Increasing Handling Qualities and Flight Control Performance using an Air Resonance Controller

This paper presents the effect of an air resonance controller on handling qualities ratings and flight control performance. The investigations were done by using the research helicopter FHS (Flying Helicopter Simulator) operated at DLR. The air resonance mode occurs when roll rate feedback loops are closed. In order to cancel the oscillatory phenomenon it was decided to develop and investigate an independent air resonance controller. An offline design environment incorporating models which reproduce the air resonance phenomenon was developed. As a result two air resonance controller concepts could be defined. These two controllers were flight tested on the FHS and analyzed towards their reduction of air resonance when closing the roll rate feedback loop. The dipole cancelling controller was selected as the most promising approach and further flight tested with respect to the influence on handling quality ratings, flight control performance and stability.