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temperature deviation vertical line. This line crosses the
“Fuel Flow-100 Pounds per Hour per Engine” index
at 11.35. This indicates that each of the four engines
burns 1,135 (100 x 11.35) pounds of fuel per hour. The
total fuel burn for the 4-hour cruise is:
8. The airplane gross weight was 140,000 pounds at
takeoff, and since 18,160 pounds of fuel was burned
during cruise and 1,350 pounds was burned during the
approach and landing phase, the landing weight is:
140,000 - (18,160 + 1,350) = 120,490 pounds
Figure 7-5. Standard atmosphere table.
Determining the Minutes of Fuel Dump Time
Most large aircraft are approved for a greater weight for
takeoff than for landing, and to make it possible for them
to return to landing soon after takeoff, a fuel jettison
system is sometimes installed.
It is important in an emergency situation that the flightcrew
be able to dump enough fuel to lower the weight to
its allowed landing weight. This is done by timing the
dumping process.
7–11
Figure 7-6. Loading data for passenger configuration.
In this example, the aircraft has three engines operating
and these specifications apply:
Cruise weight...........................................171,000 lbs
Maximum landing weight........................142,500 lbs
Time from start of dump to landing..........19 minutes
Average fuel flow during
dumping and descent......................... 3,170 lb/hr/eng
Fuel dump rate....................2,300 pounds per minute
Follow these steps to determine the number of minutes of
fuel dump time:
1. Determine the amount the weight of the aircraft must
be reduced to reach the maximum allowable landing
weight:
171,000 lbs cruise weight
- 142,500 lbs maximum landing weight
28,500 lbs required reduction
2. Determine the amount of fuel burned from the
beginning of the dump to touchdown:
For all three engines, this is 52.83° 3 = 158.5 lbs/min.
The three engines will burn 158.5° 19 = 3,011.5 pounds of
fuel between the beginning of dumping and touchdown.
3. Determine the amount of fuel needed to dump
by subtracting the amount of fuel burned during the
dumping from the required weight reduction:
4. Determine the time needed to dump this amount of fuel
by dividing the number of pounds of fuel to dump by
the dump rate:
Weight and Balance of Commuter Category
Airplanes
The Beech 1900 is a typical commuter category airplane
that can be configured to carry passengers or cargo. Figure
7-6 shows the loading data of this type of airplane in the
passenger configuration, and Figure 7-14 on Page 7-16
shows the cargo configuration. Jet fuel weight is affected
by temperature, the colder the fuel, the more dense
and therefore the more pounds of fuel per gallon. [Text
continued on page 7-15.]
7–12
Figure 7-7. Determining the loaded weight and CG of a Beech 1900 in the passenger configuration.
Figure 7-8. Weights and moments - occupants.
Figure 7-9. Weights and moments - baggage.
7–13
Figure 7-10. Density variation of aviation fuel.
7–14
Figure 7-12. Weight and balance diagram.
Figure 7-11. Weights and moments -usable fuel.
7–15
Figure 7-13. Change in CG caused by shifting passenger seats.
Determining the Loaded Weight and CG
As this airplane is prepared for flight, a manifest like the
one in Figure 7-7 is prepared.
1. The crew weight and the weight of each passenger is
entered into the manifest, and the moment/100 for each
occupant is determined by multiplying the weight by
the arm and dividing by 100. This data is available in
the AFM and is shown in the Weight and Moments-
Occupants table in Figure 7-8 on Page 7-12.
2. The weight of the baggage in each compartment
that is used is entered with its moment/100. This is
determined in the Weights and Moments- Baggage
table in Figure 7-9 on Page 7-12.
3. Determine the weight of the fuel. Jet A fuel has a
nominal specific gravity at +15°C of 0.812 and weighs
6.8 pounds per gallon, but at +25°C, according to the
chart in Figure 7-10 on Page 7-13, it weighs 6.75 lbs/
gal.
Using Figure 7-11 on Page 7-14, determine the weights
and moment/100 for 390 gallons of Jet A fuel by
interpolating between those for 6.7 lbs/gal and 6.8 lbs/
gal. The 390 gallons of fuel at this temperature weighs
2,633 pounds, and its moment index is 7,866 lb-in/100.
4. Add all of the weights and all of the moment indexes.
Divide the total moment index by the total weight, and
multiply this by the reduction factor of 100. The total
　
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