It is vital to comply with weight and balance limits established for helicopters. Operating above the maximum weight limitation compromises the structural integrity of the helicopter and adversely affects performance. Balance is also critical because on some fully loaded helicopters, center of gravity deviations as small as three inches can dramatically change a helicopter’s handling characteristics. Taking off in a helicopter that is not within the weight and balance limitations is unsafe. 
 

WEIGHT
When determining if your helicopter is within the weight limits, you must consider the weight of the basic helicopter, crew, passengers, cargo, and fuel. Although the effective weight (load factor) varies during maneuvering flight, this chapter primarily considers the weight of the loaded helicopter while at rest.
The following terms are used when computing a helicopter’s weight.
BASIC EMPTY WEIGHT—The starting point for weight computations is the basic empty weight, which is the weight of the standard helicopter, optional equipment, unusable fuel, and full operating fluids including full engine oil. Some helicopters might use the term “licensed empty weight,” which is nearly the same as basic empty weight, except that it does not include full engine oil, just undrainable oil. If you fly a helicopter that lists a licensed empty weight, be sure to add the weight of the oil to your computations.
USEFUL LOAD—The difference between the gross weight and the basic empty weight is referred to as useful load. It includes the flight crew, usable fuel, drainable oil, if applicable, and payload.
PAYLOAD—The weight of the passengers, cargo, and baggage.
GROSS WEIGHT—The sum of the basic empty weight and useful load.
MAXIMUM GROSS WEIGHT— The maximum weight of the helicopter. Most helicopters have an internal maximum gross weight, which refers to the weight within the helicopter structure and an external maximum gross weight, which refers to the weight of the helicopter with an external load.
WEIGHT LIMITATIONS
Weight limitations are necessary to guarantee the structural integrity of the helicopter, as well as enabling you to predict helicopter performance accurately. Although aircraft manufacturers build in safety factors, you should never intentionally exceed the load limits for which a helicopter is certificated. Operating above a maximum weight could result in structural deformation or failure during flight if you encounter excessive load factors, strong wind gusts, or turbulence. Operating below a minimum weight could adversely affect the handling characteristics of the helicopter. During single-pilot operations in some helicopters, you may have to use a large amount of forward cyclic in order to maintain a hover. By adding ballast to the helicopter, the cyclic will be closer to the center, which gives you a greater range of control motion in every direction. Additional weight also improves autorotational characteristics since the autorotational descent can be established sooner. In addition, operating below minimum weight could prevent you from achieving the desirable rotor r.p.m. during autorotations.