Airplane doesnt fly well

[Jetsim]

But why should plane have canards in front of the wings, if plane can pitch with ailerons alone if they can act as canard if they are wide enough? Like the example above.

[Hodo]

But why should plane have canards in front of the wings, if plane can pitch with ailerons alone if they can act as canard if they are wide enough? Like the example above.

If your ailerons are inline with the CoM of the craft they wont actually do anything for pitch. Which is where you ideally want your Ailerons. But if you have them before or after your CoM they can affect your pitch when you roll.

[Jetsim]

How can F-15 pitch without canards? I still dont understand. F-15 has only ailerons.

[Alshain]

How can F-15 pitch without canards? I still dont understand. F-15 has only ailerons.

Because they are significantly behind the center of mass.

Did you ever sit on one of these as a child?

What happens if one of the riders of that toy moved closer to the center? Would it still function as intended? Nope. Same thing with your ailerons/elevons. If they are at the center they will help you roll but not pitch, just like the toy which represents pitch.

Edited July 24, 2014 by Alshain

[Jetsim]

But Hodo said that plane could pitch only during rolling.

[Alshain]

But Hodo said that plane could pitch only during rolling.

I don't think he said that. You must have misunderstood. You have to pitch to get off the runway, hopefully not while rolling.

[Jetsim]

So I can have pitch from main wings only if I place ailerons behind, this will make possible to make different designs. But how do I know what is best for what purpose?

Also how to make those ailerons then keep their roll-ability? They dont roll much if they are behind CoM.

[Greenfire32]

Did you ever sit on one of these as a child?

http://gnr8.cachefly.net/gnr8biz/images/seesawmain.jpg

No, but I did as an adult.

Didn't see the appeal.

[Alshain]

So I can have pitch from main wings only if I place ailerons behind, this will make possible to make different designs. But how do I know what is best for what purpose?

There are lots of different designs, that's why not all planes look alike. I thought I posted this earlier, but this guide here is very explanatory of position for wings, control surfaces, center of mass, lift and thrust. It's well illustrated (and slightly comical). Give it a read, you will learn a lot.

[RoboRay]

How can F-15 pitch without canards? I still dont understand. F-15 has only ailerons.

The F-15 does not have only ailerons. It has ailerons on the wings. The horizontal tail-surfaces are all-moving "stabilators" that perform the elevator function of pitch-control. They tilt up and down to raise or lower the nose in flight.

Here... I'll label all the F-15 flight control surfaces for you:

Edited July 24, 2014 by RoboRay

[Hodo]

Just a few minutes I will post some pictures of different aircraft that I have made, and what EACH one of the control surfaces do. Need to upload the pictures and take them. All the while helping my girlfriend get ready for a trip.

- - - Updated - - -

The F-15 does not have only ailerons. It has ailerons on the wings.

Here... I'll label all the F-15 flight control surfaces for you:

http://i.imgur.com/IgdCcoU.jpg

One minor problem the elevators are actually elerons on the F-15. They assist in roll.

[RoboRay]

One minor problem the elevators are actually elerons on the F-15. They assist in roll.

Yes, but I didn't want to add that as it might confuse him further. Sticking to "one purpose per surface" is probably best for an elementary introduction.

[Jetsim]

But how do airplanes with only elerons can roll? Rolling requires controllers being lined up with CoM.

[RoboRay]

See?

(sigh)

Unlike pitch, having the surfaces forward or back from the CoM doesn't make them significantly less effective at roll control.

It does have some controllability complications, but that's really getting into advanced topics.

Edited July 24, 2014 by RoboRay

[Alshain]

The F-15 does not have only ailerons. It has ailerons on the wings. The horizontal tail-surfaces are all-moving "stabilators" that perform the elevator function of pitch-control. They tilt up and down to raise or lower the nose in flight.

Here... I'll label all the F-15 flight control surfaces for you:

Nice. Just to add to that, these are some approximations (CoL may be a little too far back but you get the idea)

Edited July 24, 2014 by Alshain

[RoboRay]

CoM is actually about in the middle of the speed brake (which is why the speed brake is right there), but that's close enough for this discussion.

[Alshain]

CoM is actually about in the middle of the speed brake (which is why the speed brake is right there), but that's close enough for this discussion.

Yeah, my editor kept wanting to snap it somewhere. I was lucky to get it where it was.

[RoboRay]

Editor? Hell, I used MS Paint!

[Hodo]

Here is the settings for most of my control surfaces, ignore the ordinance on one of the craft. But I have canards, ailerons, and elerons on different craft. The ones with Pitch and Roll set to one control surface are generally considered elerons.

Javascript is disabled. View full album

[Alshain]

Editor? Hell, I used MS Paint!

ROFL, well I used snag it. Which is designed more for screenshots than image editing.

[LethalDose]

How can F-15 pitch without canards? I still dont understand. F-15 has only ailerons.

I think it may be worth noting that canards and elevators typical serve the same purpose: Pitch control. If I correctly understand the widely accepted use of the terms, we usually use the term "canard" to refer to pitch surfaces ahead of the wing, and elevators to refer to pitch surfaces behind the wing. As with many technical terms, though, there's probably a some degree of laxity in exactly what those terms mean to different people. There's also no reason you can't use both elevators and canards in the same design.

As pointed out above, the F-15 has elevators for pitch control to the aft, which is why it has pitch control without canards.

I look at control surfaces the way I look at RCS thruster placement: I want them as far away from the axis around which I want them to cause rotation and centered around the CoM. So pitch and yaw control surfaces should be as far forward and as far back from the CoM as possible. roll control surfaces should be as far lateral (out to the sides) as possible.

I typically choose to use elevators (aft) or canards (fore) based on where my aircraft CoL is in relation to the CoM. I tend to favor canards in my designs because the distance from my aircrafts' CoM to nose is usually longer than the distance from their CoM to tail, so canards tend to be more effective than elevators, and I favor wing designs that put my CoL pretty far back, so I can afford to shift the CoL forward a bit. I emphasize this about my designs because every aircraft is different, every player designs aircraft different, and every player flies differently.

Lots of novice players want simple, clear rules to decide where to put wings and control surfaces on aircraft, but you gotta accept they don't exist. Designing aircraft in KSP is as much art as it is science, in that there are a few guidelines that help in design, but almost all of them can and should be broken in certain circumstances. The strictest "rule' I can think of is "Keep your CoM in front of your CoL in hypersonic aircraft".

[Jetsim]

I am trying to build plane that turns as quickly as possible, but cant figure out how. All planes turn more or less slow.

[Pecan]

I am trying to build plane that turns as quickly as possible, but cant figure out how. All planes turn more or less slow.

Large, heavy aircraft are generally less responsive, it's that easy.

B U I L D S M A L L E R A N D S I M P L E R

Read http://forum.kerbalspaceprogram.com/threads/52080-Basic-Aircraft-Design-Explained-Simply-With-Pictures

[Hodo]

I am trying to build plane that turns as quickly as possible, but cant figure out how. All planes turn more or less slow.

If you have the CoL to far behind the CoM, it will turn like a school bus. But if you place the CoL close to or nearly centered on the CoM, it will turn like a humming bird. It is the difference between a stable design and an unstable design. Military fighter aircraft are designed to be aerodynamically smooth but unstable, so their CoL is REAL close to the CoM.

Like this fighter, turns like a dream when subsonic, but turns like a truck when going faster than mach 2.

Note how the CoL is just behind the CoM.

But this Cessna knock off turns great all the time, not that it could ever break the speed of sound anyway.

And this fighter is a dream to fly in a dogfight, it turns on a dime and is quite quick.

Note how the CoL is almost centered on the CoM.

So Jetsim, post a picture of the craft you are having problems with and we can tell you what you are doing wrong.

[Jetsim]