Originally Posted by
DingerX
[blockquote]Estimated speed abeam the camera : 100 kt[/blockquote]
To those who would suggest that the movement of the camera would exaggerate the speed, or that the perspective of the runway (going from abeam to moving away) would make it appear to be slowing down, here's how that figure is arrived at: in the 4 seconds it's on camera, the aircraft travels 5 plane lengths. Length of an A320 is 37 meters and change, so back-of-the-envelope gives 170 kph, or approximately 100 kt.
We strongly disagree with the assessment by Flight Global, that the airplane was travelling at 100 knots at that point. If that was true, the airplane would definitely have stopped before the runway end, given that the airplane had already slowed down from their touch down speed of around about 150 knots (tailwind 10 knots plus reduced IAS due to density altitude taken into account). If those 100 knots were true, the airplane would have slowed down at a rate of 2.4 meters/second/second at minimum (touch down at the threshold) up to 4.5 meters/second/second in maximum (touch down at the aiming markers, 4.5 m/s/s or 9 knots/s being quite some more than maximum autobrakes) since touch down, suggesting that the airplane would have stopped between 450 to 700 meters before the runway end with that (continued and constant) deceleration.
See the computations and considerations here:
http://avherald.com/h?article=4077cedf/0022
If speed was indeed a factor, the airplane must have been quite a lot faster than 100 knots at that point 650 meters past the threshold and 1000 meters before the runway end.
I would rather wait for the data off the FDR ...
Servus, Simon