Hard pitching causes plane to roll to the right?

[AndMakesPlanes]

Hello all,

Currently when I'm trying to design planes it seems that every time I try to do high g pitch turns, my plane rolls to the right while doing it.

So is there anyway I can counter-act the roll or stop it from rolling?

Thanks

[Plusck]

In the SPH, have you right-clicked on each control surface and made sure that they only do what they are intended to do? That means that your rudder should only be controlling yaw, elevators only controlling pitch, and ailerons only controlling roll (unless elevators and ailerons are combined, in which case they should be available to do both).

By default any control surface will be considered usable for each axis, which can give very wrong results (for example, a rudder which is located above the horizontal axis of the aircraft will be able to contribute to roll... so the game will use it even if that induces a huge amount of yaw in the process).

Edited April 2, 2016 by Plusck

[surge]

So, in real life, that's a thing that happens when you stall, either by flying too slowly or pitching to a ridiculous angle of attack - due to the random nature of the atmosphere, one wing stalls a little earlier than the other and you get a sudden, violent roll as it loses all lift capability.

I'm pretty sure KSP doesn't model that though, so:

a) Make sure the wings are symetrical?

b) Is the tailplane centred properly, and only set to control only yaw?

c) Does it fly stably in a straight line without input? Is the centre of mass in front of the centre of lift? If this is wrong, it usually causes the plane to do backflips, but if you've strapped on 15 bazillion SAS units on it to stop that, I can imagine the physics might turn it into a roll.

d) Tried anyone else's craft? I think most of the stock examples still fly.

e) Do you have joysticks or other psuedo-analog controls? I find that sometimes my pedals seem to cause KSP to register a permanent full yaw input (not necessarily to the right). It seems to be a bug in the game, but a simple restart fixes it, so it's an annoying, but relatively easy workaround. Also, at high g maneuvres, the tiniest yaw will usually translate into violent roll though, so even if you *think* they are centred, they might not be.

f) If you're trying to get fancy and building in dihedral, it's normal for the plane to try to correct itself back to level, especially in hard pitch maneuvres.

 

Edited April 3, 2016 by surge

[pincushionman]

In KSP, there's a long-standing bug that causes stiffness of mirrored parts to be slightly different. Enough so that under a hard pitchup, the wings twist different ammounts, resulting in differential lift, resiuting in roll.

The best you can hope to do is reduce this - either add MOAR STRUTS between your wing segments, install the mod Kerbal Joint Reinforcement, or both.

[surge]

So it does model reality? I'm amazed!

[AndMakesPlanes]

3 hours ago, Plusck said:

In the SPH, have you right-clicked on each control surface and made sure that they only do what they are intended to do? That means that your rudder should only be controlling yaw, elevators only controlling pitch, and ailerons only controlling roll (unless elevators and ailerons are combined, in which case they should be available to do both).

By default any control surface will be considered usable for each axis, which can give very wrong results (for example, a rudder which is located above the horizontal axis of the aircraft will be able to contribute to roll... so the game will use it even if that induces a huge amount of yaw in the process).

Yes I have done this, thanks for the suggestions

2 hours ago, surge said:

So, in real life, that's a thing that happens when you stall, either by flying too slowly or pitching to a ridiculous angle of attack - due to the random nature of the atmosphere, one wing stalls a little earlier than the other and you get a sudden, violent roll as it loses all lift capability.

I'm pretty sure KSP doesn't model that though, so:

a) Make sure the wings are symetrical?

b) Is the tailplane centred properly, and only set to control only yaw?

c) Does it fly stably in a straight line without input? Is the centre of mass in front of the centre of lift? If this is wrong, it usually causes the plane to do backflips, but if you've strapped on 15 bazillion SAS units on it to stop that, I can imagine the physics might turn it into a roll.

d) Tried anyone else's craft? I think most of the stock examples still fly.

e) Do you have joysticks or other psuedo-analog controls? I find that sometimes my pedals seem to cause KSP to register a permanent full yaw input (not necessarily to the right). It seems to be a bug in the game, but a simple restart fixes it, so it's an annoying, but relatively easy workaround. Also, at high g maneuvres, the tiniest yaw will usually translate into violent roll though, so even if you *think* they are centred, they might not be.

f) If you're trying to get fancy and building in dihedral, it's normal for the plane to try to correct itself back to level, especially in hard pitch maneuvres.

 

Thanks! For all of these, I'll definitely try to build a dihedral or move my center of lift closer to the center of mass

1 hour ago, pincushionman said:

In KSP, there's a long-standing bug that causes stiffness of mirrored parts to be slightly different. Enough so that under a hard pitchup, the wings twist different ammounts, resulting in differential lift, resiuting in roll.

The best you can hope to do is reduce this - either add MOAR STRUTS between your wing segments, install the mod Kerbal Joint Reinforcement, or both.

I'll look into the mod.

I'll try all of these and post an update tomorrow 

[surge]

Quote

Thanks! For all of these, I'll definitely try to build a dihedral or move my center of lift closer to the center of mass

Not closer, son, the centre of mass must be IN FRONT OF the centre of lift. Depending on how you do the wings it needs to be by quite alot.

pastebin isn't working right now, but I would give you a Su-27 replica that can easily do a "cobra" maneuvre, and it's centre of mass is nearly 1m in front of the lift.

On the other hand, I suspect you'll find pincushionman's solution the most appropriate - your wings are bending during high load and causing a roll. I don't consider it a bug, except that KSP doesn't model that for slow flight, so... me is sad.

 

Edited April 3, 2016 by surge

[AndMakesPlanes]

Yep, pincushion man's solution did greatly reduce the roll of my plane.  Kudos to him.

 

[Vanamonde]

Don't overlook the obvious. Is your joystick perhaps wearing out? Maybe go to settings and increase the dead zone on the roll axis? 

[pincushionman]

5 hours ago, AndMakesPlanes said:

Yep, pincushion man's solution did greatly reduce the roll of my plane.  Kudos to him.

I only know because the exact same thing happened to me, and I didn't believe the explanation until I bit the bullet and installed KJR. I saw the light and now preach that gospel.