+67% is a despatch requirement. In flight if proceeding to planned destination and no a/c system degredation,then landing perfomance would not be an issue.
If enroute any a/c system degradation leading to higher Vapp or stopping capablity occurs then actual landing distance needs to be calculated-
ALD+CORRECTIONS(for the failure,wind,pressure alt etc)=CORRECTED LANDING DISTANCE.
In theory this should be enough to land and stop.Faa insists on adding 15% to this as a safety margin
I agree
