeed indication and ordered the First Officer to stop descending and to reduce speed, because the readings were unreliable. However, the First Officer disregarded the Captain's commands and deployed the wings' slats to maintain their altitude and lower the plane's stall speed. Consequently, at this point the airplane was actually flying at a higher speed than normal; it was descending, which further increased airspeed to a point dangerously near to V_NE, the "never exceed speed", above which structural damage to the aircraft might occur. With the slats extended at a speed beyond their operational limits, one of them was torn from the aircraft, causing catastrophic asymmetry in the airflow over the wings. The aircraft immediately became uncontrollable and crashed.

Investigation

According to an investigation by both the

and Uruguayan Air Forces, the pitot tube—the primary instrument for measuring aircraft airspeeds—froze when the aircraft passed through a high cumulonimbus cloud, blocking the instrument and causing it to give a false reading. Compounding this problem was the absence of the alarm designed to report such a malfunction (raising serious questions about inspection irregularities by the Argentine Air Force). During the descent, the FDR recorded an increase in the airspeed from to in three seconds, which could only signify the sudden unfreezing of the pitot tube. Specialists estimated that the aircraft crashed at a 70-degree nose down attitude, at a speed of . Depending upon the source, the crater left by the crash was deep and wide, deep and wide, or deep and wide.

References

External links

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Boletín Informativo Nº 29
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'' Junta de Investigaciones de Accidentes de Aviación Civil'' {{DEFAULTSORT:Austral Lineas Aereas Flight 2553 Aviation accidents and incidents in Uruguay Accidents and incidents involving the McDonnell Douglas DC-9 Aviation accidents and incidents in 1997 Airliner accidents and incidents caused by instrument failure Airliner accidents and incidents caused by pilot error 1997 in Uruguay October 1997 in South America 1997 disasters in Uruguay