Plane spins/lurches to the side during takeoff?

[NecessaryWeevil]

As the title says, my plane dips and turns to the side, clips its wing on the runway and loses it, does the same on the other side, then crashes and explodes, without even getting airborne. Everything looks perfectly symmetrical as far as I can tell. Any ideas? All I have are the parts from the Aerodynamics tech and the gear bay (wheels).

I'd post a screenshot if I knew how.

[Langkard]

The problem could be due to several issues. The plane is clearly unstable. See the tutorial below. But also check to make sure that your wheels are placed symmetrically and your engines are aligned properly. Either one of those being misaligned will cause instability on the runway during takeoff (and the engines misaligned will cause flight problems). Center of Mass and Center of Lift are the usual causes of instability. The tutorial below explains everything very well.

The best written tutorial on how to build planes/spaceplanes in KSP is here:

http://forum.kerbalspaceprogram.com/threads/65638-Basic-Airplane-Space-Plane-Aero-Tutorial

It takes you step by step through the ways designs go wrong, has you build and test so you see why things went wrong and explains the best way to design a plane. Also be sure to follow the link near the beginning to an even simpler tutorial.

[Acus]

1. make sure your main gear is not wobbling (ie. if mounted on not struted part)
2. put your main gear slightly behind center of mass. if its too far behind plane cannot lift.
3. make sure your center of mass is slightly in front of center of lift force.

[DaS]

as Shkeec said check gear check gear check gear. It's a prolem enough I have sever differen gear subassemblies that are stable (un wobbly) I can then position depending on COM.

generally any time your Kerbal crash test vehi...plane does weird stuff while nominally on the ground it's a gear/COM issue, if it does wacky stuff while in air it's usually a lift/COM and or fuel balance issue.... or you let Jeb at the controls

Idealy you want your plane to to sit on the runway at 0 throttle and alllllmmmooooossstt want to tip back, but not quite. Makes for a much shorter takeoff roll

[Aoi Blue]

If you are using B9 Rocketery or other parts that utilize Firesplitter, this is normal. Real planes do this as well. It is due to the spinning up of the engines.

The way to reduce it is twofold:

1. Put on your breaks as you spin up your jet engines.
2. Include (A)SAS in your assembly and make sure it's on during launch.

Other things that can cause this are asymetric designs. Do things symetrically left to right, even if you don't need to (for instance, cockpit ladders should be symetrical). If you only need one of something, put it on the top or bottom.

[IronHawx]

I found biggest cause of this as well as not being able to possibly correct is having sas on during takeoff, make sure that is off during take off and should find problem is less likely to occur, but I too struggle to make working space planes even when center of lift, mass, thrust are all as needed.

[El Rushbo]

I don't have any mods but sometimes a problem may be a simple bug. I've had stability issues in planes where I'd have proper gear setup, balanced weight and lift. Sometimes taking things off and re-attaching them does it, or you may have to go so far as to scrap the design and rebuild.

[NecessaryWeevil]

Thanks for all the help. I worked through the tutorials and I think my problem was most often a lack of lift, or perhaps more accurately sufficient control surfaces. I was attaining high speeds on the runway without getting off the ground, which made the plane yaw back and forth.

The problem is mostly solved. The Kermins have a much improved life expectancy!

[TheUnluckyOne]

I just built a plane but when i launch it just slides and spins slowly to the right, any ideas on why this is happening?

[Chibbity]

Originally posted by SCP - 163:

I just built a plane but when i launch it just slides and spins slowly to the right, any ideas on why this is happening?

A picture of the plane would help.

Also, please don't turn me into a zombie oh mighty necromancer.

Off the top of my head:
Not enough intake to feed both engines so only one is running at full power.

[Acus]

Originally posted by SCP - 163:

I just built a plane but when i launch it just slides and spins slowly to the right, any ideas on why this is happening?

Check if landing gear is aligned 90-deg to plane. Also if you have wheels attatched to wings add struts to eliminate wobbling. Look in hangar if your mass distribution isnt moved left or right