W
EIGHT AND
B
ALANCE
R
EVISION
:
-
D
ATE
:
12/29/04
P
AGE
:
3
Copyright
2004 Glasair Aviation, LLC Arlington, Washington All rights reserved
Datum
— an imaginary vertical plane from which all moment arms are
measured for weight and balance purposes. The datum is
perpendicular to the waterline plane when the aircraft is in level-
flight attitude.
Empty Weight
— Weight of an airplane including full operating fluids,
unusable fuel, full oil and optional equipment.
Mean Aerodynamic Chord
(MAC)
— a chord is the straight-line
distance from the leading edge to the trailing edge of an airfoil
section. The MAC is the average chord across the entire wingspan.
The MAC of a straight, constant-chord wing like the Sportsman’s is
the same as the actual chord at any point in the span. Aircraft CG
locations are specified as percentages of MAC; these distances are
measured from the leading edge of the wing.
Maximum Gross Weight
— Maximum weight approved for flight
operations.
Moment
— the product of an item’s weight multiplied by its arm.
Payload
— Weight of occupants and baggage.
Station
— a horizontal distance from the reference datum given in
inches.
Tare
— The weight of chocks, blocks, stands, etc., used on the scales
when weighing an airplane.
Useful Load
—
Difference between maximum gross weight and empty
weight.
Waterline
—
A horizontal reference plane running longitudinally
through the fuselage.