Specifications

SECTION VII
MODEL 560 FLIGHT PLANNING AND PERFORMANCE
WEIGHT AND BALANCE
The center-of-gravity (CG) of an airplane can be defined as the point on the longitudinal axis about
which the airplane would balance. The force of weight always acts through the center-of-gravity. The
forces of lift attempt to rotate the airplane about the center-of-gravity.
In flight, the forces of gravity and lift from the wing and horizontal stabilizer must balance about the
center-of-gravity so that stability is achieved.
CENTER-OF-GRAVITY FORCES
As the center-of-gravity changes forward or aft due to airplane loading, the lever or moment arm of the
wing and tail lifting surfaces changes.
The horizontal stabilizer must be capable of providing an equalizing moment to that which is produced
by the remainder of the airplane. Since the amount of lift produced by the horizontal stabilizer is limited, the
range of movement of the center-of-gravity is restricted so that equilibrium can be maintained. Loading
must be calculated as being within the allowable envelope to achieve proper stability and control.
The center-of-gravity of an empty airplane is found by accurate weighing to determine the balance
point. This point is then defined by labeling it in inches aft of a fixed reference line located forward of the
airplane nose. This line is called the Reference Datum Line. Selection of the Reference Datum Line is
arbitrary, but it does provide a standard from which center-of-gravity movement along the longitudinal axis
can be measured.
Figure 7-1. Center-Of-Gravity Forces
I 56OMB-01 Configuration AA 7-3