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Originally Posted by meritflyer Yep. The aircraft pivots around the CG not the CP. The CP is a balancing force or fulcrum for the airplane. |
This is exactly right. The reason you may have trouble picturing this is because you are thinking about a see-saw as the example of your lever. Think instead about a wheelbarrow. In a wheelbarrow the fulcrum (pivot point) is at one end and there are two forces in opposite directions on one side of the pivot point. In a wheelbarrow, the pivot point is the wheel, and the load (whatever you are hauling) provides a down force that is balanced by your hands providing the up force.
In an airplane, the same thing happens. The Cg is the pivot point, and aft of it is the Cp, providing an up force. Even further aft of that is the tail, providing a down force to balance the Cp. If you moved the Cg aft until it was aft of the Cp, the Cp's up force would tend to raise the nose and the tail's nose down force would tend to raise the nose also. The aircraft would be virtually uncontrollable.
In a canard aircraft, the see-saw analogy works better. Both forces are in the same direction (UP) with the Cg (pivot point) in between.