Well, whatever the arguments, F=uR always applies. If F is the resistance to motion available ( torsional friction at the wheel hub) at max antiskid brake pressure, its effectiveness can only be influenced by the interaction of surface coefficient of friction with weight on wheels. On a frictionless runway, F will always be zero. If u has any value above zero, any increase in R (the weight) will always lead to a higher effective value of F (retarding force)
EEngr: sorry, but your observation is wrong in the case we are discussing. F=ma applies to linear forces, but F=uR is about a vertical interaction. F=uR will produce a particular value of 'F' in F=ma. Since the aircraft mass is a constant, the deceleration (a) depends on F, which is in turn dependant on uR. Your view that more weight at the wheels would require greater retardation force is incorrect, since we are considering that the brakes are being applied at max antiskid pressure to a fixed mass. The fixed mass of the aircraft still needs to be stopped and it is the value of F that will do it.
Last edited by 777fly; 10th Oct 2012 at 22:05.