What is the ACF?

I was lurking around the forums, and saw a few people talking about something to do with the ACF, I googled it; found nothing but a mech battle featuring it, nothing in description saying what it was.

So, anyone want to tell me what the ACF is? and perhaps a download link.

Anyone know?

Normally used in tank wars ACF is a damage system based on prop size and weight, with realistic weapons"
(Still unreleased)