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flight characteristics, or other
qualities affecting airworthiness; or
(2) That is not done according to
accepted practices or cannot be done
by elementary operations.
Figure 5-1. Typical Part 23 weight and balance record.
5– 2
Figure 5-2. A typical CAR 3 airplane weight and balance revision record.
5– 3
Weight and Balance Revision Record
Aircraft manufacturers use different formats for their weight
and balance data, but Figure 5-2 is typical of a weight and
balance revision record. All weight and balance records
should be kept with the other aircraft records. Each revision
record should be identified by the date and the aircraft make,
model, and serial number. The pages should be signed by the
person making the revision and his or her certificate type and
number must be included.
The computations for a weight and balance revision are
included on a weight and balance revision form. The date
these computations were made is shown in the upper righthand
corner of Figure 5-2. When this work is superseded, a
notation must be made on the new weight and balance
revision form, including a statement that these computations
supersede the computations dated “xx/xx/xx.”
Appropriate fore and aft extreme loading conditions should
be investigated and the computations shown.
The weight and balance revision sheet should clearly show
the revised empty weight, empty weight arm and/or moment
index, and the new useful load.
Weight Changes Caused by
a Repair or Alteration
A typical alteration might consist of removing two pieces of
radio equipment from the instrument panel, and a power
supply that was located in the baggage compartment behind
the rear seat. In this example, these two pieces are replaced
with a single lightweight, self-contained radio. At the same
time, an old emergency locator transmitter (ELT) is removed
from its mount near the tail, and a lighter weight unit is
installed. A passenger seat is installed in the baggage
compartment.
Computations Using Weight, Arm, and Moment
The first step in the weight and balance computation is to
make a chart like the one in Figure 5-3, listing all of the items
that are involved.
The new CG of 36.4 inches aft of the datum is determined
by dividing the new moment by the new weight.
Figure 5-3. Weight, arm, and moment changes caused by a typical alteration.
After an Alteration
When determining the new weight and CG after an alteration, take
these steps:
1. Subtract the weights and moments of all items removed.
2. Add the weights and moments of all items added.
3. Determine the new total weight and total moment.
4. Divide the total moment by the total weight and the new CG in
inches from the datum.
Useful load (GAMA): Difference
between takeoff weight, or ramp
weight if applicable, and basic
empty weight.
5– 4
Computations Using Weight and Moment Indexes
If the weight and balance data uses moment indexes rather
than arms and moments, this same alteration can be computed
using a chart like the one shown in Figure 5-4.
Subtract the weight and moment indexes of all the removed
equipment from the empty weight and moment index of the
airplane. Add the weight and moment indexes of all
equipment installed and determine the total weight and the
total moment index. To determine the position of the new CG
in inches aft of the datum, multiply the total moment index
by 100 to get the moment, and divide this by the total weight
to get the new CG.
Empty-Weight CG Range
The fuel tanks, seats, and baggage compartments of some
aircraft are so located that changes in the fuel or occupant
load have a very limited effect on the balance of the aircraft.
Aircraft of such a configuration show an EWCG range in the
TCDS. [Figure 5-5] If the EWCG is located within this range,
it is impossible to legally load the aircraft so that its loaded
CG will fall outside of its allowable range.
Figure 5-4. Weight and moment index changes caused by a typical alteration.
If the TCDS lists an empty-weight CG range, and after the
alteration is completed the EWCG falls within this range,
then there is no need to compute a fore and aft check for
adverse loading. But if the TCDS lists the EWCG range as
“none” (and most of them do), a check must be made to
determine whether or not it is possible by any combination
of legal loading to cause the aircraft CG to move outside
of either its forward or aft limits.
Adverse-Loaded CG Checks
Most modern aircraft have multiple rows of seats and often
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