Hello,
While preparing the FNPT II class simulator for certification, we encountered an issue with very little aircraft response to the Dutch Roll (EASA 2.d.7 test).
How by modifying Aircraft.cfg we are able to increase Dutch Roll effect? At this moment, the aircraft performs only one oscillation after dynamic pressing and releasing the rudder. However, it should do at least 6 oscillations.
I would be very grateful for any help. We're working on both P3D v3 and v5.
Best regards
Michal Boniecki
Little aircraft response to the Dutch Roll
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seanmcleod
- Posts: 55
- Joined: Thu Mar 24, 2011 1:18 pm
Re: Little aircraft response to the Dutch Roll
First off, are you sure you don't have any sort of yaw damper installed which is damping the Dutch roll mode?
From - Flight Dynamics Principles (Third Edition)
"Both the damping and stiffness in yaw, which determine the characteristics of the mode, are largely determined by the aerodynamic properties of the fin, a large fin being desirable for a well behaved stable dutch roll mode. Unfortunately, this contradicts the requirement for a stable spiral mode. The resulting aerodynamic design compromise usually results in aeroplanes with a mildly unstable spiral mode and a poorly damped dutch roll mode. Of course, the complexity of the dynamics associated with this mode suggests that there must be other aerodynamic contributions to the mode characteristics in addition to the fin. This is generally the case, and it is quite possible for the additional aerodynamic effects to be as significant as the aerodynamic properties of the fin, if not more so. However, one thing is quite certain: It is very difficult to quantify all aerodynamic contributions to the dutch roll mode with any degree of confidence."
From Flight Stability and Control you can see the various coefficients which determine the undamped natural frequency and damping ratio. In this case - "If we consider the Dutch roll mode to consist primarily of sideslipping and yawing motions, then we can neglect the rolling moment equation."
From - Flight Dynamics Principles (Third Edition)
"Both the damping and stiffness in yaw, which determine the characteristics of the mode, are largely determined by the aerodynamic properties of the fin, a large fin being desirable for a well behaved stable dutch roll mode. Unfortunately, this contradicts the requirement for a stable spiral mode. The resulting aerodynamic design compromise usually results in aeroplanes with a mildly unstable spiral mode and a poorly damped dutch roll mode. Of course, the complexity of the dynamics associated with this mode suggests that there must be other aerodynamic contributions to the mode characteristics in addition to the fin. This is generally the case, and it is quite possible for the additional aerodynamic effects to be as significant as the aerodynamic properties of the fin, if not more so. However, one thing is quite certain: It is very difficult to quantify all aerodynamic contributions to the dutch roll mode with any degree of confidence."
From Flight Stability and Control you can see the various coefficients which determine the undamped natural frequency and damping ratio. In this case - "If we consider the Dutch roll mode to consist primarily of sideslipping and yawing motions, then we can neglect the rolling moment equation."
