Development of a Hybrid Fluidic Damper Control for an Aircraft Yaw Axis

This paper describes the concept and development of an all fluid (hydraulic) system for yaw axis stability augmentation of a commercial jet aircraft. This unique system uses a fluidic accelerometer as a sensor, a bellows actuated flapper nozzle circuit for signal amplification, and a conventional spool type power stage driving an actuator with mechanical position feedback. The system replaces a rate sensor and differentation network and most of the signal amplification stages found in more conventional fluidic stability augmentation systems. A complete analog simulation, along with prototype testing, was performed to insure the required performance of the final design. Also included in the paper is a summary of system performance testing.