Are the aircraft physics really, really bad?

[Pokletu]

Hey guys,

After this patch, (.25), I can't get my plane to NOT roll up and tumble apart, from the level flight I last saved at. I stand to kill Jeb just because of this patch, and I don't want to.

The flight surfaces just don't have a proper bite on the air, in my experience. Most of it's been that way before this patch, but at least I could manage it. The plane seems to want to tumble around it's gyro, internally, instead of follow the aerodynamics. It's not just my own constructions, either. Forever, every patch, I've tried to land the space plane provided in the spacestation scenario, with no luck.

I thought if I installed FAR, that would fix it, since it's so popular, but that just made all my controls frozen. Same with NEAR.

I see others land/fly planes with seeming little problem. Is a patch to aerodynamics coming? What are you guys doing to make aircraft viable?

Thanks...

[Beachernaut]

I haven't experienced any trouble. My planes fly like they always have.

[Jatwaa]

Hey guys,

After this patch, (.25), I can't get my plane to NOT roll up and tumble apart, from the level flight I last saved at. I stand to kill Jeb just because of this patch, and I don't want to.

The flight surfaces just don't have a proper bite on the air, in my experience. Most of it's been that way before this patch, but at least I could manage it. The plane seems to want to tumble around it's gyro, internally, instead of follow the aerodynamics. It's not just my own constructions, either. Forever, every patch, I've tried to land the space plane provided in the spacestation scenario, with no luck.

I thought if I installed FAR, that would fix it, since it's so popular, but that just made all my controls frozen. Same with NEAR.

I see others land/fly planes with seeming little problem. Is a patch to aerodynamics coming? What are you guys doing to make aircraft viable?

Thanks...

There is a bit of a difference between .24 and .25 I have noticed it too. I have since adjusted my build techniques but I don't really like the new space plane components as much as the older ones so I intend on holding on to them after the grace period. Try installing NEAR, it seems to handle better with that mod.

[Jon Tash]

I don't have this problem either. Is your landing gears aligned correctly? Are you using SAS, if so how much is your maximum torque value? Is your landing gears to much behind the center of mass? It would be best if you showed to us with a screenshot.

[Zylark]

I've done nothing different in designing or flying my aircraft - using stock atmosphere / aerodynamics. And whilst the 'souposphere' is as thick as ever and the aerodynamics is very simplistic, I've not noticed anything different in how aircraft handle between .25 and .24.2.

If you got problems with aircraft pitching up, it is probably some balance issue. You want Center of Lift to be more or less on your Center of Mass indicator. You also want to balance out fuel. Meaning either you got one fuel tank at your CoM _or_ two tanks equally spaced from CoM _and_ managed by a mod like say Goodspeed Fuelpump to keep the tanks balanced.

Also consider wing-placement. High wing is inherently stable, low wing inherently unstable. Mid wing a nice compromise between the two. For the tail (elevator/rudder) you want as big control surfaces as you can get away with - preferably the entire thing should act as a control surface. Though that part is only available quite late in the tech-tree. Can't remember the name right now.

Last - Center of Thrust should be level with your Center of Lift. If CoT is below CoL, you'll pitch up and vice-versa.

Edited October 13, 2014 by Zylark

[Alshain]

Stock aerodynamics have always been really really bad, but if your installing FAR to stop your aircraft from breaking, that's the wrong thought process. Your problem is your flying or your construction.

In the real world you can't do a 45 degree pitch in a few seconds while traveling 300 m/s. FAR simulates this by breaking the aircraft if you try, which is what would happen. You have to move slow and smooth or the sudden air pressure change becomes too much for the craft to handle. If your craft tumbles out of control, that could be too much force on the craft as well, just not enough to break it. Think of it this way, your plane is traveling forward with the wind going over it and suddenly you want to turn east, you roll and pull back hard but your going so fast that now your traveling with the bottom side of the plane facing the direction of travel because even though the plane turned, it turned too fast to change direction and it's still traveling the direction you were before, the plane wasn't build to do that and you lose control.

If your controls are "frozen" you may not have your ailerons configured correctly, though that would be strange because their default is to control everything (also fairly bad but will kinda work). It's more likely your construction is off somehow, but we would need more info on where the problem is and what happens to diagnose. Are you having trouble taking off? Turning? Pitching up? Landing? Screenshots of the craft would help too, make sure you show at least the Center of Mass and Center of Thrust.

NEAR and FAR make it more intuitive and as long as you don't fall back to bad practices that KSP has taught you, it should be easier because your craft will fly more like you would expect it to by looks rather than some oddball flight.

Edited October 13, 2014 by Alshain

[Pokletu]

Yeah, it wants to veer off the runway even on takeoff.

You don't need to explain the principles of flight to me, I have an A&P license, lol.

The plane's parts seems like they're spaced in-between, now. Not solidly connected.

Does anyone know the name of that mod that gives kerbals an EVA parachute? If I could find that, I'd dump the plane, and save him. Right now, this savegame is doomed, lol...

[Alshain]

Yeah, it wants to veer off the runway even on takeoff.

Oh, that's easy. The wheels aren't aligned OR they are attached to something that is flexing out of alignment (in which case, use struts). It's hard to see sometimes, but that's nearly always the case when your plane won't go down the runway straight. The Firespitter plugin has wheel alignment guides but sadly it's not updated for 0.25 yet.

You don't need to explain the principles of flight to me, I have an A&P license, lol.

And I was supposed to know that... how?

The plane's parts seems like they're spaced in-between, now. Not solidly connected.

Not sure what you mean, screenshot? The editor can be strange sometimes. Some parts are just like that, the large 1.25m LFO tank for example has a lip but the entire collision mesh is inline with that lip rather than the rest of the tank. It shouldn't affect anything.

Does anyone know the name of that mod that gives kerbals an EVA parachute? If I could find that, I'd dump the plane, and save him. Right now, this savegame is doomed, lol...

Vanguard Technologies.

Edited October 13, 2014 by Alshain

[Jon Tash]

Does anyone know the name of that mod that gives kerbals an EVA parachute? If I could find that, I'd dump the plane, and save him. Right now, this savegame is doomed, lol...

You probably are looking for this : Vanguard Technologies - EVA parachutes

[herbal space program]

I've actually found that my space planes work better than they did before. Of course I hadn't actually built one since the wobbly days 0f 0.21, so I couldn't comment on how it compares to 0.24. The first one I built used Mark 2 components with 2 RAPIER engines. It could almost make orbit on jet fuel alone and took only a few minutes to get to a 1500+ m/s flameout at 27km or so. Control was smooth as silk the whole way. Of course when I tried to add parachutes, cargo bay, VTOL capability, and science instrumentation it was another story, but I eventually got all of that working too on a plane that could make orbit in something like 14 minutes on about 300 units of jet fuel. I don't think I could have managed that with what was available in 0.21.

Anyway, when a plane wants to fly backwards, it's usually because the center of lift has gotten in front of the center of mass. This often happens as your fuel gets consumed, since the tanks get emptied from the front to the back. the best remedies for this I have found are to put the bulk of the fuel load as close to the center of mass as you can, and also to run a fuel line from the rearmost tank forward to the one closest to the center of mass. This will cause the fuel to drain from both ends towards the center rather than from front to back. Failing to do this for me always ended up producing planes that were nose-heavy at takeoff and then pitched up uncontrollably after burning half their fuel.

[herbal space program]

In addition to mis-aligned landing gear, too much weight on the front wheel will also often produce veering behavior. You might try lightening the front of the plane or moving your nose wheel back towards the center of mass to increase the angle of attack. raising your elevators part way once you get above about 35 m/s also helps quite a bit. All these things take weight off the nose wheel.

[r_rolo1]

On the title, yes, they are bad: too much drag ( that is a direct function ( almost ) of the mass of the ship ) and independence of the ship orientation, almost like a weaker cousin of gravity that pushes backwards at low altitude.

On your issues, it definitely looks like a misaligned / flexing front landing gear. Also, consider that in general 0,25 aerodynamic parts are heavier than 0,24 ( and that landing gears in 0,25 also have weight, unlike in 0,24 and previous ), so you might be unconsciously putting more weight in the plane than you think ...

[Duke23]

I had a quite successful ssto I had just built before the update, and I rebuilt it with the new stock parts while looking at a picture of it. Now it's extremely slow and seems to lose lift above 10km a lot worse than it did before. So something has to be different, maybe it's the weight or lift of certain parts.

[SorryDave]

My son had the same comments, something changed. He builds mostly in the space plane builder but had a hard time building aircraft that flew well. Some if his favorite designs were impossible to fly straight.

[Pecan]

Apart from the spaceplane + parts the major change was that landing-gear now has mass in-flight. Since, as a rule, I like to put gear on the bottom of my 'planes that should lower the CoM and make the planes pitch-down. Oddly enough though all the old designs now have a tendency to pitch-up under thrust. One of my - small, slow, stable - designs is now too twitchy to fly while at least two others won't even take-off (CoM has shifted forwards and they don't have the lift or pitch authority to rotate on the runway). The rest of the fleet - some 10 planes - seem to be functioning more or less the same as they always have.

[Alshain]

The wheels have so little mass in the grand scheme it shouldn't affect anything. Maybe on tiny ion gliders, but not most planes. Your pitch up is likely being caused by the new body lift, which undoubtedly move the CoL a little closer to the CoM.

[Engineer of Stuff]

I love the bad aerodynamics! You can get away with so many things!

(But I do want a better aerodynamics).

[NathanKell]

Pokletu: sounds like you might be using KSP Windows x64? (did FAR and NEAR come up with warnings when you started KSP?) That would explain them not working. Even if you have 64bit Windows, you should use 32bit KSP.

[Red Iron Crown]

Apart from the spaceplane + parts the major change was that landing-gear now has mass in-flight.

My smallGearBay.cfg still has "PhysicsSignificance = 1" in it. I believe that means that they are still massless (and dragless in stock aero) when in flight.

[Motokid600]

Also it sounds as If the savegame your running is from 24.2. Is that so?

[monophonic]

Also it sounds as If the savegame your running is from 24.2. Is that so?

I also read it as thus. Which of course means all bets are off as a lot of the plane parts changed values and even shapes in the update.

[BDelacroix]

While I may not be able to get a plane to do much other than eat oxygen out of atmosphere like a candy starved kid eats pixie stix, I have not noticed that flying them is much different in the atmosphere.

[Pecan]

The wheels have so little mass in the grand scheme it shouldn't affect anything. Maybe on tiny ion gliders, but not most planes. Your pitch up is likely being caused by the new body lift, which undoubtedly move the CoL a little closer to the CoM.

Aha! I didn't realise the old parts had been made lifting bodies (these are old designs that no longer work, or no longer work as they did). Hehe, the SP+ lifting bodies are giving a different - but entirely sensible - problem in another way; I'm having to re-learn by re-entry and transition to flight stats because I keep overshooting the runway. Those things don't like coming down do they!