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FMC Progress page?

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FMC Progress page?

Postby Karanza » Fri Oct 18, 2013 9:08 pm

Hi,

Does anyone know if there is a progress page for the FMC, which gives you like the distance, the estimated time that you will arrive at the waypoint/destination, and the estimated fuel.

I happen to find this important because every time i do long haul flights i am always worried about how much fuel i will have once i get to my destination airport.

Thanks!
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Re: FMC Progress page?

Postby Johan G » Sat Oct 19, 2013 11:25 am

The FMCs and their CDUs (the device in the cockpit that you enter route data etc. into) are specific to each aircraft. At the other hand there is also the route manager, which is available with all aircraft that have not disabled it. Which aircraft are you are you asking about?
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Re: FMC Progress page?

Postby Hooray » Sat Oct 19, 2013 12:12 pm

I think this is one of those "holy grails" in FlightGear, I am not aware of any aircraft that currently support a proper "progress" page - creating the page is trivial, but making it functional requires some more work - look for threads with the keywords "performance database", and you'll see that this has been talked about for over half a decade meanwhile:

(computing remaining fuel vs. fuel consumption per hour is fairly trivial, but once you want to compute range, you need to be fully aware of the flight plan (speeds, altitudes) and weather/configuration (and aircraft/engine performance in particular) to make a reasonable guess at remaining range).

Subject: Getting started with Route Manager

Hooray wrote:
macnab wrote:I understand the problem of vertical-change programmimg. Hence the disappointment for the person who wanted FG to implement terrain-following. That must be a significant part of the cost-price of modern-day military planes.


Regarding terrain following, you may want to read this (which still holds true as of 10/2011) : http://www.flightgear.org/forums/viewto ... 513#p89686

In that thread, I also outlined how you could start simulating this by using some clever Nasal code, interacting with the autopilot PID controllers by using some intermediate properties. Basically, you'd need a "gradient hold" mode and a way to do proper "energy/performance management", as zakalawe mentioned already.

Computing required and actual gradients would be a no brainer in Nasal, and could be easily done using "geodinfo()" calls, given that this particular function is heavily used by the local weather system, and given that it has been optimized to be 50 times faster than it used to be, that should be a promising route.

zakalawe wrote in Thu Oct 13, 2011 12:03 pm:(Vertical modes also tend to depend more on fuel/load and performance data from the FMS, which is an area that's been lacking, so hard to model the climb and descent profiles meaningfully)


This is VERY true and probably the single most important reason why this isn't yet supported by FlightGear, which boils down to a lack of support by the FDMs (JSBsim/YaSim) actually.

If you are truly interested in the technical details: there has been a rather lengthy discussion over at the jsbsim issue tracker here: http://sourceforge.net/tracker/?func=de ... tid=369399

So far, the general consensus has been that it simply isn't yet possible in FlightGear to properly implement VNAV.

This discussion took place almost 6 years ago, and Jon (JSBsim) mentioned in 2008:
Jon wrote:I've seen the use of simple simulation within a simulation, where
performance data is being calculated. It was not within JSBSim, however.
This is an interesting prospect. Nobody has ever done this, up to now. My
initial reaction was pessimistic. However, the flight control components
within JSBSim are fairly capable, and you are permitted to define arbitrary
functions. So, my guess at this time is, yes, you should be able to set up
JSBSim to calculate *some* performance data. It may be a lot of work, but
it should be possible.


http://www.flightgear.org/forums/postin ... =6&p=51952
MAKG wrote in Thu Nov 05, 2009 5:55 pm:
flameout wrote:As far as guessing the path the autopilot will take, that will be very difficult. It tries to fly to the given parameters, but guessing where it will go on its way will be difficult.


Without being very familiar with the FG source code, the usual way to do this is to call the FDM. Isn't that sort of thing exactly what JSBSim is for?

The distinction between a flight planner and a flight simulator is the bounds on the integrations. A simulator will integrate over a frame; a flight planner much longer.



Back then, Jon mentioned that it might be possible to use some cascaded <system> controllers in JSBsim to accomplish this:

http://www.flightgear.org/forums/viewto ... 290#p52637
jonsberndt wrote in Thu Nov 12, 2009 2:48 am:
MAKG wrote:Without being very familiar with the FG source code, the usual way to do this is to call the FDM. Isn't that sort of thing exactly what JSBSim is for?

The distinction between a flight planner and a flight simulator is the bounds on the integrations. A simulator will integrate over a frame; a flight planner much longer.


Yes, this is an interesting problem. I worked on the Shuttle Abort Flight Management project several years ago. At each second during the shuttle ascent, several simulations were run quickly to determine viable abort locations at that instant and given the vehicle configuration. It has occurred to me that a JSBSim control <system> could be created that would use a simplified approach to predicting where the aircraft would be in ten, twenty, and thirty seconds into the future, based on current velocities, rates, and accelerations. I think it's possible. It would be a good exercise for someone!

jb


zakalawe is the one currently working on this, and he mentioned plans to provide the required infrastructure so that it becomes accessible from Nasal space:
viewtopic.php?f=14&t=12499#p128052
zakalawe wrote in Tue Jun 21, 2011 11:48 am:
scotth1 wrote in Tue Jun 21, 2011 9:35 am:One thing I would add is that the existing waypoints don't seem to contain enough information, I've written some more Nasal classes to handle SID/STAR/IAP, Top of Climb and Top of Descent pseudo waypoints and Altitude constraints versus FMS calculated altitudes etc.

Right, and that's the next question - I don't want to hard-code that kind of logic in C++, if I can avoid it - but we need to work out a way for Nasal to set the values into the route-manager or GPS data, so the ND can pick it up - especially all the cruise/phase-of-flight/altitude/energy stuff. I apologise for being lazy, but can you remind me where the relevant Nasal code is? Then we can have a discussion (possibly involving some other people) about which parts can be in C++, and some standard locations the ND can look for Nasal-computed value, and so on.

BTW, I'm lacking a good set of photos of the Airbus displays - the sooner I know what I need to cover, the happier I'll be - do you know of any suitable resources?



Hooray wrote:As you can see, there have been lots of discussions on this topic, doing a forum or mailing list search, you should be able to find even more pointers: viewtopic.php?f=46&t=2577&p=35664&hilit=performance+database#p35664

I guess that is one of those feature requests that really deserves its own wiki page eventually...


viewtopic.php?f=40&t=13777&hilit=performance+database&start=15#p140269
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Re: FMC Progress page?

Postby Karanza » Tue Oct 22, 2013 7:54 pm

Johan G wrote in Sat Oct 19, 2013 11:25 am:The FMCs and their CDUs (the device in the cockpit that you enter route data etc. into) are specific to each aircraft. At the other hand there is also the route manager, which is available with all aircraft that have not disabled it. Which aircraft are you are you asking about?
Im asking about the boeing 777-200, 777-300, both ER and LR aircraft.
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