Equipment list. A list of items approved by the FAA for installation in a particular aircraft. The list includes the name, part number, weight, and arm of the component. Installation or removal of an item in the equipment list is considered to be a minor alteration.

Fleet weight. An average weight accepted by the FAA for aircraft of identical make and model that have the same equipment installed. When a fleet weight control program is in effect, the fleet weight of the aircraft can be used rather than requiring every individual aircraft to be weighed.

Fuel jettison system. A fuel subsystem that allows the flight crew to dump fuel in an emergency to lower the weight of an aircraft to the maximum landing weight if a return to landing is required before sufficient fuel is burned off. This system must allow enough fuel to be jettisoned that the aircraft can still meet the climb requirements specified in 14 CFR part 25.

Fulcrum. The point about which a lever balances.

Index point. A location specified by the aircraft manufacturer from which arms used in weight and balance computations are measured. Arms measured from the index point are called index arms.

Interpolate. Determine a value in a range between two known values.

Landing weight. The takeoff weight of an aircraft minus the fuel burned and/or dumped en route.

Large aircraft (14 CFR part 1). An aircraft of more than 12,500 pounds maximum certificated takeoff weight.

Lateral balance. The balance around the roll, or longitudinal, axis.

Lateral offset moment. The moment, in pound inches, of a force that tends to rotate a helicopter about its longitudinal axis. The lateral offset moment is the product of the weight of the object and its distance from butt line zero. Lateral offset moments that tend to rotate the aircraft clockwise are positive, and those that tend to rotate it counterclockwise are negative.

LEMAC. Leading edge of the mean aerodynamic chord. A reference point for measurements, and specified in inches from the datum to allow computations to relate percent MAC to the datum.

Load cell. A component in an electronic weighing system that is placed between the jack and the jack pad on the aircraft. The load cell contains strain gauges whose resistance changes with the weight on the cell.

Load factor. The ratio of the maximum load an aircraft can sustain to the total weight of the aircraft. Normal category aircraft must have a load factor of at least 3.8; utility category aircraft, 4.4; and acrobatic category aircraft, 6.0.

Loading graph. A graph of load weight and load moment indexes. Diagonal lines for each item relate the weight to the moment index, eliminating the need for calculations.

Loading schedule. A method of calculating and documenting aircraft weight and balance prior to taxiing to ensure the aircraft will remain within all required weight and balance limitations throughout the flight.

Longitudinal axis. An imaginary line through an aircraft from nose to tail, passing through its center of gravity.

Longitudinal balance. The balance around the pitch, or lateral, axis.

MAC. Mean aerodynamic chord.

Major alteration. An alteration not listed in the aircraft, aircraft engine, or propeller specifications (1) that might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or (2) that is not done according to accepted practices or cannot be done by elementary operations.

Maximum landing weight. (GAMA) The maximum weight approved for the landing touchdown.