A320 landing distance without failure

[simyoke]

Let's do a rather simple arithmetic here.
Assuming all the parameters same for both dry and good to medium runways;


conf: full
auto brake: low
weight: 100000 lbs
spd: assume no speed increment is needed
alt: 0 ft
wind: no wind
temp: ISA
slope: 0
reverser: both are operative


Let's add or subtract as directed in the table ....
,which yields


5870 ft for dry runways
5350 ft for good to medium runways

To me, it seems counter intuitive.
Looking up GETTING GRIPS WITH A/C PERFORMANCE, One thing that I can think of is precipitation drag.


The major difference comes from the second note since GOOD TO MEDIUM runways let you subtract twice as much as DRY runways
for weights under 150000 lbs.