Plane unstable on take off/landing

[vitorboschi]

Hi all! Can someone help me fix the stability of my plane? It flyes really well, but I can't make it stable on take off / landing. When it reaches about 50 m/s, it begins to steer and then I quickly lose control and it crashes.

Pics:

I tried to add the struts under the wings, but they doesn't seem to help.

Thanks in advance!

[G'th]

I would say your wheel configuration has something to do with it. You don't need it angled that much, especially for a plane that small.

You also have a canard on your tail. Those don't really go there, so you're trying to fly without any real yaw control. Its possible that its causing your plane to veer a bit on takeoff.

[Hodo]

I am going to say, I think your wing wheels are not straight. I think they maybe toe'd in just a bit which is causing your problems.

I think the Firespitter wheels have a right click and check alignment option, you should see some lines show up in the SPH when you do this. It will show you if they are in alignment or out.

[vitorboschi]

I would say your wheel configuration has something to do with it. You don't need it angled that much' date=' especially for a plane that small.

You also have a canard on your tail. Those don't really go there, so you're trying to fly without any real yaw control. Its possible that its causing your plane to veer a bit on takeoff.[/quote']

Changed the canard to a tail fin and it seens just a little better on take off, but it's still bad. Now I'm trying ti muck with the wheels alignment.

- - - Updated - - -

I am going to say, I think your wing wheels are not straight. I think they maybe toe'd in just a bit which is causing your problems.

I think the Firespitter wheels have a right click and check alignment option, you should see some lines show up in the SPH when you do this. It will show you if they are in alignment or out.

It looks there's no aligment check option. Maybe its part of another mod? Anyway, I'm trying to change the wheels angle a bit. Update: This is new in version 6.3.1. You have to press F2 to activate it. Restarting KSP and checking wheels!

Edited June 18, 2014 by vitorboschi

[vitorboschi]

Alright, Firespitter says the wheels are all aligned, so I took the front wheel a bit more to the nose, and it helped a bit. I can now go up to about 65m/s before it becomes unstable. Any other ideas?

[xcorps]

Is there any movement anywhere at all when the plane loads? Any wing movement during flight?

If so, add struts.

Are you making any manual movements during launch? If so, try turning on SAS then only steering as needed left and right. Don't try to pull up, let the runway launch you. Sometimes trying to pitch up adds weight to your rear landing gears and they might camber, which will make your plane roll.

Also try adding another engine to the back using a bi-adapter, then adjust the wings for COL. More thrust!

[vitorboschi]

Is there any movement anywhere at all when the plane loads? Any wing movement during flight?

If so, add struts.

Are you making any manual movements during launch? If so, try turning on SAS then only steering as needed left and right. Don't try to pull up, let the runway launch you. Sometimes trying to pitch up adds weight to your rear landing gears and they might camber, which will make your plane roll.

Also try adding another engine to the back using a bi-adapter, then adjust the wings for COL. More thrust!

I didn't noticed any flexing on the structure of the plane, however, removing the two kethane extractors made the plane really stable, so I guess the problem is excessive loading. Thanks guys!

[i like turtles]

also, make sure that the CoL is not too far away from CoM. Make sure it is just behind CoM.

[feudalord]

This is a bug of this game, it cant be fixed guys! I spent almost 2 weeks testing different aircraft configurations but the cause of this wobble during take off just cannot be identified. Although I have on occasions successfully created aircrafts tat can go high speed on the runway, ususally my aircraft will wobble during take off. I have experimented with those aircraft tat are stable on the runway and found tat even the tiniest shift in the position of landing gears, like a centimeter shift in whichever direction will cause a stable aircraft to become unstable. I have tried putting landing gears as far apart as possible, removing all fins and wings, make aircraft super light, make aircraft super heavy, hanging weights on either side of the aircraft, allow steering, disable steering, use different landing gear, shifting center of mass and pressure, use symmetry, dont use symmetry, unicycle, bicycle, tricycle, quadracycle, manually rotating and aligning landing gear, use alignment guide lines, giant centipede with 20 wheels... you name it, every single thing tat can be done has been done. I have scoured the internet for a solution, even learned some physics along the way.

[LethalDose]

I can personally say I've never had a problem with aircraft stability on the ground that couldn't be fixed by making sure the gear had zero camber and straddled the CoM.

Also, I think your CoL should be ahead of the rear wheels, but I've never had the CoL and CoM so far apart this was an issue. It may be an issue with the plane above.

[Van Disaster]

I've had some problems with Retrofuture nosewheels just not being stiff/strong enough and bending, which causes all sorts of wild steering shenanigans - as I wanted to actually use them I tried a bunch of things, but usually end up using Bahamut0's adjustable gear. Your craft may just be too heavy for the FS gear.