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flight, use the CG limits envelope in Figure 4-5 (which is
typical of those found in the POH/AFM). Draw a line
vertically upward from the CG of 43.54 inches, and one
horizontally to the right from the loaded weight of 3,027
pounds. These lines cross inside the envelope, which shows
the airplane is properly loaded for takeoff, but 77 pounds
overweight for landing.
Loading Graph Method
Everything possible is done to make flying safe, and one
expedient method is the use of charts and graphs from the
POH/AFM to simplify and speed up the preflight weight
and balance computations. Some use a loading graph and
moment indexes rather than the arms and moments. These
charts eliminate the need for calculating the moments and
thus make computations quicker and easier. [Figure 4-5]
When planning the flight, fill in the blanks in the worksheet
with the specific data for the flight. [Figure 4-4]
Pilot ............................................................................ 120 lbs
Front seat passenger .................................................. 180 lbs
Rear seat passengers ................................................. 175 lbs
Fuel 88 gal ................................................................. 528 lbs
Baggage A.................................................................. 100 lbs
Baggage B.................................................................... 50 lbs
Determine the moment of each item by multiplying its weight
by its arm. Then determine the total weight and the sum of
the moments. Divide the total moment by the total weight to
determine the CG in inches from the datum. The total weight
is 3,027 pounds and the CG is 43.54 inches aft of the datum.
Figure 4-4. Completed weight and balance worksheet.
CG limits envelope: An enclosed
area on a graph of the airplane
loaded weight and the CG location.
If lines drawn from the weight and
CG cross within this envelope, the
airplane is properly loaded.
Loading Graph Method
Loading graphs simplify weight and balance computations because
they eliminate the need for multiplication when computing a loaded CG.
Moment index: A moment that has
been divided by a reduction factor to
obtain a smaller number to make
computations easier and reduce the
likelihood of mathematical errors.
Loading graph: A graph of load
weight and load moment indexes.
Diagonal lines for each item relate
the weight to the moment index
without having to use mathematics.
4– 3
Figure 4-5. Center of gravity limits chart from a typical POH.
Moment Indexes
Moments determined by multiplying the weight of each
component by its arm result in large numbers that are
awkward to handle and can become a source of mathematical
error. To eliminate these large numbers, moment indexes are
used. The moment is divided by a reduction factor such as
100 or 1,000 to get the moment index. The loading graph
provides the moment index for each component, so you can
avoid mathematical calculation. The CG envelope uses
moment indexes rather than arms and moments.
Loading Graph
Figure 4-6 (see Page 4-4) is a typical loading graph taken from
the POH of a modern four-place GA airplane. To compute
the weight and balance, using the loading graph in Figure 4-
6, make a loading schedule chart like the one in Figure 4-7.
In Figure 4-6, follow the horizontal line for 300 pounds load
weight to the right until it intersects the diagonal line for pilot
and front passenger. From this point, drop a line vertically to
the load moment index along the bottom to determine the load
moment for the front seat occupants. This is 11.1 lb-in/1,000.
Record it in the loading schedule chart.
Determine the load moment for the 175 pounds of rear seat
occupants along the diagonal for 2nd row passengers or cargo.
This is 12.9; record it in the loading schedule chart.
Reduction factor: The number,
usually 100 or 1,000, that is used to
divide the moment to get the
moment index.
Loading schedule: A chart filled in
by the pilot during preflight planning
that lists the weight and moment
indexes of all occupants, fuel, and
baggage.
Figure 4-7. Loading schedule chart.
4–4
Figure 4-6. Loading graph.
4– 5
CG moment envelope: An enclosed
area on a graph of the airplane
loaded weight and loaded moment.
If lines drawn from the weight and
loaded moment cross within this
envelope, the airplane is properly
loaded.
Determine the load moment for the fuel and the baggage in
areas A and B in the same way and enter them all in the
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