Identification of Aircraft Stall Behavior from Flight Test Data

TL;DRAbstract

An unsteady 5-DoF aerodynamic model for flow separation and stall is presented. The model formulates lift, drag, and the moments in pitch, roll and yaw as a function of an internal state, namely the position of the flow separation point along the wing chord. In a quasi-steady case, this position is described as a function of the angle of attack and its rate of change, whereas in a transient case it is described in a state-space form using a first order differential equation. Using airfoil wind tunnel data, the plausibility of the model structure is discussed. In a second step, the parameters of the quasi steady and the transient model are identified for two different aircraft using stall flight test data. Validation plots demonstrate the model accuracy and it can be seen clearly that there are considerable unsteady effects at high angles of attack where flow separation occurs, which cannot be described properly using flight mechanic models for attached flow.

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