Help me turn my plane

[code99]

Hello, I've been having a problem with my planes (plane actually, only got one.).So, after a lot of attempts of making a plane i finally ended up with a fast and surprisingly stable aircraft. I can take off no problem, i can reach speeds over 1000 m/s, the plane doesn't spin out of control and flies straight. And there is the problem, it just flies straight. It takes me forever to turn this thing. It either turns very slowly or starts to turn fast but then returns back straight even tho im still pressing S ...Altho recently, with my latest attempt at it, the plane steers very slowly. What's going on? Im on 24.2, i dont have FAR or NEAR and i am typing from my phone so i can't post pics about my plane.Currently my center of lift is slightly behind the center of mass.Ideas?

[capi3101]

Steering issues with spaceplanes (well, planes in general) are usually due to a lack of a sufficient number of control surfaces. What kind of control surfaces are you employing (what parts and for which purposes)? You should also consider adding a few reaction wheels.

Can't posts pics - that's fine. Can you give us a general description of your plane? How about its mass at take-off?

Edited October 15, 2014 by capi3101

[Alshain]

Pitch control surfaces should be as far from the center of mass as possible in front (canards) or behind (elevator).

Roll surfaces can be in line with the center of mass (ailerons), or the elevator can be dual purposed and do both roll and pitch (elevon).

Yaw surfaces are on the vertical stabilizer (rudder), rudders are not required for flight but a fixed vertical stabilizer is.

However, regardless of design, pitch surfaces are always as far from the center of mass, they act as a force on the plane where the center of mass is the fulcrum and the plane is a lever.

Here are examples, these planes are in the link in my signature, but they are balanced for the ferram mods, which makes them behave as they should.

Edited October 15, 2014 by Alshain

[Alshain]

One other note on turning. Some beginners mistakenly believe yaw is for turning. That is not correct. To turn, bank the craft by rolling (Q and E on the keyboard) and pitch up (S). Use the yaw control if you decide to implement it to keep your nose on the horizon as you turn (A and D), however as mentioned before yaw is not required.

[Taki117]

... or starts to turn fast but then returns back straight even tho im still pressing S ...Altho recently, with my latest attempt at it, the plane steers very slowly. ...

Post snipped for brevity. This is indicative of a misunderstanding. You are pressing 'S' which is a pitch control, not a yaw control (This goes with the common newbie mistake of trying to use yaw to turn) What this tells me is that you either:

A. Don't have enough control authority (in the form of control surfaces or reaction wheels)

Or

B. Trying to turn at all but instead trying to adjust your pitch which is a very different scenario, in which case your thrust might be misaligned.

In either case a pic of your craft would really help, preferably with the CoM, CoL, and CoT icons activated.

[Oafman]

As has been said, plenty of well-positioned control surfaces will fix your issue.

Make sure you right click on them (in the SPH or on the runway, but SPH is easier as it duplicates for symmetry) and select which things you want each one to control. So, a vertical control surface attached to a tailfin (a rudder) should only control yaw, not pitch or roll. While elevons on the back of your wings should be set to control pitch and roll, but not yaw. Setting this up correctly makes such a big difference to how your plane handles.

And yeah, roll then pull up to turn, don't try to turn far by yawing.

Edited October 15, 2014 by Oafman

[EdFred]

a fixed vertical stabilizer is. [required for flight]

Beechcraft disagrees with you. See their V-series. Ruddervators also work in KSP.

[code99]

The way i turn is i first roll then pitch up (Q then S).

Anyway, after some more fiddling around ive substituted my normal turbojet engines with 2 F119 Turbofan Engines from B9 (F22 Raptor style engines) which have venturing thrust and took my plane for a spin.

It improved the turning ability a bit but it still feels slow ...

I then moved back my wings so the control surfaces for pitch are all the way back near the engines and it seemed to have improved the turning capability (altho now its easier to flip the aircraft).

Now tho at altitudes over 8000 m the plane just gets almost impossible to control, ii even flown backwards ...

My plane is 12.4 tons heavy at launch.

Pitch control surfaces are at the back (at the back of the wings, near the engines), yaw controls are non existent and roll surfaces are at the front on the cockpit sides accomplished by 2 delta deluxe winglets.

I also have 2 vertical stabilizers without rudder at the back that look just pretty.

All my control surfaces are dedicated, meaning pitch control surfaces only pitch and nothing else.

Edited October 15, 2014 by code99

[Alshain]

Beechcraft disagrees with you. See their V-series. Ruddervators also work in KSP.

Ok, but that's still technically a pair of vertical stabilizers. Vertical stabilizers do not have to be 100% vertical, another example of this is the Predator and Reaper UAVs. This just illustrates the open ended design possibilities with KSP. "Fixed" was a wrong term, I apologize for that, I was just trying to differentiate between a vertical stabilizer and a vertical stabilizer with a rudder. The first image I posted has an active vertical stabilizer/rudder. All I was trying to say is you must have a vertical stabilizer (of some kind) if you want to fly straight without wobbling around but do not need to have yaw control if you don't want it.

Edited October 15, 2014 by Alshain

[EdFred]

I don't recall any vertical stabilizers on the B2, though I haven't tried building one in KSP.

[Alshain]

I don't recall any vertical stabilizers on the B2, though I haven't tried building one in KSP.

In that unique case I believe the body design may act in that purpose. (I'm not an expert on that though). However intuitively on the B9 the body ejects up from the wing creating nearly flat vertical surfaces for the air to go around which I would think would stabilize it.

It may be possible to fly without one, but it's an exception, not the rule. In most cases, you want to have one and I'm not sure KSP can go to B2 design levels.

Edited October 15, 2014 by Alshain

[ratchet freak]

In that unique case I believe the body design may act in that purpose. (I'm not an expert on that though) It may be possible to fly without one, but it's an exception, not the rule. In most cases, you want to have one and I'm not sure KSP can go to B2 design levels.

the B2 had differential thrust to assist in yaw stability

[Sean Mirrsen]

The B2 uses so many computers to fly, in KSP it'd drain a 2.5m battery bank in under an hour. It probably does stabilization via thrust differentiation or airbrake-like control surfaces.

edit: ninja'd.

[capi3101]

My plane is 12.4 tons heavy at launch.

Pitch control surfaces are at the back (at the back of the wings, near the engines), yaw controls are non existent and roll surfaces are at the front on the cockpit sides accomplished by 2 delta deluxe winglets.

I also have 2 vertical stabilizers without rudder at the back that look just pretty.

Okay...suggestions then - put a pair of control surfaces (I'd suggest Small Control Surfaces but use elevons if you're going for aesthetics) as far outboard on the wings as you can; you've got very little roll authority as it is and need some ailerons. You can make them function as proper elevons (pitch and roll axes) if you so choose, but you need more roll authority. Lose the delta-deluxe winglets; for the mass they don't provide much in terms of steering authority whatsoever. You'd be better off with Advanced Canards, Standard Canards or even AV-8s there - but I'd use them for pitch authority, not roll. A few (3-4) Reaction Wheels wouldn't hurt either; assuming a Mk-2 fuselage design, you could easily cram that many into a small cargo bay, shut the doors and be set. And if you're using Rockomax-sized parts in your fuselage, a single Large ASAS Module will do the trick instead. Finally, I'd replace those vertical stabilizers with something that could give you some yaw authority. AV-8s work well in that role; you shouldn't need a lot of yaw capability with a plane that light, but a little won't hurt.

[code99]

Okay...suggestions then - put a pair of control surfaces (I'd suggest Small Control Surfaces but use elevons if you're going for aesthetics) as far outboard on the wings as you can; you've got very little roll authority as it is and need some ailerons. You can make them function as proper elevons (pitch and roll axes) if you so choose, but you need more roll authority. Lose the delta-deluxe winglets; for the mass they don't provide much in terms of steering authority whatsoever. You'd be better off with Advanced Canards, Standard Canards or even AV-8s there - but I'd use them for pitch authority, not roll. A few (3-4) Reaction Wheels wouldn't hurt either; assuming a Mk-2 fuselage design, you could easily cram that many into a small cargo bay, shut the doors and be set. And if you're using Rockomax-sized parts in your fuselage, a single Large ASAS Module will do the trick instead. Finally, I'd replace those vertical stabilizers with something that could give you some yaw authority. AV-8s work well in that role; you shouldn't need a lot of yaw capability with a plane that light, but a little won't hurt.

Ok, ill try your suggestions, thanks to you an to the others for your help so far.

I should mention tho that in my current config i have no problems whatsoever with roll.

[Sean Mirrsen]

Yeah, two delta-deluxes is plenty for roll of a small craft. What you have problems with is A) having enough pitch authority, and having enough wing surface. The latter is a problem because the plane won't spontaneously change direction, it needs its wings to push it into the new direction first, which may be a problem with smaller wings at higher speeds.

[MrChittyChad]

note that turning in this simulator is completely wrong. even when banked at 45 degrees, it still flies straight. when someone tells you to just pitch up, you loose lots of speed and realistically that's not how turning happens unless you are doing high bank turning. it still suprises me that ksp hasn't fixed this issue.

[KOCOUR]

5 hours ago, MrChittyChad said:

note that turning in this simulator is completely wrong. even when banked at 45 degrees, it still flies straight. when someone tells you to just pitch up, you loose lots of speed and realistically that's not how turning happens unless you are doing high bank turning. it still suprises me that ksp hasn't fixed this issue.

Not true, I do create and fly planes a lot in KSP and i know for sure that if you bank, the plane starts turning slowly to the direction you are banked. 45 degrees gives you nice turnrate, offcourse you would also have tu use elevator to compensate, as the planes tend to also slightly dive when banked.

I recommend using  FAR, KAX, and Firespitter, as Stock KSP is somewhat dull in airplane area.

 

Edited September 12, 2016 by KOCOUR

[steve_v]

5 hours ago, MrChittyChad said:

note that turning in this simulator is completely wrong.

Nice necro of an almost 2 year old thread, the aerodynamics has been completely overhauled since 0.24.

On that, planes turn just fine - though you may want to turn off SAS or it will fight you.