Every aircraft type certificated by the FAA, before leaving the factory for delivery to its new owner, receives a weight and balance report as part of its required aircraft records. The weight and balance report identifies the empty weight of the aircraft and the location at which the aircraft balances, known as the center of gravity. If the manufacturer chooses to do so, it can weigh every aircraft it produces and issue the weight and balance report based on that weighing. As an alternative, the manufacturer is permitted to weigh an agreed upon percentage of a particular model of aircraft produced, perhaps 10 to 20 percent, and apply the average to all the aircraft.
After the aircraft leaves the factory and is delivered to its owner, the need or requirement for placing the aircraft on scales and reweighing it varies depending on the type of aircraft and how it is used. For a small general aviation airplane being used privately, such as a Cessna 172, there is no FAA requirement that it be periodically reweighed. There is, however, an FAA requirement that the airplane always have a current and accurate weight and balance report. If the weight and balance report for an aircraft is lost, the aircraft must be weighed and a new report must be created. If the airplane has new equipment installed, such as a radio or a global positioning system, a new eight and balance report must be created. If the installer of the equipment wants to place the airplane on scales and weigh it after the installation, that is a perfectly acceptable way of creating the new report. If the installer knows the exact weight and location of the new equipment, it is also possible to create a new report by doing a series of mathematical calculations.
Over a period of time, almost all aircraft have a tendency to gain weight. Examples of how this can happen include an airplane being repainted without the old paint being removed, and the accumulation of dirt, grease, and oil in parts of the aircraft that are not easily accessible for cleaning. When new equipment is installed, and its weight and location are mathematically accounted for, some miscellaneous weight might be overlooked, such as wire and hardware. For this reason, even if the FAA does not require it, it is a good practice to periodically place an aircraft on scales and confirm its actual empty weight and empty weight center of gravity.
Some aircraft are required to be weighed and have their center of gravity calculated on a periodic basis, typically every 3 years. Examples of aircraft that fall under this requirement are:
- Air taxi and charter twin-engine airplanes operating under Title 14 of the Code of Federal Regulations (14 CFR) part 135, section (§)135.185(a).
- Airplanes with a seating capacity of 20 or more passengers or a maximum payload of 6,000 pounds or more, as identified in 14 CFR part 125, §125.91(b). This paragraph applies to most airplanes operated by the airlines, both main line and regional, and to many of the privately operated business jets.