D

dmaher

Active Member
Hi, I’ve been developing an RV7 add-on for MS flight simulator, FSX...before I get started for real.
I know some folks are familiar with the project; it’s been in development a very-very long time - years :)
It’s sort of hard to believe but there are more hours in it now than a real one.

The biggest remaining task is defining all the aerodynamic coefficients.
While, I’m enjoying impersonating an aerospace engineer, it’s going to take more time than I’ve got to become one.

So I’m wondering, are these numbers already available somewhere?
If not, are they easily determined through experimentation?
Or, is there software that I could use to determine reasonable approximations.

I’m really hopeful there is software that can sort of lead me through this.
Right now I’m looking at Xfoil…and I will try AVL soon.

I’ll post a sample of the aerodynamics section.
I have a good idea of what each coefficient and tables means, I just don’t know yet the best way to determine them.
Below is the aerodynamics section; there is also a section for: ground effect, control surfaces, AOA, Mach, engine, and propeller.
Here’s a link to the complete set…http://msdn.microsoft.com/en-us/library/cc707067.aspx

Does this stuff look familiar to anyone? :)

Danny

For more project details...
http://www.baytower.ca/
forum


Code: 
;**** BEGINNING OF REQUIRED AERODYNAMICS ************************

    ;The following 6 blocks define the base stability and control derivatives
    ;Lift, Drag, Pitch, Side Force, Roll, and Yaw.
        TOKEN_BEGIN     AIR_80_LIFT_PARAMS 
                REAL8   0.000000        ; CL spoiler
                REAL8   1.2             ; CL flaps
                REAL8   0.000000        ; UNUSED
                REAL8   0.715988        ; CLih
                REAL8   -0.273018       ; CLde
                REAL8   0.000000        ; UNUSED
        TOKEN_END 

        TOKEN_BEGIN     AIR_80_DRAG_PARAMS 
                REAL8   0.065           ; CDo
                REAL8   0.07            ; CD flaps
                REAL8   0.007000        ; CD gear
                REAL8   0.000000        ; CD spoiler
        TOKEN_END 

        TOKEN_BEGIN     AIR_80_PITCH_PARAMS 
                REAL8   2.133893        ; CMih
                REAL8   -1.6            ; CMde
                REAL8   -0.051200       ; CMde due to propwash
                REAL8   -2.601277       ; CLq
                REAL8   0.988016        ; CL adot
                REAL8   2.0             ; CM adot
                REAL8   -28.770823      ; CMq
                REAL8   -10.000000      ; CMq due to propwash
                REAL8   0.0             ; CMo
                REAL8   -0.07           ; CM flap
                REAL8   -1.066947       ; CM delta trim
                REAL8   0.020000        ; CM gear
                REAL8   0.000000        ; CM spoiler
        TOKEN_END 

        TOKEN_BEGIN     AIR_80_SIDE_FORCE_PARAMS 
                REAL8   -0.569647       ; CyB
                REAL8   0.038363        ; CyP
                REAL8   0.018805        ; CyR
                REAL8   -0.153025       ; Cy Delta Rudder
        TOKEN_END 

        TOKEN_BEGIN     AIR_80_ROLL_PARAMS 
                REAL8   0.045           ; ClB
                REAL8   -0.9            ; ClP
                REAL8   -0.061076       ; ClR
                REAL8   0.000000        ; Cl Delta Spoiler
                REAL8   -0.269225       ; Cl Delta Aileron
                REAL8   0.010           ; Cl Delta Rudder
        TOKEN_END 

        TOKEN_BEGIN     AIR_80_YAW_PARAMS 
                REAL8   0.099757        ; CnB
                REAL8   0.034553        ; CnP
                REAL8   -0.524805       ; CnR
                REAL8   -3.000000       ; CnR due to propwash
                REAL8   0.000000        ; UNUSED
                REAL8   0.000000        ; UNUSED
                REAL8   -0.002345       ; Cn Delta Aileron
                REAL8   0.063277        ; Cn Delta Rudder
                REAL8   0.002048        ; Cn Delta Rudder due to propwash
        TOKEN_END 

    ;CL vs. Alpha
    ;The first entry defines the number of data points (maximum 47 entries)
        TOKEN_BEGIN     AIR_CL_ALPHA 
                dd      13      ; Number of Entries

                REAL8     -3.142,     0.000 
                REAL8     -2.356,     0.500 
                REAL8     -1.571,     0.000 
                REAL8     -0.366,    -1.528 
                REAL8     -0.078,     0.000 
                REAL8      0.017,     0.590 
                REAL8      0.262,     2.096 
                REAL8      0.288,     2.183 
                REAL8      0.314,     2.096 
                REAL8      0.340,     1.528 
                REAL8      1.571,     0.000 
                REAL8      2.356,    -0.500 
                REAL8      3.142,     0.000 
                 
        TOKEN_END 

    ;CM vs. Alpha
    ;The first entry defines the number of data points (maximum 47 entries)
        TOKEN_BEGIN     AIR_CM_ALPHA 
                dd      13       ; Number of Entries

                REAL8   -3.142,   0.000  
                REAL8   -0.550,  -0.545 
                REAL8   -0.375,  -0.545 
                REAL8   -0.305,  -0.273 
                REAL8   -0.288,  -0.227 
                REAL8   -0.271,  -0.189 
                REAL8    0.000,   0.000  
                REAL8    0.271,   0.189  
                REAL8    0.288,   0.227  
                REAL8    0.305,   0.273  
                REAL8    0.375,   0.545  
                REAL8    0.550,   0.545  
                REAL8    3.142,   0.000  
                 
        TOKEN_END 

    ;**** END OF REQUIRED AERODYNAMICS ************************************************





 
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hi danny,

great that you're still working on it!
thought it was another one of these promising but never finished or published flightsim projects :-(

we'll have the first flight of our -7A shortly, would love to aid in beta testing... we do have 1s datalogging capability, but that's probably too slow to derive the dynamic properties, should work for the more static ones.

as for the air file, i would caution against starting from scratch but rather take e.g. the extra as a base and start tweaking away to get near 7 performance... it doesn't matter if the numbers end up being "real" but rather how the model "feels"...

rgds, bernie

P.S. please do a 7A tipup :)
 
flyvans.com said:
as for the air file, i would caution against starting from scratch but rather take e.g. the extra as a base and start tweaking away to get near 7 performance... it doesn't matter if the numbers end up being "real" but rather how the model "feels"...
Click to expand...

For "feel". the RV7 is more along the lines of the payware RealAir SF260 than the MSFS Extra. You might want to check out the SF260 if you don't already have it. The SF260 just seems "comfortable" & not annoying, if I load up a flight simulation after flying my 6A.

L.Adamson
 
Glad to see you're still at it, Danny. I agree, use the SF260 to get close and tweak a bit if desired. I'm sure aficionados will do their own tweaking; you might even enlist some as beta testers and use their tweaks on release.

I hesitate to ask: RV-10 next? ;)
 
I have used the SF260…it’s very well done – probably the best really.
I think that’s the sort of standard I’d like to aim for…eventually.
It’ll take some time to get there…so I think the strategy will be about setting up some sort of process.
A process where the dynamics are refined as better data becomes available over time.
The aerodynamic data could be laid out so folks can get a handle on it - inspect it, and revise it.
I think the RV is in a real good position to use precise data as the foundation.
Mostly because, the RV uses a simple wing design and overall design…and RV builder/pilots know their aircraft.

FSX is setup with two levels of aerodynamic settings.
Hardcore Jan Roskam-type performance coefficients are stored in the .air file.
And, aircraft dimensions and tuning parameters are in the .config file.

Using the tuning parameters in the .config I can actually get the Mooney to almost "feel" like an RV.
So I’m hopeful getting some precise numbers in the air file will establish an even better foundation.
I really hope AVL is a good starting point.

Bernie, there is a 7A tip-up too (there are 4 models: 7/7a-sldr, 7/7a-tip)

- these are unpainted...so they shows up black.
fsx_rv7a-tip.jpg


fsx_rv7-tip.jpg
 
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