3,200
3,100
3,000
2,950
2,900
2,800
2,700
2,600
2,500
2,400
2,300
2,200
2,100
2,000
1,900
1,800
1,450
1,400
1,350
1,300
1,250
1,200
1,150
1,100
1,050
1,000
950
900
850
+32 +34 +36 +38 +40 +42 +44 +46
850 900 950 1,000 1,050 1,100 1,150 1,200
Aircraft CG location
Inches aft of datum (Sta. 0.0)
Loaded aircraft weight (lb)
Loaded aircraft weight (kg)
Aircraft CG location
Millimeters aft of datum (Sta. 0.0)
CG limits
Takeoff and landing
Takeoff only
If takeoff weight is more than
landing weight of 2,950 pounds,
allow flight time for fuel burn-off
to 2,950 pounds before landing
Figure 5-5. CG limits chart from a typical POH.
Loading Graph Method
The charts and graphs found in the POH/AFM can help
simplify and expedite the preflight weight and balance
computation process. Some use a loading graph and moment
indexes rather than the arms and moments. These charts
eliminate the need for calculating moments and make
computations quicker and easier. [Figure 5-6]
Moment Indexes
Moments determined by multiplying the weight of each
component by its arm result in large numbers that are awkward
to calculate and can become a source of mathematical error.
To eliminate these large numbers, moment indexes are
sometimes 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
to avoid mathematical calculations. The CG envelope uses
moment indexes rather than arms and moments.
The CG limits envelope is the 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
Figure 5-6 is a typical loading graph taken from the POH
of a modern four-place airplane. It is 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
mathematical calculations.
Compute Weight and Balance Using the Loading
Graph
To compute the weight and balance using the loading graph
in Figure 5-6, make a loading schedule chart like the one
in Figure 5-7. In Figure 5-6, 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 divided by 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
second row passengers or cargo. This is 12.9; record it in the
loading schedule chart.
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
loading schedule chart. The maximum fuel is marked on
the diagonal line for fuel in terms of gallons or liters. The
maximum is 88 gallons of usable fuel. The total capacity is 92
gallons, but in our example, 4 gallons are unusable and have
already been included in the empty weight of the aircraft. The
weight of 88 gallons of fuel is 528 pounds and its moment
index is 24.6. The 100 pounds of baggage in area A has a
moment index of 9.7 and the 50 pounds in area B has an
index of 5.8. Enter all of these weights and moment indexes
in the loading schedule chart and add all of the weights and
moment indexes to determine the totals.
Transfer totals to the CG moment envelope in Figure 5-8.
The CG moment envelope is 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. The loading
schedule from the example in Figure 5-7 shows that the total
weight of the loaded aircraft is 3,027 pounds, and the loaded
airplane moment divided by 1,000 is 131.8.
550
500
450
400
350
300
250
200
150
100
50
0
250
225
200
175
150
125
100
75
50
25
00 5 10 15 20 25 30 35
0 50 100 150 200 250 300 350 400
Load moment/1,000 (lb-in)
Load weight (lb)
Load weight (kg)
Load moment/1,000 (kg-mm)
Note: Line representing adjustable seats shows pilot and front seat passenger CG on adjustable seat positioned for an
average occupant. Refer to the Loading Arrangements diagram for forward and aft limits of occupant CG range.
80 (302.8)
70 (265.0)
65 gal reduced
Loading graph
60 (227.1)
50 (189.3)
40 (151.4)
30 (113.6)
20 (75.7)
10 (37.9)
88 gal max (333.1liters)
Baggage (Area “B”) (60 lb max)
Baggage (Area “A”) (100 lb max)
Fuel (6 lb/gal)
Pilot & front passenger
2nd row passengers or cargo
Figure 5-6. Typical loading graph.
Figure 5-7. Loading schedule chart.
Item Weight Moment/1,000
67.7Airplane (BEW)
Front seats
Rear seats
Fuel
Baggage A
Baggage B
Total
1,874
300
175
528
100
50
3,027
11.1
12.9
24.6
9.7
5.8
131.8
3,200
3,100
3,000
2,950
2,900
2,800
2,700
2,600
2,500
2,400
2,300
2,200
2,100
2,000
1,900
1,800
1,450
1,400
1,350
1,300
1,250
1,200
1,150
1,100
1,050
1,000
950
900
850
55 65 75 85 95 105 115 125 135 145
650 850 1,050 1,250 1,450 1,650
750 950 1,150 1,350 1,550
Loaded aircraft moment/1,000 (lb-in)
Loaded aircraft weight (lb)
Loaded aircraft weight (kg)
Loaded aircraft moment/1,000 (kg-mm)
Center of gravity
Moment envelope
Takeoff and landing
Takeoff only
If takeoff weight is more than
landing weight of 2,950 pounds,
allow flight time for fuel burn-off
to 2,950 pounds before landing.
Figure 5-8. CG moment envelope.
Referring to Figure 5-8, draw a line vertically upward from
131.8 on the horizontal index at the bottom of the chart and
a horizontal line from 3,027 pounds in the left-vertical index.
These lines intersect within the dashed area, which shows
that the aircraft is loaded properly for takeoff, but it is too
heavy for landing (similar to the previous example). Because
of this, if the aircraft had to return for landing immediately
after takeoff, it would need to fly long enough to burn 77
pounds (slightly less than 13 gallons) of fuel to reduce its
weight for landing.