179.0
65.0
65.0
104
148
120
109.9
198,050
2,148
12,350
11,050
53,040
5,920
66,360
348,918
Max Gross Weight = 3,200 lbs. CG Range 106.0 – 114.2 in.
Figure 7-5. In this example, the helicopter’s weight of 1,700
pounds is recorded in the first column, its CG or arm of 116.5
inches in the second, and its moment of 198,050 poundinches
in the last. Notice that the weight of the helicopter,
multiplied by its CG, equals its moment.
Lateral
Datum
+ –
+ –
Front View
Top View
7-5
Once you are satisfied that the total weight is within
prescribed limits, multiply each individual weight by
its associated arm to determine its moment. Then, add
the moments together to arrive at the total moment for
the helicopter. Your final computation is to find the
center of gravity of the loaded helicopter by dividing
the total moment by the total weight.
After determining the helicopter’s weight and center
of gravity location, you need to determine if the CG
is within acceptable limits. In this example, the
allowable range is between 106.0 inches and 114.2
inches. Therefore, the CG location is within the
acceptable range. If the CG falls outside the acceptable
limits, you will have to adjust the loading of the
helicopter.
LOADING CHART METHOD
You can determine if a helicopter is within weight and
CG limits using a loading chart similar to the one in
figure 7-6. To use this chart, first subtotal the empty
weight, pilot, and passengers. This is the weight at
which you enter the chart on the left. The next step is to
follow the upsloping lines for baggage and then for fuel
to arrive at your final weight and CG. Any value on or
inside the envelope is within the range.
SAMPLE PROBLEM 1
Determine if the gross weight and center of gravity are
within allowable limits under the following loading
conditions for a helicopter based on the loading chart
in figure 7-6.
To use the loading chart for the helicopter in this example,
you must add up the items in a certain order. The
maximum allowable gross weight is 1,600 pounds.
ITEM POUNDS
Basic empty weight 1,040
Pilot 135
Passenger 200
Subtotal 1,375 (point A)
Baggage compartment load 25
Subtotal 1,400 (point B)
Fuel load (30 gallons) 180
Total weight 1,580 (point C)
1. Follow the green arrows in figure 7-6. Enter the
graph on the left side at 1,375 lb., the subtotal of
the empty weight and the passenger weight.
Move right to the yellow line. (point A)
2. Move up and to the right, parallel to the baggage
compartment loading lines to 1,400 lb. (Point B)
3. Continue up and to the right, this time parallel to
the fuel loading lines, to the total weight of 1,580
lb. (Point C).
Point C is within allowable weight and CG limits.
SAMPLE PROBLEM 2
Assume that the pilot in sample problem 1 discharges
the passenger after using only 20 pounds of fuel.
ITEM POUNDS
Basic empty weight 1,040
Pilot 135
Subtotal 1,175 (point D)
Baggage compartment load 25
Subtotal 1,200 (point E)
Fuel load 160
Total weight 1,360 (point F)
Follow the blue arrows in figure 7-6, starting at 1,175
lb. on the left side of the graph, then to point D, E, and
F. Although the total weight of the helicopter is well
below the maximum allowable gross weight, point F
falls outside the aft allowable CG limit.
As you can see, it is important to reevaluate the balance
in a helicopter whenever you change the loading. Unlike
most airplanes, where discharging a passenger is
unlikely to adversely affect the CG, off-loading a passenger
from a helicopter could make the aircraft unsafe
to fly. Another difference between helicopter and airplane
loading is that most small airplanes carry fuel in
the wings very near the center of gravity. Burning off
fuel has little effect on the loaded CG. However, helicopter
fuel tanks are often significantly behind the center
of gravity. Consuming fuel from a tank aft of the rotor
mast causes the loaded helicopter CG to move forward.
As standard practice, you should compute the weight
and balance with zero fuel to verify that your helicopter
remains within the acceptable limits as fuel is used.
A B
C
D
F
1,600
1,500
1,400
1,300
1,200
1,100
104 105 106 107 108 109
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