Asas problems with spaceplane

[Vlorp]

Dear fellow kerbolnauts, it is with some reservation that I call upon your combined knowledge. Because figuring things out is half the fun normally i figure things out for myself. However when it stops being fun and i feel like i've exhausted every source of knowledge i call upon you, so here it goes.

I've created an ssto with the centre of mass en centre of lift at the same point (i've experimented with this and olso had COM in front of COL).

When i see a youtube tutorial on how to fly a spaceplane everyone is using ASAS. However when i try to do this it start over compensating and oscilating and eventually stalls.

I think this is probably because my plane isn't as balanced as i think it is. So I tried the same plane as in the tutorial

same problem.

Eventually i tried the far plugin, lowering me graphics settings, adjusting the delta physics time all to no avail.

Please help i really want to fly a spaceplane succesfully.

[3_bit]

Please post a .craft file or use Imgur to insert pictures. If there's no ASAS that may be your problem, or you may have your center of thrust far enough off that it causes these problems. Additionally, it could be due to too many/too few control surfaces (thrust-vectoring engines, canards, etc. From my experience, RCS has never overcompensated with ASAS, at least not bad enough to make the situation worse. You should consider turning it on at times if you're about to flip over.

Remove the far plugin (it's for pros who like tweaking their planes for hours), and if that doesn't work, someone else will hopefully reply with more useful tips.

[Vlorp]

Please post a .craft file or use Imgur to insert pictures. If there's no ASAS that may be your problem, or you may have your center of thrust far enough off that it causes these problems. Additionally, it could be due to too many/too few control surfaces (thrust-vectoring engines, canards, etc. From my experience, RCS has never overcompensated with ASAS, at least not bad enough to make the situation worse. You should consider turning it on at times if you're about to flip over.

Remove the far plugin (it's for pros who like tweaking their planes for hours), and if that doesn't work, someone else will hopefully reply with more useful tips.

Thanks for reading and replying if made some picture as for the hours of tweaking the plane don that already

If you need more images let me know

[Zephram Kerman]

The plane in SM's tutorial is the Aeris4A. Even with his improvements, it's pretty hard to fly. Using that one as a reference point, here are some things to consider:

• if you don't have a joystick, Caps Lock makes keyboard controls more gentle;

• CoM (Center of Mass) always ahead of CoL (Center of Lift), even a meter or two is ok;

• put fuel tanks at CoM, so that this point doesn't change as fuel empties out;

• CoL seems to change while maneuvering; try tilting your plane in SPH to see what I mean;

• canards are very powerful (and inherently unstable), so they make a plane more difficult to control;

• it is preferable to make your plane controllable with only tail elevators, since these are inherently stable;

• there are several different control schemes:

~ ASAS tries to hold the same direction as when it was turned on;

~ Avionics Package tries to match the plane to its current velocity vector (the prograde marker);

~ I usually prefer MechJeb surface mode, which is more like real-life Pitch Hold / HDG Hold, even though it uses yaw and I have to bank manually.

Also consider that flight controls actually work differently than they should, because they are mapped the same way as RCS thrusters. Take a look at what your elevators do when you try to roll. One elevator splits and goes the other way, to help with the roll command. This split elevator messes up the pitch trim.

[Shrike42]

I've managed extremely stable ASAS flight at all altitudes, but only on craft where the elevators/flaps are at almost the back end of the craft, and very close in to the main body. Everything else seems to produce the oscillations that make the ASAS module practically worthless. I've also got a bit of an idea that the number of moving control surfaces causes the ASAS PID controls to overcompensate.

As an addendum to what ZK posted above, I try to move things with constant weight forward, to move the CoM up and keep it as steady as possible. I also used tilted tail fins (no moving surfaces/canards) at the nose to increase my lift without adding additional control surfaces.