Well I don't think I was imagining 40 degree setting in the 172N that I took my instrument checkride in.

Here's something I surfed up:

"...not until the 1981 model year was the maximum flap extension reduced from 40 to 30 degrees."

http://search.netscape.com/ns/boomfr...2FA02P0136.asp

C172Ps were the last of the 1980's Skyhawks, and were introduced in 1981 according to wikipedia. So, my guess is that was where the 40 setting actually ended, when the P was introduced. I never found much use for the 40 degree setting as it slowed down touch n goes due to retraction time. I think they were for super-short field landings which no one does anymore, perhaps a sales gimmick. As far as I know they only only added drag which is of little value when forward slipping because that does it so much better.

Some airfoils exhibit buffeting prior to a stall, some do not (super-critical foils). But buffeting can also be caused by airflow patterns which have nothing to do with a stall...

I looked up the TCDS for the 172N. I had a seaplane, so that's where I got the 30 degrees of flaps, from. The landplane did have 40 degrees. The P models and newer had 30 degrees.

There's also some places that put a strip of metal preventing flap extension past 30 degree's also. Not a bad idea really. Most training/rental pilots really don't need to be using it IMO. If you need that level of flap extention, you probably need to consider another approach or alternate.

There are also some models that want you to avoid prolonged slips due to fuel starvation.....good to know in my opinion!