Max Kingsley-Jones/LONDON
A possible flight-instrument or air-data-computer problem is likely to be the initial focus of the investigation into the 2 October loss of an Aero Peru Boeing 757, which crashed into the Pacific Ocean killing all 70 people on board. Peruvian transport minister Elsa Carrera de Escalante says: "We have to find out why the computers went crazy."
The 757 (built in 1992), one of two Pratt & Whitney PW2000-powered aircraft leased to the airline by Ansett Worldwide Aviation Services (AWAS), was operating to Santiago, Chile, from Lima, Peru.
Shortly after take-off from Lima, the crew called air traffic control (ATC) to request a return to Lima with "mechanical problems". There followed 30min of conversation between the pilot and ATC before radar contact was lost. The 757 crashed into the Pacific Ocean off Pasamayo, around 75km (40nm) north of Lima, at night in fog. The reported conversation between the crew and the ground indicates confusion on the flight deck, with the crew either being deprived of, or receiving conflicting, flight information. The pilot is reported to have told ATC: "We have lost the basic instruments for height and for speed-I am reducing engine power, but the aircraft is still accelerating."
Two events affecting Boeing 757/767s this year evoke the Peru accident. On 26 May, a Martinair 767-300ER crew lost its entire electronic flight-instrument system on a transatlantic flight and had to land the aircraft using standby electromechanical instruments (Flight International, 5-11 June).
The last 757 crash involved a Birgenair aircraft, which had taken off from Puerto Plata, in the Dominican Republic, bound for Germany in February. All 189 people on board were killed. That aircraft also crashed into the sea at night within half an hour of take-off, and data from its flight-data recorder and cockpit voice-recorder (Flight International, 27 March-2 April) show a crew confused by conflicting messages from the flight-management system.
The problem in this case appears to have been caused by a blocked pilot tube which fed conflicting airspeed information to the air-data computer.
Source: Flight International
