DETERMINING EMPTY WEIGHT
A helicopter’s weight and balance records contain essential data, including a complete list of all installed optional equipment. Use these records to determine the weight and balance condition of the empty helicopter.
When a helicopter is delivered from the factory, the basic empty weight, empty weight center of gravity (CG), and useful load are recorded on a weight and balance data sheet included in the FAA-Approved Rotocraft Flight Manual. The basic empty weight can vary even in the same model of helicopter because of differences in installed equipment. If the owner or operator of a helicopter has equipment removed, replaced, or additional equipment installed, these changes must be reflected in the weight and balance records. In addition, major repairs or alterations must be recorded by a certified mechanic. When the revised weight and moment are recorded on a new form, the old record is marked with the word “superseded” and dated with the effective date of the new record. This makes it easy to determine which weight and balance form is the latest version. You must use the latest weight and balance data for computing all loading problems. 

BALANCE
Helicopter performance is not only affected by gross weight, but also by the position of that weight. It is essential to load the aircraft within the allowable center-of-gravity range specified in the rotorcraft flight manual’s weight and balance limitations.
CENTER OF GRAVITY (CG)
The center of gravity is defined as the theoretical point where all of the aircraft’s weight is considered to be concentrated. If a helicopter was suspended by a cable attached to the center-of-gravity point, it would balance like a teeter-totter. For helicopters with a single main rotor, the CG is usually close to the main rotor mast.
Improper balance of a helicopter’s load can result in serious control problems. The allowable range in which the CG may fall is called the “CG range.” The exact CG location and range are specified in the rotorcraft flight manual for each helicopter. In addition to making a helicopter difficult to control, an out-of-balance loading condition also decreases maneuverability since cyclic control is less effective in the direction opposite to the CG location.
Ideally, you should try to perfectly balance a helicopter so that the fuselage remains horizontal in hovering flight, with no cyclic pitch control needed except for wind correction. Since the fuselage acts as a pendulum suspended from the rotor, changing the center of gravity changes the angle at which the aircraft hangs from the rotor. When the center of gravity is directly under the rotor mast, the helicopter hangs horizontal; if the CG is too far forward of the mast, the helicopter hangs with its nose tilted down; if the CG is too far aft of the mast, the nose tilts up. [Figure 7-1]