Plane takeoff problems :(

[MrAnonymous]

For some reason, everytime I takeoff on the runway, the plane spontaneously rolls left and right until it explodes. I see the landing gear spazzing out. Is that normal? Am I doing something wrong or is it a bug? I make descent planes only finding out that it explodes on takeoff. Maybe I need to arrange the landing gears a certain way. BTW I use the landing gears on B9 pack a lot. I just need to know whats going on. Help? thanks in advance.

[horndgmium]

If you're using B9 landing gear you're definitely going to want to do two things:

1. Keep the wheels perfectly perpendicular to the ground

2. Make sure you have the Firespitter, Resgen, and ExurgentEngineering in your gamedata folder as well

Also, pulling up before you reach lift off speeds can cause you to yaw left or right on the runway, which causes lots of problems. You also may need to increase the structural integrity of the plane as a whole, because if your wings are not firmly anchored to the plane and you start to yaw even a LITTLE bit on the runway you'll topple over.

[iStickyDuck]

A couple of things to check:

Is the center of mass along the middle of the craft with the center of lift just behind it?

Are the wheels straight?

Do you have a tail fin?

[MrAnonymous]

If you're using B9 landing gear you're definitely going to want to do two things:

1. Keep the wheels perfectly perpendicular to the ground

2. Make sure you have the Firespitter, Resgen, and ExurgentEngineering in your gamedata folder as well

Also, pulling up before you reach lift off speeds can cause you to yaw left or right on the runway, which causes lots of problems. You also may need to increase the structural integrity of the plane as a whole, because if your wings are not firmly anchored to the plane and you start to yaw even a LITTLE bit on the runway you'll topple over.

Wheels perpendicular, got it.

[capi3101]

That certainly sounds like you don't have the gear on perpendicular to the ground. KSP's kind of annoying about that sometimes.

The other possibility is too much weight on the gear - that one's a little harder to quantify. May we see some screenies of your designs?

[MrAnonymous]

A couple of things to check:

Is the center of mass along the middle of the craft with the center of lift just behind it?

Are the wheels straight?

Do you have a tail fin?

I have all of those. Just curious, how far do u really have to put the COL behind the COM. How I do it is I make the COL's ball part barely stick out at the back of the COM.

[BubbaWilkins]

I have all of those. Just curious, how far do u really have to put the COL behind the COM. How I do it is I make the COL's ball part barely stick out at the back of the COM.

Depends on how fast the craft is intended to go, or how much the CoM is going to change due to fuel consumption.

Also, if you're using B9 wheels, it helps to edit the config files and change the sideways stiffness to .01 or .001. Check the B9 thread for the correct answer. There is also separate B9 correction thread that might help.

Other tips,

- wing and structural flex com into play. If your craft is heavy, its going to flex when on the landing gear deflecting them slightly. Either make your structure stiffer or add more wheels.

- if you have a negative angle of attack while sitting on your gear, this just adds more downforce pressure the faster you go. Craft should be level or nose up for best results.

- related to the flex thing, but heavy craft will also tend to flex the wings as the load is shifted from the wheels to them. Sometimes the wheels don't like this.

- rear wheel placement should be just barely behind your CoM so that minimal control force is required to force the nose up. If your gear is too far behind it, it may take forward canards and other control surfaces to get you airborne.

- Check your control surfaces! Don't let wing flaps have pitch authority (unless its a rear delta wing configuration).

[MrAnonymous]

Depends on how fast the craft is intended to go, or how much the CoM is going to change due to fuel consumption.

Also, if you're using B9 wheels, it helps to edit the config files and change the sideways stiffness to .01 or .001. Check the B9 thread for the correct answer. There is also separate B9 correction thread that might help.

Other tips,

- wing and structural flex com into play. If your craft is heavy, its going to flex when on the landing gear deflecting them slightly. Either make your structure stiffer or add more wheels.

- if you have a negative angle of attack while sitting on your gear, this just adds more downforce pressure the faster you go. Craft should be level or nose up for best results.

- related to the flex thing, but heavy craft will also tend to flex the wings as the load is shifted from the wheels to them. Sometimes the wheels don't like this.

- rear wheel placement should be just barely behind your CoM so that minimal control force is required to force the nose up. If your gear is too far behind it, it may take forward canards and other control surfaces to get you airborne.

- Check your control surfaces! Don't let wing flaps have pitch authority (unless its a rear delta wing configuration).

Thanks a lot. Ill try them out now.

[MrAnonymous]

That certainly sounds like you don't have the gear on perpendicular to the ground. KSP's kind of annoying about that sometimes.

The other possibility is too much weight on the gear - that one's a little harder to quantify. May we see some screenies of your designs?

I'm a noob. I don't know how. LOLZ

[capi3101]

Screenies - hit the F1 key. It's saved in a subfolder of your KSP main folder called "screenshots". You can then post them to a hosting site like imgur and link it in to the forum.

[Hodo]

The B9 wheels are horribly wobbly. There is a few fixes for them in the B9 thread. But the best bet if you dont feel like figuring out the cfg file for them is to make sure they are perfectly straight, with zero camber and caster.

[EtherDragon]

Usually that wobbliness is due to your center of lift being too far behind the center of mass.

This causes the back of the plane to try and lift off first - putting all the weight distribution on the front wheel, hence wobble, then crash.

[MrAnonymous]

[barrenwaste]

Ok, from what I can see in those, you have a structural problem, need to strengthen it up with struts, and the wheels are to far out on the wings. Wheels need to be a certain distance apart to provide stability, true. Unfortunately there comes a point where putting them farther out makes them less stable. On a side note, you probably are going to want to put more inclination into the gear, bring that nose up, tail down. Doesn't look like there is any as it sits right now. Could just be the pic, though.