marciovp, for my part, thanks for posting that material. It clearly represents the firsthand views of two serving pilots, and is therefore as relevant as any other part of the (inevitably somewhat speculative) information that has been posted on this thread. People can accept it or reject the information as they choose; but, as you say, there's no reason to 'shoot the messenger.'
Originally Posted by Dozywannabe
Quote:
2. Why does the availability of autobrake depend on spoilers
At a guess I'd say this is because without spoilers the aircraft will become considerably harder to stop and the designers considered it better in that situation to promote a go-around and a second attempt to land or a diversion.
Tend to agree. Ever since the Lauda Air accident (R/T deployed in flight) there have been numerous safeguards on all makes of airliner to prevent the pilots OR the systems carrying out 'after landing' procedures while the aircraft is still in the air; and still leave open the go-around option.
A possible 'hole' in the A320 logic, though, is that because one TL was not retarded (or not recorded as having been retarded) the systems prevented deployment of the ground spoilers and autobrakes but ALLOWED the deployment of reverse thrust. With hindsight, it might be better to organise the systems so that they take R/T deployment as proof of the pilots' intention to land rather than go-around; though I accept that that might make further complications requiring careful adjustment of the logic of other 'interlocking' systems.
I still feel that this accident is 80% certain to be the result of 'pilot error.' But, in addition, that the REASONS for that error must also be identified and rectified. From the CVR/FDR recordings of both Taipei and Congonhas, it is clear that the pilots were utterly confused as to what was CAUSING their problems. The Taipei crew thought that they had a brake malfunction, the Congonhas one that they had a ground spoiler malfunction. In both cases, had they been able immediately to identify the problem - a misplaced or jammed TL - the accidents could have been avoided, or at least very much reduced in terms of severity.
In that connection I keep thinking back to that Taipei report I quoted back in Post 2198:-
"During landing, the FWC has delivered four aural “RETARD” alerts and then after touchdown two seconds it came to stop. But at this moment the thrust control lever no.2 was not pulled back to idle or reverser position yet. In this situation, one of thrust control lever is not in proper position but the aural “RETARD” alert already stopped. The aural “RETARD” alert should continue or there should be other ways to remind the pilots of pulling back thrust control lever to reduce the probability of an accident caused by human error."
Airbus confirmed in their evidence at Taipei that the problem existed, and that retarding even one TL was sufficent to turn off the RETARD' call:-
Q2/ Why does the message "Retard" stop 2 s after the nose gear touched down? Is it as per design?
A. As soon as one TLA is set to REVERSE (whatever the other TLA position), the internal FWC signal "TLA inhibition" becomes true. If "TLA inhibition" is true, RETARD is inhibited.
Airbus also developed a modification to provide a specific warning if one TL was left out of 'Idle' - but neither they nor the regulating authorities chose to make the mod. mandatory.
I for one hope that it is now made both mandatory AND urgent. If it is even possible (leave alone probable, as in this case) that pilots can become utterly confused at such a critical moment, it is not enough just to add a line to the manuals. The design should be modified to ensure that, as far as possible, the same situation cannot occur again.