Adverse yaw moment during taxi with high NWS sideslip angles - Page 2 - ED Forums
 


Notices

Reply
 
Thread Tools Display Modes
Old 09-15-2018, 11:19 PM   #11
Deano87
Senior Member
 
Deano87's Avatar
 
Join Date: Dec 2014
Posts: 2,265
Default

I think we can all agree that whatever it does it shouldn't be turning in the opposite direction of the commanded turn direction. I've never experianced a car understeer left while I'm turning the wheel right.
__________________
Ignore me I’m probably wrong - Now with 42% extra sarcasm - May contain nuts.

Proud owner of:
PointCTRL VR : Finger Trackers for VR -- Real Simulator : FSSB R3L Force Sensing Stick. -- Deltasim : Force Sensor WH Slew Upgrade -- Mach3Ti Ring : Real Flown Mach 3 SR-71 Titanium, made into an amazing ring.

My Fathers Aviation Memoirs: 50 Years of Flying Fun - From Hunter to Spitfire and back again.
My Screenshots
Deano87 is offline   Reply With Quote
Old 09-16-2018, 12:46 AM   #12
Weta43
Veteran
 
Weta43's Avatar
 
Join Date: Feb 2005
Location: Aro Valley Wellington New Zealand
Posts: 7,295
Default

That's because of the steering geometry in your car (in that it's symmetrical around the car's axis)

Watch the video, and the geometry of the nose wheel steering.

At the point you turn the NWS to high, and turn the wheel left, it stops providing any lateral turning force (it's locked, not turning and just skidding), but that skid is still providing retarding drag.

The wheel trails the suspension strut, so at the point you apply full left rudder, the wheels are to the right of the strut.

No turning force from the tyre + a retarding force to the right of the suspension strut (& so to the right of the aircraft's axis) = a slow right turn.

As the aircraft yaws relative to its direction of travel, the force becomes more asymmetrical, and the aircraft will 'spin out' - just as a car will.

No pilot would actually allow this circumstance to occur.
Attached Thumbnails
Click image for larger version

Name:	NWS.JPG
Views:	222
Size:	13.7 KB
ID:	194069  
__________________
Cheers.

Last edited by Weta43; 09-16-2018 at 12:55 AM.
Weta43 is offline   Reply With Quote
Old 09-16-2018, 03:55 AM   #13
Aluminum Donkey
Member
 
Aluminum Donkey's Avatar
 
Join Date: Dec 2014
Location: Cambridge, ON, O Canada, Eh
Posts: 858
Default

Weta43 seems right to me. The nosewheel has trail--the wheels themselves are behind the steering axis, so when you crank them over and they skid, they produce more drag on the side opposite your steering input, and the plane turns the other way.
Of course, doing this in real life would destroy the tires, which is why they don't do this in real life. But, the real F/A-18C may very well behave like this.


Oh man, lots of discussion over this little detail... Let the ED dudes work on stuff that matters


AD
__________________
Kit:
Asus Z170-P, i5-6600k at 4.5 GHz, 1.35V w/ CM Hyper 212 EVO, 2 x 8GB GSkill Ripjaws 4 @ 3000MHz 15-15-15-35, Zotac GTX 1080 Ti AMP Extreme Core Edition, EVGA SuperNova 750 G2 PSU, HP Omen 32" 2560x1440 single screen, Thrustmaster Cougar HOTAS fitted with Leo Bodnar's BU0836A controller.

Flying is the art of throwing yourself at the ground, and having all the rules and regulations get in the way!

If man was meant to fly, he would have been born with a lot more money!
Aluminum Donkey is offline   Reply With Quote
Old 09-16-2018, 08:01 AM   #14
JaBoG32_Dirty
Junior Member
 
Join Date: Dec 2004
Location: All the way up front
Posts: 35
Default

This IS stuff that matters! :-)

..yea yea,... I know...

I agree, that there are more pressing issues on the table for the developers right now. It's not like I can no longer enjoy the beauty of this module. But isn't this forum also a little bit about education, technical understanding and a fair appreciation of the insane amount of detail a modern PC-based flightsim can provide? To me, that is what flightsimming is all about. I want to understand this behaviour at least as much as I want the developers to fix it (IF it needs fixing).

Weta43 picked up the point that I made in my second post and what I already said in the video: The nosewheel has a caster. That shifts the contact surface of the wheels over to the side opposite of where you are steering. The point where wheel drag applies shifts with it. So far,... everything appears make sense :-) But that is only the first step of the argument!

The second is this: The point where the drag ACTS on the airframe shifts over adversely (due to caster), but the direction where it POINTS is still way over to the provers side. Or to be more precise: The vector of that force still passes the centre of gravity on the provers side --> huge provers yaw moment.

All these arguments are founded on the premise, that friction is a force opposite to the direction of the relative motion of the SURFACES involved. Keep in mind: The relative motion of the surfaces is a superposition of the vehicle motion and the motion due to the freely spinnig wheel. That wheel still spins at cos(NWS_angle°)*Groundspeed.
The behaviour that can be observed however could be nicely explained if friction was (wrongfully) modelled as a force acting opposite to the direction of motion of the VEHICLE alone. I don't think this is a coincidence. I think it points directly to where the devs should look for a fix :-)

I tried my best to explain this in simple words and as math-free as possible. I know, that this topic will not raise huge attention with 99% of the forum members, but maybe there is someone among the other 1% who can confirm or correct my hypothesis. I'd be thrilled either way!

As long as I go to bed tonight a little smarter then I woke up,... it was a day worth living :-)

Dirty :-D
JaBoG32_Dirty is offline   Reply With Quote
Old 09-16-2018, 08:25 AM   #15
wernst
Member
 
Join Date: Jan 2014
Location: EDTF
Posts: 294
Default

Quote:
Originally Posted by Aluminum Donkey View Post

Oh man, lots of discussion over this little detail... Let the ED dudes work on stuff that matters
OMG . . . yes AD, if people start complaining about issues like “NWS HI isn’t simulated correctly” leads to the conclusion,
that all major systems of the hornet are already simulated perfectly and only minor issues have to be solved.

AD, you’re 100% right. Let the ED team solve real issues and don't let them get headaches from nullities.
wernst is offline   Reply With Quote
Old 09-16-2018, 08:43 AM   #16
Flamin_Squirrel
Senior Member
 
Flamin_Squirrel's Avatar
 
Join Date: Jan 2009
Location: UK
Posts: 2,480
Default

Quote:
Originally Posted by wernst View Post
OMG . . . yes AD, if people start complaining about issues like “NWS HI isn’t simulated correctly” leads to the conclusion,
that all major systems of the hornet are already simulated perfectly and only minor issues have to be solved.

AD, you’re 100% right. Let the ED team solve real issues and don't let them get headaches from nullities.
While this NWS business may not even be a bug, it's unwise to suggest that small bugs aren't important to fix. The irritations of multiple small bugs can add up to ruin the feel of any game.
Flamin_Squirrel is offline   Reply With Quote
Old 09-16-2018, 08:52 AM   #17
JaBoG32_Dirty
Junior Member
 
Join Date: Dec 2004
Location: All the way up front
Posts: 35
Default

Hey Weta43,

I'd like to comment on your post, if I may :-)
Please take this in a friendly way. Open-minded and respectful. After all, we wouldn't be here if we weren't infected with the same borderline insane obsession with simulated flying. I really don't care WHO's right, but I do care very much WHAT's right :-)


Quote:
Originally Posted by Weta43 View Post
That's because of the steering geometry in your car (in that it's symmetrical around the car's axis)
Cars also have caster wheels. It is what lets you feel the lateral forces in your steering wheel when cornering. Even modern power-drive steering provides such feedback. It is essential for controlability in any car.


Quote:
Originally Posted by Weta43 View Post
At the point you turn the NWS to high, and turn the wheel left, it stops providing any lateral turning force (it's locked, not turning and just skidding), but that skid is still providing retarding drag.
It is not static. It does still spin. It spins at cos(NWS_angle)*groundspeed. It even does so in DCS. Exactly how it should be. If it weren't spinnig you'd be right, but it is :-)


Quote:
Originally Posted by Weta43 View Post
As the aircraft yaws relative to its direction of travel, the force becomes more asymmetrical, and the aircraft will 'spin out' - just as a car will.
Correct! ....for a vehicle in an OVERsteering situation :-) A situation where the angular rate is higher than the wheel deflection demands. A situation where PROverse yaw is being induced from differing friction coefficients between the front and rear tyres. This situation is indeed unstable (at least in fwd motion) but that is not the case here. It is not OVERsteering, it is not even UNDERsteering,... it is ADVERSELY steering :-)


Quote:
Originally Posted by Weta43 View Post
No pilot would actually allow this circumstance to occur.
...hmmmm... *blushing_slightly* ...let me PM you :-)



I guess many of you understand, that the caster wheel will offset to the adverse side when deflected. What I'm trying to convince you guys to do, is take the "next step" and ask yourselves: where does the resulting force point?

Dirty :-D
JaBoG32_Dirty is offline   Reply With Quote
Old 09-16-2018, 08:53 AM   #18
wernst
Member
 
Join Date: Jan 2014
Location: EDTF
Posts: 294
Default

Quote:
Originally Posted by Flamin_Squirrel View Post
While this NWS business may not even be a bug, it's unwise to suggest that small bugs aren't important to fix. The irritations of multiple small bugs can add up to ruin the feel of any game.
Unfortunately the Hornet sim has quite a few major bugs or open issues to be solved, these may ruin the feel of the game.
The “NWS business” is the first minor bug and it surely won’t ruin my feel of the game at all.
wernst is offline   Reply With Quote
Old 09-16-2018, 09:08 AM   #19
discwalker
Senior Member
 
discwalker's Avatar
 
Join Date: Nov 2015
Posts: 1,313
Unhappy

Quote:
Originally Posted by wernst View Post
The “NWS business” is the first minor bug and it surely won’t ruin my feel of the game at all.
That depends on how many times killed you this bug on the Stennis.
Sim is about for me plane flying in the air+rolling on the ground, about controllability.
discwalker is offline   Reply With Quote
Old 09-16-2018, 09:10 AM   #20
JaBoG32_Dirty
Junior Member
 
Join Date: Dec 2004
Location: All the way up front
Posts: 35
Default

Quote:
Originally Posted by wernst View Post
AD, you’re 100% right. Let the ED team solve real issues and don't let them get headaches from nullities.
Yes, yes,... I said it before, I say it again: This is NOT pressing, major-issue, important, urgent, deal-breaker, necessary,... etc.

This is simply an attempt to find like-minded people to discuss with and exchange ideas about something we are all somewhat interested in and passionate about. In mutual respect and with full knowledge and acceptance of the others thoughts and ideas being their own and not a copy of mine.

If someone finds other aspects of the sim worthy of discussion, they may start a thread and I'd be willing to add my point of view to it, if I have anything substantial to say about the topic of discussion.

But at no point will you ever see me questioning the very existence of the discussion itself. If I ever did that, I'd have to question my own participation in it first!

Dirty
JaBoG32_Dirty is offline   Reply With Quote
Reply

Tags
annoying, bug, f/a-18c, hornet, nws, taxi

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT. The time now is 12:07 AM. vBulletin Skin by ForumMonkeys. Powered by vBulletin®.
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.