PK-KAR,
On those 2 phases, on braking, the chime can come from hot brakes, A/B fault when armed, or HYD SEL FAULT
Yes, but there are so many messages -not related to braking- that could re-appear on phase 8.
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)...
Your guess is as good as mine. Where our assumptions match is that they had a very narrow margin of error...But still they should have stopped inside the runway distance...but did not.
safetypee,
Alternatively, if the SOP was to call ‘decel’ based on the PFD speed trend, then the conclusion is that aircraft was decelerating.
I have enquired and I don't know of an airline with a *decel* call-out based on the PFD speed trend.
I disagree with the assertion that “The kind of deceleration we are talking about here will be felt, …”
This level ( remember i was talking of a .35G deceleration) should be felt, physically.
If the runway condition involved low friction, then the majority of the deceleration would come from reverse. After cancelling reverse, the relative ineffectiveness of the brakes could be perceived as a failure.
I would agree with you on principle and for low values of negative G forces, but not this high. The figures I gathered showed up to the 70 kt call a very healthy, effective braking. Hell broke loose one second later.
Problems in this area stem from training / experience, where IMHO crews are not familiar with maximum manual braking on a wet runway; auto-brake removes an important cue, and with everyday use of reverse, it masks the brake contribution to the total deceleration.
I agree. Pilots should be practicing manual braking, trying for a close turn-off...etc...but that crew had a good experience of short runway ops, so they would have known.
One question remains, though : As the crew was apparently treating this landing as routine, why did they realise so late that they were running out of runway ? Is there a problem seeing the runway end ?