AIR File vs CFG File

[Greystone]

I have been unable to successfully find an AIR file replacement for the CFS2 F4U to make it more realistic. I have, in the past, done some tweaks to the CFG file for aircraft to make them more, well, responsive to some flight characteristics I desire. But I do not have the experience to know what this does to the aircraft performance vis-a-vis the AIR file. A dummy's guide to this would be useful, since I am obviously a dummy.

Thanks in advance

[merlin2]

Have you tried the !% flight models? I know that Netwings, the host is gone, but there was talk about hosting the 1% models here at the outhouse.

thanks

merlin2

[Tango_Romeo]

Entries in the CFG file will over-ride entries in the AIR file.

[Milton Shupe]

I have been unable to successfully find an AIR file replacement for the CFS2 F4U to make it more realistic. I have, in the past, done some tweaks to the CFG file for aircraft to make them more, well, responsive to some flight characteristics I desire. But I do not have the experience to know what this does to the aircraft performance vis-a-vis the AIR file. A dummy's guide to this would be useful, since I am obviously a dummy.

Thanks in advance

The question was posed at Simviation for someone to help with the mystery of .air files. I thought I would share my response here as well, for what it's worth. :-)

First, let me say that I am not an aeronautics engineer, nor an expert of flight modeling. I do use the tools to create flight models and know a little about FS flight model relationships. After 4 years exposure, I still rely on the works and advice of fellow simmers like the late Ron Freimuth, Ian, Herve Sors, Jerry Beckwith and others who really specialize in the inner workings. With that said, I offer what little I can here from a user perspective. I hope that if I state anything wrong that one of the aforementioned gentlemen or someone here will correct it.

The .air file contains the necessary data to drive the flight sim's flight dynamics engine to respond the way your model should in the real world if defined correctly. Since that same FD engine must simulate a 747, a Cessna, an ATR500, and a hang glider, the .air file defines the attributes to the FD engine so proper responses to input can be made.

The aircraft.cfg file gives you and me an easy way to manipulate some parts of the .air file easily. Actually, there are many more tables of data in the .air file that can't be modified than can be modified this way.

Air files do seem to be confusing to us all. However, with research, a knack for aerodynamics and the mechanics of flight, lots of patience and interest, you can overcome the "mystery".

It may help to put .air files into some kind of visual/graphic reference to help debunk some misconceptions. The attached graphic depicts an air file with its many data cells necessary to drive the sim's flight dynamics engine. The various colors defined in the legend show why we get so confused at times.

As Flight Sim evolved, more data cells were added, some stayed behind (no longer used - like placeholders) for compatibility for the older sims, some used by all, some not at all. :-) When loading your aircraft and .air file tables, I believe that the FSim modifies these .air file tables with data specified in the aircraft.cfg. These memory cells are then used as input to the flight dynamics engine.

Hope this helps get a visual of the air file concept, its general makeup, and interaction with the aircraft.cfg.

There are 100's of tables of data, some multi-dimensional.

You can download SDK's to help understand the aircraft.cfg (Aircraft Container SDK) and generating and maintaining air files. These help with the basics and get you started with a template approach. Later, you may wish to get more control of your flight model.

http://support.microsoft.com/kb/555857/en-us

Herve has a great site with tools and documents, and links to help you understand and manipulate flight models more in-depth. Be sure to get AirEd, Ron's aired.ini updates, Ron's aircraft.cfg file explanation, and Tom Goodrick's .pdf on the basics of flight dynamics. For testing, Herve's AFSD test program gives real time feedback on the flight model. This is a great site to start collecting information and tools.

http://pagesperso-orange.fr/hsors/index.html

If you truly wish to pursue flight modeling and do the research and get the tools, AirEd is a nice tool to allow changes to the .air file basics. Here are a couple shots of the internals. You will see things that are in the aircraft.cfg and many that are not.

These early tables have been around since early days of flight sim. Many of these early table basics can be overridden by the aircraft.cfg. For example, table 1004 is contact point data.

You see here many of the core tables that cannot be modified by the aircraft.cfg. Also on table 1101, there are many of the key table elements that one will modify such as lift, drag, pitch, yaw, side forces, etc. Some of these table elements may be overriden by other tables further down the air file, if present.

If you are familiar with aerodynamics terms, much of this will be familiar to you. You will also notice gaps in table numbers as table series usually represent a grouping or category of data, not necessarily old or outdated tables. Table definitions here are provided by AirEd and the AirEd.ini description file by Ron Freimuth.

Other notes:

1. Some table data is overriden by aircraft.cfg data, if specified.

2. Some tables, if present, override other tables, depending on which FS version is used.

3. Some table data, if not specified in the air or cfg files, is calculated by the sim at run time.

4. Unless you restrict it, flight sim will update some fields in the aircraft.cfg file at run time. In the aircraft.cfg, General section, Editable = 0 turns off updates

5. If invalid data is specified, it may be ignored or recomputed.

6. The lack or either an .air or .cfg file will keep your aircraft from loading.

Now, with all that said, there are other sources of great flight models, and many of you know them and can share, and there are other tools out there to help you out. Sparks' Flight Dynamics Work Book (requires MS Excel SS) is one as is his AirWrench (payware for most applications).

http://www.mudpond.org/

The AVHistory 1% work is also excellent for the CFS world.

[Greystone]

A most excellent explanation. I shall try to get AirEd and do the readings you recommend.

Many thanks.

[Tango_Romeo]

Tables in the AIR file can actually be modified, though it is a good deal of trouble. The 'Table' is really a graph of a table. It can be saved to M$ Excel, redrawn and reinserted into the AIR file, though the results are seldom worth the effort required when there are simpler alternatives.

[Milton Shupe]

Actually, all of the table data can be modified right in AirEd itself either in tabular form or as the graphs are pulled up. Read the AirEd instructions for more info.