Textron 172R180HP, Pilot Operating Handbook

Page: 27 / 396

CESSNA
MODEL 172A (180 HP)
SECTION 1
GENERAL
WEIGHT AND BALANCE TERMINOLOGY
Reference
----.._ Datum
Station
Arm
Moment
� Center of
Gravity
(C.G.)
� C.G.
Arm
C.G.
\ Limits
Standard
Empty
Weight
Reference Datum is an imaginary vertical plane from
which all horizontal distances are measured for
balance purposes.
Station is a location along the airplane fuselage given
in terms of the distance from the reference datum.
Arm is the horizontal distance from the reference
datum to the center of gravity (C.G.) of an item.
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.)
Center of Gravity is the point at which an airplane, or
equipment, would balance if suspended. Its distance
from the reference datum is found by dividing the
total moment by the total weight of the airplane.
Center of Gravity Arm is the arm obtained by
adding the airplane's individual moments and dividing
the sum by the total weight.
Center of Gravity Limits are the ex1reme center of
gravity locations within which the airplane must be
operated at a given weight.
Standard Empty Weight is the weight of a standard
airplane, including unusable fuel, full operating fluids
and full engine oil.
Basic Empty Basic Empty Weight is the standard empty weight
Weight plus the weight of optional equipment.
Useful Load Useful Load is the difference be
t
ween ramp weight
and the basic empty weight.
MAC
Nov 24/99
MAC (Mean Aerodynamic Chord) is the chord of an
imaginary rectangular airfoil having the same pitching
moments throughout the flight range as that of the
actual wing.
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