Harrier aircraft control law clearance analysis using a bifurcation-based method

This paper provides a demonstration of control law clearance analysis on an industry-scale aircraft model using a technique based on bifurcation analysis and continuation methods. The approach was developed as part of the GARTEUR Flight Mechanics Action Group 11, set up to find more efficient means of clearing aircraft control laws. Results are presented for criteria based on eigenvalues and Nichols stability margin. It is shown that the worst case combination of uncertainties found by this analysis technique is ‘worse’ than that chosen by the conventional (baseline) method. Significantly, these uncertainty combinations violated the criteria for three cases in which the conventional method cleared the model. The technique offers substantial time savings over the baseline, identifies the exact conditions at which a criterion is violated and retains a strong link with the physics of the system.