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these problems. This chapter gives a comparison of the
methods of determining the CG of an airplane while it is being
weighed. First, determine the CG using a simple electronic
calculator, then solve the same problem using an E6-B flight
computer. Then, finally, solve it using a dedicated electronic
flight computer.
Later in this chapter are examples of typical weight and
balance problems (solved with an electronic calculator) of the
kind that pilots and AMTs will encounter throughout their
aviation endeavors.
Using an Electronic Calculator to Solve
Weight and Balance Problems
Determining the CG of an airplane in inches from the mainwheel
weighing points can be done with any simple electronic
calculator that has addition (+), subtraction (–),
multiplication (?), and division (÷) functions. Scientific
calculators with such additional functions as memory (M),
parentheses (( )), plus or minus (+/–), exponential (yx),
reciprocal ( 1/?), and percentage (%) functions allow you to
solve more complex problems or to solve simple problems
using fewer steps.
The chart in Figure 8-1 includes data on the airplane used in
this example problem.
Figure 8-1. Weight and balance data of a typical nose
wheel airplane.
Positive/Negative Key
The (+/–) key changes the number just keyed in from a positive to a
negative number.
According to Figure 8-1, the weight of the nose wheel (F) is
340 pounds, the distance between main wheels and nose
wheel (L) is –78 inches, and the total weight (W) of the
airplane is 2,006 pounds. (L is negative because the nose
wheel is ahead of the main wheels.)
To determine the CG, use this formula:
Key the data into the calculator as shown in red, and when
the equal (=) key is pressed, the answer (shown here in blue)
will appear.
(340)(?)(78)(+/–)(÷)(2006)(=) –13.2
The arm of the nose wheel is negative, so the CG is –13.2, or
13.2 inches ahead of the main-wheel weighing points.
Using an E6-B Flight Computer to Solve
Weight and Balance Problems
The E6-B uses a special kind of slide rule. Instead of its scales
going from 1 to 10, as on a normal slide rule, both scales go
from 10 to 100. The E6-B cannot be used for addition or
subtraction, but it is useful for making calculations involving
multiplication and division. Its accuracy is limited, but it is
sufficiently accurate for most weight and balance problems.
8 –2
The same problem that was just solved with the electronic
calculator can be solved on an E6-B by following these steps:
Then, divide 26,500 by 2,006: [Figure 8-2b]
• On the inner scale, place 20, which represents 2,006,
opposite 26.5 on the outer scale. (26.5 represents 26,500)
(Step 3).
• Opposite the index, 10, on the inner scale, read 13.2 on
the outer scale (Step 4).
• Determine the value of 13.2 by estimating: 20,000 ÷ 2000
= 10, so 26,500 ÷ 2,006 = 13.2.
• The arm (–78) is negative, so the CG is also negative.
The CG is –13.2 inches, or 13.2 inches ahead of the datum.
Figure 8-2a. E6-B computer set up to multiply 340 by 78. Figure 8-2b. E6-B computer set up to divide 26,500 by 2,006.
First, multiply 340 by 78 (disregard the – sign): [Figure 8-2a]
• Place 10 on the inner scale (this is the index) opposite 34
on the outer scale (this represents 340) (Step 1).
• Opposite 78 on the inner scale, read 26.5 on the outer scale
(Step 2).
• Determine the value of these digits by estimating:
300 ? 80 = 24,000, so 340 ? 78 = 26,500.
8– 3
Using a Dedicated Electronic
Flight Computer to Solve Weight
and Balance Problems
Dedicated electronic flight computers like the one in Figure
8-3 are programmed to solve many flight problems, such as
wind correction, heading and ground speed, endurance, and
true airspeed (TAS), as well as weight and balance problems.
Typical Weight and Balance Problems
A hand-held electronic calculator like the one in Figure
8-4 is a valuable tool for solving weight and balance problems.
It can be used for a variety of problems and has a high
degree of accuracy. The examples given here are solved with
a calculator using only the (? ), (÷), (+), (–), and (+/–)
functions. If other functions are available on your calculator,
some of the steps may be simplified.
Figure 8-3. Dedicated electronic flight computers are
programmed to solve weight and balance problems as well as
flight problems.
The problem just solved with an electronic calculator and
　
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