I've just started Fredding away on something that will end up resembling an SP campaign and I can't find any operator that responds to hull integrity. There's no way in hell there isn't one, seeing as the FS2 main campaign uses it frequently, and I don't see why Volition would have disallowed it. I've looked pretty hard for an apropriate "hull-integrity-is" type operator, as I don't want to ask something this basic and embarrassing, but there doesn't seem to be one. Is my brain or my copy of FS2 stuffed?

Probably not, on both counts. What you'r lookingfor are the < and > sexps. Chuck one of those in your tree, then pull the hits left sexp from the status menu. So, if you wanted it to trigger at fifty

- when
- - >
- - - 50
- - - his-left
- - - - GTD My ship
- - do something

You can also use the equals sign in place of greater than or less than, but this isn;t reccomended, as unless your ship hits exactly that figure (ie. doesn;t go direct from 51 - 49 because a bomb hits it or whatever) the sexp will not fire.

Oh yeah, and

I geddit... and I've got it. Thanks a lot!