Spaceplane help - how to stop this bouncing?

[PoopyJoe]

I've been playing KSP for a while but really haven't tried hard with spaceplanes. But I have made some awesome planes. And really the problem I'm seeing now is that they keep bouncing when SAS is on. Is that due to the center of mass fighting the lift or vise versa? or is it just KSP mechanics. It's probably just my design or something. Can anybody shed some light on how to fix it?

I do have FAR installed and some common part packs.

[Taki117]

IT's due to SAS trying to keep your heading. It's adjusting the control surfaces many times a second to attempt to maintain heading and as such is affecting the lift characteristics. It then has to correct this so it moves your control surfaces more, resulting in the bouncing.

[Claw]

I can't speak to FAR, but I find that if my planes a rapidly bouncing around, it is usually the flight controls. If I have too many flight controls (and too much control surface), they start fighting each other and start shaking back and forth. most notably when I get to a nearly perfect attitude like perfectly level. I think my case is due to SAS programming, but I don't know for sure.

If I deactivate some of the surfaces, it seems to fix it.

[Col_Jessep]

It often helps to disable roll in the tweakable right-click menu for all but one small pair of control surfaces in my experience.

[capi3101]

^^^

Which set do you typically leave active? Let's say I've got two control surfaces along the wing - inner set or outer set?

[Thogapotomus]

Once you are off the runway and in the direction you want to go, try flying by using trim adjustments. It's more useful for holding pitch but can allow for smoother movements overall and it works particularly well with FAR. Hold Alt and press the control keys to input trim. For example, if my plane keeps diving, I'll hold Alt while pressing S until the plane can hold its heading. Playing around with this function can greatly increase your flying ability and enjoyment. Also pressing Alt+X will reset all trim adjustments. This can also be used with Caps-lock for really fine control.

[Claw]

^^^

Which set do you typically leave active? Let's say I've got two control surfaces along the wing - inner set or outer set?

The set I leave active depends on the airplane / space plane. Typically I will leave the inner set active. However, if I want/need a lot of roll authority, then the outer set stays active.

If I have an upper and lower set (i.e. they are stacked), then I will leave the lower ones active. This usually leaves the plane a little more stable since high wings won't twist or change lift. But again, it depends on the plane...

[RTK]

Tweak the control surfaces in SPH by RMB on the various flaps etc. tail rudder should control Yaw only so deselect the Pitch and Roll on the Tail Rudder. Flaps on the wings should only control Pitch and Roll so deselect Yaw for the flaps on wings. Also you may need to strut your plane to ensure it is rigid and you may need to do a few trial take-offs to find the right amount for the "control maximum" setting on your flaps to find the right balance for smooth flying and take-off.

I hope this helps I'm recovering from a heavy night so excuse the poor format etc