Seeking documentation of the Aerodynamic Forces and Moments Block

Can anyone provide documentation of the equations used by this block?

The help documentation explains the axes transformation but not the calculation done inside the block. Through some experimentation, it appears that forces are calculated by:

and moments are calculated by:

However I can't figure out what the reference span does.

Answer 1

[patrick1704]

Hi there,

aerodynamic forces/moments are normally described as dimensionless coefficients because there are some similarity relations (keywords: Reynolds and Mach number; Similarity Parameters (nasa.gov)) that are used in their description.

The symbols generally specify:

• q: dynamic pressure (=)
• ρ: density
• V: airspeed
• : reference area (normally wing area)
• : reference length (mostly mean aerodynamic chord)
• : force/moment coefficient

Hope you can work with this.

[John McNeil]

Thanks for the fast response!

I'm familiar with the terms and symbology posted, but I've been unable to find any documentation of how that's implemented in this specific block.

Do you know how the block is using the reference span?

[patrick1704]

Normally the reference length for roll and yaw moment is the reference span (which is most often the half-wingspan), while for the pitch moment it is the mean aerodynamic chord ("reference length").

This is how Matlab handles it as well and you can also see that when you select the option of the block to "Look under the Mask".

[John McNeil]

"Look under the Mask" did the trick, thanks!