I don't know whether others have a similar impression to mine, that the discussion seems to be spinning its wheels now. Part of it may just be length - 1,800 messages is a lot to go through to see what was noted already and what was not.
But I must say I am not finding the discussion here of ergonomics and cognitive psychology of much help in furthering my partial understanding of this accident. I understand that stories of the sort "they would have seen this, and then they would likely have been thinking this, and then ...." are of use in seeing how one might oneself react in similar situations, but they are of limited use in explaining the accident, or in figuring out how we may change things to avoid a repeat, since there are lots of such, differing, stories and we have no way of deciding between them.
I find others of the ergononic arguments equally unpersuasive. For example, STS provides us with a Boolean expression equivalent to the condition for spoilers to be deployed, and asks us if we imagine we can understand it quickly, but fails to argue why we must judge *this* formulation rather than some other. Lemurian correctly points out that there are other, equivalent, expressions that are cognitively more straightforward to understand.
Others try to identify some "gotcha" in the spoiler operation, and fail to persuade the Airbus pilots amongst us of their point. There are two acid tests of a gotcha: either the operators agree with you, or it recurs regularly in operations. Well, the operators don't agree; what about regular recurrence? As far as we can tell something similar has happened once, maybe twice before (and we won't be able to decide that, because the one report was so sparse). Bit thin on that criterion too, it seems.
There are some pertinent ergonomical observations that don't seem to have surfaced yet. People have been talking about the braking systems and the (complex or not-complex) trigger logic, as well as evoking principles of cognitive simplicity (or complexity). But no one has yet observed that, when landing with autobrake armed, braking is cognitive simplicity itself. Your braking is concentrated in one control: your thrust levers. Pull them back, you brake; don't pull them back, you don't brake. And if this doesn't work (you don't get the "decel" light), you stomp on the pedals. It couldn't be simpler, could it?
If one is being honest about trying to figure out the ergonomics of the situation, one must take this simplicity into account when weighing up, say, whether to encourage people to grab for the spoiler handle if things aren't going right (by giving it a supplementary function on rollout which it currently does not have). My inclination would be to maintain the simplicity, and not give people lots of other options to think about in the time-constrained, critical phase of touchdown and rollout.
But what happens when this setup doesn't work? Short, slippery runway, maybe? Well, can we figure out what is "short" and what is "slippery"?
Sort-of-maybe. We can have a go at guessing parameters of "short"ness (say, length of runway needed to perform all SOP actions) "slippery"-ness (say, using rate of deceleration). For example, we can try to figure out if the TAM aircraft would have stopped had manual braking been applied ASAP. A ball-park guess would proceed along the following lines. Take the demonstrated acceleration on application of brakes, which I estimate to be about -1.26 m/s/s, and figure out how long it takes to stop from a touchdown speed of 70 m/s. (Remember calculus? Integrate a = -1.26 with respect to time to get v = -1.26.t + v0, put in v= 0 and v0 = 70 to get t, integrate again s = -1/2.(1.26) t^2 + v0.t, put in v0 = 70 again and the value of t you have just calculated).
This gives me something just over 1940 m, so the answer is probably no, it is unlikely they would have stopped. (Please don't forget this is ball-park - a good analyst will wiggle the input numbers some to see how much the answer changes, and will also not forget that constant acceleration is an approximation, but a pretty attractive one remembering the lengths to which ELAC had to go to try to estimate braking performance taking more parameters into account.)
So then one might ask at what speed they might have gone off the end. Here is how one might do that. One guesses where touchdown would have occurred (displacement from the threshold), subtract from LDA, put that distance for s in the quadratic equation above, use the Quadratic Formula to solve for t, and substitute this value of t back in the formula for v to solve for v. Say we use an s of 1600 m, meaning with an LDA of about 1880 m we are saying they touched down at about 280 m beyond threshold. Turns out to give about 30 m/s or 60 kts.
We can wonder what might have happened then if the aircraft had belly-flopped onto the road, remembering Kegworth and how many people survived that, but I think the game of "what if" gives out here, given that they still had quantities of fuel.
I think the more pertinent conclusions lie in asking how such calculations might affect operations. Acceleration of -1.26 m/s/s is degraded braking, certainly (autobrake LO has a target of -1.7 m/s/s [Edit: I changed "MED" here to "LO" after my mistake was pointed out by TripleBravo]). How often does one get that kind of degraded acceleration? Under what conditions? Never? Once in how often? Once in too-often? And at distributed airports? Or just one or two? Some data-mining in the FOQA readouts could maybe give guidance. So, for example, you find that at airport XYZ it has happened M times in N units of operation. So now you look at the LDA at XYZ, do the ball-park calculation as above to figure out how much room you need (and don't forget that couple of seconds for a leisurely application of braking after WoW) and maybe alter your ops accordingly. Maybe quite a few operators are now doing exactly these sorts of calculations.
Which, incidentally, they would not be able to do if we couldn't estimate the mean braking effectiveness but had to wait (a year? more?) for the official report. (PJ2 reminded me privately of a short note I wrote in the Risks Forum on this over a decade ago
http://catless.ncl.ac.uk/Risks/18.44.html#subj4.1)
BTW, for those who haven't noticed it, there is a major difference between the Warsaw overrun accident and this one. At Warsaw, there was nothing the pilots could do to get the braking they needed. To my mind, that is why there was a deep discussion about, and a change in, the braking logic. As far as we know so far, that isn't the case in the Congonhas accident, or in its putative analogies.)
I am also somewhat sceptical, as others here (such as Lemurian) about adding warnings, such as that suggested in the Taipei-Sungshan report. Given that there is one braking control in this configuration, namely the thrust levers, and given that pilots have not responded to a *very specific* suggestion to activate it ("Retard"), one may wonder what would lead one to think that they would then respond more appropriately to a *general* warning (CRC, red master warning light), or whether the general hullabaloo would not be more likely to distract them further from the task at hand.
PBL