GRUMMAN AMERICAN
FOR TRAINING USE ONLY – SECTION 1
MODEL GA-7/COUGAR
GENERAL
1-12
Issued: April 10, 1978
WEIGHT AND BALANCE TERMINOLOGY
Arm
Arm is the horizontal distance from the reference datum to the center of gravity (c.g.) of an
item.
Standard Empty
Weight
Weight of a standard airplane including unusable fuel, full operating fluids and full oil.
Basic Empty
Weight
Standard weight plus optional equipment.
Center of
Gravity (c.g.)
Center of Gravity is the point at which an airplane would balance if suspended. Its distance
from the reference datum is found by dividing the total moment by the total weight of the
airplane.
c.g. Arm
Center of Gravity Arm is the arm obtained by adding the airplane’s individual moments and
dividing the sum by the total weight.
c.g. Limits
Center of Gravity Limits are the extreme center of gravity locations within which the airplane
can be operated at a given weight.
Gross Weight
Gross Weight is the maximum weight to which the airplane is certificated.
Jack Point
One of the points on the airplane designed to rest on a jack.
Maximum
Landing Weight
Maximum Landing Weight is the maximum weight approved for the landing touchdown.
Maximum
Takeoff Weight
Maximum Takeoff Weight is the maximum weight approved for the start of the takeoff run.
Moment
Moment is the product of the weight of an item multiplied by its arm. (Moment divided by
the constant 1000 is used in this handbook to simplify balance calculations by reducing the
number of digits.)
Reference
Datum
An imaginary vertical plane from which all horizontal distances are measured for balance
purposes.
Station
Station is a location along the airplane longitudinal axis given in terms of the distance from
the reference datum.
Tare
Tare is the weight of chocks, blocks, stands, etc., used when weighing an airplane, and is
included in the scale readings. Tare is deducted from the scale reading to obtain the actual
(net) airplane weight.
Unusable Fuel
Unusable Fuel is the quantity of fuel that cannot be used in flight.
Usable Fuel
Usable Fuel is the fuel available for flight.
Useful Load
Useful Load is the difference between maximum gross weight and the basic empty weight.
