Implementing VNAV support in FlightGear: Difference between revisions

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Implementing VNAV support in FlightGear (view source)

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'''Related:''' {{Issue|640}}.
'''Related:''' {{Issue|640}}.
== Background ==
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{{FGCquote
  |for over a decade, FlightGear had extremely poor support for any modern avionics (PFD, ND, CDU, FMC/FMS) - in particular in comparison to MSFS/FSX and the plethora of commercial addons - this has recently changed (well since 2.8 ), due to TheTom's Canvas system, which now makes it possible for everybody to easily create modern avionics like a PFD/ND or CDU, without having to be an expert C++ programmer with OpenGL/OSG experience - but supporting VNAV/LNAV still is tricky for other reasons, and currently not on anybody's agenda - it's not just something that can/should be tackled by a single aircraft developer, it requires lower-level changes in FlightGear's architecture and the way FDMs are used.
  |{{cite web |url=http://forum.flightgear.org/viewtopic.php?p=195138#p195138
    |title=<nowiki>Re: "triple 7" fmc development status?</nowiki>
    |author=<nowiki>Hooray</nowiki>
    |date=<nowiki>Sat Nov 30</nowiki>
  }}
}}
{{FGCquote
  |FlightGear's support for airliner/bizjet-style "glass" avionics is only just beginning to emerge thanks to the Canvas system, EFIS modeling (PFD, ND, CDU, EICAS etc) and aircraft systems fidelity is non-existent basically and overall FG avionics are far from anything that you can find in (even outdated versions) of MS FS and X-Plane, which applies even more so to commercial add-ons
  |{{cite web |url=http://forum.flightgear.org/viewtopic.php?p=213506#p213506
    |title=<nowiki>Re: What to expect from FlightGear 3.2?</nowiki>
    |author=<nowiki>Hooray</nowiki>
    |date=<nowiki>Thu Jun 26</nowiki>
  }}
}}
{{FGCquote
  |those are limitations in FG itself (and in its supported FDMs), not specific to the 777 - it is true, that we currently do not have any aircraft with a properly working FMS and performance database support.
  |{{cite web |url=http://forum.flightgear.org/viewtopic.php?p=195138#p195138
    |title=<nowiki>Re: "triple 7" fmc development status?</nowiki>
    |author=<nowiki>Hooray</nowiki>
    |date=<nowiki>Sat Nov 30</nowiki>
  }}
}}
{{FGCquote
  |Overall, the 777 remains one of the most developed aircraft/airliners in FG, especially in comparison to hundreds of other aircraft. But compared to airliners supported by FSX or X-Plane, we are still lacking in that department and do not provide a complete solution (yet). And it is also not  foreseeable when that will change, because it will require changes in the FDMs we're using or use of some 3rd party/proprietary performance database. Otherwise, it is not currently feasible to come up with VNAV/LNAV modes that properly work for different aircraft. The 3rd party approach is being used for TPPs data, but in the case of FDMs, we would need 100% accurate FDMs, too - so it would be better to directly use the FDM for computing a performance DB.
  |{{cite web |url=http://forum.flightgear.org/viewtopic.php?p=195138#p195138
    |title=<nowiki>Re: "triple 7" fmc development status?</nowiki>
    |author=<nowiki>Hooray</nowiki>
    |date=<nowiki>Sat Nov 30</nowiki>
  }}
}}
{{FGCquote
  |Some of our best-developed airliners have fairly extensive performance problems, i.e. frame rate / frame spacing - for example, the 777-200. In addition, FG itself (and its FDMs) lacks some hooks to support a real performance database, so that related autoflight (M/CDU) VNAV modes cannot currently be implemented (easily). These are the main showstoppers when it comes to modern airliners and bizjets in FG.<br/>
Overall, if you're primarily interested in modern glass cockpit aircraft (or have a background/experience with proprietary add-ons), you'll probably not enjoy FG as much as FSX and/or X-Plane for the time being.
  |{{cite web |url=http://forum.flightgear.org/viewtopic.php?p=213506#p213506
    |title=<nowiki>Re: What to expect from FlightGear 3.2?</nowiki>
    |author=<nowiki>Hooray</nowiki>
    |date=<nowiki>Thu Jun 26</nowiki>
  }}
}}
{{FGCquote
  |FlightGear can definitely be very frustrating for people getting started with it, unfortunately this even applies to people who are intimately familiar with other flight simulators, including real life pilots. There are some great flight simulation products out there, and some commercial add-ons are awesome and must have taken thousands of hours to develop. FlightGear is mostly a volunteer effort, i.e. 95% of the people contributing to it, do so in their spare time, while having to work within certain constraints, such as multi-platform open source development, but also the GPL itself.
Obviously, this steep gradient between features offered  by FG vs. commercial counterparts is something that we're hoping to address over time - but it is often a difficult effort to literally compete with commercial and proprietary products, simply because we do not have certain resources available, so we often need to make compromises and come up with unintuitive workarounds.
  |{{cite web |url=http://forum.flightgear.org/viewtopic.php?p=195145#p195145
    |title=<nowiki>Re: "triple 7" fmc development status?</nowiki>
    |author=<nowiki>Hooray</nowiki>
    |date=<nowiki>Sat Nov 30</nowiki>
  }}
}}
{{FGCquote
  |Also, please keep in mind that there's nothing really wrong about FSX (or X-Plane) - and some of the more established commercial addons are of excellent quality, developed by teams with dozens of fulltime programmers who could often consult back with ATPL holders and type-rated pilots, but also freely use all sorts of data and documentation, we do not typically have this sort of expertise and support available here - which is why some things may take a while to mature unfortunately...
  |{{cite web |url=http://forum.flightgear.org/viewtopic.php?p=195138#p195138
    |title=<nowiki>Re: "triple 7" fmc development status?</nowiki>
    |author=<nowiki>Hooray</nowiki>
    |date=<nowiki>Sat Nov 30</nowiki>
  }}
}}


== Problem ==
== Problem ==
Retrieved from "https://wiki.flightgear.org/Special:MobileDiff/83177"

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