Outerra forum

User mods, screenshots & videos => Aircraft => Flight Model Development => Topic started by: bomber on July 23, 2014, 05:14:21 pm

Title: jsbsim additional moments due to force applied not at CoG
Post by: bomber on July 23, 2014, 05:14:21 pm

Hi guys,

Code: [Select]

<location name="AERORP" unit="IN">
<x> 0.0 </x>
<y> 0.0 </y>
<z> 0.0 </z>
</location>
<location name="VRP" unit="IN">
<x> 0.0 </x>
<y> 0.0 </y>
<z> 0.0 </z>
</location>

    </metrics>

    <mass_balance>
        <ixx unit="SLUG*FT2"> 1000000 </ixx>
        <iyy unit="SLUG*FT2"> 1000000 </iyy>
        <izz unit="SLUG*FT2"> 1000000 </izz>
        <emptywt unit="LBS"> 100000 </emptywt>
        <location name="CG" unit="IN">
            <x> 0 </x>
            <y> 0 </y>
            <z> 0 </z>
        </location>
As you can see any force I apply is at the CoG point 0,0,0

However I'm seeing additional moments of rotations specifically the pitch, but roll to some degree....

I'm using an identical fdm (no code changes) to one used in Flightgear, in Flightgear there's no additional moments, but in Outerra there are..

Can the devs look into this ?

If you tell me what version of JSBsim we're using I'll ask on the jsbsim forum for them to have a look see, cause I can't see how an Outerra installation of a 'black box' jsbsim application can be anything but a jsbsim fault....

Then again.....

regards

Simon

Title: Re: jsbsim additional moments due to force applied not at CoG
Post by: alialiali on July 24, 2014, 06:08:21 am

I'd check the fuel tank locations. I believe they contribute to the balance as far as I know.

Title: Re: jsbsim additional moments due to force applied not at CoG
Post by: bomber on July 24, 2014, 07:43:21 am

No fuel tank.

Title: Re: jsbsim additional moments due to force applied not at CoG
Post by: bomber on July 28, 2014, 03:41:26 pm

Can I ask..

Is the lack of response because of...

a) It's being looked at be patient.
b) Don't believe your observations so not looking at.
c) Gone fishing be back next week.
d) Didn't understand the problem.

I'm only asking as I don't want this to fall into a black hole.

Title: Re: jsbsim additional moments due to force applied not at CoG
Post by: TheLoneExplorer on July 28, 2014, 09:35:44 pm

Just keep bumping my friend :)

BUMP

Title: Re: jsbsim additional moments due to force applied not at CoG
Post by: cameni on July 29, 2014, 12:01:46 am

Angrypig gone fishing, and only he can answer that (if it's a problem in OT).

Title: Re: jsbsim additional moments due to force applied not at CoG
Post by: ZeosPantera on July 29, 2014, 12:44:35 am

Gone fishing.. OR "Is swimming with the fishes" as we italians are prone to saying.

Title: Re: jsbsim additional moments due to force applied not at CoG
Post by: Jagerbomber on July 29, 2014, 01:10:43 am

Did the sharks or piranhas like the pork more?

Title: Re: jsbsim additional moments due to force applied not at CoG
Post by: PytonPago on July 29, 2014, 01:36:55 am

Just wait you two till Angry comes whyte a half-ton of fish. :D

www.youtube.com/watch?v=1EEgL038zKc (http://www.youtube.com/watch?v=1EEgL038zKc)

Title: Re: jsbsim additional moments due to force applied not at CoG
Post by: bomber on August 10, 2014, 04:04:47 pm

When you do get back from fishing, don't spend any time on this I'm still experimenting, it might be something else... need to investigate more..

Regards

Simon.

Title: Re: jsbsim additional moments due to force applied not at CoG
Post by: bomber on August 11, 2014, 01:56:36 pm

ok this is resolved JSBsim's working correctly.