Internationale Zeitschrift für Fortschritte in der Technologie
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Aircraft Nonlinear Coupling Longitudinal Mode

Ashraf Omran

In this research, a new definition of one nonlinear mode in the longitudinal motion of aircraft is presented. There are two linear modes for aircraft longitudinal motion: short- and long-period. The proposed mode is caused by the nonlinearity of the drag coefficient as a function of the angle of attack. The proposed mode is a coupling between linear short-period and linear phugoid modes. Volterra theory is used to model the proposed nonlinear mode in both time and frequency domains. The proposed nonlinear mode using the Volterra model can be used to estimate the nonlinear drag coefficient in both wind tunnel tests as well as flight tests. The Volterra-based estimation technique is verified using nonlinear simulation from the F-16 NASA report.