Rough stopping distance estimate from FDR graphs
This is a very rough estimate, based on the deceleration shown in the FDR graphs.
If I read that right, the achieved deceleration at full manual brake application was around 1.5m/s^2.
When noticing "no spoilers" they were still going at around 140kt, which is about 72m/s.
The stopping distance (SD) for a known (assumed constant) deceleration (a) and known initial speed (v0) is:
SD = v0^2 / 2a, thus
SD = (72 m/s)^2 / (2*1.5m/s^2)
= 1728m.
In practice probably a bit shorter, since with less lift, WoW and thus normal force, and thus deceleration will become higher.
Still, this looks worse than earlier estimates.
It is interesting to note that, contrary to what I said above, deceleration at the onset of manual braking reached about 2m/s^2 for a few seconds, and then decreased to between 1 and 1.5.
(1g is 9.81m/s^2, so 0.1g is roughly 1m/s^2, precise enough for this estimate)
Bernd
Last edited by bsieker; 10th Aug 2007 at 10:58.
Reason: minor correction in the units.