Alexka,
I am not a "technical flyer", so we'll have to wait for others to come along and give us the correct definition of a "slip". However, I believe it simply refers to flying with "crossed controls", i.e. rudder and ailerons deflected in different directions. I think whether it's a "forward" or "side" slip just depends on the direction the nose is pointing in : if the nose is aligned with the runway centreline, I'd call it a forward slip, if you're "crabbing" while maintaining track, then it's a side slip. However, I'm probably wrong (not an unusual situation!
)
What I can tell you, however, is that you most certainly can slip a 172 (and every other Cessna I've flown) with flaps. I personally wouldn't take 40degrees of flap when attempting a wing-down landing, because the book says not to, and it knows more than I do. 10, 20 or even 30 though, and as long as you watch you airspeed carefully (bearing in mind the ASI will read incorrectly) there is no problem - there can't be, or you couldn't land in a crosswind : even a "crabbed" approach obviously has to be kicked straight sooner or later).
I am not recommending this, but I can also tell you I've been in a 172 when it was landed in a crosswind of 32kts, straight across, and the guy flying (12,000 hour+) took 40 degrees of flap. Scared the crap out of me, and if I'd still had the power of speech when I saw what he was doing, I'd probably have said something !!
FF
