Basic Aircraft Design - Explained Simply, With Pictures

[Javster]

Very good, but use its for possession, not it's.

[pebble_garden]

This absolutely brilliant tutorial gets an "excellent" vote from me. Well done!

[keptin]

Very good, but use its for possession, not it's.

Ha, I typed the whole thing without spellcheck (in Photoshop). I think I did pretty well all things considered, but thanks for the catch.

Can you point out exactly where the error is? I have no way to quickly search through the text.

[Dispatcher]

keptin, yours is an excellent tutorial. Thank you for all the work that you put into it! It is brimming with useful information, and simple enough for someone like me to comprehend. While you touched on the angle of attack of the lifting surfaces where you demonstrate a proper angle of the entire plane on a runway (nose higher than the tail), it does not specifically address any further pitching of the wings and the effect of doing so. Is this something that you tend to do only by having the entire plane essentially pitched up (on the runway)? I ask because in addition to pitching the plane nose up, so to speak, by the way the landing gear are mounted; I usually pitch my wings up as well. Normally I've had success with this approach. I'd like to get your input on this; perhaps as an expansion of the tutorial.

[keptin]

Just updated the tutorial to version 25, adding several sections and revising others.

That's 17,574 pixels of knowledge!

[keptin]

Is this something that you tend to do only by having the entire plane essentially pitched up (on the runway)? I ask because in addition to pitching the plane nose up, so to speak, by the way the landing gear are mounted; I usually pitch my wings up as well. Normally I've had success with this approach. I'd like to get your input on this; perhaps as an expansion of the tutorial.

I touched on angle of attack and its relation to the way the aircraft sits on the runway in the update just now. I want to keep the tut basic, but I'd be happy to answer any specific questions to the best of my ability. I admit, I haven't built many planes with tilted wings...maybe I should. I think early on I learned not to do that since tilted wings produce different amounts of lift relative to the elevator as the speed and air density change and it makes it more difficult to control, as opposed to building basically a controllable arrow that you simply point in the direction you want to go, but again, I haven't tried it recently.

If I was building a KSP jet plane with realistic limitations, say 12,000m alt and 250 m/s max airspeed, than it would really open up what I could slap together and still manage to control, but I often find myself building planes that have to perform well in a very wide range of conditions; 0-2500 m/s, 0-50,000m, in flight fuel ballast control, etc.

Edited October 13, 2013 by keptin

[Dispatcher]

Thank you keptin. The addition is nice and seamless; and informative. Actually, since reading your tutorial, I've been making some aircraft without pitching the wings. I think whether or not to pitch them depends on the intended use of the plane. For piloted craft, there seems to be no need to pitch the wings. For my "self flying" planes (no SAS, no autopilot, no mod, no piloting [at least on take off]), pitching the wings has often helped. Keep up the good work!

[AmpsterMan]

.

AmpsterMan: I believe the maximum_drag value represents the drag coefficient, which depends on shape. The mass dependence then represents the surface area. The actual values, however, seem to be chosen without respect to shape.

If I have something wrong, please correct me.

I know this is a little late, but thanks for the response. I THINK I get it

[Tiberion]

Cool tutorial.

One thing you didn't mention is how you get different controlsurface setups. (elevators versus elevons)

If you place a control surface flat without symmetry you get an elevator, while if you place them in symmetry, they are linked together across that axis and provide roll control. You can't actually have a pure aileron in default KSP because an aileron is a control surface only hooked up to the roll axis and doesn't respond to pitch control - in KSP they are either hooked to both pitch and roll (if symmetrically linked) or just pitch. (you can have vertical surfaces linked with roll control too, but that is just weird )

Anyway, another KSP issue related to that - elevators behind the Center of lift (or mass?) seem especially ineffective in KSP, especially when attached to wings that are attached mid-fuselage. This mostly because of the lawn dart syndrome you described, because without canards, the CoL shifts back away from the CoM and marginalized the elevators on the wings. So a Delta-wing style plane (or something like the space shuttle, which only has elevons on the main wings) is very difficult to make in KSP.

Edited October 15, 2013 by Tiberion

[keptin]

I'm hoping that in a future update players are given the ability to assign control surfaces, like you can in FAR. It'd add another step, but would be a ton better than the stupid auto-control. Maybe they can do both, have an auto default or something. Anyhoo, I left out that stuff because explaining it might confuse new players when they could more easily learn it for themselves.

I think KSP favors canards over conventional tail assemblies since it doesn't take into account many of the disadvantages they have; in-flight CoM issues with further back wings (fuel in wings), can enter irrecoverable deep stalls, turbulent air over main wing, difficult to design for, etc.

Another advantage of canards in KSP is that they don't tend to snap craft in half. Unlike conventional elevators that put downforce on the tail to lift the front of the craft, stressing the parts in between, canards simply lift the weight of the front of the craft and let the tail get pulled down by gravity.

This all being said, you can make high performing conventional craft. The big advantage that canard designs bring to the table in their difficulty to stall is also one of their biggest performance drawbacks. They can't take advantage of main wing's critical AoA (maximum lift coefficient). When it comes to the cutting edge, I think conventional tail assemblies are the way to go.

In the last atmospheric "no-intake hackery" circumnavigate the world challenge that I submitted to, this design beat out the other contenders by a decent margin:

This was the ultimate mix/max of that design: http://i.imgur.com/8LbfLa0.jpg

So there's still hope.

Edited October 15, 2013 by keptin

[AmpsterMan]

-Stuff-

-more stuff-

I don't even know what you guys are talking about but it seems to be filled with awesome. This kind of information needs to be more widely known and I thank you for this tutorial

EDIT: Are there any uses for winglets on the tips of wings in KSP?

Edited October 16, 2013 by AmpsterMan

[Galacticruler]

Well, this might solve a good 99% of my liftoff issues.

TO THE SPH!

[keptin]

Are there any uses for winglets on the tips of wings in KSP?

Maybe, but not for the same reason that winglets are used on commercial aircraft. On commercial swept-wing aircraft, winglets reduce drag-inducing vortexes forming off the wing by kind of straitening the air as it reaches the tip of the wing. The game can't simulate any of that stuff, but winglets can act as vertical stabilizers if the main wing is further away from the CoM-CoL pivot point.

Simple answer: In most cases, no.

[AmpsterMan]

but winglets can act as vertical stabilizers if the main wing is further away from the CoM-CoL pivot point.

Simple answer: In most cases, no.

Thank you for the response. I can't beleive I actually guessed correctly XD. I noticed that winglets help reduce the weird wobble that occurs when I try to Yaw and Roll on some craft.

Gosh, planss are so complicated in this game.

[Snjo]

When I want to kick back and relax after a hard day of flying planes, I chug down a cool can of Basic Aircraft Design!

It's simply the patriotic thing to do!

I fully endorse this product!

[colmo]

Excellent stuff.

Two suggestions:

1) Asymmetric drag (esp intakes),

2) Anhedral/Dihedral/Polyhedral wings and their stability v manoeuvrability.

I'm hoping to do a video on helicopter design, though I might end up doing it similar to this instead.

Edited October 17, 2013 by colmo

[Ratata]

Even after many succesfull spaceplanes i find this really informative! Thank you! Could you add something about engines? You know, Propellers,Turbofan, Ramjets.......

[keptin]

@colmo, I might add a sentence on Asymmetric drag, but I think the Asymmetric Thrust section got the point across that asymmetric forces must be countered else there be undesired consequences.

@Ratata, I'd love to add sections on engine types and their intricacies, but it's out of the scope of KSP. I want to keep the information trim so it's digestible by players. Hell, engines could double its length.

Edited October 17, 2013 by keptin

[AmpsterMan]

The pictures you drew, do you actually have those as .craft files? I've tried recreating a few of them and they are actually quite functional XD.

[Mekan1k]

I wonder... Is the majestic 'eagle' an SSTO?

[keptin]

The pictures you drew, do you actually have those as .craft files? I've tried recreating a few of them and they are actually quite functional XD.

Ha, no. Some are close to stuff I've tried in the past, others are guesswork. Go Go Taco Supreme!@!!

I wonder... Is the majestic 'eagle' an SSTO?

It's an SSTE. Single Stage To Explosion.

[altrue]

Excellent stuff !

[Simmer22]

Best KSP article on the forums right now. Period.

[Kerolyov]

Great stuff! With your trainer I landed on runway without crashing for first time

[Blaster]

Looks like I have a few things to work on to make my cupoula cockpit nine passenger orange tank fuselage 8 engine mainsail superjet fly into space...