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Post by Herman on Dec 8, 2019 17:08:37 GMT
Most of us are well aware, that a jet aircraft's fuel consumption decreases as we increase our cruising altitudes while maintaining a constant Mach number. This occurs in both real world jetliners and also in our FS Models.
My question however is, how, in the FS aircraft model is this actually calculated and applied to??? Would it be in the model code...FDE or CFG???or somewhere else.
Just curious. Herman
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Post by aerofoto - HJG Admin on Dec 8, 2019 21:35:10 GMT
It's FDE related.
The higher one goes the less one burns .... being the basic.
Where HJG flight modellimg is concerned F/F (in proportion to power setting) is genrerally always "spot on" at SL (because that's the place to start) .... but .... we then "have to" accept whatever it becones by cruising altitude due the manner in which FS (itself) works.
"In FS" .... and again where HJG flight modelling is concerned .... F/F can never be spot on within all flight regimes, but, it's always within the ball park .... based on what I've described above.
Mark C AKL/NZ
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Post by Herman on Dec 8, 2019 22:34:01 GMT
OK, thank you Mark for that explanation. I always thought that it was quite interesting that FS jet aircraft were able to duplicate this particular quality from the real world aircraft. I am always in awe of all the magical things that modern technology and people\ producers can accomplish with flight simulation. Herman
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Post by aerofoto - HJG Admin on Dec 9, 2019 0:08:54 GMT
"At SL" .... and which is the best place to start .... and it's then subjected to, and influenced by, the drag related parameters. As I mentioned .... we then have to accept whatever it becomes by the time one transitions into the high altitude cruise regime in FS. That's the way FS works Mark C AKL/NZ
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Post by Mike Monce - HJG on Dec 9, 2019 13:46:20 GMT
Mark has basically answered the question. When we set the basic parameter: fuel_flow_scalar, in the cfg file we do it by measuring the actual fuel flow at sea level @ 100N1. Then using the actual data for the specific engine ( jet-engine.net/civtfspec.html ) we adjust the scalar to match the TSFC for that engine. From there, FS takes over in their own hard code, though as Mark says, is influenced by drag parameters. To tell the truth, we usually adjust the drag parameters to get the speed and climb characteristics correct, and is done first. Fuel flow is one of the last things to adjust after the flight dynamics are done. Mark also keeps telling people over and over to make sure to match the specific plane to the correct base model as there are subtle differences. One reason is that many of our variations have different engines. We make sure we have the correct fuel flow (and thrust curves!) for the particular engine. Thus, a particular plane may have two variations with two slightly different engines, and we have accounted for that. The difference may be subtle, but it is there. Hence the annoyance on our part when people don't do as instructed when we have gone to a large effort for fidelity within the confines of MSFS. Mike
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Post by aerofoto - HJG Admin on Dec 10, 2019 3:43:49 GMT
"WELL EXPLAINED" Mike .... and "ABSOLUTELY SPOT ON" too in regard to all points Apart from static engine thrust, F/F, and drag related parameters within any FDE .... another parameter we also look at too is in regard to the spooling rate of various engines since these vary among different engine types as well .... and which is why the engines on our earliest B707 and DC-8 versions each spool more slowly than later versions of these aircraft subjects .... whereas in comparison the CV-880's and CV-990's (with their Variable Stater featured engines) each spool quite rapidly as was the case with the R/W engines on these particular aircraft types. There's really "a hell of a lot of work" (and research) that goes into each one of our FDE's and which are all worked up by George, Mike, and myself .... "The HJG Tech Team". George's FDE edits are essential for panel/gauge compatibility/functionality, whilst Mike & I then concentrate on the Flight Tuning .... then .... after we've finished all that, and the 3 of us are content, these FDE's then go to Benoit whom works up the Sound Packs based on FDE based engine parameters which we've compiled. Hopefully this'll convey how, and why, everything we do FDE, Panel/Gauge, and Audio-wise is all "INTER-RELATED" .... it can't be any other way .... and it's also why we go to great lengths to try'n encourage people (literally spelling it out for them in regard to what goes with what) to use the correct/recommended aircraft base pack, panel, and audio combinations .... for best overall FS performance. It does make for slightly more complex offerings, but, that's unavoidable and is generally for the better anyway .... and in any case "we do provide all of the necessary information" (in regard to what goes with what) .... people just have to "READ IT" Whilst some of the aircraft subjects we now host/have imported over the years (those we didn't model entirely ourselves) are also offered elsewhere too .... we/HJG do things "differently" .... in the sense that there's no point in what we do being the very same as what someone else's already done .... therefore (and particularly in regard to FDE work) we try'n incorporate as much authenticity into everything we offer .... limited only by our own knowledge, abilities, and certain FS tolerances too. Not everything can be represented in FS though .... but .... enough parameters are represented and that we can exploit/manipulate for a good, of not better, flight experience for most of the simulations we offer .... and where we're limited we can, sometimes, fudge certain other parameters/fool FS into representing what we want and the way we want it too .... BUT AGAIN .... there are "limits" of course .... simply because FS (the game) itself is composed of only a finite number of parameters which can be "easily" manipulated in the first instance. There's a couple of FDE upgrades going on in the back ground here at the moment. I was hoping some of these might have been ready for release within our next website update .... but .... due to limitations of personal time/other commitments throughout this year it's simply not been possible to advance things as quickly as I'd like to have been able to (and I'm certainly not going to hurry or see anything released that my 2 Tech Team representatives aren't content with) .... however .... it "will" all happen ... so .... patience should be rewarding. Mark C AKL/NZ
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Post by Herman on Dec 10, 2019 13:56:24 GMT
Thank you Mike and Mark for those additional and more detailed explanations dealing with this subject. It is always fascinating for me to learn more about the science and physics behind the designing and producing of an FS aircraft model, and making fly as close as possible to the real world aircraft. As you say, it is complicated and very time consuming, to get it right. Herman
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Post by Falcon on Dec 12, 2019 19:17:54 GMT
Thank you all for this very informative and interesting subject. there are so many Awesome guys here. Thank you and Merry Christmas to all.
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Post by aerofoto - HJG Admin on Dec 12, 2019 19:38:21 GMT
We try our best .... to do our best .... and sometimes we even manage to please some people in the process Thanks for your sentiments and ongoing support Denny .... much appreciated Mark C AKL/NZ
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