JohnBr -
Well I think we can agree about the 1 reverser inop point – it can’t account for the high speed in the later half of roll, even with ‘wishful thinking’. As for mech failure, I’ve heard of a total brake failure on AB – but is going to be a real rarity for a TOTAL failure – coupled with (by implication) happening after touchdown with no prior warning (hydraulic/anti skid warning messages or the like) to the crew, etc. Seems (to me) that’s a non-starter at this point in time (pending FDR). So then it’s down to the difference between this and preceding aircraft landing?
Raggyman -
Or do aircraft tyres pretty much aquaplane anyhow no matter how fast you are going?
no they don't – but the main factors affecting whether it happens or not in a given situation are runway macrotexture, speed and depth of water. By most accounts, the macrotexture in this case was poor . Good macrotexture allows frictional contact between the tyre and runway surface by virtue of the ‘roughness’ being able to penetrate the liquid layer. With poor macrotexture – the liquid film can form a hydraulic wedge between the surface of runway and tyre – when the tyre is moving above a certain speed. As far as threads are concerned – it’s not possible to make a reasonable comparison between what’s needed for an aircraft or average road vehicle. They’re in totally different regimes of speed and load. For aircraft, braking efficiency on slippery surfaces at low speed can be quite effective relative to a road vehicle – there’s a much higher load to increase friction than on a car.