[PlasmaKrab]

What is it you have in mind, of the following:
-1) changing the icon for a definite rotor type, or
-2) changing which rotor icon is used by a specific helicopter?

For 1), see explanation above, search this board for explanations on how to edit icons, some of which have been given again not long ago.

For 2), I think you are stuck, as in most cases this is hardcoded. A few helicopter icons use their own rotor, which is stored beside the fuselage icon just as for turreted AFVs, but most use a few hardcoded rotors which are stored in a separate file.
These you will find in MasterIconList as having a file image reference pair the likes of this one: {2458;679}. The second is the rotor (I don't remember the exact numbers), and this pairing is hardcoded somewhere we modders don't have access to.
The MasterIconList.txt is only a copy for reference, and editing it will change nothing at all.

Hope this helps.

Plasma