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
CHAPTER 10. WEIGHT AND BALANCE
SECTION 1 TERMINOLOGY
10-1. GENERAL. The removal or addition
of equipment results in changes to the center of
gravity (c.g.). The empty weight of the air-
craft, and the permissible useful load are af-
fected accordingly. Investigate the effects of
these changes, since the aircraft flight charac-
teristics may be adversely affected. Informa-
tion on which to base the record of weight and
balance changes to the aircraft may be ob-
tained from the pertinent Aircraft Specifica-
tions, Type Certificate Data Sheet (TCDS),
prescribed aircraft operating limitations, air-
craft flight manual, aircraft weight and balance
report, and maintenance manual. Removal of
standard parts with negligible weight or addi-
tion of minor items of equipment such as nuts,
bolts, rivets, washers, and similar standard
parts of negligible weight on fixed-wing air-
craft do not require a weight and balance
check. Rotorcraft are, in general, more critical
with respect to control with changes in the c.g.
position. Refer to the procedures and instruc-
tions in that particular model’s maintenance or
flight manual.
10-2. TERMINOLOGY. The following
terminology is used in the practical application
of weight and balance control.
a. Maximum Weight. The maximum
weight is the maximum authorized weight of
the aircraft and its contents as listed in the
specifications.
b. Empty Weight. The empty weight of
an aircraft includes all operating equipment
that has a fixed location and is actually in-
stalled in the aircraft. It includes the weight of
the airframe, powerplant, required equipment,
optional and special equipment, fixed ballast,
full engine coolant, hydraulic fluid, residual
fuel, and oil. Additional information regarding
fluids that may be contained in the aircraft
systems and must be included in the empty
weight will be indicated in the pertinent Air-
craft Specifications or TCDS.
c. Negligible Weight Change is any
change of one pound or less for aircraft whose
weight empty is less than 5,000 pounds; two
pounds or less for aircraft whose weight empty
is more than 5,000 and 50,000 pounds; and
five pounds or less for aircraft whose weight
empty is more than 50,000 pounds. Negligible
c. g. change is any change of less than 0.05%
MAC for fixed wing aircraft, 0.2 percent of the
maximum allowable c. g. range for rotary wing
aircraft.
d. Useful Load. The useful load is the
empty weight subtracted from the maximum
weight of the aircraft. This load consists of the
pilot, crew (if applicable), maximum oil, fuel,
passengers, and baggage unless otherwise
noted.
e. Weight Check. The weight check con-
sists of checking the sum of the weights of all
items of useful load against the authorized use-
ful load (maximum weight less empty weight)
of the aircraft.
f. Datum. The datum is an imaginary
vertical plane from which all horizontal meas-
urements are taken for balance purposes with
the aircraft in level flight attitude. The datum
is indicated in most Aircraft Specifications or
TCDS. On some of the older aircraft, when
the datum is not indicated, any convenient da-
tum may be selected. Once the datum is se-
lected, all moment arms and the location of the
permissible c.g. range must be taken with ref-
erence to it. Examples of typical locations of
the datum are shown in figure 10-1.
Par 10-1
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