VSP Aero Stability Analysis Questions

[Felix Rubin]

Hey Rob & Guys,

I have some questions to the VSPaero stability analysis.

1. In the VSPaero advanced tab there is the stability mode drop down menue specifying the different analysis methods available. What is meant by "steady" (documentation mentionnes an option "stability" which is not present in the most recent version)?

2. in the .stab output file there is a definition for the delta of the rates ( +1.000 rad/Tunit). Since 1 rad is about 57° we are wondering if this is a valid assumption to make since for example 57° change in pitch rate per second is a massive disturbance.

3. How are the derivatives with respect to rates nondimensionalized. E.g. for pitch rate normally in literature the derivative is nondimensionalized with (q*c / 2*V_inf). If we apply this the values turn out to be quite unrealistic.

Could you help us out? Thanks and have a nice day!!

Cheers,

Felix

[Saulo Barbosa Oliveira]

"Steady" is the same that "Stability" in documentation : Small flow and angles variations for steady state case analysis to perform linear approximations and evaluate stability derivatives.

both issues 2 and 3 seems to be related to the same analysis, correct? Your both assumption are correct, at least when i've compared with AVL, they converged to very similar results. 

Can you share your results? Maybe some dimensional issue is causing this issues.. 

best regards,

sbo