Originally Posted by
Brian Z
You are correct. I had this same converastion with my instructor today during my pre-solo brief. Here is what I came up with. The direct verbage from page 4-48 of the 172S PIM is "Steep slips with flap settings greater than 20* can cause a slight tendency for the elevator to oscillate under certain combinations of airspeed, sideslip angle and center of gravity loadings." Here is another quote from page 4-49 of the same PIM, "If flap settings of greater than 20* are used in sideslips with full ruddder deflection some elevator oscillation may be felt at normal approach speeds. However, this does not affect control of the airplane." I beleive it is that last sentance that makes it a recommentation not to perform them as to a prohibation.
Brian
The 172S is different. I got checked out in one a few years ago, and I remember seeing that in the POH. Some older Cessnas do have a limitation for full flap slips, as the one I got my private in did. As for the tail stall being an old wives tale...turbulent airflow over an airfoil is the beginnings of a stall, and with a slow enough airspeed, or sudden change in relative wind, it would be very easy for a tail stall to develop. I agree that it can probably be done and has been many times, but the recommendation and / or limitation is based on what can happen, not what will happen every time.