Empty Aircraft Inertia Values. What do they mean?

[mosherec]

Can anyone tell me what each of the three empty inertia numbers listed in the aircraft DATA.INI mean?

 

From other posts I undertand they are calculated from multiple factors and basically represent the empty mass that must be moved by a given control input along a given axis.

 

What I have not found is which number represents which axis?

 

Thanks.

[Wrench]

judging how 'things are done' (like pilot positons or lights postions) -- and I'm probably WAAAAAAAAAAAAAAAYYYY off base here --, my guess is

 

X/Y/Z

 

just a wild-ass-guess, so don't take it as gospel!

[Fubar512]

Wrench is correct, though it may help if you think of the 3 axis as "axles" around which the aircraft pivots. "X" would therefore be an axle extending from wingtip to wingtip, and would effect pitch inertia. "Y" effects roll inertia, and "Z" effects yaw inertia.

[+WhiteBoySamurai]

I was thinking about making aircraft models in the future, so I'd like to know-- How does one calculate those empty inertia values?

[Fubar512]

I was thinking about making aircraft models in the future, so I'd like to know-- How does one calculate those empty inertia values?

 

Calculating inertia for SF is almost a joke, as the series treats the distribution of masses as if every aircraft either starts with perfect, zero-center mass (all zeros), and ranges on up to ridiculous dumb-bell like high-polar moment of inertia values. The best advice I can give you, is look at what TK does for an airframe of similar configuration, and start editing from there, debugging the model against available data at every step.

 

Oh, and be careful with roll-rate data. Much of what you'll encounter on the 'net is based on initial, as opposed to sustained, roll rates. Trust me on this, no A-4 pilot has ever achieved 720 degrees per second sustained roll-rate

 

Sustained and instaneous G-rates pose another issue.