If a rising air current should cause the nose to pitch up, the
airplane will slow down and the downward force on the
tail will decrease. The weight concentrated at the CG will
pull the nose back down. If the nose should drop in flight,
the airspeed will increase and the increased downward tail
load will bring the nose back up to level flight.
As long as the CG is maintained within the allowable
limits for its weight, the airplane will have adequate
longitudinal stability and control. If the CG is too far aft,
it will be too near the center of lift and the airplane will
be unstable, and difficult to recover from a stall. [Figure
1-2] If the unstable airplane should ever enter a spin, the
spin could become flat and recovery would be difficult or
impossible