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Damping help needed

S

sxa1376

Messages
31
Country
greece
Hello guys,

I need your help in order to determine the correct roll rate (damping), the pitch rate (damping) and the yaw rate (damping) known in (1101) section as Cl_p, Cm_q and Cn_r.
For example about Cm_q maybe it depends from aircrafts length? If so and the length of the aircraft i am editing is about 130 feet then in 1101 section in Cm_q section i will put 130?
And if this is the correct thing to do what about the Cl_p and Cn_r? If not because i am just guessing now please can you explain to me how i can determine these three coefficients? Many thanks in advance.
 
You need data for the real aircraft. Or at least geometric dimensions and a CL vs AoA table for the surfaces. The damping effect is largely a result of the size and placement of the wings, horizontal stab, and rudder.
 
Dear jx,
Thank you very much for your response. I have the geometric dimensions. When you say about the damping that is a result of the size of the above what exactly you mean? Can you please make it more specific?
Probably inside fs the things might be acting different than in real life and probably I am looking to apply some equations I don't know.
 
"Probably inside fs the things might be acting different than in real life and probably I am looking to apply some equations I don't know."

FS actually models real world physics just fine.

The easiest way to solve your problem, is to time how long it takes to roll X degrees from level, with X degrees of control wheel deflection. If you can get that I can help.

Otherwise you either need tables (what kind of aircraft?) or you need the geometry and CL.

Geometry means Aileron is 12 Left, 1 foot up, and 4 feet back from CG.

CL means Aileron deflected to 15 degrees will produce X.XX Lift Coefficient (CL)

With those two pieces of information, you are able to calculate the lift force that is produced at the control surface, then the moment applied to the CG, and finally convert that to a coefficient.
 
"Methods for estimating stability and control derivatives of conventional subsonic airplanes" by Jan Roskam is helpful if you want to estmate coefficients such as Cl_p, Cm_q and Cn_r.
 
Hello guys,

The reason i want to estimate these is i want to make a b737-200 fde.
Bellow i put the charactiristics of the b732:

length: 30.53 m
wingspan: 28.35 m
wingarea: 102.0 m2
Root Chord: 7.32 m
M.A.C.(m): 3.80 m

For the 404,473 i will use these are coming with the ms default b734.
About the b734 i see from "AAM v2.2" editor that inside "1100" section the:

Cm_q=-214,1455078125
Cl_p=-4,150390625
Cn_r=-2,490234375

How they estimate these values? If i know the equation i can then estimate these corrected values for the b732 as well.
Many thanks in advance.
 
3 year old thread and it's last post has the title to the book you need to purchase to obtain the math. Internet search to locate the book is your best bet.
 
The numbers entered into the .air file sections are dimensionless. Just start putting in a bunch of numbers from similar aircraft that you feel are accurate, and adjust until you achieve the desired result.

FSX/P3D almost never use values directly calculated from specific formulae; they are compound values with many factors "baked-in" which is why it's so challenging.
 
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