Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Stability augmentation system

Aircraft Dutch Roll and State Variables Analysis Using Yaw Damper and Washout Filter

Emad N. Abdulwahab

Engineering and Technology Journal, 2009, Volume 27, Issue 7, Pages 1351-1369

Many high performance aircraft suffer from a dynamic instability problem at relatively
high Mach number and altitude regimes known as Dutch roll instability. In this study the
aircraft Dutch-roll and lateral –directional state variables may be enhanced using the yaw
damper and washout filter. The Aircraft Dutch-roll damping is improved by identifying a
suitable feedback gain matrix plus preserving the airframe's low-frequency behavior by the
use of a washout filter with a time constant. An intermediate change in terminology is used to
illustrate the procedure for including a washout filter into the aircraft lateral state equation
formulation. A stability augmentation system (SAS) and a numerical model constructed for a
Mig-21 aircraft are solved to illustrate the proposed procedure. The numerical results show
that it was sufficient to use (SAS) including both yaw damper and washout filter to improve
the aircraft sideslip angle, roll rate and roll angle response in a short time. Finally, the
verification of the aerodynamic characteristics of present model was made by comparing the
results of the method used (Low order three dimensional Panel method) with that of Cy-20
aircraft flight data test.