Spaceplane tilts to the side and clips a wing into the ground when taking off.

[gutza1]

I've run into a problem whenever I build planes. When I take off, the plane goes straight until approximately 100 m/s, then it tilts to one side and one of its wings clips the terrain. I have no idea what is causing this and I hope I am not being a newb. How can I prevent the plane from tilting?

Pics:

Top:

Front:

Back:

Side:

Edit1: Added pictures of the Valkyrie. BTW, it's SSTO.

Edited October 26, 2014 by gutza1

[Shaun]

It seems like your centre of mass is too far forward and/or your centre of lift is too far back. The nose is forced to the ground, and, assuming you have a single nose-wheel, the aircraft's nose-wheel will act like a fulcrum.

[xtoro]

Any pics of said plane? A common reason for this is that the rear wheels aren't pointed staight down to the ground and are slightly angled out to the sides.

[GoSlash27]

Also make sure your elevators and ailerons aren't responding to yaw.

Best,

-Slashy

[The_Rocketeer]

I've also had this problem when the CoT was higher then the CoM (usually due to using droptanks), causing excessive load on the nosewheel.

[MarvinKitFox]

The cause is misalinged wheels.

Likely not when stationary, but i very often use too few aircraft landing gear.

Put a heavy load on them, and they flex to one side or the other. A flexed wheel will not run straight, causing tip-over.

The synthetic "weight" of an out-of-balance COM/COL/COT will aggravate this.

[Hodo]

The cause is misalinged wheels.

This is the answer right here, the gear are most likely out of alignment.

[The_Rocketeer]

Actually I believe you're taking that quote out of context.

"Alignment" in the sense used by MarvinKitFox, can be affected by physics load and 'flex'. That doesn't mean the gears are misaligned, it means that they may become misaligned due to those effects.

[Hodo]

I know what he was saying, I just cut it down, and left the important part. It is an alignment issue, doesn't matter if it is due to flex or poor placement. If they are out of the correct camber or caster or even have the toe alignment change then they are out of alignment.

[The_Rocketeer]

On the contrary, the physics effects are what is important as they are the actual cause of the problem. The alignment being altered is a merely a symptom. To correct this problem the OP needs to reduce the load on his gear, by whatever means. Simply moving them or adjusting their alignment probably won't cut it.

[Hodo]

While that is true, without seeing the craft in question it is all speculation.

[gutza1]

Added Pictures.

[DocMoriarty]

Clearly the rear landing gears. They must go down straight, not diagonal like they do on the images.

Aside of that: Center of Lift must be a little bit behind and above Center of Mass. Rear gears are also too far behind CoM. You won't get this thing in the air in any reasonable manner like this.

Edited October 26, 2014 by DocMoriarty

[Kryxal]

I'd suggest, if you move the rear gears up, adding another wheel at the back to protect against tailstrikes ... I think you're going to need it!

[Starman4308]

There is a wonderful guide to building spaceplanes out there.

Specifically for your craft, though: wheels should be straight, rear wheels should be just behind center of mass (as close as you dare*), and center of lift should be behind, and potentially a bit above, center of mass.

*The big danger is your CoM shifting backwards as you burn fuel. I use RCS Build Aid to check where my dry CoM is. Yes, it is a pain to balance it out: if you ever happen to pick up Real Fuels, I think you can add lead ballast to help even things out.

[Hodo]

On the contrary, the physics effects are what is important as they are the actual cause of the problem. The alignment being altered is a merely a symptom. To correct this problem the OP needs to reduce the load on his gear, by whatever means. Simply moving them or adjusting their alignment probably won't cut it.

Now that there are pictures, it is exactly as I expected. The gear are out of alignment.

The other issues with that craft are, your CoM is behind your CoL, which is going to make the craft unable to fly. It will to backflips wonderfully though.

I highly suggest the OP read the post that a previous poster linked.

Here are a few pictures of some of my older Real Solar System aircraft, the same principle applies to them as they do in KSP when it comes to landing gear, CoL and CoM.

Javascript is disabled. View full album

[The_Rocketeer]

Now that there are pictures, it is exactly as I expected. The gear are out of alignment.

...

I highly suggest the OP read the post that a previous poster linked.

Agreed, there's no arguing with the pictures. Still, it goes to show there are circumstances other than just gear location that could cause similar effects.

[Redshift OTF]

As others have said your rear wheels are too far back. They need to be closer to the CoM so your plane can pitch up on the runway. If they are not then you put massive pressure on the wheels to pitch up, they buckle and you go all over the place on the runway especially if they are angled like you have them. Common problem.