Eigenstructure selection for longitudinal flying qualities considerations

A drawback to the use of eigenstructure assignment techniques for designing flight control systems for aircraft with multiple control surfaces is a lack of handling-quality guidelines to apply when selecting the eigenvalues and eigenvectors of the closed-loop system. This lack of specific eigenstructure requirements means that some uncertainty will remain as to whether the augmented control system will meet the MIL-F-8785C specifications. A method for choosing the desired eigenstructure is examined that consists of forming an optimal plant matrix which possesses desirable dynamic characteristics and performing a spectral decomposition of this matrix. The resulting eigenstructure provides the desired eigenvalues and eigenvectors during the full-state feedback process. An example using the X-29A aircraft is given