Originally Posted by
RR_NDB
F-GZCP System "memorized" PF initial NU, maintaining THS at 13deg til the end of the flight.
The system (by which I mean the flight controls) only "memorised" it because there was not a consquential opposite command to move it the other way, either from the sidestick or the trim wheel.
In TAM 3054 case both pilots didn't understand timely the system output (combinational logic).
Well, there were procedural complications in that case. The original "reverser inoperative" procedure called for the thrust levers to both be placed in idle and only the engine with the working reverser to be placed into reverse. Airbus discovered several incidents where the lever to the engine with the inoperative reverser was not pulled to idle, extending the landing distance considerably and risking an accident.
As such they came up with a new procedure where both levers were to be pulled all the way through flight idle to reverse on rollout, which made the problem go away, but led to a slight, but noticeable increase in landing distance as the engine thrust on the side with reverser inop would increase, inducing forward thrust on that side.
The TAM crew knew of this latter procedure and indeed used it on the previous leg of the flight, as evidenced by the FDR traces - however the Conghonas runway was short and known to be treacherous, especially in wet conditions. The logical theory is that the very experienced Captain knew of the increased landing distance that the new procedure caused and elected to use the old procedure, ironically, to give him an increased safety margin given the atrocious conditions at Conghonas that night. Unfortunately the crew made the same mistake that had caused that procedure to be revised in the first place and the rest is history.