Alpha8.1 PAR file questions

[andras]

I'm trying to build my own model for FMS Alpha8.1.

In the PAR file, there's an option for the engine size -- what effect does that have? Somehow the RPM doesn't seem to decrease when I decrease the engine size from 10 to 4 on the Su26. If I increase it to 40, the engine stops altogether -- weird.

Also, what are the engine resistance parameters in that file?

[andras]

Also, the coordinate system doesn't seem to be consistent, especially with respect to positive z orientation. Any definitive documentation available on that?

[Roman Moeller]

hello andras,

the positive z-axis shows downward, the x-axis in flight direction and the y-axis in wing direction (this kind of coordinate system is often used aerodynamic literature).

If you want to change the engine's size, it is important that you also adjust the fuel consumption. If you don't change the fuel consumption, this meas, that you have a smaller engine that (properly) burns the same amout of fuel as a bigger one, and hence releases more or less the same power. The engine resistance parameters usually do not vary much.

If I will find some time I will write a documentation of the new par file.

Roman

[ggunners]

andras,

You can also find some documentation re: the new .par files on .

There's an Excel spreadsheet comparing the .par files that come with the alpha8.1 download. An Excel spreadsheet that'll help you build a .par file. And a small program I wrote to transform from the Metasequoia 3D space to the alpha8 3D space for help filling out the surfaces information. I've also written a short "How-To" document explaining how to create a brand new alpha8 .par file for a beta7 model.

-- ggunners