Originally Posted by alf5071h
OVERTALK your picture links suggest that you have a close association with IASA. If that is so, I suggest that you restrict the more extreme views on how to enhance flight safety, however well intention they might be, to the IASA web site; along with the comments from possible ‘associates’ participating in this thread.
For me, it seems just the opposite. While IASA is, ad pointed out, a private lobby group, it has a rather official-sounding name, compared to, say, IATA and ICAO. Therefore, it would be better to express extreme views in Pprune , where they can be and are violently critizised, rather than on IATA website where they are not critizised and might be acted upon...
As for the matter:
So, what exactly is supposed to happen when the wheel friction decreases to the extent that the anti-skid overrules autobrake?
As the plane decelerates, the airspeed, and therefore the aerodynamic forces and momenta, decrease in one direction, continuously and smoothly.
Whereas the friction forces can change in any direction, suddenly, as the wheels encounter portions of runway where different conditions prevail.
When the friction under the main wheels changes above the point where the autobrake works at the set deceleration rate, the acceleration loads are unchanged and therefore the load distribution between main gear and nosegear are not subject to sudden changes (they change slowly, with airspeed)
The instant that the friction decreases so far the antiskid takes over, the deceleration rate falls and the weight distribution changes. The weight supported by nosegear decreases (and it was relatively small to begin with). As the nosegear loading falls, the maximum frictional force available to resist sideslip falls (and the friction coefficient may be falling at the same time).
What is the manufacturer-approved SOP pilot response (if any) to antiskid overruling the autobrake? Assuming that the nosegear remains, initially, supported by runway and has not (yet) slipped sideways?