why the hell space planes and airplanes start spinning at 20k altitude ?!?!?

[Armagedon-100]

i know the reason is one engine (the right engine) starts turning on and off and chaning his impluse very drastically, but this shouldnt happen right ?!

so, is there a way to fix that bug? 0.0

[Mudkest]

its not really a bug, more about how you build the spaceplane. there's aforum post on the official forums somewhere, cant find it now though. Anyway it has to do with the order you build the plane, specificly the jet engines and air intakes.

Say you place 8 air intakes then 2 engines, the game will assign all the air intakes to the first engine. That engine then uses all the air, any left over goes to the 2nd engine. Once the first engine uses up most of the air the 2nd engine flames out. to fix it, dont put air intakes and engines in symetry mode.

In this example, build the plane, remove any air intakes and engnes, then place 4 air intakes, 1 engine, then the other 4 air intakes and then the last engine.

[Falknir]

Your space plane has insufficent balanced air-intake for the craft at that altitude and speed, causing engine failure. Try lowering engine output before intake air is insufficent and also try leveling out to gain speed before continuing the ascent as it will increase airflow through the intakes at higher altitudes. Always keep an eye on your intake, speed, and altitude to get a better idea of how your craft performs.

At high altitudes where the atmosphere is thin, if you start losing complete control due to air-breathing engine stalls. You might have the option of throttling back hard and relying on reaction wheels and reaction control systems to put you back on course allowing you to make another attempt.

[AlexMBrennan]

but this shouldnt happen right ?!

Newsflash: Fire needs air to burn. In space, there is no air.

[undercoveryankee]

Jet engines flame out when there isn't enough air to keep them running at 10% of sea-level fuel flow. If you have multiple engines, some of them will flame out and the rest will keep running using the air that would otherwise have gone to the flamed-out engines. The order in which they flame out is based on the order in which the engines and intakes appear in some internal data structures, which you can influence by the order in which you add parts in the editor, but it's not always possible to come up with an order that gives you balanced flame-out on every possible jet.

A better jet engine simulation would explicitly keep track of which intakes are feeding which engines instead of having a plane-wide "IntakeAir" pool, so it wouldn't be affected by build order. The best we can do in KSP is test each plane design, find its limits, and set an action group to switch to rockets just before it would tumble.

[Xenothor]

I liike how you think that this is a bug rather than an engineering challenge.

A simple solution is to only use a single jet engine so that your thrust is right down the middle of the plane and then you wont flat spin when a flameout.occurs. If you must use more than one jet engine, it works best to keep them close together so that when one flames out, the other is not much off center and the force of the spin is much less and can often be controlled. If you don't care about staying realistic you can place multiple engines right on top of each other and have all your thrust right down the middle, so that a spinout will never occur.

Becoming a better pilot goes a long way as well. Ease off on your throttle when you start to hear your engines spinning down. At lower throttle engines require less air, and if you back off on you throttle incrementally as you climb you can reach much higher altitudes on jet engines. Also. at lower throttle you can often control a thrust unbalanced plane as the spin has much less force to it, and you can control against it.

Using the above I can cruze most of my SSTOs to 50K+ altitude with only one aiir intake per jet engine, and have made orbit using as little as 4 units of oxidizer. With proper piloting it's easy to achieve 80k+ apoapsis and 40k+ periapsis before ever using a rocket engine.

[Trehek]

Originally posted by Armagedon-100:

i know the reason is one engine (the right engine) starts turning on and off and chaning his impluse very drastically, but this shouldnt happen right ?!

Of course it should happen! A jet engine needs air to function and at that altitude there's not a lot of air. Add more air intakes, fly faster and/or at lower throttle to supply your engines with enough air. Keep an eye on the resources and pay attention to when you're about to run out of IntakeAir.

[Armagedon-100]

you seriusly dont get it do you...?
my plane is perfectly balanced on the left side and the right which means equal weight and fuel consumption and so on with air intake.

one engine starts to turn off and on while the other functions normally although both have exacly the same number of intakes...

and yes im a good pilot, i manage to reach orbit with that bug and actully a stable one

and this crap happens in all my planes no matter what so you cant tell me its not a bug

[AlexMBrennan]

Maybe you'd realize that we do get it if you could be bothered to actually read our responses? undercoveryankee has answered your question:

The order in which they flame out is based on the order in which the engines and intakes appear in some internal data structures, which you can influence by the order in which you add parts in the editor

[Nilfsen]

KSP have this thing with fuel flow ( and yes intakeair is considerd fuel ) that makes air intakes and engines "connected". It makes air be deliver first to connected engine and then to rest.
So if there is uneven amout of air intakes "connected" to engines it affects them when they are not getting all air needed to operate, some engines are getting more air than other so they are having stronger trust and that makes your craft spin out of controll.

You can avoid that, I think, by ataching parts in correct order. All intakes are "connecting" them self to engine atached just before them. But I can be wrong it is just some random tip I found on forums.
You can use this in two ways:
Put engine, then air intakes for this engine, next engine equal amount of air intakes and fallow this way.
Or you can put one engine as last in the line with center of trust and then put all air intakes and attaching all other engines by pairs with symetry on. It should flame out them in pairs equaly keeping this middle engine up and running and avoid uneven trust.

I saw also new mod at forum that can address that problem and allows you to manualy make mentioned connections/balance them for you. I don't remember its name but its fresh one so should be easy to find at game forums. Never tested it so I don't know if it does job done.

[Ottomic]

Originally posted by Armagedon-100:

so, is there a way to fix that bug? 0.0

Roll back the throttle, make single-engine planes, use the "prevent flameout" Mechjeb feature. There's not enough air for jets to work past the ~20k mark. It's always been like that, definitely not a bug.

[Xenothor]

Originally posted by Armagedon-100:

you seriusly dont get it do you...?
my plane is perfectly balanced on the left side and the right which means equal weight and fuel consumption and so on with air intake.

I fully understand what you are talking about, as does everyone else who has responded to you in this thread. When I talked about balance I was referring to thrust balance and not weight balance. Any plane with more than one engine will have unbalanced thrust once one engine begins to fail, but this can be overcome with plane design and piloting. Many tips have already been offered in this thread, so I wont reiterate them.

[Mudkest]

Originally posted by Armagedon-100:

you seriusly dont get it do you...?
my plane is perfectly balanced on the left side and the right which means equal weight and fuel consumption and so on with air intake.

http://forum.kerbalspaceprogram.com/threads/64362-Fuel-Flow-Rules-%280-23-5%29?p=1176695&viewfull=1#post1176695

found the topic, shows what I said in the first reply. your plane is most likely not perfectly balanced with airflow

[DCBenton]

Try putting on 1 engine and the intakes you want it to use, and then put the other engine on and it's intakes.

http://forum.kerbalspaceprogram.com/threads/92752-How-to-exploit-intake-air-flow-logic-for-profit



Also you could try this mod, it optimises your engines and intakes.

http://forum.kerbalspaceprogram.com/threads/104704-0-90-Intake-Build-Aid?highlight=intake+build

[davifernandeslima]

ow man...dozens of people helping you with your obvious ignorance and this is your response?
welcome to the Age of Denial

that's from a guy who came here with the exact same doubts as yours...thrust and airflow balance. well not anymore.

kudos to the KSP community who had helped me learn a bunch of great engineering stuff since the beginning. much much love.

Originally posted by Armagedon-100:

you seriusly dont get it do you...?
my plane is perfectly balanced on the left side and the right which means equal weight and fuel consumption and so on with air intake.

one engine starts to turn off and on while the other functions normally although both have exacly the same number of intakes...

and yes im a good pilot, i manage to reach orbit with that bug and actully a stable one

and this crap happens in all my planes no matter what so you cant tell me its not a bug

[Janz]

i wouldlike to see a picture of this magnifecent spacecraft ship