Tweaking .air file to increase adverse yaw?

[MarkH]

Does anyone know how I can increase the adverse yaw for an aircraft? I can't see anything that looks relevant in the aircraft.cfg. I have discovered AirEd, which lets me open the .air file and make edits to it, but again I don't really know where to start. I have found things that look tantalisingly close (table 1101, I think, is 'general aerodynamics') but I have tried comparing several aircraft tables side by side and it's still not clear what does what.

Basically I want to tweak the Aerosoft Twin Otter so it needs me to use the rudder. As standard it makes no difference whether I use the rudder or not in turns. It doesn't side-slip very well either, although that may be a different tweak. I'd like it to behave kind of like the DG80S glider does - overkill, I know, but in FSX we don't have any cues beyond what we can see.

 

[glh]

From what I have seen, aircraft usually have rudder throws in the 10-30 degree range. I suggest you check the "rudder_limit" parameter first in the [airplane_ geometry] section of the aircraft.cfg file. You may have a bogus entry. You can try to change the values and see if that works for you.

If not, then go here and read the section on [flight_tuning]. There are a few parameters involving the rudder(s) that you can tweak.

https://msdn.microsoft.com/en-us/libra/cc526949.aspx#SectionsoftheConfigurationFile

If you DO NOT have a [flight_tuning] section in your aircraft.cfg file, find another twin engine plane in your FSX inventory that has this section and copy it to your Twin Otter file. Then tweak to your satisfaction.

Have fun.

 

[Dev One]

There are values in the section 1101 part of the .air file that affect rudder & aileron adverse yaw, one has to experiment with a few to see any result. They are obviously in the Roll & Yaw section. I use AirEd V1.52 as well as Aircraft AirFile Manager. The latter is useful as it shows graphically what shows as a table in AirEd.
I find each aircraft is different due to their individual dimensions, weight & MOI.
Choose an aircraft model that has a good Turn & Slip indicator - I find the old fashioned Reid & Sigrist twin needle type the best & if necessary import it into the 2D panel or the VC.
HTH
Keith

P.S. the M$ link doesn't work for me!

 

[MarkH]

There are values in the section 1101 part of the .air file that affect rudder & aileron adverse yaw, one has to experiment with a few to see any result. They are obviously in the Roll & Yaw section...
Choose an aircraft model that has a good Turn & Slip indicator

Well I had hoped I might find the logic to it as there is nothing obvious in those parameters that cries out to me. As for the turn and slip indicator, the fact that I would need one means the adverse yaw isn't obvious, which is really the problem. I also read all over the place that the turn and slip indicator function in FSX doesn't work properly. With the Twin Otter the indicator stays more or less undisturbed when I bank but then gyrates wildly as soon as I touch the rudder.

Anyway, I will check out Aircraft AirFile Manager. The link doesn't work for me either but I have the SDK docs installed so I will try to find the relevant bits in there.

 

[PRB]

I recommend you post this in the Flight Dynamics forum. While it doesn't get a lot of traffic, the posts there always get good answers from several of our flight dynamics "gurus":

http://www.sim-outhouse.com/sohforums/forumdisplay.php?42-Flight-Dynamics

 

[MarkH]

I recommend you post this in the Flight Dynamics forum. While it doesn't get a lot of traffic, the posts there always get good answers from several of our flight dynamics "gurus":

http://www.sim-outhouse.com/sohforums/forumdisplay.php?42-Flight-Dynamics

Ah okay, will check it out.

 

[Bradburger]

MarkH

With AirEd (or Aircraft Airfile Manager), take look for Cn_da 'Yaw Moment Coefficient Due to Aileron Deflection' (Aileron Adverse Yaw) under record 1101 - Primary Aerodynamics. (According to AirEd, it is superseded by Record 1544 if 1539 & 1544 are in the air file).

A negative value is used, i.e. -2450.

You may or may not get the result you are looking for, as it will depend on how well the flight model was setup, so you might have to adjust some of the other yaw records as DevOne suggests.

As has been noted, slip ball behaviour can be odd at time in FS. I recommend you download and install Jerry Beckwith's FM test panel: -

http://www.mudpond.org/gauge_index.html

It has an accurate gauge (it's called 'Beta') for measuring the yaw/sideslip in degrees.

Cheers

Paul

 

[olderndirt]

It's a do it yourself thing. Roll the wings to the left and step on the right rudder - all the adverse yaw you could ever wish for.

 

[napamule]

Blind Tweak

Please try the below values in your cfg and air file (I use air ver 142) and report back (thanks). Remember that some neg values give more effect the more negative they are.
Chuck B
Napamule

------------------------------------
Given: Auto Rudder = OFF
Controller: Calibrated

Aircraft.cfg
----------------
[airplane_geometry]
rudder_area=20.000 //default //max=30
rudder_limit=30.000 //default //max=45.000

Air File:
------------------
(1101) Flight Dynamics

Rudder?=30 //default //max=64
Rudder Control Factor=128 //default //max=512

Rudder Effect on Roll=512

Center Of Lift On Wing?= -30

Yaw Stability1=296 //default //max= 128
Yaw Stability2=62625 //default //max= 2147483647

(1202) Yaw Damper=1000 //default //max=64000

 

[Dev One]

There is also Herve Sors AFSD that gives a lot of data including side slip & you can run it at the same time a flying. It works for both FS9 & FSX.
I used it to calibrate my Turn & slip indicator thats going into my Dragonfly (WIP). I am reliably informed that this aircraft needs a bootful of rudder to compensate for adverse yaw & I've got about as much as I can get at the moment!!

https://youtu.be/mtqTckp68ig

Keith

 

[MarkH]

MarkH

With AirEd (or Aircraft Airfile Manager), take look for Cn_da 'Yaw Moment Coefficient Due to Aileron Deflection' (Aileron Adverse Yaw) under record 1101

Thanks Paul, I must have squinted too hard as I didn't see that one! I will definitely check out your other suggestions when I get in tonight!

 

[MarkH]

Please try the below values in your cfg and air file (I use air ver 142) and report back (thanks).

Thanks Chuck, will do. Phew, I have a lot of stuff to try now!

 

[Bjoern]

Another essential read regarding flight dynamics: fs_flight_dynamics_v1.0.zip (on Avsim)

 

[MarkH]

Another essential read regarding flight dynamics: fs_flight_dynamics_v1.0.zip (on Avsim)

Grabbed, thanks!

[LATER: Holy cow, remember that old saying about how each equation you include halves your audience?! This document is, if it turns out to be nothing else, at least a testament to the author's awesome desktop publishing skills!]

 

[MarkH]

There is also Herve Sors AFSD that gives a lot of data including side slip & you can run it at the same time a flying. It works for both FS9 & FSX.
I used it to calibrate my Turn & slip indicator thats going into my Dragonfly (WIP). I am reliably informed that this aircraft needs a bootful of rudder to compensate for adverse yaw & I've got about as much as I can get at the moment!!

https://youtu.be/mtqTckp68ig

Keith

Sorry Keith, missed your post. I have AFSD and it's an amazing tool, so I will dig it out for this purpose.

 

[Bjoern]

[LATER: Holy cow, remember that old saying about how each equation you include halves your audience?! This document is, if it turns out to be nothing else, at least a testament to the author's awesome desktop publishing skills!]

Fortunately, you only ever need just a few of them to do what you want to do.

 

[MarkH]

I haven't had any success with this. There is indeed a parameter for 'yaw effect due to aileron' under section 1101 in the air file and from reading the fs_flight_dynamics_v1.0.zip file it appears this is included in the yaw calculation, but it doesn't seem to make any difference what I set this to for the Twin Otter. (I am able to successfully make changes to the air file using AireEd, as changing other parameters has obvious effects.) I should say that decreasing the rudder effectiveness is no use as there's no apparent need for rudder at all!

 

[Bjoern]

The [flight_tuning] section in the aircraft.cfg has yaw stability and yaw effectiveness parameters. Lowering the former and increasing the latter might help.

 

[PRB]

The effect you're after is most likely possible. Take the Milviz T-38. They did some flight model “trickenometry” to get the rudder to actually act like a rudder (novel idea yes?), in that application of it causes the aircraft to roll, a behavior absent from almost all FS planes. Most just wallow over in yaw. If they do roll, they wallow sluggishly in that axis as well, even when the rudder is applied quickly. I've been thinking about this while reading this thread. If rudders don't behave like rudders, this fact might be related to the effect you're looking for as well. In any case, it will most likely be a combination of tweaks, in creative places not obvious to people like us, who scan the air file for tables and fields with names related to the effect we're trying to affect, like yaw, which, when tweaked, doesn't appear to affect yaw!

In Googling for how adverse yaw looks from the cockpit so I could evaluate other FS planes, I found that some do appear to model it correctly. The Lionheart Creations Piper Pacer for example. If you roll using only the ailerons, the nose does indeed appear to rise in relation to the horizon, and pushing on the correct rudder pedal both centers the ball and brings the nose down. This also seems to indicate the correct behavior is possible to achieve. Don't know what to tweak, however, in a plane that doesn't do it properly. I have the old “Version 1” Aerosoft DHC-6, and it appears to behave correctly as well, best I can tell anyway.

 

[Bradburger]

I haven't had any success with this. There is indeed a parameter for 'yaw effect due to aileron' under section 1101 in the air file and from reading the fs_flight_dynamics_v1.0.zip file it appears this is included in the yaw calculation, but it doesn't seem to make any difference what I set this to for the Twin Otter. (I am able to successfully make changes to the air file using AireEd, as changing other parameters has obvious effects.) I should say that decreasing the rudder effectiveness is no use as there's no apparent need for rudder at all!

Shame it didn't work Mark!

I'm afraid I can't be of any more help, as I don't have the Aircraft in question, although I said in my previous post, it will probably depend on how accurate the other yaw (and other parameters etc.) are set in the air file, and probably some parameters in the Aircraft.cfg too.

As a side note, I use Jerry Beckwith's excellent (but sadly no longer supported or developed) Flight Dynamics Workbook for creating FSX flight models from scratch (for both payware and freeware), and all I can say is I've been very impressed with how they turn out in FSX (and formerly in FS9), and how accurately they reproduce not only the flying characteristics of the aircraft in question, but also the level of fidelity and fluidity they achieve, which is something I've never come across with in FS before, even from some of the top line developers whose FMs are highly rated! (It makes me laugh when I hear how many times I hear the FS FM engine is a load of crap or whatever!)

That all said, you still at times need to 'tweak' and adjust certain parameters used in the airfile (the Workbook lets you do this) such as adverse yaw for example, and I've found you can adjust the latter to get an accurate amount of yaw due to the ailerons, helped enormously of course if you have the recorded amount in a report!

But that's what I like about the Workbook. It does all the hard stuff for you, and leaves you to get on with the 'arty' side of an FM as some like to call it.

Cheers

Paul