How to begin?

Dumb question time. If starting from scratch, and not using Air Wrench, how do you start a new air file? What program creates an “*.air” file? Also, there are so many variables inside an air file, where do you get such data? I have an original copy of a “North American Aviation Estimated Performance Data for Navy Model T-28B blah, blah ...” document. It's filled with much priceless engineering data and flight dynamics information for that plane, but it has nowhere near the amount of data items that are found in an FS air file! I know what drag and lift coefficients are, and datums and moments, but you can't find that stuff on the “Interwebs” for any given plane, let a lone the “Cl_p Roll Moment – Roll Rate (Damping)”! Oh, it's -2250 for the Alphasim GB R1! Where does one start?

:isadizzy:

- Paul

The Flight Model in FS9 and FSX is still a Black art with no Official Documentation from MS, there never was a Flight Model section in the either SDK.

Prepar3d's SDK has a Flight Model section which could be used for FS9 or FSX however it is still not well documented and they don't list what all the possible Tokens are (known as tables to you and I).

A good place to start for second party documentation is on Herve Sor's web site

http://www.aero.sors.fr/index.html

Look in the lower left hand corner.

All of the tools I use for air files are listed on his site.

Knowing what tables do what functions has been some trial and error and help from Warchild and Fliger747.

It should be noted that for FS9 and FSX Airwrench is the only program I know of that will create a from scratch air file. All other programs are designed to modify existing air files.

I would start with the original air file and tweek it as necessary.

Quote:

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Originally Posted by PRB

1. What program creates an “*.air” file? Also, there are so many variables inside an air file, where do you get such data?
2. I have an original copy of a “North American Aviation Estimated Performance Data for Navy Model T-28B blah, blah ...” document. It's filled with much priceless engineering data and flight dynamics information for that plane,
3. You can't find that stuff on the “Interwebs” for any given plane, let a lone the “Cl_p Roll Moment – Roll Rate (Damping)”! Where does one start?

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Hi Paul.

1. You don't 'create' an air file. You use e.g. aired or aam to start with an existing airfile from a default plane that's as close as possible to the one you are creating. In case of the T-28 e.g. with the default P-51.
2. Performance data alone is too little info (IMO), you need a lot more info for a precise FDE. It would be interesting what data except performance data you r T-28 info contains!
3. Section 1101 contains a lot of important aerodynamic data and if you e.g. alter Cl_p at least 50% of all other variables in section 1101 are affected as well.

This is being complicated by the fact that FSX only very seldom can use RW data, so you have to circumnavigate FSX restrictions, limitations etc by using 'wrong' numbers to get the desired RW effect.
Last but not least achieving the correct performance like climb rate, top speed etc. is the easy part to accomplish in the FDE, you still need the handling, yaw induced roll, yaw damping, stall behaviour etc. to be 'realistic', and that's the more difficult part, as there are seldom 'hard' data available.

Interesting. I've “converted” a couple of CFS2 air files to FS9, but it was nothing compared to making one from the start. Using a similar one as a basis makes sense as a starting point. I always thought there was a program out there that made .air files. AirEd is probably the best tool, then.

The T-28 document contains a huge amount of data, and is probably “gold” to somebody making a T-28 flight model. Los sof specifications, but 90% of it is performance charts.

Quite frankly, Jerry Beckwith's Flight Dynamics Workbook (sadly no longer supported) and Air Wrench are great tools (the ONLY FM tools available, it's worth remembering!) for starting a flight model from scratch and giving good and accurate results, and do all of the hard work in the .air file for you! (Why have to worry about Cl_p Roll Moment – Roll Rate (Damping) when either of these tools does this for you).

All you need is performance data, weights and dimensions, and to set up contact points, station loads and other parts of the aircraft accurately for the visual model of the aircraft you are doing the FM for (Aircraft Container Manager is great for this) and you should be good to go!

I guess the danger when using an .air file for a similar aircraft type is just how accurate was the data in it in the first place, and what aircraft did that .air file start it's life as originally.

Of course there are some people who manage to produce good Flight Models the 'hard way' but I think they are the exception rather than the rule.

But whichever route you take, good luck!

Cheers

Paul

Rgr that Paul, but my goal here is to learn more about this "black art", as Bill would say. I have Air Wrench, although since I moved it to my new computer I need another activation code. Air Wrench almost "too good" if you want to dig into the details of these things.

To get the best look at all the tables and relationships inside the air file, Jerry Beckwith's FDWB is the answer.

You must have MS Excel to use it.

It has spreadsheets for all the table groups and data input functions, graphs of calculated results, key numbers well presented, and visual affirmation of results.

It does require key metrics, performance data, air foil data (or it will calculate one based on performance data), and allows input for things like roll response, stall response, etc.

It also allows you to tweak key numbers to correct calculated HP and provide feedback to it from testing.

The neat thing is you get to see and experience table changes with your input. This is where it is valuable to help understand actions/reactions to table data.

Yes, unsupported, but its a gem that once learned is an invaluable tool for an inside look at air file tables and relationships.

Do not sell it short.

When you have finished a session, it generates an air file and a cfg file.

Give it a try and remove some of that "mysticism".

Hi Milton,

I have the workbook. As Gerry says on his site, it's a bit scary looking. The only place I have Excel is on my laptop. Open Office's spreadsheet program open's it, but the formulas and macro language are different enough that I think I will need Excel... I like the AirUpdate program, that dumps an air file into a text file. I guess I just have to jump into the "deep end." No other way to begin to get one's head around it all. :)

- Paul

In FSX dont forget that the aircraft.cfg has gained in importance and .air files have actually shrunk (default planes at least)
the two files work in concert with one another to produce the whole effect and the cfg file can actually override/modify values in the airfile
...like flap lift and drag for example, or jet engine thrust

i like to use aired for the quick look and AAM for the detailed tweaking as AAM explains many functions of airfile data records

blackmagic or applied science?
here is an interesting flow chart i found a few years ago explaining the turbine engine records and how they build up turbine characteristics....

Attachment 72684

I have Jerry Beckwiths FWDB as well as Herve Sors AAM & Air Ed.
I do find however that using FWDB does depend upon the base .air file one starts with, so I do not do a complete update from it, but use some items inserted into my .air file of choice.
I do not like to modify .air files using AAM, but I find the visualization & later knowledge within it is better than Air ED, although I use Air Ed & Notepad to modify the parameters.
I understand that Airwrench is very good, but have no experience of it.
Even using these tools, its still a lot of guesswork/empirical/experimental work to get the required response from the airframe & I am sure that there are a lot of 'fudge' factor entries in the .cfg & .air files that bear no relationship to practical aerodynamics......My FS flight records show many experimental hours...........I have yet to fully create a good spin characteristic for example.....
One must also try to get a better response by reducing the .cfg stability factors as having them set to '1' can mask a lot of reaction.
Good luck
Keith

Air wrench is a good tool, but my major beef is that it always changes everything, you cannot manualynedit any single parameter and have ot preserved should you run it through again. It is a decent start, but also the starting point of a somewhat similar aircraft works. Intend to startnwith the weights and dimensions plus the powerplant and adjust the aerodynamics to match, as we usuallynhave the bestbdata on the engine. Lift and drag data can be found for the specific airfoils which is also a help. Testing, testing and adjustment. Herve Sors AFSD is invaluable for seeing what is going on with all sorts of performance.

T

Looking to start making .air files for CFS3. What tools do i need ? The same as FSX ? Where do i start ? Regards,Scott