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DCS World Flight Modelling Principles


Wags

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"Too low" means less than 0.5 seconds at 13 s or less than 4%?

 

It means 9.0 G's is hit at 0.64 Mach @ SL in the real jet (page B8-65 in HAF manual), whilst it can't be hit until 0.78+ Mach in DCS under identical weight, DI & atmospheric conditions. Best you get at 0.64-0.66 in DCS is 8.6-8.7 G's.

 

In short the DCS F-16 can't hit its best ITR until 0.10+ Mach later than it should.

 

 

Now I think it's linked with the lack of G-onset rate that I am even afraid to mention at this point as my last post on the matter was deleted, but here's a video of a real F-16 hitting 9 G's A LOT faster than the DCS F-16 is capable of:

https://www.instagram.com/p/BojNMR7FSps/


Edited by Hummingbird
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"Too low" means less than 0.5 seconds at 13 s or less than 4%?

 

At mach 0.4 it's a full degree per second less than your reference chart, which in a dogfight is quite significant. Given that the existing G-tolerance model prevents sustained dog-fighting over mach 0.6, which is where the DCS Viper's turn rate is accurate (and fastest), this seems like something worth fixing. It means that, in effect, most uses of the DCS Viper will occur in the least accurate areas of its flight model.

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Lol, I love the one's wheezing about ''muh fuh-del-i-TY'' lol If you want it.more realer than this, feel free to enlist! Note : They do require an education, and being able to physically squeeze into the cockpit ;)

Де вороги, знайдуться козаки їх перемогти.

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Lol, I love the one's wheezing about ''muh fuh-del-i-TY'' lol If you want it.more realer than this, feel free to enlist! Note : They do require an education, and being able to physically squeeze into the cockpit ;)

 

There's still a lot in between. Wheezing is good:D

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I wheeze every day, thank you. Cheetos dust and spice have a lot in common. It lets see...between worlds. Also causes high cholesterol. Unsure if spice does that.

Де вороги, знайдуться козаки їх перемогти.

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  • ED Team
At mach 0.4 it's a full degree per second less than your reference chart, which in a dogfight is quite significant. Given that the existing G-tolerance model prevents sustained dog-fighting over mach 0.6, which is where the DCS Viper's turn rate is accurate (and fastest), this seems like something worth fixing. It means that, in effect, most uses of the DCS Viper will occur in the least accurate areas of its flight model.

 

Where do you see 1 deg/s at 0.4 Mach?? 1 tick is not 1 deg/s but 0.5 deg/s.

 

And, 3.5 g in F-16... ridiculous. 5-7 g you can be up to eternity shows you absolutely accurate match.

 

Anyway, it is 4%. What accuracy do you think real F-16 was measured?

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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Dear DCS Pilots,

 

 

 

DCS World Flight Modelling Principles document: https://drive.google.com/file/d/1e5Jo_-2rDj33EKlD3HH5ur3NoYRxBZlj/view?usp=sharing

 

 

 

attachment.php?attachmentid=243302&stc=1&d=1595601838

 

 

 

Perhaps the least understood by customers, and the most complex task for us, is the creation of aircraft flight dynamics for DCS World aircraft. To help shine some light on this mysterious subject, our flight model engineering team created the linked document to share the sources we use, the fundamental principles behind the engineering, and the techniques we use to create and test the most accurate flight models possible.

 

 

 

It is our hope that with a better understanding of the process that you will truly appreciate the time and effort that goes into creating a flight model for DCS World and why it is not a speedy or simple task.

 

 

 

Thank you and kind regards,

 

The Eagle Dynamics Team

 

 

 

Great document, will read it soon as i am really curious on how flight models workZ

Thanks for sharing

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Not seeing density anywhere in there. We're not talking about lift, we're calculating TAS from MACH, and MACH is calculated against the speed of sound.

 

 

Still confused, but thanks for trying.

Your question was:

I am curious why you calculate TAS using air density at a particular altitude when the speed of sound (in air) is dependent on temperature and not density.

(...)"The density of a material varies with temperature and pressure. This variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object and thus increases its density."(...)

Air density/pressure and temperature are part of the "absolute temperature". As DCS is actually modelling air flow with temperature/density and then models lift from these dynamic factors...

Think about it, what is the speed of sound in 4°C water, what is it beyond the stratosphere? The temperature correlating to pressure is density ( the number of molecules in a given volume that store energy the more you compress the molecules ).

(...)"The airspeed indicator (ASI), driven by ram air into a Pitot tube and still air into a barometric static port, shows what is called indicated airspeed (IAS). The differential pressure is affected by air density. The ratio between the two measurements is temperature-dependent and(!) pressure-dependent, according to the ideal gas law.

 

At sea level in the International Standard Atmosphere (ISA) (a norm for air density/pressure) and at low speeds where air compressibility is negligible (i.e., assuming a constant air density), IAS corresponds to TAS. When the air density or temperature around the aircraft differs from standard sea level conditions, IAS will no longer correspond to TAS, thus it will no longer reflect aircraft performance. The ASI will indicate less than TAS when the air density decreases due to a change in altitude or(!) air temperature is (basically different density/pressure altitude). For this reason, TAS cannot be measured directly. In flight, it can be calculated either by using an E6B flight calculator or its equivalent."(...)

At least that is what I understood from the E6B manual etc.

The shameless Wikipedia citations were easier than going through papers and books, but should be good enough.

Shagrat

 

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Thank you Wags and ED for sharing this document. Not only is the info provided great, but transparency like this helps me understand the value I purchase when buying an ED product. Documents like this are great for reference by users and maybe help clean up some of the bickering that goes on about what is/isn't modeled.

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Books only get you so far. Time and again it seems that input from RL military pilots gets rejected as inconvenient ? Dismissing critique seems to be the preferred response.

 

All the simulations are taken as far as possible of course. It's still not the real dynamic thing, so never 100% (Edge of flight envelope) on a home pc. Some seem to think you can achieve.

 

It's still the best on the market by far and possibly as good or better as D level sims irl.

 

 

These guy's talk about how there million dollar mill sims were still not quite right. There seems to be a few vocal military pilots that think DCS on a (home pc) should be as good or better than the sims they used in the military, without the budget.


Edited by David OC

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Download PDF Tutorial guides to help get up to speed with aircraft quickly and also great for taking a good look at the aircraft available for DCS before purchasing. Link

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Its great to see this level of detail being explained, thanks for taking the time to put this together and present it.

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Not a fluid dynamics guy, not an FM guy. Not going to try and be one.

 

Just thrilled you let us peak under the hood, much appreciated.

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All the simulations are taken as far as possible of course. It's still not the real dynamic thing, so never 100% (Edge of flight envelope) on a home pc. Some seem to think you can achieve.

 

It's still the best on the market by far and possibly as good or better as D level sims irl.

 

 

These guy's talk about how there million dollar mill sims were still not quite right. There seems to be a few vocal military pilots that think DCS on a (home pc) should be as good or better than the sims they used in the military, without the budget.

 

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. :smartass:

 

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.

 

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Edited by Worrazen

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I've never taken a helicopter off or landed one in real life, but have substantial experience in DCS/VR.

 

I got over a half hour of time on a military 206C sim.

 

Not only was I able to "fly" it, I was able to do so very precisely, and even to hot dog with it. Turning about the nose, landing on top of a small building, on an LHA, all of it.

 

I was assured that flying this sim means I could fly the actual helo.

 

DCS works for this purpose, and it works well.

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I've never taken a helicopter off or landed one in real life, but have substantial experience in DCS/VR.

 

I got over a half hour of time on a military 206C sim.

 

Not only was I able to "fly" it, I was able to do so very precisely, and even to hot dog with it. Turning about the nose, landing on top of a small building, on an LHA, all of it.

 

I was assured that flying this sim means I could fly the actual helo.

 

DCS works for this purpose, and it works well.

 

Another fella had the same experience you did - I wonder if it would be the same for us fixed wing peasants?

 

https://forums.eagle.ru/showthread.php?t=249291&page=4

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Another fella had the same experience you did - I wonder if it would be the same for us fixed wing peasants?

 

https://forums.eagle.ru/showthread.php?t=249291&page=4

 

I would imagine yes it would be. Especially because flying fixed wing once airborne is orders of magnitude easier in a modern fighter aircraft.

 

Landing may be a bit of a different story though! :pilotfly:

 

It's really a testament to the accuracy of the flight models in DCS, and the fidelity that they have put into the aircraft. Any one of the guys I fly with in squadron could have done the exact same thing.

 

At least as far as the basics, DCS can give you the monkey skills 100%. And DCS was superior in more ways than one.

 

Based upon what I saw, if they had a physical cockpit that lined up with what you see in VR, such that the pilot can actually flick the switches and turn the knobs physically, and modeled the hydraulic forces on the controls, it's game over for these multi-million dollar, huge hydraulic tractor-trailer sized sims.

 

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All the simulations are taken as far as possible of course. It's still not the real dynamic thing, so never 100% (Edge of flight envelope) on a home pc. Some seem to think you can achieve.

 

It's still the best on the market by far and possibly as good or better as D level sims irl.

 

 

These guy's talk about how there million dollar mill sims were still not quite right. There seems to be a few vocal military pilots that think DCS on a (home pc) should be as good or better than the sims they used in the military, without the budget.

 

Agreed!

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FM is more accurate than your chart reading, try again.

 

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.


Edited by Hummingbird
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These guy's talk about how there million dollar mill sims were still not quite right. There seems to be a few vocal military pilots that think DCS on a (home pc) should be as good or better than the sims they used in the military, without the budget.

 

A little bird told me that they spend 5 million USD/year on a simulator at Edwards AFB, and none of the pilots want to use it.

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Can this be moved to the Community News section?

I second the motion!:smartass:

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This is good stuff! I'm curious; has anyone found a way to modify the ground effect for a given aircraft? Just curious if I can mod (or comment out completely) the reversed ground effect as it currently affects the Hornet. I can't seem to find a parameter defined for ground effect, yet it seems it would have to be aircraft specific since not all DCS aircraft have the ground effect reversed?

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