TripleBravo,
Autobrake LO = 1.7 m/sē
Autobrake MED = 3 m/sē
Average decel between 48:29 and 48:36 =~ 0.6 m/sē
Average decel between 48:36 and 48:50 =~ 1.2 m/sē
Average decel, ~55T, 146kts touchdown, WET, with autobrake MED, no spoilers, No 1 max reverse, No 2 (EPR = 1.08) =~ 1.5 m/sē (cf. Transavia 536 Report, Pg 143)
Average decel, ~55T, 146kts touchdown, 1/4" water, with autobrake MED, no spoilers, No 1 max reverse, No 2 (EPR = 1.08) =~ 1.1 m/sē (cf. Transavia 536 Report, Pg 143)
(Note that the Transavia report suggests that if you do not touch the brakes, in the config the TAM pilots were in, they would have got no decel at all, regardless of the runway state. This seems to be the case between 48:27-29)
Time between nose gear touch down and first brake application =~2 secs.
To me its looking like the pilots were actually pretty swift in getting on the brakes, albeit not to the point where their full potential was exploited. From where I sit, the application of max manual braking would not have prevented an over-run, in their particular config, but it would have been close(r).
I note also 1/4" of water is worse than 1/2" of water in terms of its effect on LDR's.
I'm not sure what Airbus SOP is, but we normally cancel reverse at ~60kts, so I contend that they would only have needed to reduce the speed to a value approaching this for them to have had another chance to identify (if they hadn't earlier) the unusual TL position(s) and taken some further action to ameliorate the situation.