Weight Calculation #

Weight #

Standard Terms:

Standard Empty Weight: Airframe and engine + standard equipment including fuel and oil
Optional Weight: Weight of all optional equipment (new GPS, fire extinguisher, etc.)
Basic Empty Weight / Basic Airplane: Weight of the airplane with all optional equipment included (GPS, transponders, etc.)
Useful Load: Difference between gross take-off weight and basic empty weight
Payload: Load available as passengers, baggage, freight, etc.
Operational Weight: Basic empty weight plus weight of pilot

Other:

Usable fuel
Unuseable fuel: Fuel remaining in the tanks after a runout test has been completed
Operational gross weight: Weight of airplane loaded for take off
Passenger weight: Weight of the passengers
Fuel and oil: Calculate based on oil / fuel weight
Float Buoyancy: For amphibious planes

Maxes:

Max gross weight: Max permissable weight of the airplane
Max take off weight: Max weight for take off run
Max ramp weight: For maneuvering
Max landing weight: Max weight for landing (only really applicable for airliners)
Max weight zero fuel: Max weight with zero fuel

C.G. forward and aft limits are established by the aircraft designers and are located in the POH.

Definitions:

Balance datum line is suiteable line selected from which horizontal distances are measured for balance purposes
Moment arm is the horizontal distance in inches from the balance datum line to the C.G.
Moment is the “twisting” force of the torque on the plane
Moment index is the balance moment of any item or of the total airplane divided by a constant such as 100,1000 or 10,000 to simplify calculations.
Balance movement is determined by multiplying the weight of the airplane by the moment arm of the airplane. Expressed in inch pounds. The balance moment of any item is the weight of that item multiplied by its distance from the balance datum line

Notes:

If loads are forward of the balance datum line, their moment arms are usually negative (-). Loads behind the balance datum line are considered positive (+).
C.G. found by dividing total balance moment in inch lb’s by total weight in lb, express inches forward - or aft + of the balance datum line.
C.G. usually express in inches from the balance datum line.
Sometimes expressed as the mean aerodynamic chord (MAC) from 25% to 35%.

NOTE: Look in the POH for max weight values as well as COG / moment arm values.

The center of gravity is 40.9" (96,212.43 in-lb / 2,352.6lb) which is within CG limits
The total weight of plane is 2,352.6lb which is within limits

You calculate the moment arm by taking the weight and dividing it by the Balance Arm:

42.52" moment arm (110,270 inch-lb / 2,593 lbs)