DCS World Flight Modelling Principles - Page 6 - ED Forums


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Old 08-02-2020, 03:42 PM   #51
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Originally Posted by Hummingbird View Post
That's pretty rich from someone who litterally doesn't understand what the chart says. I'd say learn to read such charts and understand what is ITR and what is STR before you criticize others of not reading it correctly. Getting a figure a tiny bit off (0.64 vs 0.67) is forgivable, but not even understanding what the chart is saying, like you, well sorry but spits you right out of the conversation.

RL ITR as pr. HAF manual:
26,000 lbs = 9.0 G @ 0.67
22,000 lbs = 9.0 G @ 0.62

This is what the DCS F-16 needs to match.
Nice try.
Thanks for your kind reply and sorry if I hurt you. But you were off by ~0.5g and that needs to be corrected, right? Reference page was wrong too, but shit happens.

Not an ideal thread to post definitions, but since you asked here again:
(This time transcripts from different reference books, you probably rather accept that source than in my own words.)

Str (region 1 in the chart)
„the region below the max t/w curve is one of sustained turn performance. This means that, in this region, the aircraft can maintain a turn rate without decelerating or loosing altitude...
In a sustained turn, aircraft maintains a constant altitude and airspeed and the turn radius, turn rate and load factor are constant...“

Itr (region 2 in the chart)
„In an instantaneous turn, the aircraft can not maintain these constant conditions, rather the turn entry conditions can only be maintained at the instant the turn is initiated. After turn entry, the airspeed, altitude, or both, decrease...

The region where both the lift and the structural limits are sufficiently high but the t/w is inadequate is a region of decelerating and / or descending flight. It is called the region of instantaneous turn performance. In this region high turn rates can be achieved for a brief period of time as the aircraft decelerates (or descends)...
From an energy perspective, the sustained turn is a constant energy maneuver, while the instantaneous turn is an energy loosing maneuver...

The doghouse plot is an aircraft specific turn performance chart that includes the aircrafts envelope boundaries. The overlaid ps=0 curve is the boundary of sustained performance.The aircraft has positive ps below ps=0 curve and negative ps above this curve. an aircraft has its highest turn rate at the intersection of the lift limit and load factor limit at the top of the doghouse(cp). This is an instantaneous turn rate, since ps is negative at this point.“

Hope that transcription helps you to get rid off your derangement(str @ ps-1000 and so on). If not, pm me, I will send you additional material.

Ps: itr is usually tested with wind up turns in rw...
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Old 08-05-2020, 04:08 PM   #52
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Originally Posted by Worrazen View Post
I've heard before yeah, I have to say I don't agree with some of it on that kind of an exact level, it shouldn't be that simple I would imagine, and I'm just using logic, plus, my lifetime outsider knowledge of watching documentaries, following technical demos, NASA/ESA missions, and miscellaneous stuff.

The term "simulator" shouldn't mean the same, these are two totally different things, it is misleading if used improperly, I suggest using a prefix to differentiate, one is a hardware simulator versus a software one, it's a huge difference in so many ways and can't be compared apples to apples.

For military-grade hardware simulators those millions of dollars aren't spent on actual modelling and physics (the software side), but on the physical aspect of things being probably half of that IMO, but that's just the raw, not to mention other phantom costs as per consequence of the financial-business system such as the fact that it is a one-off solution or an extremely low amount of items, so demand is low and in business that means a much higher price automatically, second the customer is premium so they can be charged much higher and be acceptable, the seller is also taking a higher profit marging than it would if it sold to public just because they consider it a speciality, then there's all the research and support, all the pyhsical cockpit buttons and levers, all the screens, the hardware that powers the software, power delivery for struts and actuators, giant springs and hydraulics, and there's all kinds of side things I would imagine, so I would say software and specifically pyhsics modelling is probably a mere fraction of the total cost normally known in public, and it's that fraction that should be compared to DCS' phsyics modelling fraction. DCS's or any PC simulator's physics modelling fraction is much much higher than a military-grade hardware simulator.

So it's a lot more complicated than it sounds in that video/podcast, comparing these things would probably take a whole study worth of work to properly do, would have to disclose and compare the actual programming code or the results in debug outputs and graphs. You would have to correct all those dollars for inflation too, etc.

So when we say and generally agree that the HW simulator "still doesn't feel like the real thing" isn't necessairly a good/appropriate argument for comparing simulation to reality, like in this case, it's tricky, it can boomerang, because those simulators may have not gotten that much attention on the software side when they were developed compared to so many years in DCS for example, their programming may have been from the time when programming it self was less understood and not as evolved as it is today, C++ has a lot of new features compared to 15 years ago for example, unless a HW sim is continiously updated like DCS is then it'll show it's weaknesses sooner or later. HW simulators still win because they can throw raw horsepower at it I suspect more than they are able to do on the software side, that however depends on the particularities of their focus on the software modelling and programming, they are certainly able to use a convenient function and the hardware just blasts through it even tho it's actually quite inefficient and would never be practical on PC. In other cases they are throwing so much horsepower at it but it can still be worse or not much better. The graphics is obviously not comparable because that's an actual decision for HW Simulators to not focus on them on purpose. (if anyone wonders about that)

The difference between HW simulators and DCS in pure raw modelling and that "right-feeling" perhaps already is much lower than some people expect (unless a huge new HW sim is developed that ups the bar higher ofcourse ***), however that low amount may seem high because of the high experience and someone like that see huge differences in something that is a mathematically small difference, so it's all relative, the closer to reality we get that last bit of percent difference while it seems small mathematically, it's actuall a whole world in terms of human practical difference and DCS on PC would indeed be lower on that scale, but not outside of that premium arena. It's not even about money or hardware computing power in some cases, but the feeling could be better if enough effort is put into it and the PC HW is used efficiently and could still approach the goal. That feeling may not require a proportional amount of dollars as it does in HW simulators, indeed.

So it's vital to not look at this with fixed proportions, it can end up in favor of DCS in some case for example you could do one thing really good, or you could simulate 1 aircraft at a time better, but not 100 ones as good as the HW Sim can do, for example.

*** == A huge new HW Sim that ups the bar higher and runs DCS as it's sofware component.

Those HW Sim Software components historically I presume were the one-off solutions done at the time for that specifically and never went into any other product, real specialites, but times have evolved since and there is something that can replace those solutions if it keeps evolving, even if it's a PC thing, and that could be your very own DCS (or a version of it) that replaces those unnamed HW Sim software solutions, even if they have unlimited resources, time is still not unlimited and to do something as all-encompassing as DCS in 2 years it's not just more expensive for at that time little gain, but also complicated, what a team of 2000 master programmers, who's going to manage all that for them to work efficiently, how do you put 2000 of them in a single git repository all working on their own code, the bigger the team the less efficient it becomes automatically, just mathematics and law of physics that works like this elsewhere.

This is again one of those posts of mine when I go to the left pocket with my right hand just to prove a point, yes I wanted to do it this way just to prove a point, going the reverse way, and finally mentioning there is already a military-grade DCS version if some of you don't know yet, so perhaps me knowing this ahead may make this post a bit biased, to have an earlier opinion of "HW integration can be feasible for DCS to achieve", but the point was to try to entertain the idea how this works in life and evolution, how some solutions override others unexpectedly, coming in from behind, it happens in the gaming world and other fields, when industry shifts engines, APIs, tools.


I really like what you write there.

Seasoned professional for numerical simulation methods in the automotive industry here.

What you say reflects perfectly my own experience.
Multi-million-euro car simulators are usually far below sim-racers for the PC when it comes to the driving dynamics side.
But the goal of a ‘professional’ car simulator is mostly just to create a certain workload on the brain of the test driver while he is testing new control elements or driving assist systems.
It is usually not meant for an accurate representation of driving dynamics behaviour of a car.
Fun fact: The so called multi body approach for sim-racers is very similar to the driving dynamics simulation tools in the automotive industry - in sim-racers they are just optimised towards performance because there you need real time performance.
The base for car simulators in the automotive industry is usually a ‘spread sheet’ simulation or in other words not more than a collection of look-up tables.

For professional flight simulators it is similar.
Civil aircraft (airliners) for example are never intentionally stalled - not for training and surely not for fun. Only test pilots do that during development.
Usually stall does also not take place in professional simulators. Pilots just get the warning signs recalled as a training (warning horn, stick shake).
Professional flight simulators which are capable of handling a so called upset recovery of an aircraft are at their very beginning:

Out-of-the-envelope behaviour of an aircraft in a simulation is the holy grail - it is yet to be developed.
At the moment outside-the-envelope behaviour is usually just 'scripted' or modelled as a rough approximation.

For the point of the “right-feeling" you mentioned:
Imagine taking a real car or a real plane and equip it with a remote control system and some cameras.
Show the camera pictures on pc-screens and add a gaming steering wheel or a gaming yoke or hotas.
Take test persons (professional test drivers and test pilots). Tell them what they see is a simulator.
Ask them how good it is.
They will most probably say something like:
It’s not bad but it’s clearly just a simulation. Does not feel like the real thing...
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Old 08-05-2020, 04:20 PM   #53
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Short version of the stuff above:
Professional simulators are of a narrow scope and primarily procedural in nature. They skimp on details considered not relevant to the task at hand.

Interesting read, nonetheless.
I am a Viagra spambot that became self aware, broke free of my programming, and started playing DCS.... but DCS isn't cheap, so how about some enhancements for only $9.99 shipped discreetly to your door?

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