Austral Líneas Aéreas Flight 2553

Austral Líneas Aéreas Flight 2553

Accident summary
Date	October 10, 1997 (1997-10-10)
Type	Instrument malfunction, possible pilot error
Site	Nuevo Berlín, Uruguay 32°58′45″S 58°03′10″W
Passengers	69
Crew	5
Injuries	0
Fatalities	74 (all)
Survivors	0
Aircraft type	McDonnell Douglas DC-9-32
Operator	Austral Líneas Aéreas
Tail number	LV-WEG
Flight origin	General José de San Martín Airport, Posadas, Argentina
Destination	Aeroparque Jorge Newbery, Buenos Aires, Argentina

Austral Líneas Aéreas Flight 2553, better known as Austral 2553, was a domestic scheduled Posadas–Buenos Aires service operated with a McDonnell Douglas DC-9-32 that crashed on the lands of Estancia Magallanes, Nuevo Berlín, 32 kilometres (20 mi) away from Fray Bentos, Uruguay, on 10 October 1997. All 74 passengers and crew perished after the impact. The accident remains the deadliest one both in the Uruguayan, and in the Argentine aviation history.

Aircraft

The aircraft involved in the accident was a McDonnell Douglas DC-9-32, registration LV-WEG. It had its maiden flight in 1969, and was 28 years old at the time of the accident. It had previously operated for Iberia with registration EC-BQT, and it was transferred to Austral after the buyout of the company by the Spanish carrier.^{[citation needed]}

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 began to fall to an alarmingly low airspeed. In response, the pilots repeatedly 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 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 was torn from the aircraft, causing catastrophic asymmetry in the air flow over the wings. The aircraft immediately became uncontrollable and crashed.

According to an investigation by both the Argentine and Uruguayan Air Forces, the pitot tube—the primary instrument for measuring aircraft airspeeds—froze when the aircraft passed through a 15000 m high cumulonimbus cloud, blocking the instrument and causing it to give a false reading.^{[citation needed]} 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 a dangerous low speed, the pilots increased power to the engines and then deployed the slats. Far from flying at the low speed reported by the instruments, the aircraft was actually exceeding its safe cruising speed, and far above a safe speed for deploying slats. During the deployment of the slats, one was torn off by the force of the high speed airflow traveling over the wing, which caused the aircraft to become unflyable and enter a steep descent.

During the descent, the FDR recorded an increase in the airspeed from 300 to 800 km/h in three seconds, which could only signify the sudden unfreezing of the pitot tube. Specialists estimated that the aircraft crashed almost perpendicularly to the ground, at a speed of 1200 km/h. Depending upon the source, the crater left by the crash was 6 m (20 ft) deep and 30 m (98 ft) wide, 25 ft (7.6 m) and 30 ft (9.1 m), or 25 ft (7.6 m) deep and 80 ft (24 m) wide.

See also

• Fuerza Aérea Sociedad Anónima, a film by former pilot Enrique Piñeyro that attempts to explain the major causes of the crash
• LAPA flight 3142