A point which is perhaps being overlooked it that on those runways where the conditions are such that the normal braking performance may not be achieved, then the maximum level of braking (brakes + reverse) will not result in uncomfortable deceleration. MAX (or RTO) is attempting to achieve a very high level of retardation, but due to anti skid action or aquaplane etc, this is not being achieved. Aspects of this are in the presentation -
Boeing slippery runways.
The deceleration during landing depends primarily on the runway friction, which is a function of materials, construction, and ‘contaminant’ – wet, dust, etc (not necessarily contaminated). The discussion should not get hung up with auto brake of definitions as it is the level of braking required / achieved that is important. It easier to understand that ‘feet on the floor’ is maximum braking requested, this is the best situation if the achieved braking is poor, and particularly if the runway conditions vary – water patches, as the best retardation is immediately available.
The point on safety margins has been discussed in other threads on runway braking conditions. The significant points are that although the certificated landing distances involve a factored distance, the resultant safety margins are not the same. We often equate a wet landing with a distance factor of 1.92 as having a safety margin of .92 (not an exact science), but in standing water (up to 3mm) the safety margins are much smaller and in some circumstances (combinations of conditions such as wet and non grooved) the margin might be nil, thus maximum braking is required throughout the landing, just in case.
Some of these issues are in UK AIC 11/98 P164 and 3/2007 P111, but these, as with some certification aspects do not give all of the assumptions or conditions; a most important one is that the unfactored landing performance is based on maximum braking (on a dry runway) and that all other aspects are calculated – factored with more assumptions.
Checking the other threads will indicate that in extreme circumstances (snow / ice contamination), even a landing with a factored distance of 2.4 may only just maintain the safety margins that we are all familiar with in daily operations. One of the references from NASA shows that a wet, non grooved runway has similar fiction characteristics to that of loose snow or thin ice!
Ignore the auto brake aspects – concentrate on stopping; PEI’s point would be better presented by stating - use ‘Maximum Braking’ in adverse conditions.