Planes / Spaceplanes unflyable!

[Morgan927]

I have been trying to create usable planes and space planes for quite a while.  I finally get the COL/COM balanced well, and I cannot yaw without pitch and roll being induced, and all rotations seem to induce rotations on the other axes.  For example, when I try to roll 45 degrees left, I get right yaw and down pitch.  Once I get on a heading, I have a VERY hard time turning.  I thought I was designing them incorrectly so I downloaded an SSTO from Marcus House's page and tried it....same thing.  Also, I used his kOS script to attempt to get it into orbit and the engines shutdown due to overheating well before the closed cycle starts.

 

I suspect I have installation issues.  Either my dual core laptop (which seems to be pegged most of the time) just can't do it, or I have some difficulty setting set to hard.  Any ideas?  I am very frustrated with the planes.

[fourfa]

A few things I can think of - first, have you unselected pitch and yaw from your roll ailerons, unselected roll and yaw from your pitch elevators, unselected roll and pitch from your yaw surfaces?  KSP's stock SAS code is pretty bad with coupling all the different control axes, along with using too much reaction wheel force, etc.

Second, there are actual coupling forces in real life, and they're modeled in KSP to an extent too.  For instance, if your rudder extends above the center of mass (as it usually will), then when you yaw you will unavoidably induce a roll moment.

I find a lot of the streamers that focus on planes make their planes fly neutral and stable with SAS off, and use trim to actually fly it.

[Snark]

40 minutes ago, Morgan927 said:

or example, when I try to roll 45 degrees left, I get right yaw and down pitch.

Very common problem.  As @fourfa says:  make sure that your vertical stabilizer has disabled control authority for everything except yaw.

The short version of why this is important:  for planes, the yaw controls are usually on surfaces that aren't symmetrically paired (e.g. you have a vertical stabilizer that sticks up from the tail, but no corresponding one sticking down).  Which means that when you want to roll, it tries to help you with the roll, and since it's not paired, it induces yaw.  The solution is to make it so that it only works with yaw and will ignore roll inputs.

 I can tell you that lots and lots of people fly planes successfully, so if your plane isn't working, it's because there's some issue with its design.  Alas, we can't tell you what the problem is yet, because there are many different things that it could be, and a lot of them come down to specific things such as the placement of control surfaces, CoM, and so forth.

So it's hard to give you any specific advice without seeing your plane.  Could you post a screenshot?  (Ideally sitting in the SPH with the CoM display turned on.)  Once we can see your plane, then we can give you specific useful advice ("oh, this thing here should be moved over there" or whatever).

[Morgan927]

I will try the yaw only, however, isn't this a craft setting, not a game setting?  I downloaded Marcus House's Trident spaceplane which flies beautifully in his videos, but not for me.  I will also try flying with SAS off, and using trim.

 

Here is the video of the spaceplane. 

 

Edited November 29, 2017 by Morgan927

[Zeiss Ikon]

I won't lie to you -- flying an aircraft with standard KSP controls is a bear.  I've got more than a hundred hours of radio control stick time, flying aerobatics, very low speed (like, edge of stall) at low altitude, inverted 8s on a plane without direct roll control -- I'm not an artist with a stick, but I'm pretty competent.  I've also built R/C and free flight model airplanes, so I have a good grasp of surface function, COM/COL relationships, and how to trim for stability.

It's all I can do to get a KSP plane that's as stable as I can build off the runway in one piece without SAS.

Previous advice about disabling extra control functions is spot on -- with my most recent spaceplane attempt, I got it to fly (in SAS) with roll/pitch surfaces combined, but it flew much, MUCH better when I put ailerons on the wings instead of elevons in the tail, and set every surface to a single function.

The vertical rudder is especially important for this -- as @Snark pointed out, it'll guarantee adverse yaw if you leave the roll function enabled on a common "upper-only".  As well, combining pitch and roll seems to result in nose-up or nose-down response on a roll command, especially if you're using "deploy" to gain a constant amount of decalage to provide pitch stability (decalage is a bad thing if you're going for high speed, BTW -- it'll cause you to make a huge loop as the speed builds up).

Best thing I can suggest is to download some designs that are mentioned as "easy flying" and "stable" and practice with them.  There's no shame in starting with a trainer; I started flying R/C with a basic sailplane, moved up to a no-aileron power trainer, which I flew the heck out of before attempting 3-axis controls.

BTW, if you're interested in flying aircraft in KSP, you might consider setting up to use a joystick, at least for pitch and roll.  Proportional control (as opposed to what old R/C pilots call "bang-bang" controls) makes the whole process far easier to learn.

[GoSlash27]

49 minutes ago, Morgan927 said:

I will try the yaw only, however, isn't this a craft setting, not a game setting?

It's an option you have to adjust in the SPH for each control surface individually. If a control surface is meant to be used as an aileron, set it to respond to roll only. Likewise for elevators; pitch only. I always design my aircraft so that rudders respond to nothing and always recommend that others do the same.

For that KOS spaceplane shown in the video... I don't like the vertical stabilizers on it. They should always be as far back as possible.

Best,
-Slashy

[Morgan927]

@GoSlash27, I have tried setting control surfaces to only one function, but was trying to be more realistic.  How in the world do real aircraft fly if they are that sensitive?

@Zeiss Ikon, I understand.  I have not hundreds, but dozens of hours flying RC, and I have 200 hours in a military F-16 simulator (worked for Singer-Link in the day) and about 10 hours in Cessnas, 2 in a C-130, 6 in T-37....etc   Never had so many problems.  I have literally thousands of hours flying various PC based sims.

I tried using joysticks.  I have four of them, but apparently, the drivers for all four of them don't work on Win7, only WinXP.  Also, not sure if the 15 pin adapter to USB for one, works with the others, 3 of them are 15 pin only.  Hate to buy another, my favorite was expensive, 15 years ago.  I am to the point where I need a shuttle so will keep at it.

Edited November 30, 2017 by Morgan927

[Snark]

1 hour ago, Morgan927 said:

I will try the yaw only, however, isn't this a craft setting, not a game setting?

Yes, absolutely.

If you're downloading someone else's planes, then I don't know what to say.  I'm mostly a rocket person, not an airplane person... but I do fly planes from time to time, and as long as the design of the plane is good, I find flying them to be very easy.  (And I'm using the standard keyboard controls, not a joystick, so that's not the issue, either.)

Of course, when I fly planes, I'm flying my planes, and I tend to design my planes for stability.  Other planes that are designed more for maneuverability (fighter jets etc.) might be a different story.  So that may be idiosyncratic to just me and the kinds of planes that I fly-- except that I can also tell you that there are lots of people posting "why doesn't my plane fly" questions here in this forum, and in my experience it's nearly always been the design rather than the piloting that was the problem.

So, the knee-jerk reaction to "plane won't fly" is "check plane design".  If you're having problems with that particular plane... try a different plane.  That one sure looks huge and fancy.  My recommendation:  build (or download) a very simple plane to start, and try that.  Get it to work, get comfortable with the piloting and design principles so that you're confident and comfortable with it.

Then try a more complex plane.

30 minutes ago, Zeiss Ikon said:

I won't lie to you -- flying an aircraft with standard KSP controls is a bear.  I've got more than a hundred hours of radio control stick time, flying aerobatics, very low speed (like, edge of stall) at low altitude, inverted 8s on a plane without direct roll control -- I'm not an artist with a stick, but I'm pretty competent.  I've also built R/C and free flight model airplanes, so I have a good grasp of surface function, COM/COL relationships, and how to trim for stability.

It's all I can do to get a KSP plane that's as stable as I can build off the runway in one piece without SAS.

Depends on the aircraft design.  I fly KSP airplanes only with the keyboard, and I've never had any problem flying them.  Of course, I tend to build planes for stability. 

 

[Morgan927]

I just remembered, I have a throttle block (4 engines with mixture), steering wheels, rudder pedals, and others, but all of those are 15 pin.

[Snark]

1 minute ago, Morgan927 said:

I just remembered, I have a throttle block (4 engines with mixture), steering wheels, rudder pedals, and others, but all of those are 15 pin.

Shouldn't need 'em.  A stably-designed plane is easily flyable with keyboard alone.

It might not be as fun or as natural or as precise as using a joystick, depending on your inclinations / preferences... but if the problem is "oh noes this keeps spinning out of control", then "using keyboard" is generally not the reason for that.

[Morgan927]

1 minute ago, Snark said:

So, the knee-jerk reaction to "plane won't fly" is "check plane design".  If you're having problems with that particular plane... try a different plane.  That one sure looks huge and fancy.  My recommendation:  build (or download) a very simple plane to start, and try that.  Get it to work, get comfortable with the piloting and design principles so that you're confident and comfortable with it.

 

I assumed it was my design so was downloading other people's, large and small.  I have gone through 12 without success.  I gave up for a while until I tried this monstrosity, because I am playing with kOS, and through it would be cool to have a large working spaceplane already scripted. 

I didn't think I would need those external devices, but I was reminiscing on all the ancient useless hardware I still have.

[bewing]

The stock game comes with several easy-flying planes. If you are in sandbox mode, you should have access to the Aeris-3A. Very very easy to fly.

 

[Morgan927]

I don't do sandbox, but I guess I should try.

[Aegolius13]

1 hour ago, Morgan927 said:

I don't do sandbox, but I guess I should try.

You can also just copy the file for the plane into your career's ships /SPH folder.   Though you may not have unlocked all parts needed to use certain craft. 

Edited November 30, 2017 by Aegolius13

[Aegolius13]

1 hour ago, GoSlash27 said:

I always design my aircraft so that rudders respond to nothing and always recommend that others do the same.

Does this make the rudder literally not move,  or does it let the SAS operate the rudder?  If the former,  seems like you might as well use a static surface or wing as a rudder. 

[Spricigo]

35 minutes ago, Aegolius13 said:

Does this make the rudder literally not move,  or does it let the SAS operate the rudder?  If the former,  seems like you might as well use a static surface or wing as a rudder. 

Literally not move. And agreed about the static surfaces (is my usual choice)

[Gordon Fecyk]

Here is the very first plane I flew in my first full career playthrough.

(Hopefully the explosive thumbnail doesn't set you off right away! It isn't often I see Jebediah with a frown! Don't worry though, he survived.)

You can ignore the FAR / Ferram Aerospace stuff and build this plane along with the video, and it should fly in Stock. You need at minimum the Aviation node unlocked for these parts, which gives you the Juno engine and small intake, the liquid fuel-only tanks, and aero parts. There's also no shame in using parachutes to land when starting out.

While this will get you off the ground, it's hardly an optimal design. You can lighten the load by replacing the Mk1 fuel fuselage with a Mk1 structural fuselage, or just empty the Mk1 tank first. You can use structural wing parts instead of the swept wings to get the same lift for less mass. You can build a complete engine nacelle with a Mk0 liquid fuel tank, small intake and Juno engine. And without the type-B tail's higher clearance, you can use a type-A tail, rotate it slightly and clip it slightly into the fuselage for a similar effect.

Getting the Aerodynamics node after this will get you Mk1 intakes and engines, better wings, retractable landing gear, and other goodies so you can graduate to this:

Again, you can ignore the FAR / Ferram Aerospace stuff and fly this plane in Stock.

If you can fly those in the air, then you can fly these to space:

...and come back safely.

[GoSlash27]

1 hour ago, Aegolius13 said:

Does this make the rudder literally not move,  or does it let the SAS operate the rudder?  If the former,  seems like you might as well use a static surface or wing as a rudder. 

^ What Spricigo said. The vertical stabilizer should literally not move in response to any input, and a static surface is fine for the job.

 KSP's SAS function tends to correct heading deviations with yaw, and that's the wrong response with airplanes. If you want to change the heading of an airplane, you should roll into the desired heading and let the nose track around smoothly on its own. Pointing the nose at the desired heading using yaw just causes a cross-controlled condition, resulting in increased drag and weird cross-coupling responses and a reduced tendency to track cleanly. 

 Airplanes (other than pure aerobatic) don't need active rudders in KSP, and making them active only hampers them from flying smoothly. Hence my recommendation to never have active rudders.

Best,
-Slashy

[GoSlash27]

3 hours ago, Morgan927 said:

@GoSlash27, I have tried setting control surfaces to only one function, but was trying to be more realistic.  How in the world do real aircraft fly if they are that sensitive?

Morgan927,

 Designing airplanes is more difficult than rockets IRL as well as in KSP. Rockets only require balancing 2 forces; thrust and weight. In airplanes, there are 4 forces that must remain balanced; thrust vs drag and lift vs mass. The airplane must be designed to keep all of the forces in balance naturally. If the plane is engineered to fly easily, then it will do so.

 Note that you also have the ability to adjust the deflection of the control surfaces...

 I won't go into a tutorial on KSP aerodynamics, since there are plenty of tutorials on the subject. But rest assured, it *is* possible to design efficient (and even pleasant) airplanes in KSP.

Best,
-Slashy

[Morgan927]

GoSlash27,

I have built many flying models and never had these problems.  Would help if the center of pressure was shown for various speeds as well as CoL.  The center of pressure moves as speed changes.

I followed a couple of the tutorials.  Nothing I didn't already know.  I even tried to re-create the same ship, but the tutorial was on such an old version I did not have the same parts to use. I have unlocked almost everything.

I wonder how much of my problems are my CPU is just overloaded.  I tried sandbox with nothing else going on in the game, no other ships....and the smaller craft work ok.  Put them in my career game and issues start.

I mean, it is not like I am a character on "Red Dwarf" or anything like that!  Sorry, I just had to say something!  lol

I see all these space planes, but if they do not have a cargo bay, what good are they?  The only reason I want them is as a shuttle to and from orbit.

Edited November 30, 2017 by Morgan927
additional

[Dunbaratu]

A couple of things:

1- Try steering by banking with Q and E instead of yawing with A and D, but note the next point about SAS when you do.

2 - SAS will prevent a plane from changing heading properly when banked.  The stock game's SAS doesn't understand that the change in heading as you turn from being banked is actually what you desire.  It sees it as a change to your direction vector, and thus something that must be fought.  So if you are, say, banked 45 degrees to the left and would thus normally change heading toward the left, SAS will fight that heading change by pushing elevator down a bit and rudder right a bit so you perform a side slip instead of a turn.  This causes people to try to steer by yawing which has all the standard problems that trying to do that has.  The correct answer is to disable SAS when you want to change heading, and have a plane trimmed appropriately to fly level without the SAS help.  (You can turn SAS back on again after you level off, as SAS is necessary when using physics warp as physics warp introduces small deflections from errors that accumulate if you don't have SAS on.)

3 - To make a plane more flyable without SAS, avoid using the S and W keys directly to pitch.  They're just too jittery.  Instead control pitch with trim, using ALT-S and ALT-W.  Note that most people don't realize these keys work because they always have SAS on, and SAS suppresses the effect of these keys making them look like they didn't do anything.  (These keys affect where the controls get centered when you let go of them, and SAS takes over the controls when you let go of them so the trim setting has no effect under SAS).

4- If you accidentally press Q,E,A, or D while you were holding down ALT because you were pitch trim adjusting, that will adjust yaw or roll trim which can really mess you up and make it a mess to fly.  Remember that ALT-X is the "back to zero" for all trims setting.  You may need to use that if you accidentally pressed, say, a few ALT-Q clicks and can't tell if you had pressed 2 of them or 3 of them so you don't know how many times to press ALT-E to put it back again.  Just remember that after you ALT-X, expect your pitch trim to go wonky again so you have to correct it again.

The pitch trim trick is important because that's what allows you to make a stable plane with COM slightly ahead of COL that you have to correct for with a small amount of up-pitch.  That "small amount of up-pitch" is a pain to do manually with just tapping the "S" key and otherwise requires SAS to be on which causes the problems mentioned above in (2).  pitch trim will allow you to fly nicely without having to resort to the wonky SAS logic that is right for rockets but wrong for planes.

 

 

[Daniel Prates]

12 hours ago, fourfa said:

A few things I can think of - first, have you unselected pitch and yaw from your roll ailerons, unselected roll and yaw from your pitch elevators, unselected roll and pitch from your yaw surfaces?  KSP's stock SAS code is pretty bad with coupling all the different control axes, along with using too much reaction wheel force, etc.

That indeed is a thing in KSP. If you assign more than a pair of surfaces for a same axis,  they will sometimes cancel themselves out,  depending on where they are placed.

[Plusck]

3 hours ago, Steven Mading said:

A couple of things:

[snipped: lots of very useful info about pitch trim and flying planes]

Finally!

I'd even go further and say that you should ONLY use pitch trim (well, virtually all of the time anyway) and no SAS to fly planes in KSP.

Still, one does have to bear in mind that KSP was never intended to be a flight simulator.

 

9 hours ago, Morgan927 said:

@GoSlash27, I have tried setting control surfaces to only one function, but was trying to be more realistic.  How in the world do real aircraft fly if they are that sensitive?

Realistic is attaching one set of flight control surfaces /engines to one set of controls. Rudder is not so useful in KSP since its main uses in the real world (cross-winds, unequal buffeting of prop wash, preventing side slip when turning) either don't apply or are not a significant problem in KSP.

Planes are that sensitive in the real world, too. Get your CoM wrong in a small plane (heavy passengers, too much fuel) and you can very easily crash and die. Happens all the time. The advantage of the real world is that you have force feedback stopping you from slamming the controls all over the place (though pilots have memorably managed to do just that with the rudder and broke the tail off a passenger jet a few years ago, killing everyone in the process).

[GoSlash27]

7 hours ago, Morgan927 said:

I see all these space planes, but if they do not have a cargo bay, what good are they?  The only reason I want them is as a shuttle to and from orbit.

Morgan927,

 I build my space planes for the same purpose; shuttling to and from orbit. Mine never have cargo bays because I never use them to haul cargo. I find space planes too restrictive on the size and shape of the cargo. Instead, I use them for shuttling crews and supplies (fuel, monoprop, etc).

As for why your craft function fine in sandbox but go wonky in career... I have no idea.

Best,
-Slashy

[Dilli]

Try pressing CAPS LOCK to enable smaller incremental controls, for most aircraft I have built it is usually the difference between flying them and wrestling a wing gorilla onto a heading.

As mentioned above limiting control surfaces to there proper functions also helps. 

Most SSTO's are designed to go up and down on a fairly flat trajectory with limited control inputs. They may not be the best place to look for normal planes