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"triple 7" fmc development status?

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"triple 7" fmc development status?

Postby hamzaalloush » Sat Nov 30, 2013 7:28 pm

i must have seen recently atleast a dozen fixes for the triple 7 in the fgdata repo.

what is the current status of development?

i know it sounds a bit lazy for me, that i haven't tried it yet. just asking for a summery.

i just got in a lengthy phone conversation with a type-rated triple 7 pilot. so he can walk me through a startup and a summation of the performance of flight(climb speed, land speed, etc).

bieng a commercial aircraft with varying weight he kept refering me to the FMC perf section. so the aircraft would show me F1, F2 etc speeds on decent.

oh boy that was a mistake.

*no init position when asked to review the aircraft's GPS cordinatees.

*no X(X-Ray) button bug when instructed to input position of origin(KLAX). two W in the keypad instead.

*also could not adjust reserve or fuel quantity via FMC. had to do it with fuel and payload gui, also could not adjust route.

i had to stop him there... he told me something, is to get the proffesional aircraft that my younger brother flies(that pilot is my father), which is embarrasing considering it was an FSX aircraft. :oops:
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Re: "triple 7" fmc development status?

Postby Hooray » Sat Nov 30, 2013 8:42 pm

he kept refering me to the FMC perf section. so the aircraft would show me F1, F2 etc speeds on decent.
oh boy that was a mistake.

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.
The changes you saw, were mostly about the cockpit and avionics, more recently, the PFD and ND.


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.

For a more detailed explanation, please see: viewtopic.php?f=25&t=21104&p=192038&hilit=performance+vnav#p192038
viewtopic.php?f=40&t=13777&p=140255&hilit=#p140255

Finally, please understand that 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.

It really is a long-standing issue and has been discussed hundreds of times (as you'll see when you check out those links), but so far it's not a priority - but please do feel free to file a feature request: http://code.google.com/p/flightgear-bug ... %20request

You would need to be really familiar with FDM internals, airliner performance and have strong maths skills to solve this just for a single airliner.

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 takes a while to mature unfortunately... If you should have any expertise/documentation to contribute, I suggest to get in touch with Hyde, who will surely appreciate such feedback and resources!

PS: It's V-speeds not F-speeds :D
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Thanks & all the best,
Hooray
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Re: "triple 7" fmc development status?

Postby hamzaalloush » Sat Nov 30, 2013 9:11 pm

i don't have any gripes with it(the plane), it's just that i'm sharing my first impressions when going through the procedure with a pilot and was frustrated when i was unable to follow instructions.

i will still continue with FlightGear because i prefer the opensource way and don't like getting stuck with properiarty software. and i don't excpect anything to be fixed unless i lead by example and start coding around the plane, it's just the nature of open source so please don't take this the wrong way. also not comparing it to other commercial providers as the goals and the nature of these projects are not the same as FlightGear.

i'm the first guy to defend my use of FlightGear even though i'm invited by the regular from my brother to try all these different software to try(legitimately bought) but i'm still here.

i will read through these threads to try to get a better understanding of the progress of the plane.

PS: my knowledge is limited around commercial aviation as most of the conversation went straight above my head, some of it was concerning the use of the VNAV with FLCH and the distinction in using it against the use of the Altitude "hold". but the impressions i got is that most of this system is related to the use of FMC so i couldn't get to practiclly learn the procedure when a feature is not avaliabe.

also to the F1 remark, must be an abrevation they use as the flaps incrementals during flight. but it was the indication of the V-speed in the PFD.

anyway thanks for taking the time to respond to me
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Re: "triple 7" fmc development status?

Postby hamzaalloush » Sat Nov 30, 2013 9:13 pm

Hooray wrote in Sat Nov 30, 2013 8:42 pm:If you should have any expertise/documentation to contribute, I suggest to get in touch with Hyde, who will surely appreciate such feedback and resources!


i would be happy to if i can contribute with resources. as long as it is thought out specific inquiries, so i don't look dumb when i try to help (because my knowledge is limited) :mrgreen:
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Re: "triple 7" fmc development status?

Postby Hooray » Sat Nov 30, 2013 9:26 pm

No need to justify anything, my response wasn't intended as an attack - I just tried to explain why things are the way they are - there are many things in/about FlightGear that have a reached a certain state for a reason that may not be obvious to newcomers - even though that doesn't necessarily mean that "we" (as in, "we, the community of contributors") like it this way.

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.

You can see some examples in FlightGear's extensive use of XML and plain text formats, over closed/proprietary binary formats that were so common in the MSFS/FSX/X-Plane/Elite world. Or FlightGear's property tree that removes the needs for something like FSUIPC. Another example is our use of open-source cross-platform scripting via Nasal, vs. binary plugins in MSFS/XPlane.

Contributing to an airplane like the 777 doesn't necessarily require lots of coding skills/knowledge - many things can be done without any coding background at all, not just texturing or 3D modeling - editing XML files and adding features still missing is straightforward to do, and Hyde is exceptionally responsive when it comes to the 777 - so if there's anything that you'd like to help with, just get in touch, and I'm sure you can work out some mutually satisfying way to contribute.

If you are planning on going through the various lnav/vnav threads here, I would also be interested in adding a summary to the wiki, because it is a fairly common complaint/question and it helps to provide a dedicated place/article for people interesting in this - so please do feel free to copy/paste things over to the wiki. The second link I posted also contained pointers about missing AP features to implement a full FMS on top - like HHS suggested back then, the AP must be fully developed for any FMS to work properly, so that's a first step - which could be done even right now.
EDIT: http://wiki.flightgear.org/Performance_Database_via_FDM

The AP system is extensively documented (see the wiki) and we have lots of guys familiar with it, so if that's what you are interested in, that would be a possible start.
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,
Hooray
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