Brazil's accident investigation agency CENIPA is not ruling out mechanical failure as its probe into the TAM Airbus A320 crash at São Paulo Congonhas airport in July seeks to establish why the crew did not retard the No 2 engine's thrust lever on touchdown.
All 187 passengers and crew on board died in the crash, as well as 12 people on the ground, when the aircraft overran on landing and slammed into an airport building on 17 July.
Brigadier Jorge Kersul Filho, head of CENIPA, says the investigation will cover mechanical or system failures and pilot error as well as airport infrastructure. Based on information from the A320's flight data recorder and cockpit voice recorder transcripts and data prepared by the US National Transportation Safety Board, Airbus has issued an Accident Information Telex that states that the pilots, after landing, had moved the No 1 engine's thrust lever from the "Climb" position and selected maximum reverse thrust, at which time the aircraft's autothrust system had properly disengaged.
But Airbus reveals that "the engine 2 throttle is recorded in the 'Climb' position and remained in this position to the end of the recording".
Significantly, No 2 engine's thrust reverser was locked out because of maintenance, but this should have had no bearing on the thrust lever drill during landing. But with the thrust lever remaining in the "Climb" position Airbus says the No 2 engine's thrust remained at the value it was at when the autothrust disengaged - approximately to 1.2 EPR. Compounding the problem, the lever's position would have prevented the ground and flight spoilers and autobrakes from activating.
CENIPA's Kersul says that the right-hand throttle may have been stuck in the forward position, commenting that a voice not mentioned in the CVR transcripts had said: "The lever won't move, it's jammed." Kersul reveals that throttle quadrant had been recovered in the crash, and that the right-hand level was advanced, although he cautions that crash forces may have changed the position.
Investigators will probably delve deeper into the CVR, which was translated from Brazilian Portuguese to English, to verify alternative meanings to the pilots' words and expressions. Kersul also says that investigators will analyse the control logic in Airbus systems to determine if hardware, software or logic errors could have played a role.
Airport infrastructure issues under the spotlight will be the relatively short length of the runway at Congonhas as well as a lack of grooving, which helps water drain from the surface. The CVR recording reveals that pilots and controllers both were aware that the surface that evening was "wet and slippery".
Source: Flight International