FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 10. Weight and Balance | 1. Terminology | 10-2. Terminology
9/27/01
AC 43.13-1B CHG 1
FIGURE 10-2. Illustration of arm (or moment arm).
h. Moment. The moment is the product
of a weight multiplied by its arm. The moment
of an item about the datum is obtained by
multiplying the weight of the item by its hori-
zontal distance from the datum. A typical
moment calculation is given in figure 10-3.
i. Center of Gravity. The c.g. is a point
about which the nose-heavy and tail-heavy
moments are exactly equal in magnitude. If
the aircraft is suspended from the c.g., it will
not have a tendency to pitch in either direction
(nose up or down). The weight of the aircraft
(or any object) may be assumed to be concen-
trated at its c.g. (See figure 10-3.)
j. Empty Weight Center of Gravity.
The empty weight c.g. is the c.g. of an aircraft
in its empty weight condition, and is an essen-
tial part of the weight and balance record.
Formulas for determining the c.g. for tail and
nosewheel type aircraft are given in fig-
ure 10-4. Typical examples of computing the
empty weight and empty weight c.g. for air-
craft are shown in figures 10-5 and 10-6.
k. Empty Weight Center of Gravity
Range. The empty weight c.g. range is deter-
mined so that the empty weight c.g. limits will
not be exceeded under standard specifications
loading arrangements. Calculations as out-
lined in paragraph 10-16 should be completed
when it is possible to load an aircraft in a
manner not covered in the Aircraft Specifica-
tions or TCDS (extra tanks, extra seats, etc.).
The empty weight c.g. range, when applicable,
is listed in the Aircraft Specifications or
TCDS. Calculation of empty weight c.g. is
shown in figures 10-5 and 10-6.
l. Operating Center of Gravity Range.
The operating c.g. range is the distance be-
tween the forward and rearward c.g. limits in-
dicated in the pertinent Aircraft Specifications
or TCDS. These limits are determined for the
most forward and most rearward loaded c.g.
positions at which the aircraft meets the re-
quirements of Title 14 of the Code of Federal
Regulation (14 CFR). The limits are indicated
in the specifications in either percent of mean
aerodynamic chord (MAC) or inches from the
Par 10-2
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