The A320 plane had its right-side reverse thruster broken at least since Friday, July 13. On July 16, a Monday, the day before the tragedy, the aircraft had had trouble stopping and almost went off the runway at the same Congonhas airport. The trouble with the A320 had been detected by the plane's electronic checking system.
TAM's president, Marco Antonio Bologna, and the airline's vice president Ruy Amparo confirmed that the reverse thruster wasn't working and had been turned off. According to them, however, this didn't represent any danger to the plane, since the jet's manual in these cases only recommend that the failed equipment be checked in ten days, but doesn't tell to stop flying the aircraft.
Bologna and Amparo, however, didn't confirm the information given by Jornal Nacional that the Airbus had trouble landing the day before the crash. According to the news show, the A320 commander had told airport authorities that the tarmac was slippery and that he had a hard time trying to stop the plane upon landing on July 16.
It was about 6:45 pm on Tuesday when the Airbus that had taken off at 5:16 pm from Porto Alegre in the South of Brazil, tried to land in Congonhas and instead skidded off the runway crossing the busy Washington Luís avenue and slamming into a TAM building where some employees were working at the time. The plane burst into flames which spread to neighboring structures. 188 deaths have been confirmed until now, but the work of rescuing bodies continues.
In 1996, a reverse thruster failure was pointed as the reason for another crash in the same airport. At that time, a Fokker-100 also belonging to TAM crashed over a residential area, a few seconds after takeoff. killing 99 people.
The failure of a reverse thruster is always a security risk, according to Roberto da Mota Girardi, a professor of aerodynamics at the renowned Aeronautics Technological Institute (ITA). "This is dangerous," Girardi told reporters, "especially in a short tarmac as the one in Congonhas.".
A plane without a reverse thruster would need a bigger runway to stop, informed the ITA professor. "I'm not familiar with the Airbus's operation manual or the details of TAM's maintenance system, but it seems odd that they would allow a period of ten days to evaluate the problem."
The reverse thruster is the aircraft's main brake during landing. When it's turned on the plane's turbines flow is inverted, causing the aircraft to quickly lower its speed. Only then the landing gear's mechanical brake system is activated.