FM Tweaking Tutorial--anyone interested?

[Herr Prop-Wasche 7]

Greetings, gents and lasses.

 

Anyone interested in a flight model tweaking tutorial? I have been messing around in the files (again) and have a few thoughts about the FM and the various tweaks that are available. For instance, Olham mentioned that he thought the Alb III was somewhat of an underperformer. I created an Excel spreadsheet and made some interesting discoveries about the comparative performance of all of the scouts in OFF. In general, I agreed with almost all of the FM settings, but there were a few "anomalies."

 

I have also noted some oddness while flying some aircraft. For instance, has anyone else noticed that the Sopwith Triplane can dive in speeds in excess of 260 mph? Actually, I wonder if almost all of the aircraft in OFF dive a little too fast for what are basically motorized kites. There is a setting (or two) that can help adjust this, but you have to be careful changing it because changing one variable can have an effect on other variables.

 

I don't claim to be an expert in all (or even most) things FM, but I have played around with some of the settings and found that you can (successfully) alter a few parameters such as max speed, climb rate, and turn radius, among others. I know that messing around with the FM is likely to be a controversial matter and is not likely to be popular among some folks such as people who like to fly in multi-player because they need to have identical FM's. But, since OFF is primarily a single player game, I thought there might be a few folks who might be interested in this topic. If not, I can shut my yap and quietly back out of the room!

 

Besides, it seems to have gotten a little too quiet in here recently. Nothing like an FM discussion to warm things up a bit!

[Duce Lewis 3]

...you can (successfully) alter a few parameters such as max speed, climb rate, and turn radius, among others.

HPW, I think there are others who've fiddled with the FM

Trouble is; where do you fly it?

Doesn't it create a type mismatch that cancels any Campaign or QC?

I think the modified FM crates will only fly in cfs3 QC ...correct?

[Herr Prop-Wasche 7]

Good question, Duce. So far, my changes work in QC. I haven't yet tried them in CFS3 QC or in the campaign. I will report back.

 

UncleAl--Contrary to your experience, I was able to recover from a 260 mph dive in the Tripe. True, I did have some "high speed stress damage" and the elevator was sluggish, but I did recover. Compressibility shouldn't be a factor at speeds under 400+ mph. At any rate, the main point is that the Tripe should not dive at such a fast speed with three wings and all of those wires and struts.

 

There is a variable you can set in the .cfg file that adjusts parasitic drag. Currently, this is set to 1.00 for all OFF aircraft. Since CFS3 is originally a WWII flight-sim, I think an argument can be made that this setting should be set to > 1.00 for all OFF planes, as they are much less streamlined than their WWII counterparts. Although I have found that setting this variable higher than 1.00 does reduce dive speed, it also tends to reduce level flight speed a bit. However, that can also be adjusted.

Edited April 25, 2010 by Herr Prop-Wasche

[Herr Prop-Wasche 7]

Something else I have noticed about the FM, particularly for German planes. Although super or turbo-charging was not used in any operational aircraft in WWI, many of the German aeroplanes in OFF have this setting checked to true.

 

I assume this was a decision by the devs to simulate the negative effects of increasing altitude on engine performance and how the German engineers got around this problem by intentionally "leaning" the fuel mixture of their engines at sea level (if you are interested in long, technical discussions here is a link to one about this issue from our friend Bletchley at the aerodrome http://www.theaerodr...ght=turbo+super ).

 

How does turbocharging a simulated WWI engine which shouldn't have turbocharging effect the overall performance of German (and some later Allied) aircraft in the sim? Instead of using turbocharging, I was wondering if it is possible to simulate the better German performance at high altitude simply by increasing the rated horsepower of their engines at sea level? Besides falsely increasing aircraft performance at sea level in exchange for more realistic performance at altitude, what might be the drawbacks of this approach?

[Herr Prop-Wasche 7]

I can confirm that the altered planes do work in campaign mode. However, you have to be very careful when editing the files with Airwrench. It's better to make adjustments directly in the .cfg file and just use Airwrench to observe the effects of your changes. NEVER save a file with Airwrench, even if it begs and pleads with you to do so.

[Dej 17]

I happily glean any information about the FMs and players' impressions of them that they care to let drop, so I would be interested. I'd appreciate a copy of that spreadsheet for one thing and I'm intrgued by your avatar for another what is it?

[Olham 164]

Thank you for investigating, Herr Prop-Wasche.

Of course, it would be phantastic, if you could find a way to eliminate wrong performance data

without mixing up the whole FM balance. So I wish you success; and I would even test a varied

FM for the Albatros.

But it must be done with a lot of care. I would backup the whole sim and the C-partition,

so it could be restored.

 

The devs have said, that some data, which seem wrong at first look, may have been set that way

to achieve an overall behaviour of all craft, mainly that of the AI aircraft.

So, if you tweak and test some changes, make sure you watch the AI aircraft of that type;

how they behave and perform, and if they are getting better or worse.

 

Some craft in OFF seem to be a bit better (Tripe) or easier to handle (Camel) than they really were.

Others are lacking a bit of performance (Albatros, Dr.1). If you find a way to balance that out,

it would be great. How much time do you have to invest (I'm afraid it might take very long).

 

I do not believe, it is an easy undertaking; otherwise the team surely would have done it already.

So take care, HPW - and when you have a tweak to test on the Albatros; I will have more time

next weekend.

[Olham 164]

PS: ...and be prepared, that all your work might be for a short period of time -

the devs may have changed a lot to the better with P4?

[Duce Lewis 3]

Besides falsely increasing aircraft performance at sea level in exchange for more realistic performance at altitude, what might be the drawbacks of this approach?

Sounds like one of the many conundrums that Pol has had to wrestle with

Good luck with the mods/testing HPW

I'll help with testing if you'd like

[Crossbones 1]

Would it be possible to "Copy" and "Paste" one FM over another?

 

Crossbones

[Bullethead 12]

Anyone interested in a flight model tweaking tutorial?

 

Such a thing would be very helpful to me. I am in the process of making a new plane for OFF and when I get to the FM part of the process, my plan is to start with the OFF files for an existing, similar plane and tweak them to match my new plane.

 

The tutorials I have at present are rather dated. For instance, they rely on fligh-testing your new CFS3/OFF plane in CFS2 using an instrumentation mod for that game. I have no idea how to get around that problem; I can't find a similar instrumentation mod for CFS3.

[cptroyce 0]

PropW- As an ol' FM hand from RB days, I'd really enjoy seeing what you have found to improve the OFF FM. I don't have the time nor the inclination to go learn the Airwrench editor ( which looks terrific btw) or the cfg. file, but would like to partake of your "discoveries".

Please include me in the "class"; or emails, PM etc.

 

At one time, in RB anyway, I had volumes of excel spreedsheets comparing the FM variables to historical reference and anecdote...unfortunately they disappeared into the digital blackhole after a computer crash.

 

Besides, everyone knows that the DR1 is "porked!

 

Regards,

Royce

[hairyspin 1]

Very interesting thread! A few thoughts, since FMs are something anyone rash enough to build a model will have to tackle one way or another.

 

1. You'll need to ask Pol et al if they still use the MS flight model, since we all know P3 has modified its CFS3 parent almost beyond recognition. If they don't, AirWrench or any of the other FM tools are useless without an OFF SDK.
2. Cut 'n' pasting one FM over another might yield horrible results - especially if a model has a different reference datum to the source of the FM. Don't go there.....
3. If the CFS3 flight model is still used (q.v.) then the .cfg file is only part of the story. Notepad or any other text editor is enough to edit aircraft.cfg, but you'll need an air file editor for the .air file: there are several including AirEdit (the freeware standard) and AirWrench. The beauty of AirWrench is that it deals with both files simultaneously - you can also pull a FM to pieces without changing anything until the Edit mode is selected.

Flight modelling is almost another hobby itself and the workarounds needed to give a really good FM in CFS3 are not obvious - plus those who know tend to keep their cards well hidden. Good luck!

 

 

BH - buy a copy of CFS2, they're really cheap nowadays!

Edited April 25, 2010 by hairyspin

[Herr Prop-Wasche 7]

Thanks for all of the replies, guys.

 

In no particular order:

 

I will definitely be in need of testers. There are too many planes to tweak and test for one person, so any help will be greatly appreciated!

 

I am unfamiliar with AirWrite. How does it compare with Airwrench? Airwrench is good, but it has a few bugs and snags. I have found that if I save anything using Airwrench, I frequently get a "plane not available yet" message when I try to fly it in OFF. Saving the .cfg file seems to avoid this problem, fortunately. As for the .air file containing a lot more data than the .cfg file, it is hard for me to say. Airwrench seems to cover only a fraction of variables that are contained in the .cfg file, and has few, if any, additional variables of its own. The .air file, of course, is a hex file, and although I have looked at it, I don't have a lot of hex experience and can't make much out of it. Doesn't help, of course, that the CFS3 coders did not put in any remarks in the file to help you identify variables.

 

There is a limited ability to copy FM's, but only from one of the same or very similar types to the other. For instance, you can copy an Alb DII_AC1 directly to an Alb DII_QC1 and only have to change the "AC" to "QC" at the top of the file. You could probably also copy an Alb DVa to a Alb DVa 200 with only a few more alterations. I would NOT recommend copying the FM for a Sopwith Pup to a Sopwith Tripe, however. Although...it might be possible.

 

Dej, PM me and I will send you a copy of the spreadsheet in Excel format. It only contains game data, however. And my avatar is simply a poster for the last WWI fly-in in Dayton, which I didn't get to go to because of work and lousy weather. :nea:

 

Cptroyce, I am very familiar with your FM work on RB3D. I used several different FM's and thought that yours was one of the best. I also helped Bluevoss (remember him) in testing out his FM, which even predates yours!

 

And yes, the DrI IS PORKED!!!!!!!

[Herr Prop-Wasche 7]

As promised, here is part one of my basic flight model tweaking tutorial.

 

Basic Flight Model Tweaking Tutorial, part one.

 

Recent discussions about the flight model for the Albatross D III got me interested in whether the individual user can tweak OFF's flight model to one's personal tastes. The simple answer is, yes! A more sophisticated answer is yes, but it's not easy. There are at least three reasons for this: 1) While you do not need to be an aeronautics engineer to adjust the FM, it helps if you have a basic understanding of physics, and more importantly, you can use Google and are willing to learn stuff. 2) The FM settings in CFS3 are not intuitive and do not allow you to easily see the results of your changes. Fortunately, there is a 3rd party tool you can use called Airwrench which helps tremendously in this regard. Unfortunately, Airwrench itself is a source of a third problem. 3) Airwrench has a glitch which make it frustrating to use to alter OFF's FM settings. Ultimately, I had to stop using Airwrench to change the files and instead use it only to observe the changes I make manually. Fortunately, it does this rather well. N.B. HairySpin has pointed out another flight editor called AirEdit is available and is the "standard" in FM editing. I have no experience with AirEdit and so will confine my comments to Airwrench, at least for now. Now, on to the tutorial!

 

1) If you decide to go ahead and toy with the aircraft FM, you MUST first back up two critical files: the aircraft.cfg file and the *.air file. Both of these files are found in the Windows folder of each individual aircracft in OFF. Failure to do this may result in an aircraft that OFF will refuse to load. Make a copy of both of these files and rename them so you can use them again if something you do causes OFF to throw a hissy fit.

 

2) Download Airwrench (or AirEdit). In order to see the effect of your FM changes "on the fly," you have to use one of these tools. Airwrench shows not only the many different components and parameters that can be altered in OFF, but also calculates and displays the result of these changes on such things as turn radius, cruising speed, climbing ability, and many others. Here is a picture of the main screen in Airwrench.

 

 

 

You can find Airwrench here: http://www.mudpond.org/

 

3) Okay, we are now ready to tweak! Virtually all of your tweaking will take place in the aircraft.cfg file for each airplane you are interested in tweaking. Open up the file with a text editor. I use Textpad, which is easily obtainable on the web and works much better than any of Microsloth's text editors. Next, start Airwrench. Click past the "activation" prompt, and click on the "Select Air File" button in the upper left. In the dialog box, be sure to pick EXACTLY the same aircraft whose .cfg file you just opened in your text editor. The boxes should now fill up with data. These are the FM specs for your selected aircraft. Go ahead and look around. Click the tabs to see data for all of the components of your aircraft, including weight, aircraft dimensions, engine type, wings, etc. Although there are 12 tabs, we will be concentrating for the most part on only three: the Specs, Dynamics, and Tuning tabs.

 

A word of caution. NEVER, EVER answer "yes" if prompted by Airwrench to save your file. The only major glitch with the program is that saving your airfile with Airwrench can cause your .air file to get out of sync with your .cfg file. If this happens, OFF will get very angry with you and refuse to load your aircraft, making it unuseable. Obviously, we do not want this to happen. So, even if Airwrench begs and pleads with you to save your file, politely decline and ignore it if it complains. Instead, all of OUR changes will be made in the .cfg file. We will use Airwrench simply to read the results.

 

4) Okay, let's go back to the Airwrench Specs tab. Although there are a lot of boxes with data in them, there are only a few which can be changed if Airwrench is in "evaluation mode." The most important are listed on the left, under the Performance Specifications label. There we have settings for Vmax @ sea level, weight used to calculate climb rate, and weight used to calculate estimated stall speed (which mainly effects turning radius). There are other boxes, such as clean stall speed, Max Load (G's), and Static Margin which can be changed, but we will not fool with them now. Notice that you can toggle between mph, knots, and kph by choosing the appropriate radio button near the top of the page. Also, leave the "Edit" button alone for now. You don't need it to change values and it can mess up your .cfg file, causing a mismatch if you are not careful.

 

5) Although we will not be using it, go ahead and click on the "Dimensions" tab. Basically, this page controls all of the settings for the control surfaces of the aircraft. Unless you know something about the dimensions of the aircraft that you don't think OBD already knows about, I would leave most of the settings on this page alone. There is one setting that you may consider adjusting, if you are careful. That is the setting for the "Oswald Efficiency Factor," a calculation that estimates the lift ability of the wings on your aircraft. Airwrench will automatically estimate this for you, but I have noticed that most of the airplanes in OFF have this setting set manually higher anywhere from as little as several hundredths to as much as one or two tenths higher than that recommended by Airwrench.

 

I think that's enough for now. Later, I will go over the contents of the Dynamics, Engine, and Tuning tabs, and then will describe where you can find all of the variables we have already talked about in Airwrench in the aircraft.cfg file for each plane. Until then, happy flying!

 

HPW

[Bullethead 12]

Basic Flight Model Tweaking Tutorial, part one[/u].

 

Domo arigato gozaimasu! It'll take me a while to grok this..

[Herr Prop-Wasche 7]

You are welcome, Bullethead, san.

 

Thanks for the drinks!

[Duce Lewis 3]

Hey Mr. Roboto ...err Bullethaed

Good to see you back in these parts!

Mind if I crash the party?

I figured you were chiseling away on sumtin

Good luck with the crate

 

 

HPW, Got the Airwrench DL and looking forward to the tutorials

[hairyspin 1]

Don't mean to interrupt you in mid-flow, but AirEdit only deals with the .air file. Only use it if you know what you're doing. No, I don't!

Also AirWrench has certain limitations in 'free', evaluation mode: to quote from mudpond.org:-

In demonstration mode, AirWrench will open and analyze the flight dynamics files for any aircraft, and for limited aircraft types, it will even save updated flight dynamics files.

 

Demonstration mode restrictions are as follows:

 

• Piston engine type only.
• Max Rated HP less than 230 HP.
• Normally aspirated.
• Gravity Carburetor only.
• Fixed Pitch Propeller only.
• Maximum speed at sea-level less than 130 mph.
• Basic Weight less than 2500 lbs.

which may help explain the .cfg and .air files getting 'out of step'. I haven't looked, but it also expects these files to be in the same directory and leaves backup copies of each in the same directory, which might also explain unhappiness with OFF P3.

 

If you want full function from AirWrench, it will cost you $20. I think it's worth it...

Edited April 26, 2010 by hairyspin

[Fortiesboy 3]

Just seen this Chris, - interesting as always- and unlike my tweaks in FM, a lot deeper-lol

 

I have for some while been flying modified FMs of some aircraft in my single play. Unfortunately the way i do it means that the plane will not load in campaign - as Duce said earlier-

 

I altered the Dr1- and the Albatrosses and the pfalz, on the basis that all of them have RPMs, as shown in flight, which are well below the spec max RPM-

E.g Fly the vanilla Dr1 and you will see the RPM is barely 1000- It's spec was 1200. Mine flies at 1200- and is a different plane- it now does "climb like a monkey " etc

 

But, as i say, it will only fly in CFS3 QC - but that is no hardship as that is where I do most of my OFFing anyway !

[Bullethead 12]

I figured you were chiseling away on sumtin

 

Sadly, I haven't had time to work on my airplane for about 6 weeks now. I have been chiseling lately, but only on stone and bone, making trinkets to sell in the current spring tourist season.

 

Also AirWrench has certain limitations in 'free', evaluation mode: to quote from mudpond.org:

 

Hmmm..... I got AirWrench about 6 months ago and that demo version will let you edit contact points ONLY. I suppose that would be useful if you were using renamed existing files for your new plane and wanted it to set correctly on the ground, but that's it. It supposedly does the full analysis but doesn't let you change any aerodynamic values--read-only on that stuff.

 

Someday I'll get to the point where I actually need AirWrench. Then I'll buy the thing. But for now, seeing how I don't know what I'm doing with it, I think it's safer to just look at things in AirWrench without the possibility of screwing them up accidentally.

[Duce Lewis 3]

Sadly, I haven't had time to work on my airplane for about 6 weeks now. I have been chiseling lately, but only on stone and bone, making trinkets to sell in the current spring tourist season.

Why not chisel some homebrew for the tourists?

"You'll catch more flys with beer than vinegar" ...or sumthin like that

[Bullethead 12]

Why not chisel some homebrew for the tourists?

"You'll catch more flys with beer than vinegar" ...or sumthin like that

 

I did that, too. The wife of a friend of mine has bad cancer and there was a benefit concert for her. I donated a batch of homebrew to the cause, which sold better than the Buttwiper, and for a higher price. Glad nobody had a wreck on the way home.

[Duce Lewis 3]

I did that, too. The wife of a friend of mine has bad cancer and there was a benefit concert for her. I donated a batch of homebrew to the cause, which sold better than the Buttwiper, and for a higher price. Glad nobody had a wreck on the way home.

Amazing and a nice gesture too, hope she's recovered

[Herr Prop-Wasche 7]

Odd that Airwrench is only allowing you to edit the contact points, BH. What plane were you working on, or was it one of your own creations? I have noticed that some of the planes in OFF cannot be "opened" in Airwrench.* For those, you have to directly edit the .cfg file. There is a section for contact points in the .cfg file, unless you are building one from scratch. If that is the case, I would suggest looking at the .cfg file of a roughly similar plane to yours and using that as a template.

 

*I believe the reason some planes are not editable in Airwrench is that they have had their engines set as turbocharged in the .cfg file. Non-turbocharged aircraft can be edited in Airwrench. This is probably due to the limitations of the free version of Airwrench, as described by hairyspin, above.

Edited April 27, 2010 by Herr Prop-Wasche