Susceptibility of F/A-18 flight controllers to the falling-leaf mode: Linear analysis

Abhijit Chakraborty, Peter Seiler, Gary J. Balas

Research output: Contribution to journalArticlepeer-review

37 Scopus citations

Abstract

The F/A-18 Hornet aircraft with the original flight control law exhibited a nonlinear out-of-control phenomenon known as the falling-leaf mode. This unstable mode was suppressed by modifying the control law. This paper employs the falling-leaf phenomenon as an example to investigate the applicability of linear analysis tools for detecting inherently nonlinear phenomenon.Ahigh- fidelity nonlinear model of the F/A-18 is developed for controller analysis using F/A-18 High-Alpha Research Vehicle aerodynamic data in the open literature. A variety of linear analysis methods are used to investigate the robustness properties of the original (baseline) and the revised F/A-18 flight control law at different trim points. Classical analyses, e.g., gain and phase margins, do not indicate a significant improvement in robustness properties of the revised control law over the baseline design. However, advanced robustness analyses, e.g., μ analysis, indicate that the revised control law is better able to handle the cross-coupling and variations in the dynamics than the baseline design.

Original languageEnglish (US)
Pages (from-to)57-72
Number of pages16
JournalJournal of Guidance, Control, and Dynamics
Volume34
Issue number1
DOIs
StatePublished - 2011

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