Basic Aircraft Design - Explained Simply, With Pictures

[kc5qnk]

There is a fundamental flaw in this explanation, however.  In "conventional" aircraft (i.e., not canard or tandem-wing), the horizontal stabilizer actually provides a DOWN force, not an "up" force contributing to the overall lift of the design.  It is there to "balance" the aircraft.  The lift vectors you drew should be down for the horizontal stabilizer.  NASA has a nice explanation:  https://www.grc.nasa.gov/www/k-12/airplane/trim.html

Cheers!

Rusty

[Program Kerbal Space]

How about the elevons? Because that's what i have trouble with.

[kc5qnk]

You mean like the control surfaces?  Kind of like the "ruddervator" on a v-tail, they work through a mixer arrangement.  Work together to control pitch, in opposition to control roll (on a delta wing, like the Shuttle).  

 

[Program Kerbal Space]

5 minutes ago, kc5qnk said:

You mean like the control surfaces?  Kind of like the "ruddervator" on a v-tail, they work through a mixer arrangement.  Work together to control pitch, in opposition to control roll (on a delta wing, like the Shuttle).  

 

Yes i do

[MR L A]

Does the explanation of KSPs drag model still hold true? i.e. more parts = more drag regardless of placement? 

[OrbitalBuzzsaw]

3 minutes ago, MR L A said:

Does the explanation of KSPs drag model still hold true? i.e. more parts = more drag regardless of placement? 

No. KSP aerodynamics make sense-ish now. @keptin might want to fix that

[Program Kerbal Space]

Why aren't you sticked anymore I thought the sticked you? Also nice tutorial!

[Errol]

Perhaps because some of the post is out of date regarding the drag model, as it has been significantly updated since this was written.

[Mechtech]

yeah, getting this updated and made into a KSPedia really needs to happen. love this guide SO MUCH.

[canisin]

I just wanted to say that your tutorial is so beautiful! Thanks a lot for your hard work!

[Gh0stReaper]

On 11/10/2013 at 6:56 AM, LtHeckard said:

As long as the center of lift is inside the center of mass, it should be a pretty stable aircraft.

Not exactly. Because I have had many crafts that have the CoL and the CoM in the same place but flip every time. It depends on where the CoM is compared to the rest of the aircraft.

If the CoM is at the front it is nose heavy.

If the CoM is at the back it is unstable.

[Crispynaut]

Great guide, I know it's a few years old now but hasn't stock KSP upgraded the aerodynamic to be slightly more realistic? (Rocket fairings are actually useful now?)

[kcs123]

16 hours ago, Crispynaut said:

Great guide, I know it's a few years old now but hasn't stock KSP upgraded the aerodynamic to be slightly more realistic? (Rocket fairings are actually useful now?)

Yes it is. KSP stock areo is much better than at time of writting OP, but besides that old bug other stuff are pretty much valid even today.
Anyone who want to learn more how it is done in real life, I have come across to nice videos of university lessons. It might be too much for someone who just want to play game, but it is quite good for people who want to learn more and fill gaps with some books about it too.
Basic course Aerospace Engineering Lessons

[samuel9900]

I know this is probably a stupid question, but I made a dihedral plane which works great in flight, but when it lands it automatically drifts to the side. If I try hard enough it looks badass but usually it just destroys the whole plane. I looked at the veering off solutions and I didn't find a working one for my situation.

 

[Mechtech]

try using the Hanger Grid mod (here) which lets you force alignment and adjust things very precisely.

 

you might also just be having Pilot Error problems, because landing perfectly flat is a cast-iron poodle.

 

but then, I've basically never been able to actually LAND a plane in KSP even WITH autopilot help, so I may not be the best advise-giver in this case.

[Blaarkies]

1 hour ago, Mechtech said:

try using the Hanger Grid mod (here) which lets you force alignment and adjust things very precisely.

you might also just be having Pilot Error problems, because landing perfectly flat is a cast-iron poodle.

but then, I've basically never been able to actually LAND a plane in KSP even WITH autopilot help, so I may not be the best advise-giver in this case.

Use the rotation gizmo, press "f" until you see it is in "absolute mode", press "c" until you are in the 5 degree snap mode (the default mode). Now click the part to align, touch the rotation circles and done. (Hanger Grid does have some extra functionality though)

Works great to do wheel-alignment, or aligning wing mounted engines to point forward after adding incidence to the wing, align surface mounted docking ports and stuff inside cargo bays.

Landing, just take it easy. Fly slowly(no jerky movements) and figure out how slow you can fly before falling. Remember that speed, then just fly 10m/s faster than that for a landing. Come in as low as possible, and practice on the flat fields north of the Runway
Its like docking really, but with mother Kerbin 

[kcs123]

I don't think that is issue with bad alignment, but it does not hurt to check it regardless.

If that does not fix issue, change friction on wheels. Instead of automatic, put some lower value on front wheel and higher on rear wheels. turn off brakes on wheels that were on wingtips, most probably those are ones that cause all mess as it in rare occasion preassure on them are evenly distributed.

Put higher braking force on rear wheels. It is hard to see, but try to separate more widely that rear wheels if possible. Not way too much, only by width of 3-4 wheel width.
Put air brakes much more near tail, that would help to produce more drag near end of craft and helping to keep plane going in straight line.

I ususaly use tri-cycle wheel combo and I was having issues with too wide rear wheels placement in some of craft designs. Usualy wide placed rear wheels helps with stability, but if you place it too spread compared to distance between front and rear wheel (nose - tail wise) it can be overkill and cause instability if you try to steer slightly.

Edited October 18, 2017 by kcs123

[samuel9900]

On ‎15‎. ‎5‎. ‎2017 at 4:32 PM, kcs123 said:

I don't think that is issue with bad alignment, but it does not hurt to check it regardless.

If that does not fix issue, change friction on wheels. Instead of automatic, put some lower value on front wheel and higher on rear wheels. turn off brakes on wheels that were on wingtips, most probably those are ones that cause all mess as it in rare occasion preassure on them are evenly distributed.

Put higher braking force on rear wheels. It is hard to see, but try to separate more widely that rear wheels if possible. Not way too much, only by width of 3-4 wheel width.
Put air brakes much more near tail, that would help to produce more drag near end of cradt and helping to keep plane going in straight line.

I ususaly use tri-cycle wheel combo and I was having issues with too wide rear wheels placement in some of craft designs. Usualy wide placed rear wheels helps with stability, but if you place it too spread compared to distance between front and rear wheel (nose - tail wise) it can be overkill and cause instability if you try to steer slightly.

Thank you so much! My plane even flies better (somehow...)

[Grand Ship Builder]

One note:
Some planes, including the Concorde, have an additional wheel at the back, similar to taildraggers. They are useful at preventing tailstrikes, especially for planes with a high level of attack, like the Concorde.

This could be useful for planes with a high level of attack, so you could add that in.

[baozidai]

Amazing. it helps me a lot.thanks

[baozidai]

I translate it into  Simple Chinese,but I can't send you a PM.    the Chinese version is here http://bbs.3dmgame.com/forum.php?mod=viewthread&tid=5586843&page=1&extra=#pid192551452

I hope you can see this reply

@keptin

Edited May 29, 2017 by baozidai
I want to make sure the author see this.

[kcs123]

6 hours ago, baozidai said:

I translate it into  Simple Chinese,but I send you a PM.    the Chinese version is here http://bbs.3dmgame.com/forum.php?mod=viewthread&tid=5586843&page=1&extra=#pid192551452

I hope you can see this reply

To make sure taht is readed, you can put OP name in your post, Start with "@", and forum will let you to choose  @keptin, so he can be notified about it. Btw, picture is either, quite high resolution or it is on very slow server, but regardless, members from Chinese community would apreciate it.

[baozidai]

28 minutes ago, kcs123 said:

To make sure taht is readed, you can put OP name in your post, Start with "@", and forum will let you to choose  @keptin, so he can be notified about it. Btw, picture is either, quite high resolution or it is on very slow server, but regardless, members from Chinese community would apreciate it.

About slow.  The picture can be open quickly in China. in other countries ,in case of our firewall,  you 'll open it slow.  And thank you tell me how to /@ someone

[Grand Ship Builder]

On 9/3/2015 at 1:48 PM, BadLeo said:

Could use a nice tutorial like this on VTOL, because I'm currently being beat hard by KSP while attempting to build one.

For VTOL, your CoT must be exactly on the CoM.

[Mechtech]

or at least 'close enough' that only minor tilting is needed to get things lined up right- I did a Harrier-alike using KAX's inline VTOL engines that (due to also being a 'traditional' flyer, need to not be super flip-happy) that had to nose up about 15° to take off properly (read: without flopping over onto its back) but a helicopter type thing would need its CoT on the CoM (though in that case having the CoL above the CoM is a necessity for actually flying like a helicopter, IE 'tilt rotor in desired travel direction')

 

....

quadcopters are fun. launching Soyuz upper stages from Quadcopter platforms are more fun.