i wouldnt go demanding stuff mate lol. but then im guesing you're only asking.
anyway. i think its a variable or some sort of thing in fsds. certainly not come across it in gmax. try looking on freeflightdesign at the tutorials, you can find links all accross this site.
or just wait for someone who knows the answer. but then i'm only trying to help!
regards and good luck.
dano  8)