my planes keep going upside down after launch

[harrypotterjames011]

i mostly use rockets but today i tried to make a plane to go to space i had three rapier engines and one swivel on it to go to orbit and do science  but after takeof it went upide down imediatly so how should i make my plane so that it does not tip over

[Streetwind]

Your description tells us close to nothing, so we can only guess...

...but my guess is that your combined center of thrust is not pointing through your center of mass. In other words, your engines are thrusting off-COM and creating torque that turns over your plane.

Imagine if you built a bog standard rocket, but instead of attaching a pair of solid boosters, one on each side, you attached only one booster to one side. This rocket will not fly straight - it will constantly turn sideways. Because the single SRB is not thrusting through the center of mass. It is hanging off to the side, and there is no matching booster on the other side to counteract the torque it is creating.

The same principle holds for planes, except worse. Because people have this image in their head of "I can just sling my engines under the wing, that's what they do IRL". No, you cannot "just sling them under the wing". If all your engines hang below the center of mass, they torque your plane head over heels whenever they run. Real-life planes are far more complicated than you think, and not all aspects of aerodynamic flight are precisely modeled in KSP.

To check if this is your problem, you can turn on the display for center of mass and center of thust in the hangar/editor. If the arrow representing the direction of thrust is not pointing precisely at (or through) the COM, you'll need to rebuild your plane.

[Vanamonde]

Pictures of the plane would help diagnose the problem. You can upload screenshots to a service like imgur.com (it's free) and link to them in your posts. 

[DeadJohn]

A picture of your plane would be very helpful. What do you mean by "upside down"?

Are you flying mostly horizontal like a plane and somehow rolling so that the cockpit is looking down instead of up? You might need to reconfigure your wings or ailerons. Or, if you have heavy equipment stacked on top of the fuselage, redistribute some of that mass so the plane's not top heavy.

Are you tumbling so that the engines flip to the front of your travel direction which makes everything uncontrollable? That generally means your mass is too far back relative to the wings. Offset wings backwards or shift mass forwards.

[Matrazuchi]

9 hours ago, harrypotterjames011 said:

 after takeof it went upide down imediatly so how should i make my plane so that it does not tip over

For a plane to be controllable, it needs to be slightly nose-heavy;  not much, just enough to prevent it from tipping over. When building it, check the center of mass (yellow sphere) and center of lift (blue sphere); The blue sphere should be slightly behind the center of the yellow sphere, but not too much. I'd say either just inside the yellow sphere, or maybe half in and half out.
Also, check what happens when your fuel tanks go empty, you don't want the center of mass to shift back too much. If that's the case, move the center of lift further back, even if that means your plane will be a bit too nose heavy when it starts flying...

- If the blue sphere is too much behind, your airplane will be very nose-heavy and you'll have a hard time to prevent it from going nose-down. 
- If the blue and yellow spheres centers coincide, your aircraft will fly, but it will be incredibly uncontrollable, the slightest control surface correction will send it into uncontrollable spin ... and we all know where that ends
- Finally, if your center of lift is in front of center of mass, then your aircraft will behave exactly as you described it: it will flip over the moment it loses contact with ground.

[harrypotterjames011]

it goes upside down by picching upwards but currently my keyboard is a bit broken and it does not take screenshots in a few days my new keybord will come and i will send an image of the plane  

[king of nowhere]

7 hours ago, harrypotterjames011 said:

it goes upside down by picching upwards but currently my keyboard is a bit broken and it does not take screenshots in a few days my new keybord will come and i will send an image of the plane  

screenshots are important whenever you ask something here. "my vessel does not work as intended" could be due to dozens of different problems. for us to identify which one is the true problem, we need as much information as you can get.

[jimmymcgoochie]

Some combination of the below are likely to be playing at least some part in your troubles:

• Centre of Mass behind Centre of Lift. This is unstable as the drag produced by the wings  will slow the front end down more while the greater weight at the back will have more inertia and won’t slow down as much so it’ll pivot around quite readily. Many a rear-engined car has had the same issue as the heavy engine in the back made it very unstable and prone to spinning, but for a plane the issue is compounded by being able to spin vertically as well as horizontally and the addition of aerodynamic forces that will make the draggy end go to the back. Look at a dart: the weight is at the front and the fins (drag) are at the back, giving it the stability needed to fly straight. To fix this, shift fuel tanks forwards and tweak the tank priorities so the aircraft remains balanced as fuel is burnt.
• Centre of mass too far back. Even if your CoM is behind the CoL, if it’s just too near the tail then as you pitch up the fuselage itself will produce significant drag; the nose slows down, the heavy tail keeps on going (often aided by lots of thrust) and the result is predictably explosive. Shift that CoM towards the centre of the craft, adjusting the wings as necessary so it’s still stable.
• Centre of thrust too low. If all your engines are under the wings then that’ll add a significant torque force to the plane when at full power, as you are at takeoff. If this force is great enough and/or combined with the control surfaces trying to pitch up to take off, the result can be a sudden pitch up that the controls just can’t counteract in time, if at all. Try to keep the centre of thrust in line with the centre of mass if possible; mounting engines in pairs above and below the wings can help, as can putting them on the back of the plane.
• No angle of attack on the wings. KSP wings only generate lift if they’re angled to the airflow so they need a positive angle of attack (front edge higher than back edge) to produce any lift. If you angle your wings a few degrees with the rotate tool- turn angle snap off!- and/or position your landing gear so the nose is higher than the tail on the runway, you can produce enough lift in some cases to lift right off the ground without even needing to apply any pitch input at all, though for larger planes it’s more of a helping hand along with the pitch controls. A set of front canards (any control surface at the front, not the specific canard parts) can help you get more lift at the front to lift off the runway too.

Without seeing the plane in question that’s as much advice as I can give you. The centre of mass/lift/thrust overlays are toggleable using the buttons in the bottom left of the editor- mass is yellow, lift blue and thrust purple.