Austral Líneas Aéreas Flight 2553

Austral Líneas Aéreas Flight 2553

An Austral Líneas Aéreas McDonnell Douglas DC-9-32 similar to the aircraft involved in the accident
Accident summary
Date	10 October 1997
Summary	Instrument malfunction, possible pilot error
Site	Nuevo Berlín, Uruguay 32°58′45″S 58°03′10″W / 32.97917°S 58.05278°W / -32.97917; -58.05278Coordinates: 32°58′45″S 58°03′10″W / 32.97917°S 58.05278°W / -32.97917; -58.05278
Passengers	69
Crew	5
Fatalities	74 (all)
Injuries (non-fatal)	0
Survivors	0
Aircraft type	McDonnell Douglas DC-9-32
Operator	Austral Líneas Aéreas
Registration	LV-WEG
Flight origin	General José de San Martín Airport, Posadas, Argentina
Destination	Aeroparque Jorge Newbery, Buenos Aires, Argentina

Austral Líneas Aéreas Flight 2553, also known as Austral 2553, was a Argentinian 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 died upon impact. The accident remains the deadliest in Uruguayan history.

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.

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 indicator began to fall to an alarmingly low indicated airspeed. Unbeknownst 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 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 35,000 feet and reaching 31,700 feet, 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 Vne, the "never exceed speed", above which structural damage to the aircraft might occur.