Empty Weight Center of Gravity Range
For some aircraft, a center of gravity range is given for the aircraft in the empty weight condition. This practice is not very common with airplanes, but is often done for helicopters. This range would only be listed for an airplane if it was very small and had limited positions for people and fuel. If the empty weight CG of an aircraft falls within the empty weight CG limits, it is known that the loaded CG of the aircraft will be within limits if standard loading is used. This information will be listed in the Aircraft Specifications or Type Certificate Data Sheet, and if it does not apply, it will be identified as “none."
Operating Center of Gravity Range
All aircraft will have center of gravity limits identified for the operational condition, with the aircraft loaded and ready for flight. If an aircraft can operate in more than one category, such as normal and utility, more than one set of limits might be listed. As shown earlier for the Piper Seneca airplane, the limits can change as the weight of the aircraft increases. In order to legally fly, the center of gravity for the aircraft must fall within the CG limits.
Standard Weights Used for Aircraft Weight and Balance
Unless the specific weight for an item is known, the standard weights used in aircraft weight and balance are as follows:
Example Weighing of an Airplane
In Figure 4-20, a tricycle gear airplane is being weighed by using three floor scales.
The specifications on the airplane and the weighing specific data are as follows:
By analyzing the data identified for the airplane being weighed in Figure 4-20, the following needed information is determined.
To calculate the airplane’s empty weight and empty weight center of gravity, a six column chart is used. Figure 4-21 shows the calculation for the airplane in Figure 4-20.
Based on the calculation shown in the chart, the center of gravity is at +50.1", which means it is 50.1" aft of the datum. This places the center of gravity forward of the main landing gear, which must be the case for a tricycle gear airplane. This number is the result of dividing the total moment of 66,698 in-lb by the total weight of 1,331.5 lb.
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