A320 ops on contaminated RWY

[che ci dò che ci dò!]

Dear all,
with reference to the two weight corrections on FCOM 2.04.10 P5 for the determination of MTOW on a contaminated RWY: one has to apply the first decrement to the MTOW on dry RWY and then one has to enter the other table below to get the MTOW and speeds for the relevant contamination.
This process is clear but...one of these two weight corrections must be for the contamination itself, any idea about the reason for the other one?
Thanks!

[WildCatFromWildBush]

There are two cases:

First line "With clearway" - if your MTOW for DRY was calculated using RTOW and clearway was used for calculation. Second, "Without clearway" have to be used if MTOW was calculated using RTOW for runway without clearway or MTOW was calculated by QRT. By the way, no more FCOM 2.04.10 exists because new FCOM format - refer to PER-TOF-CTA chapter.

[che ci dò che ci dò!]

...ok, in the first table you've to apply a decrement versus T.O. config, RWY length and clearway availability. I understand this weight decrement is because of the contamination. Right below there's an other set of tables, one per each T.O. configuration and, in there, you've to claculate once again a corrected weight which is used thereafter to get T.O. speeds. What's the reason for this new weight decrement? Vmc limitation ?!?

[WildCatFromWildBush]

Low weight only.

As you can see, such correction for MTOW have to apply for low weight only. In my opinion, weight decrement from upper table increase sharply when weight decrease. So, to avoid unnecessary penalty for whole weight range, additional limitation was introduced.