Buccaneer roll damper

[crl848 9]

I have found the Buccanner too sensitive in roll for a large heavy strike aircraft, and made some simple ini edits to the roll damper settings a while back to sort this out to my satisfaction. I was prompted by a simHQ thread to post them there and thought it might be useful here too. It's the only thing I thought was off in a really excellent mod, so if the twitchy roll is getting in the way of your enjoyment of this magnificent aircraft, feel free to give this a go.

 

Please note that this is my personal view, and if you're happy with the original flight model then I'm happy too. If you want to try it out, make the following changes:

 

In the aircraft data.ini, comment out the clp entry for the wings and replace as follows.

 

[LeftWing]

//Clp=-0.0142

Clp=-0.0468

 

[RightWing]

/Clp=-0.0142

Clp=-0.0468

 

[LeftOuterWing]

//Clp=-0.0519

Clp=-0.1286

 

[RightOuterWing]

//Clp=-0.0519

Clp=-0.1286

[+baffmeister 1,205]

Thanks for that, I'm going to try it out. I find the rudder response a bit wonky as well so will try a few things. Cheers.

[+baffmeister 1,205]

Roll fix works for me.

[Fubar512 1,350]

That's a roll moment that you're editing (not a roll damper), and imbuing each panel with that large a value may result in unintended consequences. Such as a model that may still fly on an even-keel with half a wing missing (instead of rolling towards the side with reduced lift)

 

Moderately reducing the roll moment values, in conjunction with a reduction in the "Y" axis inertia value, would be a better course of action.

[crl848 9]

Well, what I did works for me, no unintended consequences so far. I'm not imposing my solution on anyone else. In fact I didn't post it before, and only did today because someone at SimHq was complaining about the roll rate and I thought it might help them.

 

And, er, not to be a smart alec but didn't you call the clp parameter "roll damping" in a previous post?

 

http://combatace.com/topic/49522-change-or-roll-rate/page__p__355437__hl__clp__fromsearch__1#entry355437

Edited February 6, 2012 by crl848

[Fubar512 1,350]

Well, what I did works for me, no unintended consequences so far. I'm not imposing my solution on anyone else. In fact I didn't post it before, and only did today because someone at SimHq was complaining about the roll rate and I thought it might help them.

 

And, er, not to be a smart alec but didn't you call the clp parameter "roll damping" in a previous post?

 

http://combatace.com/topic/49522-change-or-roll-rate/page__p__355437__hl__clp__fromsearch__1#entry355437

 

Not really, that was a list of definitions originally posted by Charles at either Thirdwire or SimHQ.

 

From the wiki:

 

Cl and Cp relationshipThe coefficient of lift for an airfoil with strictly horizontal surfaces can be calculated from the coefficient of pressure distribution by integration, or calculating the area between the lines on the distribution. This expression is not suitable for direct numeric integration using the panel method of lift approximation, as it does not take into account the direction of pressure-induced lift.

 

 

where:

 

CpL is pressure coefficient on the lower surface

CpU is pressure coefficient on the upper surface

LE is the leading edge

TE is the trailing edge

When the lower surface Cp is higher (more negative) on the distribution it counts as a negative area as this will be producing down force rather than lift.

 

So you can see that the "official" explanation is at odds with what the actual value does in this series...

Edited February 6, 2012 by Fubar512

[crl848 9]

Fubar, I'm afraid all that's beyond me. I got the idea from your original post, that's how I know you said it ;). Until someone posts a better "solution" to this "problem" (a matter of opinion) I'll stick with mine.

 

Roll fix works for me.

 

Thanks.

[+baffmeister 1,205]

Thanks for the detailed info Fubar.

[+baffmeister 1,205]

Something I just noticed on the "Buc", the control rate on the ailerons is only set to 2. If I set the control rate to 5 and leave the CLP numbers as they were, it improves the behavior quite a bit. Not quite what I would like so may try changing the CLP numbers a wee bit. Cheers.

[Spinners 15,986]

Interesting stuff which prompts to ask have you simply tried altering the Roll Damper line in the Flight Control section of the data.ini?

[crl848 9]

Interesting stuff which prompts to ask have you simply tried altering the Roll Damper line in the Flight Control section of the data.ini?

 

Yes. For example, I changed the rolldamper setting from 0.4 to 2, with no discernable impact at all. That's why I searched the forums, found the post I linked to above where Fubar discussed the inputs to roll, saw that clp is something to do with roll damping, and hey presto, sorted it out.

 

As a quick test, load up a default Bucc, fly straight and level at c.500kt without ordnance. From wings level, roll with full stick input until 90degs (wings pointing up and down), then let go of the stick quickly. You will end up at about 220degs, i.e the aircraft will have rolled another 135degs and be inverted past the 180. With my edit, you end up at about 112degs, i.e. the aircraft rolls about 22degs more. You'll find that this is much more controllable and in my view realistic. The proof of the pudding is in the eating, try it out.

[crl848 9]

Something I just noticed on the "Buc", the control rate on the ailerons is only set to 2. If I set the control rate to 5 and leave the CLP numbers as they were, it improves the behavior quite a bit. Not quite what I would like so may try changing the CLP numbers a wee bit. Cheers.

 

I tried this, and it does improve the "out of control" feeling of the original FM, but still leaves the plane with a roll rate that feels way too fighter-like to me. I'm going to stick with my trial and error clp edit which IMHO provides a nice balance between heaviness and controllability.

[+ravenclaw_007 7,633]

i´m so glad that there are no other problems on that bucc

[crl848 9]

The main problem is waiting for SF:NA to do some proper anti-ship missions with it

[+Cliff7600 1,148]

Hi guys, here's my 2 cents if you don't mind.

 

1) The behaviour is different if you fly it on hard or normal mode.

 

2) If it rolls too quick it's better to leave the wings as they are and edit the ailerons :

 

[LeftAileron]

MaxDeflection=

MinDeflection=-

ControlRate=

 

[RightAileron]

MaxDeflection=

MinDeflection=-

ControlRate=

 

That's what I'd do...

 

 

[crl848 9]

I think the main issue is roll inertia, not roll rate (I see I could have worded my initial post better, sorry). Most aircraft should stop rolling when control input is stopped, otherwise it is very difficult to aim the weapons. Currently, the plane exhibits a lot of roll inertia, i.e. it keeps on rolling for ages after you center the stick. Here's an extract from Andy Bush's old SimHQ review of SFP1's original flight model (which has since been corrected for the stock planes):

 

"Roll performance is the next problem area. Roll inertia refers to the plane’s tendency to resist the initiation of a roll…and its tendency to continue a roll when the aileron is neutralized. Initial roll rate is good. These jets roll at rates that approximate real life. No problem there. The problem comes in when we want to stop the roll.

 

Both of these jets exhibit too much roll inertia. This simply means that they continue to roll when the aileron input is taken out (neutralized). In real life, these aircraft tended to stop rolling quickly, particularly if a little opposite aileron was used to counter the roll. This flight model feature was necessary to achieve the ability to point the jet quickly at a target. The roll axis needed to be easily controlled. Not so in this sim. Both jets will over-shoot the roll out point unless the aileron input is taken out early in the roll. The tendency to continue rolling is likened to a pendulum effect…once the roll is established, the roll will try to resist an attempt to stop it. The result is typically an over-banked attitude that the pilot must then correct. This is both irritating and a waste of time when time is often critical. The only correction for the simmer is to moderate roll inputs so that the pendulum effect is minimized."

 

See here: http://www.simhq.com/_air/air_030b.html

 

Whether my edits or something else works best to sort this out is a moot point. Feel free to post other solutions.

Edited February 8, 2012 by crl848

[+ravenclaw_007 7,633]

the problem here is a to high value for the Cldc entry on the Ailerons , change the value on both Ailerons from Cldc=0.0400 to Cldc=0.0090

you will still encouter a slight tendency to roll if you center you stick , i will look if i can eliminate that as well

 

this is the only change i made so far , it result´s in a more modest roll rate

 

NOTE you have to use the original settings for all other entry´s

 

Cldc = Roll moment due to control surface deflection

 

as for the issue "roll-damping" i have a list that shows Clp as "Roll moment due to roll rate (roll damping)" i dont know how old this list is or if this particular statement is wrong

 

[LeftAileron]

SystemType=CONTROL_SURFACE

InputName=ROLL_CONTROL

MaxDeflection=12.5

MinDeflection=-12.5

CDdc=0.0269

Cldc=0.0090

Cndc=-0.0014

CldcAlphaTableNumData=15

CldcAlphaTableDeltaX=4.00

CldcAlphaTableStartX=-28.00

CldcAlphaTableData=0.000,0.110,0.336,0.673,0.890,0.980,1.000,1.000,1.000,0.980,0.890,0.67

3,0.336,0.110,0.000

CndcAlphaTableNumData=15

CndcAlphaTableDeltaX=4.00

CndcAlphaTableStartX=-28.00

CndcAlphaTableData=1.644,1.537,1.429,1.322,1.215,1.107,1.000,0.893,1.000,1.107,1.215,1.32

2,1.429,1.537,1.644

ControlRate=2.0

MaxControlSpeed=200

ModelNodeName=Left_Aileron

ReverseModelOrientation=TRUE

 

[RightAileron]

SystemType=CONTROL_SURFACE

InputName=ROLL_CONTROL

MaxDeflection=12.5

MinDeflection=-12.5

CDdc=0.0269

Cldc=0.0090

Cndc=-0.0014

CldcAlphaTableNumData=15

CldcAlphaTableDeltaX=4.00

CldcAlphaTableStartX=-28.00

CldcAlphaTableData=0.000,0.110,0.336,0.673,0.890,0.980,1.000,1.000,1.000,0.980,0.890,0.67

3,0.336,0.110,0.000

CndcAlphaTableNumData=15

CndcAlphaTableDeltaX=4.00

CndcAlphaTableStartX=-28.00

CndcAlphaTableData=1.644,1.537,1.429,1.322,1.215,1.107,1.000,0.893,1.000,1.107,1.215,1.32

2,1.429,1.537,1.644

ControlRate=2.0

MaxControlSpeed=200

ModelNodeName=Right_Aileron

ReverseModelOrientation=TRUE

 

 

hope that helps a bit

 

here is the list i have , dont know if all statement are correct

 

CL0 Lift coefficient at zero angle of attack (AOA)

CLa Lift coefficient due to AOA

CD0 Zero-lift drag coefficient

CDL Drag coefficient due to lift (induced drag effect)

Cmq Pitching moment due to pitch rate (pitch damping)

Cmad Pitching moment due to AOA rate

(aero interaction between wings and horiz tail)

Cyb Side force due to sideslip

Cyp Side force due to roll rate

Cyr Side force due to yaw rate

Clb Roll moment due to sideslip

Clp Roll moment due to roll rate (roll damping)

Clr Roll moment due to yaw rate

Cnb Yaw moment due to sideslip

Cnp Yaw moment due to roll rate

Cnr Yaw moment due to yaw rate (yaw damping)

CLiftdc Lift due to control surface deflection

CDdc Drag due to control surface deflection

Cydc Side force due to control surface deflection

Cldc Roll moment due to control surface deflection

Cmdc Pitch moment due to control surface deflection

Cndc Yaw moment due to control surface deflection

DeltaStallAlpha Increase in max angle-of-attack before stall

Xac X-location of aerodynamic center

Edited February 8, 2012 by ravenclaw_007

[bwild 5]

 

 

as for the issue "roll-damping" i have a list that shows Clp as "Roll moment due to roll rate (roll damping)" i dont know how old this list is or if this particular statement is wrong

 

 

 

I have been digging through my old lecture notes on flight dynamics, C_lp is indeed a measure for roll damping, due to the change in angle of attack along the wing span because of the rolling moment. I can list some coefficients for actual aircraft from flight tests.

 

Cessna Citation (cruise) -0.3444

Fokker F-27 (cruise) -0.60

Lockheed Constellation (cruise) -0.5200

Concorde (approach) -0.1410

X-15 (cruise) -0.3150

De Havilland Beaver (approach) -0.5500

[crl848 9]

@Ravenclaw, I've tried your edit and it certainly works to reduce roll inertia to something much more manageable. On the other hand, I've noticed another issue which my previous clp edit had been masking, which is that using the rudder rolls the aircraft very smartly in the wrong direction to the rudder input (i.e. right rudder, rolls left etc.). With your new edit you can now actually roll the aircraft faster with opposite rudder than with ailerons .

 

Seeing as the Buccaneer IRL had severe adverse yaw issues at low speeds it would be good to be able (required?) to use rudders to roll in the right direction!

Edited February 8, 2012 by crl848

[+Cliff7600 1,148]

The stock ThirdWire planes have the same behaviour with the rudder (F-4 if I remember correctly)

 

Try this (hard mode) :

 

[Rudder]

Cldc=-0.0170

[Fubar512 1,350]

I think the main issue is roll inertia, not roll rate

 

I did suggest that you edit that value (the "Y" axis vaule) in my first reply, remember? EmptyInertia=X,Y,Z

[crl848 9]

The stock ThirdWire planes have the same behaviour with the rudder (F-4 if I remember correctly)

 

Try this (hard mode) :

 

[Rudder]

Cldc=-0.0170

 

OK, weird one. I tried this with Ravenclaw's edit, and although it now rolls with the rudder in straight & level flight, it rolls strongly opposite rudder under g/alpha. Any ideas?

[+ravenclaw_007 7,633]

OK, weird one. I tried this with Ravenclaw's edit, and although it now rolls with the rudder in straight & level flight, it rolls strongly opposite rudder under g/alpha. Any ideas?

 

are you using the hard-mode ????

[crl848 9]

Yes.

[+ravenclaw_007 7,633]

do me a favor and try it in normal-mode just to test if it is still the same , by the way we never made the aircraft for the hard-mode