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David Tong | 4 Jun 2003 04:25

Parasite drag as a function of aoa

Hi All:
 
I'm new to FlightGear.  I had a general simulation question that I was curious about.
 
Does jsbsim handle parasite drag changing as a function of aoa?  If so, how do you go estimating how to model that?  If examples would help we could use the jsbsim P-51D model you guys have created as a reference.
 
Thanks!
 
David
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Jon Berndt | 4 Jun 2003 05:44
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RE: Parasite drag as a function of aoa

 
Hi All:
 
I'm new to FlightGear.  I had a general simulation question that I was curious about.
 
Does jsbsim handle parasite drag changing as a function of aoa?  If so, how do you go estimating how to model that?  If examples would help we could use the jsbsim P-51D model you guys have created as a reference.
 
Thanks!
 
David 
 
If the data was available in the form of aerodynamic coefficients as a function of alpha, then yes, we could. The P-51D model that JSBSim now uses is an interim model until I finish the more detailed model.  I am using Digital DATCOM to estimate coefficients for that version of the P-51D aero model.  In the simplest case, now, one provides a minimum drag coefficient and the induced drag can be calculated.  We can also estimate drag contributions due to flaps, gear, etc.  We would of course have a much better model if we estimated parasite drag effects due to alpha and beta.  Like I said, though, there's no reason this could not be done, as JSBSim allows any number of aero coefficients to be specified.
 
I hope that helps a little bit at least.
 
Jon
 
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David Tong | 4 Jun 2003 21:05

RE:Parasite drag as a function of aoa

>>We would of course have a muchbetter model if we estimated parasite drag effects
due to alpha and beta.  Like I said, though, there's no reason this could not
be done, as JSBSim allows any number of aero coefficients to be specified.

Thanks for the response Jon.  Believe it or not there's actually a report from
North American Aviation that has at least the Cdp varying with aoa.  I've asked
for a copy from NASM and Boeing (we'll see who responds first hehe!).  When
I get it I'll post it so that it can be added to the JSBsim P-51D flight model.

My question really is if there is an appropriate and accepted way to estimate
Cdp variation witih aoa for other aircraft when you don't have data from flight
or wind tunnel tests like might be in the case for the P-51D.

David
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Tony Peden | 5 Jun 2003 00:13
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Re: RE:Parasite drag as a function of aoa

On Wed, 2003-06-04 at 12:05, David Tong wrote:
> >>We would of course have a muchbetter model if we estimated parasite drag effects
> due to alpha and beta.  Like I said, though, there's no reason this could not
> be done, as JSBSim allows any number of aero coefficients to be specified.
> 
> Thanks for the response Jon.  Believe it or not there's actually a report from
> North American Aviation that has at least the Cdp varying with aoa.  I've asked
> for a copy from NASM and Boeing (we'll see who responds first hehe!).  When
> I get it I'll post it so that it can be added to the JSBsim P-51D flight model.
> 
> 
> My question really is if there is an appropriate and accepted way to estimate
> Cdp variation witih aoa for other aircraft when you don't have data from flight
> or wind tunnel tests like might be in the case for the P-51D.

JSBSim does not attempt to derive the characteristics of a given
aircraft. It just computes forces and moments from the coefficient data.

> 
> David
> 
> 
> 
> 
> 
> _______________________________________________
> Flightgear-flightmodel mailing list
> Flightgear-flightmodel <at> flightgear.org
> http://mail.flightgear.org/mailman/listinfo/flightgear-flightmodel
--

-- 
Tony Peden <apeden <at> earthlink.net>
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David Culp | 11 Jun 2003 21:31
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Aero-Matic

Opinions, anyone, on whether this idea

http://home.attbi.com/~davidculp2/fmm.html

is useful, allowable, fun,  ...etc.

"Aero-Matic,  it passes the smell test"

Dave Culp
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Jon S Berndt | 11 Jun 2003 21:39
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Re: Aero-Matic

On Wed, 11 Jun 2003 14:31:18 -0500
  David Culp <davidculp2 <at> attbi.com> wrote:
>Opinions, anyone, on whether this idea
>
>http://home.attbi.com/~davidculp2/fmm.html
>
>is useful, allowable, fun,  ...etc.

Yes, Yes, Yes!

I've thought about it time and again, but I have no time 
to spare for it.  I think it would be great if someone 
wrote such a thing, though.

Jon
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WillyB | 11 Jun 2003 23:44

Re: Aero-Matic

On Wednesday 11 June 2003 12:39, Jon S Berndt wrote:
> On Wed, 11 Jun 2003 14:31:18 -0500
>
>   David Culp <davidculp2 <at> attbi.com> wrote:
> >Opinions, anyone, on whether this idea
> >
> >http://home.attbi.com/~davidculp2/fmm.html
> >
> >is useful, allowable, fun,  ...etc.
>
> Yes, Yes, Yes!
>
> I've thought about it time and again, but I have no time
> to spare for it.  I think it would be great if someone
> wrote such a thing, though.
>
> Jon

That would be really useful :)

WillyB

>
> _______________________________________________
> Flightgear-flightmodel mailing list
> Flightgear-flightmodel <at> flightgear.org
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Jon Berndt | 9 Jun 2003 19:35
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New document for JSBSim

I have completed the largest part of a document aimed at making control
system/autopilot authoring much easier for JSBSim.  You can find the
document here:

http://jsbsim.sf.net/AutoFlightInJSBSim.pdf

Please let me know if you have any comments. There are some parts that are
not completed, yet, but it is quite useful as is.  The additions I need to
make yet are adding descriptions for each static property and another
autopilot example.

Note that this is not intended to be a direct assault on the method used by
the FlightGear side to model autopilots.  It is meant (at least initially)
for JSBSim in a standalone mode, and scripted runs.  Some of the approaches
used might be good to implement in FlightGear, though.  An autopilot can be
designed, tweaked, etc. without any coding/compilation whatsoever.

Have a look.

Jon
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Jon S Berndt | 16 Jun 2003 17:40
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JSBSim output messages

Was there a request at one time to reduce the logging 
messages that JSBSim by default puts out?  I can do this 
easily, I just need to remember what the decision was on 
this.

Jon
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Erik Hofman | 16 Jun 2003 18:07

Re: JSBSim output messages

Jon S Berndt wrote:
> Was there a request at one time to reduce the logging messages that 
> JSBSim by default puts out?  I can do this easily, I just need to 
> remember what the decision was on this.

I don't know the current situation, but it would be nice to sync them 
with the FlightGear log levels, so if you reduce the number of 
FlightGear output messages the JSBSim output messages would get reduced 
also.

Erik
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Gmane