A/B Med = 3m/s/s decel rate, progressively applied starting 2 secs after ground spoiler deployment.
Decel Light comes on when actual deceleration is 80% of the selected rate.
"On slippery runway, the predetermined deceleration may not be reached due to antiskid operation. In this case, DECEL light will not illuminate. This does not mean that A/B is not working."
But, they went on manual braking anyways... so we're down to the antiskid?
Antiskid should operate until down to 20kts GNDSPD.
I'm quite interested in that single chime about 4 secs after the 70 kts call. I assume the 70kts was IAS, and that the aircraft was about 80kts gndspeed given the 10kt tailwind, and higher GND SPD with the altitude, hence it is either in phase 8 or 9 of the flight.
On those 2 phases, on braking, the chime can come from hot brakes, A/B fault when armed, or HYD SEL FAULT (failure of brake normal selector valve or NWS selector valve in open position)... the only one extending to phase 9 is A/B fault when armed.
Now a BSCU fault would not yield the chime, the A/B fault shouldn't matter because they went for manual braking... but the antiskid is BSCU controlled no? And it controls the selection of green and yellow HYD ? Both BSCU failures wouldn't yield the chime on phase 8, but could it yield in a screw up in the brake normal selection valve and loss of antiskid?
And finally that the Captain said - his last words, as it turned out - "Cancel, cancel the........"
MASTER CAUTION?
Lemurian... if they did hit the runway at 300m, they reach "70KIAS" at 1340m... 70 + 10 = 80KIAS... and about 4 secs until the chime.
at 3.4m/s/s, if the constant decel continued, then during that 4secs they went down to 25.3m/s or abou 52kts GNDSPD and covered about 128.5m
1340 + 128.5 = 1468.5
And then 4.5 secs later (when all the loud noises started), they went a further 114m assuming no decel... this would give 1582m... from "FORTY"
If the deceleration was correct and continued all the way... could the have stopped from 52kts within say 130m? Well, they could have stopped in 80m, or, if they had 1/2 the decel after the chime, they would stop within 96m.
Let's go and work this backwards...
from runway excursion to the chime = 114m
"70" call to chime = 128.5m
Reversers deployed to "70" = 586m
T/D to reversers deploying = 454m
So how much did they have on touchdown? Add them all up and it says 1282m
There's 1650m from threshold to threshold... assuming 300m threshold to t/d, they should have touched down with 1350m to go... they should have been able to stop... even if the decel halved after the chime even with only 1282m to go on t/d... they should have been able to stop with even 1/10th the deceleration after the chime (ie: only 0.34m/s/s)...
From all these extrapolations and guessculations, I would think that it is very difficult to guess at this time that other than anti skid failure/total brake failure this landing would have ended up where it is. Had they landed faster, there's would have been greater deceleration to reach that "70" call out at the given time, hence would not have made much difference since they would have the same or more distance to stop from 80kt GNDSPD until going off the end.
OK, enough of my rubbish for tonight...