When full flaps are added, the combination of increased downwash and the aft movement of the center of lift
further increase the angle of attack of the elevator.
What would happen if an airframe was designed so that its wing's center of lift (CL) and its center of gravity (CG) were in precisely the same location?
Instead, designers evolved a relatively simple fix: They placed the center of gravity forward of the center of lift.
The horizontal stabilizer--stabilator in the case of many Piper designs--provides required stability in the lateral axis, balancing the loaded airplane's center of gravity against the wing's center of lift.
Many airplanes are designed with the wing's center of lift aft of the center of gravity (CG).
You'll recall from your private pilot written that in most airplanes, the wing's center of lift
is aft of the center gravity.
It comes from the ingenious disbursement of an airplane's weight and the lift provided by its wings, where the center of gravity lies in front of the center of lift
, and the "tail down" force we learned about in ground school counteracts that moment.
The critical angle of attack is reached when an increasingly unfavorable pressure gradient from higher pressure at the trailing edge to the lowest pressure at the center of lift
above the wing collides with the relative wind from the front of the wing and has nowhere to go but away from the airfoil, which it does in churning torrents.
Please, if you are going to fly aircraft with the CG behind the center of lift
as shown on page 10, name me as a beneficiary in your life insurance.