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Some Features of Longitudinal Dynamics of Civil Aircraft in the Case of Aerodynamic Hysteresis

Surkov Nikita Alekseevich and Shelyukhin Yuri Federovich

Central Aerohydrodynamic Institute (TsAGI), Zhukovsky 140180, Russia


Abstract: Experimental data given by wind tunnel and real flights researches show that aerodynamic hysteresis of characteristics such as lift force and pitch moment appear at high AoA (angles of attack). This phenomenon caused by delay of flow rebuilding in the case of quick changing of AoA. As the result, dynamics research in the case of aerodynamic hysteresis is the cutting edge goal. As the base model of aerodynamic hysteresis for this research, the authors chose the model of non-steady longitudinal aerodynamic characteristics proposed by TsAGI and actively used in researches via flight simulator. Then this model was modified and was used for mathematical simulation of aircraft longitudinal motion at high angles of attack. This research show that modified model is in good agreement with results given by wind tunnel and flight for different regimes. Research of aircraft’s dynamics shows that hysteresis can lead to self-oscillation regimes of aircraft without flight control augmentation at high angles of attack, where flow starts to rebuild. Also the pitch damper affect on aircraft’s dynamics in the case of aerodynamic hysteresis is considered.

Key words: Non-steady characteristics, aerodynamic hysteresis, lift force, pitch moment, high angles of attack.
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