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Physics in FG

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Physics in FG

Postby Ger272 » Sat Feb 17, 2018 9:56 am

Hey Guys
I have a general question about the physics in FG. It seems like the aircrafts in Flightgear accelerate and lift off (climb) pretty fast. In real life it look a bit slower.
Is that due to the aircraft (engine power/ weight) or is everything correct with FG?
Just wondering...
Download-Links to all available Ger272 liveries:

A320/A319 - A350XWB - A<380 - A310MRTT - C-160 Transall

--- DUE TO THE A320 RE-DESIGN ALL MY A320 TEXTURE AND LIVERY DEVELOPMENTS ARE ON A HOLD ---

For "How to download" check topic: Ger272 HQ Liveries.
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Re: Physics in FG

Postby Hooray » Sat Feb 17, 2018 10:46 am

Please don't send support requests by PM, instead post your questions on the forum so that all users can contribute and benefit
Thanks & all the best,
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Re: Physics in FG

Postby Thorsten » Sat Feb 17, 2018 11:13 am

It seems like the aircrafts in Flightgear accelerate and lift off (climb) pretty fast. In real life it look a bit slower.


Generally it's not so much a question of the physics solver but of the data it gets. In the cases where there is a huge body of wind tunnel data (the Space Shuttle, the Saab Viggen,...) the output resembles the capabilities of original even in small details (in fact, the JSBSim code is benchmarked against NASA orbital dynamics codes, so we may assume the physics is really sound...)

In cases where the coefficients essentially have to be guessed, it's up to how good the guess is.
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Re: Physics in FG

Postby Richard » Sat Feb 17, 2018 10:00 pm

Ger272 wrote in Sat Feb 17, 2018 9:56 am:I have a general question about the physics in FG. It seems like the aircrafts in Flightgear accelerate and lift off (climb) pretty fast. In real life it look a bit slower.


Unlike other flight sims[1] Flightgear allows the aerodynamics modelling to be as real life as the data that the modeller has, or can create. So take out the F-15, F-14, both of which have real life wind tunnel derived aerodynamic models and between 160 and 500 kts clean both of these craft will be using a realistic, wind tunnel based aerodynamic model. Not all craft have the same data available, *but* FlightGear allows the modeller to model anything that they have data for, whereas the other flightsims[1] impose a certain type of modelling behavoir, that works better well within the normal flight envelope.

-----------------
[1] (FSX, P3D, Xplane)
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Re: Physics in FG

Postby Octal450 » Sun Feb 18, 2018 1:36 am

@Richard, there are exceptions, for example, the Majestic Q400 and FlightFactor A320 use JSBsim actually for their flight dynamics, and use real data. Also, more advanced planes such as the FSLabs A320 and PMDG MD-11 (etc) have realistic outside the normal flight envelope. It does, however, require the developer to do much more work than for something like JSBsim which is very flexible.

Kind Regards,
Josh
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Re: Physics in FG

Postby sidi762 » Fri Feb 23, 2018 11:18 am

Are you using full thrust during takeoff?
that could be the reason
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Re: Physics in FG

Postby Ger272 » Fri Feb 23, 2018 2:29 pm

Mostly I'm flying the A319 (IDG) and I use the MCT/Flex Mode. I usually rotate with around 150 kts and Flaps at 1+F. Recently I rotated with 143 kts with 100% load, which made it be bit more real.
Download-Links to all available Ger272 liveries:

A320/A319 - A350XWB - A<380 - A310MRTT - C-160 Transall

--- DUE TO THE A320 RE-DESIGN ALL MY A320 TEXTURE AND LIVERY DEVELOPMENTS ARE ON A HOLD ---

For "How to download" check topic: Ger272 HQ Liveries.
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Re: Physics in FG

Postby Wecsje » Fri Feb 23, 2018 2:45 pm

I would suggest you use the newest A320 versions from IDG instead (A319 was removed from the package temporarely), and you should aim for rotation in all A320fam's between 125-135 kts, check the tools.xml for an excel takeoff calculator, to calculate Vspeeds yourself. For A330/A340 aim for something between 135-145.

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Re: Physics in FG

Postby Octal450 » Fri Feb 23, 2018 2:47 pm

Wecsje is right here.
Major FDM improvements were made long after the A319 was temporarily removed from the IDG Airbus package. The previous version was not correct on rotating behavior, which as been corrected.

Kind Regards,
Josh
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Re: Physics in FG

Postby Ger272 » Sat Feb 24, 2018 10:36 am

@Wecsje and @it0ucpods:
thanks wecsje for the info :). yes I know that you removed the A319 and that you are not working on that right now. But there are still some people who don't want to update there library every 6h. And there are still some people who want to fly the A319 or created some stuff for it. So I guess it is okay if I use the A319 as long as you removed it from your package.
Download-Links to all available Ger272 liveries:

A320/A319 - A350XWB - A<380 - A310MRTT - C-160 Transall

--- DUE TO THE A320 RE-DESIGN ALL MY A320 TEXTURE AND LIVERY DEVELOPMENTS ARE ON A HOLD ---

For "How to download" check topic: Ger272 HQ Liveries.
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Re: Physics in FG

Postby Octal450 » Sat Feb 24, 2018 2:17 pm

It is okay, but then don't complain about bugs or problems as they will be fully ignored!!!
In this case, you are still experiencing a flight model that has unrealistic behavior during rotation, and some other parts (touchdown). If you do not want to update your plane, please do no complain about problems.

Kind Regards,
Josh
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Re: Physics in FG

Postby Ger272 » Sat Feb 24, 2018 6:31 pm

@it0uchpods: I don't know if you read the initial question but I didn't complain about the aircraft at all. I was wondering how real the physics in FG are. So why don't you calm down (bold type and !!!). It was a nice general question, no personal attack.

BtW: 1) You always say that questions about old versions of the A320-Family will be ignored. Well why do you answer at all? Not very kind...
2) An update of the A319 is (as you may know) currently not available. So how do you want me to update the A319?
Download-Links to all available Ger272 liveries:

A320/A319 - A350XWB - A<380 - A310MRTT - C-160 Transall

--- DUE TO THE A320 RE-DESIGN ALL MY A320 TEXTURE AND LIVERY DEVELOPMENTS ARE ON A HOLD ---

For "How to download" check topic: Ger272 HQ Liveries.
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Re: Physics in FG

Postby Octal450 » Sun Feb 25, 2018 5:02 am

@Ger272
I usually state that the first time, but not multiple times. I am not angry you, please don't misinterpretation my words. :)

I don't know what is this "A320-Family", I developed no model under this name. I developed "A320Family" which became "IDG-A32X" to avoid naming confusion.

Not sure why you ask about updating the A319 specifically, as I have made no package named that. Physics are independent to each FDM, therefore if you ask about the physics and mention my plane, I will chime in! ;)

Kind Regards,
Josh
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Re: Physics in FG

Postby Ger272 » Sun Feb 25, 2018 9:03 am

1) I did not mention your plane in the initial question (read above).
2) Are you serious about the "A320-Family"/"A320Family" issue? It is just a "-". So I believe you are smart enough to know what I have meant. Btw: There is no real IDG-A32X - so I guess by avoiding the naming issue you are confusing even more.
3) You created a "A320Family" (now "IDG-A32X") which included the A319 (correct?) and you do not support the A319 anymore as you removed it from the package (correct?). So if I say that I use the A319 it is weird to refer to the update (which now does not include the A319). As a consequence there is no more A319 update ;)
So I won't be able to update the A319...
4) If you don't want to give advise to people who still use the A318/A319/A321 (because these are not included/updated anymore... and there are many people who do so) it is fine. But I don't understand why you have to tell those people that you are not willing to help them. That doesn't help at all...
Download-Links to all available Ger272 liveries:

A320/A319 - A350XWB - A<380 - A310MRTT - C-160 Transall

--- DUE TO THE A320 RE-DESIGN ALL MY A320 TEXTURE AND LIVERY DEVELOPMENTS ARE ON A HOLD ---

For "How to download" check topic: Ger272 HQ Liveries.
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Re: Physics in FG

Postby Octal450 » Sun Feb 25, 2018 1:50 pm

I don't need the attitude. Once you mentioned that you were using an aircraft which has known faults (which you seemed to complain about in this very post here), I stepped in to clarify. I have no way of knowing what you do or do not know until you state it.

Ger272 wrote:Btw: There is no real IDG-A32X - so I guess by avoiding the naming issue you are confusing even more.

Well, by that logic, there is no PMDG 747, so that plane must not exist. Its actually common sense, A32X airplane developed by IDG.

I don't understand your point here. There were versions of the "IDG-A32X" which had the 319 still included, so the naming has little to do with anything.

Actually, you are the first person I've seen still flying the old version. You are aware that the 319 was just a 320 with different 3D? FDM and such was straight from the 320, which is why we decided to remove it, as it is not realistic like that!

Why do I not support older versions?
Since older versions contain issues that I have fixed, so 99% of the time I will get a report about something that isn't even relevant (such as an FDM issue I corrected already), which causes me stress. This is why I have a update notification in the first place.

If you prefer to use an out of date package to fly, that is fine, but then don't ask why certain things aren't right before checking the latest version.

Kind Regards,
Josh
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