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FG 3.0 747-400 Autopilot

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FG 3.0 747-400 Autopilot

Postby azims » Thu Feb 20, 2014 8:08 pm

Hello,

I installed the latest FG3.0 release and downloaded the 747-400 (latest) as I am used to flying the aircraft. It has worked well in the past for pre-3.0 FG versions. But for some reason in 3.0 the autopilot doesn't seem to work well and then can't fly the plane. The IAS, V/S and ALT parameters are set, but the plane makes a steep climb and then descends rapidly and this goes on forever. I reverted back to the old version of the 747-400 and it works fine.

I like the new cockpit - good job by Gijs and team, but can't fly the plane. Any help on this is appreciated.

thanks.

AS.
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Re: FG 3.0 747-400 Autopilot

Postby HelldiverSquadron » Fri Feb 21, 2014 5:17 pm

Hi, I'm no expert, but is the 3.0 version even out yet?
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Re: FG 3.0 747-400 Autopilot

Postby FGRS » Fri Feb 21, 2014 6:36 pm

Unofficially ,it is.

You can download it easily.

Cheers
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Re: FG 3.0 747-400 Autopilot

Postby Philosopher » Fri Feb 21, 2014 6:43 pm

what do you mean "unofficially"? there's a release announcement, downloads are up with the 3.0 label: http://www.flightgear.org/news/flightge ... -released/
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Re: FG 3.0 747-400 Autopilot

Postby Lydiot » Fri Feb 21, 2014 6:58 pm

Philosopher wrote in Fri Feb 21, 2014 6:43 pm:what do you mean "unofficially"? there's a release announcement, downloads are up with the 3.0 label: http://www.flightgear.org/news/flightge ... -released/


I think he's talking specifically about the version of the aircraft, not FG.
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Re: FG 3.0 747-400 Autopilot

Postby HelldiverSquadron » Fri Feb 21, 2014 8:19 pm

yeah, sorry I was talking about the aircraft. i have 3.0 already. awesome stuff
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Re: FG 3.0 747-400 Autopilot

Postby sanhozay » Fri Feb 21, 2014 9:16 pm

I experience the same instability on altitude hold but I'm getting such a low frame rate, I wondered if that was causing it?
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Re: FG 3.0 747-400 Autopilot

Postby azims » Tue Mar 04, 2014 12:07 am

I have tried with various settings (speed, alt, pitch, heading, fuel and payload) and many different airports. The new 747-400 Autopilot is unresponsive and crashes the airplane. It is a wonderful plane, shame that it is not working for me. Any ideas?
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Re: FG 3.0 747-400 Autopilot

Postby Lydiot » Tue Mar 04, 2014 12:49 am

Does anyone know what is different between the versions?
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Re: FG 3.0 747-400 Autopilot

Postby f-ojac » Tue Mar 04, 2014 12:01 pm

It's written on the release annoucement : http://www.flightgear.org/news/flightge ... -released/ . The full changelog is here: http://wiki.flightgear.org/Changelog_3.0 ...
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Re: FG 3.0 747-400 Autopilot

Postby azims » Tue Mar 04, 2014 2:58 pm

I think there is a misunderstanding here - I am using Flightgear version 3.0. The 747-400 is the latest version (most recently updated) and I downloaded from the flightgear website, which I think is an official release.

The best person to answer or resolve this would be Gijs and his team as they are the primary developers.
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Re: FG 3.0 747-400 Autopilot

Postby sanhozay » Tue Mar 04, 2014 5:23 pm

Same problems here: lateral modes of autopilot are OK, vertical modes result in instability and excessive pitching (+/- 30 degrees). Using Ctrl-u to buy some time shows that the oscillations get worse until it goes nose down or even over on its back.

I thought it might have been my poor frame rate that was messing with the controllers in the autopilot, so I tried copying a few likely looking files from 2.12.1, based on a diff. The autopilot.nas and autopilot.xml didn't make any difference, but when I copied in 747-400.xml, stability returned to vertical modes. I wouldn't recommend this as a workaround because just copying that one file seems to break the speed control but my money is on something in that file being the problem.
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Re: FG 3.0 747-400 Autopilot

Postby Gijs » Tue Mar 04, 2014 5:38 pm

Hi guys,

the 744's FDM has seen quite some changes in 3.0, based on a NACA document for the simulation of a 747-100. Unfortunately I didn't manage to finish the pitch axis, so some parts of the FDM don't match 100% yet. The autopilot was done by buster, but for the old FDM. Once I'm done with the FDM, the autopilot will have to go through some maintenance to finetune it for the new performance. In fact, my plan is to port the AP to a JSBSim native system, so its stable at all sim rates (eg. if you speed up the sim, the autopilot will be as stable as at normal speed).

I was about to suggest replacing the FDM with the old one, as reported above that does indeed help. Auto throttle isn't handled by 747-400.xml, so I'd be suprised if there was any change on that aspect...

I'm sorry for the inconvenience. I'd prefered to have a fully working version for 3.0, but real life got in the way.

Cheers,
Gijs
Airports: EHAM, EHLE, KSFO
Aircraft: 747-400
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Re: FG 3.0 747-400 Autopilot

Postby azims » Tue Mar 04, 2014 6:03 pm

Gijs,

Thanks as always for your response. I will replace the 747-400.xml from the old version.

And no need to be sorry - you are doing an awesome job!
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Re: FG 3.0 747-400 Autopilot

Postby Lydiot » Tue Mar 04, 2014 6:07 pm

f-ojac wrote in Tue Mar 04, 2014 12:01 pm:It's written on the release annoucement : http://www.flightgear.org/news/flightge ... -released/ . The full changelog is here: http://wiki.flightgear.org/Changelog_3.0 ...


I was talking about the 747-400
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