KSP 1.0.2 Plane SAS issue

[Diabloblaze24]

Hello having severe issues with SAS while in flight with a particular set up on a plane everything regarding CoM and CoL, seems to be correct the CoL is behind CoM. but the second I enable SAS in flight the whole craft will go begin a full pitching up and/or down violently without stopping, sometimes it simply occolates between full pitch up or pitch down other times it holds full pitch up/down and makes a loop without me touching anything. Help would be appreciated

[eddiew]

Are you sure that none of your control surfaces are accidentally inverted? If the SAS tries to pull up and instead the control surfaces send it further down, then you'll get all kinds of wacky behaviour. Done it myself a few times

Also pictures will help

[Slugy]

I suspect the pretty bad SAS we have is now really struggling with the new aero - it's always liked applying full deflection/gimbal, and often (but not always!) seems to lack damping.

Using Alt-S/W to manually set trim may help with getting a smooth ascent.

[Diabloblaze24]

Thanks slugy i'll give that a try

Even with no changes to control surfaces I have the same issue I even attempted disabling the torque from the capsule in flight and it still has the same issue, currently not at my home computer with images but i will try and get some pasted in when i get home.

[Diabloblaze24]

http://imgur.com/zabp2G1

http://imgur.com/mDPClbZ

Images for anyone still willing to help.

[Diabloblaze24]

Well found the answer myself after extensive research, apparently having multiple engines in a swept wing design with the angled control surfaces causes this issue, now i wonder if this is a bug or intended so no idea where to go from here....

[Dunesands]

You need horizontal stabilizers on the back of your plane to control pitch. The tail fin part placed horizontally and mirrored on both sides will do.

[Chris_2]

Hello having severe issues with SAS while in flight with a particular set up on a plane everything regarding CoM and CoL, seems to be correct the CoL is behind CoM.

I don't think so. Your center of lift is really close to the center of mass. The CoL doesn't just need to be 'behind' the CoM, but the larger the distance is between the two, the more stable the plane becomes. And the center of mass will move even further backwards when using fuel. Just move the CoL further backwards to make it more stable.

[Ion Man]

Well found the answer myself after extensive research, apparently having multiple engines in a swept wing design with the angled control surfaces causes this issue, now i wonder if this is a bug or intended so no idea where to go from here....

Yes,

your design is unstable in itself. You want to control the aircraft at the back with vertical and horizontal surfaces. Your plane looks like a lifting body, where the control surface is spanning from in front of the COM to Behind of the COM. This results in inconclusive unstable flight.

The contol surfaces can't be adjusted individually to the point that makes the plane stable in KSP. In real life, the B2 bomber is fully automatic, fly by wire, algorythm controllend to stay in the air.

[Diabloblaze24]

Ok thanks for the info just not used to a better aerodynamic model so thought that the CoL only had to just be behind the CoM I see that's not the case, why is it that i can control the craft fine when SAS is not enabled?