3434. Evaluation of Single Engine Weight and Center of Gravity Determination Methods


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Patrick Brown: 3434. Evaluation of Single Engine Weight and Center of Gravity Determination Methods. 2007.



There is no greater task for a Weight Control Engineer than determining an aircraft?s weight and center of gravity (CG). Although the concept of balance or CG is easy to grasp, calculating or measuring it for complex objects, such as an aircraft, is very difficult. The accurate calculation of an aircraft?s CG is a primary factor in any flight operation. It directly affects aircraft safety, performance, and mission capability. This paper contains a comparative analysis of four potential methods for weight and CG measuring for single-engine aircraft. They are analytic, current, simplified weigh on wheels, and weigh on wheels, respectively. Each of the four methods is analyzed using historical data obtained from Cessna Aircraft Company. The methods are evaluated using statistical queuing and variation analysis. The queuing analysis, based on the Allen-Cunneen approximation model, assumes a normal probability distribution for both the arrival and service rates. It also considers only the known move rate of one product line. It does not consider either multiple lines or multiple move rates. However, it does consider both the capability and the productivity gains as a function of the weighing method selected. The variation analysis compares the results with the guidelines established in Advisory Circular (AC) 120-27E and its Cessna corollary, CSPS-011. These are 1.0% of the fleet weight and 0.5% of the mean aerodynamic cord. For the Cessna model considered in this investigation, these are +/-20.6 pounds (9.344 kg) and +/-0.29 inches (0.7366 cm), respectively. Probability plots contain the results obtained for each method. The plots also illustrate some interesting relationships between the measurements of weight and distance and the calculation of center of gravity (CG).


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