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.
Same thing when dropping the gear, but for different reasons: Instead of moving the center of lift
, you've introduced drag, which slows the airplane further.
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. This has the happy effect of forcing the nose down when the wing stalls.
You'll recall from your private pilot written that in most airplanes, the wing's center of lift is aft of the center gravity.
Also, when flaps are extended, the main-wing center of lift moves further aft, increasing the nose-down moment and requiring the tail to provide more downforce.
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.
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.