Figure 2 depicts a plot of control column force as it relates to normal acceleration for a stable airplane. It does not represent the data for any specific airplane, but instead reflects the typical maneuvering stability characteristics of a conventional, unaugmented airplane. The left axis displays elevator column force values that increase in the up direction, while the bottom axis displays normal acceleration (g) values that increase in the right direction. The lower the slope, the less the maneuvering stability. The lower-left corner of the graph shows that a certain amount of force must be applied before the airplane starts to move from 1g flight. Called friction and breakout, this situation results from the need to overcome control column static friction and the feel system centering spring.
The plot makes it obvious that CG location and its effect on positive longitudinal static stability influence maneuvering stability. The maneuvering stability, or stick force per g, is higher at a forward CG, regardless of altitude. In other words, at any altitude, the stick force per g is higher when the CG is forward than when the CG is further aft. This has significant consequences for steep turning maneuvers. For example, to perform a level turn at 60 degrees of bank requires 2g in any airplane. While the plot shows that the airplane is still more stable at a forward CG than an aft CG, it also shows that altitude greatly affects the force required to pull the same 2g at any CG location. This plot graphically demonstrates that maneuvering at high-altitude requires less column force than it does at low altitude.
A column force is required to maneuver longitudinally. For most airplanes, static stability attempts to maintain the airplane in 1g flight at the trimmed angle of attack. The column force generates a pitching moment through the elevators, or stabilizer in some airplanes, that is eventually balanced by the damping moment created by the horizontal tail and the moment due to the change in angle of attack. At this point, if the force is maintained, and there is enough thrust to maintain airspeed, the airplane stabilizes at a new angle of attack, with corresponding changes in lift and g. Since the pitching moments are now balanced, the pilot must hold the column force. If the column force is released, the pitching moment due to the elevator or stabilizer goes to zero, and the moments due to pitch rate and angle of attack drive the pitch rate to zero, and the airplane returns to 1g flight. This description of maneuvering flight points out that maneuvering stability for a given configuration manifests itself to the flight crew as the column force required to maintain a certain level of g. This is commonly called "stick force per g."