Development of apparatus and methods for experimentally finding mass properties of small UAS

The main methods in the design labs at Oklahoma State University for finding the mass properties of in-house fabricated aircraft is to find the CG by performing weight and balance calculations with the aircraft level and to use the aircraft’s CAD for the inertia matrix. While these methods are not inherently wrong they do have some short comings, as CG is only found in one dimension and the inertia matrix only holds true in perfect conditions. This thesis develops experiments and methods for finding these mass properties in order to provide a greater understanding of the flight characteristics of an aircraft before it takes off. This method for finding the CG of an aircraft reaches its goal by suspending the aircraft from points fore and aft at various angles to find the longitudinal and vertical CG in conjunction. Experimentation results from performing the tests on a homogenous beam with known mass properties found the longitudinal cg within 1.6% at a delta of five degrees and .73% at a delta of 60 degrees of the theoretical CG location, while the vertical CG was found to be 57% at a delta of 5 degrees and 3.3% at a delta of 60 degrees. These tests show that the larger the change in angle between points results in higher accuracy in the data and that this method can be utilized for aircraft. The experimentation method utilized for finding the inertia matrix of the homogenous beam provided satisfactory results for the y and z axes but due to the small cross section the x axis values had large errors. Once a cross beam was added to the homogenous beam inertia values were found for the x, y, and z axes to have an error of 1.4%, 3.3%, and 10.9% respectively of the theoretical values. This method for finding the inertia matrix of an object is valid only when its Ixx values are of similar magnitude to its Iyy values, this is due to the propagation of uncertainty from measurements within the experiment. These methods can be utilized to strengthen mass properties understandings here at OSU.