Static, The regulation are for required landing distance .Dry R/W ,actual ldg distance divided by .6 . Wet 115% of that for a dry surface .(there is regulations for contaminated surface for JAR -OPS . And also for auto land ). Before dispatch the pilot must check that the R/W length at destination for the forecasted ldg wt is at least equal to the req dist . in case of departure with a sys failure affecting ldg dist known before dispatch the req ldg dist without failure multiplied by the coefficient given in the MMEL is what the pilot needs .Coming to your point with failures in flight affecting the ldg performance the R/W length to be considered is the actual ldg dist without failure multiplied by the coefficient given in the QRH . I hope this clarifies the subject .