The Zimmerman-Weissenburger approach presents an innovative tool to predict the onset of flutter during a flight test. This approach computes flutter margins as the distance from any test point to that onset point by noting a flutter function, which relates stability of the aeroelastic dynamics, has approximately a quadratic dependency on dynamic pressure. The approach has assisted envelope expansion for many flight tests; however, it is limited to consideration of 2-mode coupling for the

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... r instability. This paper introduces an extension to the Zimmerman-Weissenburger approach that accounts for multi-mode coupling in the flutter instability. The resulting flutter margins are actually computed by analyzing a combinatorial set of modal pairings which may be related through a multiplicative or norm formulation. Also, a metric of flutter confidence is formulated that associates how well the data used to generate these flutter margins adheres to the theoretical assumptions used in the approach. Flutter margins are computed for a modified 747 aircraft with a 4mode instability to show that the multi-mode approach with associated confidence is able to accurately predict the onset of flutter.