[FAR] Oscilations, Stability Derivatives

[theend3r]

Since BahamutoD recently released his [URL="http://forum.kerbalspaceprogram.com/threads/140460-1-0-5-BDynamics-Mk22-Cockpits-v1-0"]awesome cockpits[/URL], I immediately built a plane to test it out.
It flies great and can do a U-turn in mach 1.5 in 5 seconds without breaking apart BUT suffers from oscilations, mainly in pitch. How can I correct this? I assume either by lowering control authority, which I do not want, or by setting CoM and CoL further apart which is possible albeit a bit hard to do. (are there any mods with small parts that just add weight?)

Also, the lateral simulation looks pretty bad since the lines shouln't diverge as far as I can understand. Is that the problem?

[imgur]lqFkM[/imgur] Edited November 25, 2015 by theend3r

[ferram4]

So the lateral simulation tells you that you're unstable in the dutch roll mode; you've got too much dihedral effect / too little yaw stability for your plane. You'll need to either, 1) reduce wing sweep, 2) add more vertical tail, or 3) make the wings have slight anhedral (negative dihedral angle) to compensate.

As for the other oscillations, everything actually looks perfect. Your plane is very close to the way real ones are. The rest is all stuff that should be handled through control systems, so you might want to activate the pitch damper when you fly this thing. That, or add one of the other control mods; this isn't something you really want to fix with changing the plane design, because you'll just lose out in terms of performance as a result.

[theend3r]

[quote name='ferram4']So the lateral simulation tells you that you're unstable in the dutch roll mode; you've got too much dihedral effect / too little yaw stability for your plane. You'll need to either, 1) reduce wing sweep, 2) add more vertical tail, or 3) make the wings have slight anhedral (negative dihedral angle) to compensate.

As for the other oscillations, everything actually looks perfect. Your plane is very close to the way real ones are. The rest is all stuff that should be handled through control systems, so you might want to activate the pitch damper when you fly this thing. That, or add one of the other control mods; this isn't something you really want to fix with changing the plane design, because you'll just lose out in terms of performance as a result.[/QUOTE]
Thanks a lot, both for the advice and this great mod.