Stability File Outputs

[Alan Duong]

Hello,

Could I be provided with a description of what the stab file contents are? Are the moment coefficients with respect to stability axis or what axis? 

For example, I am unsure of what the middle group of data are. What are those deltas for alpha, beta, etc. ?

Another thing, the stability derivatives. There are some that are listed as "w.r.t U per u". What exactly is that trying to tell me? 

Thanks,

Alan

[Rob McDonald]

Both...

Forces & moments about body axes:

CFx          CFy          CFz          CMx          CMy          CMz          

Forces & moments about wind axes:

CL           CD           CS           CMl          CMm          CMn

When you run a stability case, VSPAERO actually runs 7 (or more with control surfaces) times -- a baseline, and then six perturbations in order to finite-difference the derivatives.  The 'Delta' column documents how big a perturbation was taken for each derivative.

The wrt U column is not one of the basic six -- I'm not sure if it gets activated for certain other cases, but it is safe to ignore that one for now.  The others say 'wrt Alpha per rad' means that the column gives the derivatives for the coefficients for each row with respect to Alpha, in units of per radian (as opposed to per degree).

CFx - Coefficient of force in X direction (body) , derivative with respect to Alpha, with units of 1/rad.

Rob

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[Alan Duong]

Rob, 

Thank you very much, this was very helpful. 

Best,

Alan

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