Plane going left as soon as I start engines

[phemark]

SOLVED - dont put anything behind engines!

Hi,

I made several planes today, and all were acting fine. However, with this, I cannot understand where the problem is.

It has 2 turbo jets, and if I turn them both on, it instantly turns left. However, if I keep right engine off, it goes straight...

I removed all but one central intake, still the same.

Any reason what is happening?

You can see that all wheels are straight, and its going straight with 1 engine.

As soon as 2nd engine is engaged, it goes to the right.

And here you can see that everything is fine - CoL is just behing CoM, and CoT is centred...

I also tried various wheel positions, still the same...

Any ideas?

Edited November 6, 2014 by phemark

[worir4]

From the bottom picture it looks like the gear on the right might not be on symmetrically as the one on the left.

Also if you ignite the center engine with the other two turned off does it still happen?

Edited November 6, 2014 by worir4

[Starman4308]

Possibly screwed-up staging, though the usual candidate for veering off the runway is misaligned landing gear, or having too much weight on your landing gear, causing them to misalign.

[LABHOUSE]

No, worrir, of only the left engine worked then it would ever right... it has to do with the runway and the curve of kerbin, it the runway is perfectly flat but kerbin is not...

[Taki117]

No, worrir, of only the left engine worked then it would ever right... it has to do with the runway and the curve of kerbin, it the runway is perfectly flat but kerbin is not...

This really has nothing to do with it. The Runway is perfectly straight, it's more than likely an issue with landing gear.

[worir4]

The runway is flat so that wont affect it. OOO wait check the thrust limiter! Perhaps the left engine is on less power than the right.

[Alshain]

The runway is flat so that wont affect it. OOO wait check the thrust limiter! Perhaps the left engine is on less power than the right.

The runway is not flat, but it's curve travels the length of it so it won't affect left to right. Don't believe me? Put a plane on the runway with the brakes off and watch it roll, it should stop in the middle of the runway. It's an effect of the curvature of the planet in the modeling system. You can't have a truly flat runway on a round planet.

phemark, make sure your strutting the wings and the tanks they are attached to back to the base. This problem can often be caused by slight flexing in the wings when mounting wheels to them.

[phemark]

I rebuild everything using the same engines, yet it still steers left. I think its something to do with them. When I run them both, one generates 0.03 electricity, another 0.04 - shouldnt it be the same? (both 100 limit)

[Alshain]

I rebuild everything using the same engines, yet it still steers left. I think its something to do with them. When I run them both, one generates 0.03 electricity, another 0.04 - shouldnt it be the same? (both 100 limit)

Nah, that's most likely a symptom of floating point math. The cause is that the wheels aren't straight, either because they weren't mounted correct, or more likely because the mounting surface is flexing under physics. I can nearly promise that is the problem.

[phemark]

It was advanced canards! I put them as elevators, and they mess things up.

Strange thing is, that even if they are disabled for everything, and dont move, plane still steers.... anyone experienced this?

Anyway - dont use Advanced Canards as elevators.

[Alshain]

It was advanced canards! I put them as elevators, and they mess things up.

Strange thing is, that even if they are disabled for everything, and dont move, plane still steers.... anyone experienced this?

Anyway - dont use Advanced Canards as elevators.

Really? Well that is strange. I gotta say I didn't anticipate that.

Did you turn yaw and roll off on them? In the VAB right click and disable the roll and yaw if you didn't (especially yaw).

The only other reason would be because it's in the exhaust and reducing the thrust to 0, but I would expect that to have affect both engines.

[worir4]

Canards are ment to go on the front I think. Oh well, just don't tell any one that you put them on. Blame it on Bill.

[phemark]

Ok, another question - what could be wrong, that when I start engines, I dont move, and only start moving, if I push planes nose down ​(W key)?

Could it be because CoM and CoL are very far to front?

P.S. I think all of my problems in this thread, is because of CoL a lot in front, as when it was in back/middle, all was normal..

[phemark]

Ok, more pics:

Full throttle, standing still (back wheel is lower than front)

And this is what I noticed - blue arrow is pointing forward:

1) Why?

2) Shouldnt it affect only after plane got some speed, not at 0 speed?

[Alshain]

Ok, another question - what could be wrong, that when I start engines, I dont move, and only start moving, if I push planes nose down ​(W key)?

Could it be because CoM and CoL are very far to front?

P.S. I think all of my problems in this thread, is because of CoL a lot in front, as when it was in back/middle, all was normal..

Do you have brakes on in the wheel's tweakables? On a tail dragger like this, pushing forward would lift the back wheel off the ground, so check that one.

There is this thing with KSP, any object placed in the exaust of an engine will reduce the engines thrust to 0. I can't say I've ever designed a plane where that was a problem with the jet engines (usually see it on rockets), but the fact your tail plane is in the exaust may be all the problems your having. Consider a T-Tail or Cruciform Tail

Edited November 6, 2014 by Alshain

[phemark]

Tested, brakes are all fine.

What I discovered now:

1) Start engines - dont move

2) Push W (nose down), get 10m/s, continue at 10m/2

3) Doesnt accelerate more

4) Push W again, get 10m/s more

5) and so on

So it only accelerates for a bit, when I push W... weeeeeird

If anyone want to try it out, here is craft file:

https://www.dropbox.com/s/vfh20afvgdok8l3/Small%20sattelite%20lifter%20v2.craft?dl=0

And if anyone wont offer any solution, ill have to give up with this type of plane...

[phemark]

There is this thing with KSP, any object placed in the exaust of an engine will reduce the engines thrust to 0.

This was it!!!!!

Life saver!

Tested by moving to a side, and works.

Explains removing canards as elevator too:)

Thanks again Alshain!

P.S. It is stupid rule, to be fair:)

[Syhrus]

[Withdrawn - actually I was wrong]

[Alshain]

Glad that worked. I wasn't sure if it applied to the jets. Can't tell you how many landing craft I screwed up because I put something too close to radial mount engines though.