need help with Plane construction (Cthulhu rising, sort of.)

[Warscribe]

So, with remotetech, i wanted to position some dishes on ciritcal points around kerbin. Since i am still a sucker with getting into the right orbit path to land on a specific point, i turned to planes. They fly where i want them, land and ill just leave them there.

I used the stock plane Aeris 4 and modified it accordingly:

So the problem here is, that right from the start, the plane gets a hefty punch to the left and explodes if i thrust at full speed. if i do get past this constant left-drag and actually get up in the air, it behaves nice. until i turn on the SAS (the kill rot control that looks like a shuttle nose)

The plane then starts spazzing out like an epileptic cthulhu, making it unstearable. You can't see it in the screenshot, but the flaps are actually UP and Down at the same time. landing this thing is impossible.

Any suggestions?

[Deadpangod3]

If I know what you mean, that shuttle nose as you call it, is the avionics package, not SAS, but avionics package makes the plane easier to control, I don't know why it'd cause you to lose control

[Warscribe]

ah yes, the avionics. Yeah, i tried other stock planes and the avionics behaved quite well. On this thing though, it just takes control, meaning i cant steer the plane, it will just go the same direction as before, but i need to completely disable the package to do anything. I'm thinking it may has something to do with the remote probe and a manned cockpit on one ship, but i took this away too and it still spazzed out.

[ferram4]

Try extending the central line of tanks in the fuselage back a little bit and put a larger vertical tail back their; that should help with any yawing tendencies.

Then I'd go and get rid of most of those control surfaces; the code they use creates thrust when they are deflected, which could make flying more difficult. You actually don't need too many control surfaces to maneuver a plane, you just need to make sure that the CoL is very close (but just behind) the CoM. This should also help with the Avionics freak-out, since fewer control surfaces should help reduce the effect of SAS overcompensation.

Finally, I'd try flying the plane without SAS activated; if you can't fly it without SAS, you need to make it more stable. Use the trim function (ALT + WASDQE) to balance the plane instead and try flying it manually, since it will be easier to land the plane manually than hoping that the autopilot works.

[Warscribe]

5 dead Kerbals later, i can say that didnt do much. Now i can't even get off the starting ramp.

Now, i tried something whilst waiting for answers..and i am not happy with my findings.

Every stock plane i modified with Dishes, solar, batpack and the remote control will have this hefty punch the moment of luiftoff, taht knocks them to the left (sometimes right) and tears off several parts of the plane. Now, if i remove the parts i added (so its basically reverse engineered back to the stock-form) has the same thing now.

Edit: to be clear, i added those extra control surfaces because of the freak out (and it didnt better or worsen the situation), at first i just placed the remotetech parts there without really altering the plane.

[ferram4]

Try getting rid of the docking port on the plane, since you shouldn't need it.

Make sure that the main landing gear is directly underneath the CoM so that it can rotate on the runway.

Make sure that the control surfaces are as far forward / backward as possible.

It's possible that adding the remotetech stuff to the plane is overloading the landing gear a bit. Try using struts to keep them straight up; when the gear starts wobbling bad things can happen.

[Warscribe]

I reconfigured.

The plane starts to drift again at about 60-70m/s, at which point i just throttled up and tried to get that thing from the ground.

I was surprised it worked. And not even that, the liftoff knocked off the last tank (with the tail fin and the avionics package)..i still had some autopilot from the remotetech. its currently flying.

i think the remotetech SAS and the avionics maybe contradict themselves and create the freak out?

[vencaslac]

the lateral lean might be due to the orientation of he wheels... the same happens with rovers where if your wheels aren't perpendicular to the ground, the rover will drift to one side or the other... that plane certainly looks airworthy... you could also have a look at the indicators for center of mass, lift and thrust and ensure they are coliniar as an offset center of thrust can cause the plane to drift to one side

Edit: removed statement saying i can't see your avionics pack... i'm obviously blind

[Warscribe]

My last config just crashed into the land. Landing is still impossible.(im deploying it with parachutes now)

new configuration.

Everything seems alright. weight is at center. im locking the gimbal of the engines and deactivating the remote module for the flight now.

[vencaslac]

looking at those indicators i'd say the center of lift is too far back relative to the center of mass... try adding a couple of canards about where the front chutes are and bring the center of lift to where the two indicator spheres intersect but the mass is still forward... that should make the torque from weight pulling down on the front and the lift pulling up on the back a little less significant and make it easier for the nose to come up when you need it to... not to plug my own stuff but it's the closest illustration of this point i have at hand <- at minute 29 or so i highlight the centers of mass and lift... that's about the way i keep them on all my planes

edit: alternatively if you're not a fan of canards (although they do add a lot of control) you can just move the engine+wing assembly forward a bit... it will shift your center of mass slightly forward the the center of lift will be more significantly affected so you should still be able to achieve the effect i mentioned

Edited April 21, 2013 by vencaslac

[Warscribe]

the last one did have a good liftoff and would have made it (if i didnt accidently click on the flight computer that sent the plane spinning like the girls head from exorcist)

I'm trying this one now. i'll keep you posted if that works.

Edit: i removed the "tail fins" at the center and the tail fins on the side. they stopped my engines, apparently.

Edit: Success! still a bit wobbly with the SAS on, but steerable. and landable.

Edited April 21, 2013 by Warscribe