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loading schedule chart. The maximum fuel is marked on the
diagonal line for fuel in terms of gallons and liters. The
maximum is 88 gallons of usable fuel. The total capacity is
92 gallons, but 4 gallons are unusable and have already been
included in the empty weight of the aircraft. The weight of
88 gallons of gasoline 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 these values to the
CG moment envelope in Figure 4-8.
The loading schedule shows that the total weight of the loaded
aircraft is 3,027 pounds, and the loaded airplane moment/
1,000 is 131.8.
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-hand 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.
If the aircraft had to return for landing, it would have to fly
long enough to burn off 77 pounds (slightly less than 13
gallons) of fuel to reduce its weight to the amount allowed
for landing.
Figure 4-8. CG moment envelope.
Usable fuel (GAMA): Fuel available
for flight planning.
4–6
Multiengine Airplane Weight
and Balance Computations
Weight and balance computations for general aviation
multiengine airplanes are similar to those discussed for singleengine
airplanes. Computations for large airline and cargo
airplanes are discussed in Chapter 6. See Figure 4-9 for an
example of weight and balance data for a typical twin-engine
general aviation airplane.
The airplane in this example was weighed to determine its
basic empty weight and EWCG. The weighing conditions and
results are:
Fuel drained —
Oil full —
Right wheel scales — 1,084 lbs, tare 8 lbs
Left wheel scales — 1,148 lbs, tare 8 lbs
Nose wheel scales — 1,202 lbs, tare 14 lbs
Determining the Loaded CG
Beginning with the basic empty weight and EWCG and using a
chart such as the one in Figure 4-11, the loaded weight and CG
of the aircraft can be determined. [Figure 4-10]
The aircraft is loaded as shown here:
Fuel (140 gal) ............................................................ 840 lbs
Front seat ................................................................... 320 lbs
Row 2 seats ................................................................ 310 lbs
Fwd. baggage ............................................................. 100 lbs
Aft baggage ................................................................. 90 lbs
Figure 4-9. Typical weight and balance data for a twin-engine
general aviation airplane.
Figure 4-10. Twin-engine airplane weight and balance diagram.
4– 7
The Chart Method Using Weight, Arm,
and Moments
Make a chart showing the weights, arms, and moments of
the airplane and its load.
Figure 4-11. Determining the loaded center of gravity of the
airplane in Figure 4-10.
Determining the CG in Percent of MAC
Refer again to Figures 4-10 and 4-11.
The loaded CG is 42.47 inches aft of the datum.
The MAC is 61.6 inches long.
The LEMAC is located at station 20.1.
The CG is 42.47 – 20.1 = 22.37 inches aft of LEMAC.
Use this formula:
The loaded weight for this flight is 5,064 pounds, and the
CG is located at 42.47 inches aft of the datum.
To determine that the weight and CG are within the allowable
range, refer to the CG range chart of Figure 4-12. Draw a line
vertically upward from 42.47 inches from the datum and one
horizontally from 5,064 pounds. These lines cross inside the
envelope, showing that the airplane is properly loaded.
Figure 4-12. Center of gravity range chart.
The loaded CG is located at 36.3% of the mean aerodynamic
chord.
The Chart Method Using Weight
and Moment Indexes
As mentioned in the previous chapter, anything that can be
done to make careful preflight planning easier makes flying
safer. Many manufacturers furnish charts in the POH/AFM
that use weight and moment indexes rather than weight, arm,
and moments. They further help reduce errors by including
tables of moment indexes for the various weights.
Consider the loading for this particular flight:
Cruise fuel flow = 16 gallons per hour
Estimated time en route = 2 hours 10 minutes
Reserve fuel = 45 minutes = 12 gallons
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