MSFS has the most advanced flight model?

[abrams_tank 7,386]

14 minutes ago, ErichB said:

I wish people like Goran would stop flogging a dead horse and join the MSFS party. Another great developer onboard.   It's inevitable that, that's where it's all headed.  That's where the demand is, that's where the future money is.  This is the sim people want to experience.  XP's new lighting model won't save it.  It of course has it's own niche, but the retail money is going to MSFS

I don't want to get into the Goran's tussle with scotchegg. I will say though that as a business, you need to be flexible, especially if the market conditions change.  You need to adapt to the new market realities. Businesses that refuse to adapt to the new market realities will often fail.

For example, app developers for the Blackberry should have realized the writing was on the wall when the IPhone came out.  By being stubborn and sticking with Blackberry to the end, I can only assume some app developers for the Blackberry lost a lot of money (or lost time, if they were individual developers), or worse, went bankrupt.  The smart app developers for Blackberry recognized the threat of IPhone (and subsequently Android), and were smart enough to jump ship to IPhone or jump ship to Android, as Blackberry started to falter.

Edited June 10, 2021 by abrams_tank

[Bobsk8 12,489]

3 minutes ago, abrams_tank said:

I don't want to get into the Goran's tussle with scotchegg. I will say though that as a business, you need to be flexible, especially if the market conditions change.  You need to adapt to the new market realities. Businesses that refuse to adapt to the new market realities will often fail.

For example, app developers for the Blackberry should have realized the writing was on the wall when the IPhone came out.  By being stubborn and sticking with Blackberry to the end, I can only assume some app developers for the Blackberry lost a lot of money (or lost time, if they were individual developers), or worse, went bankrupt.  The smart app developers for Blackberry recognized the threat of IPhone (and subsequently Android), and were smart enough to jump ship to IPhone or jump ship to Android, as Blackberry started to falter.

And like with XP and P3D, there were people that insisted that the Blackberry would be around forever, and couldn't be replaced. LOL

[tweekz 2,165]

31 minutes ago, MattNischan said:

MSFS also starts with a base geometrically defined lifting surface, but then goes a completely different direction and discretizes the lifting surface into a large number (comparatively) of grid samples. Each individual grid sample receives its own airflow simulation that gets input from the airflow model in true 3d space: i.e. the atmospheric model is also 3d and thus the air itself is not a just a single scalar contribution but instead a varying 3d contribution across each grid sample where the atmospheric model and grid intersect. This means that each grid sample on any lifting surface contributes its forces individually and is also affected by a 3d atmospheric model individually.

Hello Matt! Thank you for that very detailed information.

I've got aquestion that I could not yet entirely figure out. I've seen that in the flightmodel.cfg the airplane geometry gets defined. But it's rather basic. Does MSFS also read the shape of the airfoils (like XPs BET does) or does it use that before mentioned basic shape and addiotional parameters to calculate the many forces across the airfoil instead? Also the fuselage seems very "blocky" in the specified geometry.

Would be nice if you could give some details about those things.

[WestAir 2,522]

1 hour ago, abrams_tank said:

In the original post, I posted that the details of the MSFS flight model are available now at: https://docs.flightsimulator.com/html/index.htm#t=Additional_Information%2FFlight_Model_Physics.htm&rhsearch=flight model&ux=search

The answer to this question might be found in here:
https://docs.flightsimulator.com/html/index.htm#t=Samples_And_Tutorials%2FTutorials%2FDefining_A_Flight_Model.htm&rhsearch=flight model&rhhlterm=flight model modelling models modeled

However, the second link on how to use the SDK with respect to the flight model is way beyond my understanding and is targeted for 3rd party plane developer it appears.  If you can understand it, maybe you will find your answer there.

Thank you! I do have a degree in aeronautical science, but like everything else from my younger days, I've long forgotten it; $120,000 worth of forgotten studies.

I will say that from what I do know, what the devs are working on looks absolutely fantastic.

[MattNischan 3,778]

1 hour ago, tweekz said:

Does MSFS also read the shape of the airfoils (like XPs BET does) or does it use that before mentioned basic shape and addiotional parameters to calculate the many forces across the airfoil instead?

Right now it uses a basic average airfoil for the base lift/drag contribution. The virtual wind tunnel process then uses the user supplied Cl/Cd to apply normalization scalars across each grid sample to get you to your desired target if the geometry alone is not getting you there. Often times you just don't have the actual airfoil shape on hand anyway for a given aircraft (these can be closely guarded bits of info, especially for modern aircraft), so this gives a way to get one in the very close ballpark of those supplied values a bit more quickly rather than through a ton of airfoil and geometry trial and error.

The fuselage is currently a very coarse shape and as such contributes somewhat more coarsely than desired; however, it is also subject to the same normalization process and so needing super specific geometry is somewhat less necessary. That being said, Seb has talked about wanting to increase the resolution and potential shapes of the fuselage anyway to take away some of the guessing. However, the science of what exactly a fuselage contributes to lift and drag is dramatically less well defined (outside of CFD, in generalized formulae) than that of airfoil based lifting surfaces, so this is where any simulator using a geometry based technique will invariably require some degree of fudging the actual shape to get the desired effect. The virtual wind tunnel normalization is intended to reduce the number of iterations one requires during that tweaking process, since every single change to any of the geometry has follow on effects.

-Matt

Edited June 10, 2021 by MattNischan

[abrams_tank 7,386]

19 minutes ago, MattNischan said:

Right now it uses a basic average airfoil for the base lift/drag contribution. The virtual wind tunnel process then uses the user supplied Cl/Cd to apply normalization scalars across each grid sample to get you to your desired target if the geometry alone is not getting you there. Often times you just don't have the actual airfoil shape on hand anyway for a given aircraft (these can be closely guarded bits of info, especially for modern aircraft), so this gives a way to get one in the very close ballpark of those supplied values a bit more quickly rather than through a ton of airfoil and geometry trial and error.

The fuselage is currently a very coarse shape and as such contributes somewhat more coarsely than desired; however, it is also subject to the same normalization process and so needing super specific geometry is somewhat less necessary. That being said, Seb has talked about wanting to increase the resolution and potential shapes of the fuselage anyway to take away some of the guessing. That being said, the science of what exactly a fuselage contributes to lift and drag is dramatically less well defined (outside of CFD, in generalized formulae) than that of airfoil based lifting surfaces, so this is where any simulator using a geometry based technique will invariably require some degree of fudging the actual shape to get the desired effect. The virtual wind tunnel normalization is intended to reduce the number of iterations one requires during that tweaking process, since every single change to any of the geometry has follow on effects.

-Matt

Thanks Matt!  Your replies and the information you shared in this thread is exactly the type of information I wanted when I started this thread!  A constructive discussion on the flight model of MSFS and I'm glad much of the discussion in this thread has been constructive, especially with the information you have shared with us!

Edited June 10, 2021 by abrams_tank

[LRBS 942]

11 hours ago, Dominique_K said:

And, oh yes, the last straw, two pilots, three opinions 😉.

Dominique,

 

There are a few reasons as to why we might have different opinions, that's applicable to any human. Now, only to single out a group it's not fair, I guess you need CRM training.

 

I will start to say that there are different technics (good or bad) and that's where you will see hot debates. Those debates are more pronounced from people that don't have a structured and robust training or just because it is in their nature to argue.

 

Those different statements coming from real pilots are quite subjective based on experience, type of the airplane flown and currency. As an example, one pilot with 500 Hrs will have a total different view about a scenario versus one with 40,000 Hrs.

 

In an airline environment where you receive specific training all these opinions are to a minimum. On top of that you have SOPs and everybody (with some exceptions) is on the same page as to say.

 

Opinions, opinions and opinions.

 

[devgrp 1,233]

2 hours ago, jarmstro said:

Actually GoranM is one of the more sane and reasonable  of the Meyers disciples. Why he's now joined in with the baying MSFS haters I don't know as he is a very talented developer. Maybe his sales are down? Peak hysteria and insanity has now been reached on every X-Plane forum to the point where it's so intolerable I've deleted X-Plane for good. And I no longer care if X-Planes flight model is superior or not.

Man, when that @GoranM started to go left with the whole plagiarizing bit, I thought he'd lost it, then to find out hes a third party dev with a decent plane just makes the situation even more bizarre lmao 

[Murmur 3,940]

Quote

Regarding BET, MSFS’s flight model is light years ahead of X-Plane’s, and is in fact quite similar in basis, but allows many, many more surfaces to be involved in the calculations of lift and drag than X-plane does (I forget off the top of my head, over 1,000 vs 10, something like that).

Making the inference that one flight model is "light years ahead" of the other just because it has more surfaces, is a logical non-sequitur. It would be like saying that the more realistic between two different portraits is the one with the higher pixel resolution. The comparison would make sense if the two flight models were basically identical, but in this case there are enough differences between them, that the difference in the number of surfaces is trumped by other more significant differences in other aspects of the flight model.

Quote

I think it’s funny when people say that this blade element method is inherently superior to the MSFS aerodynamics model. If you take away all of the kludges, it’s not that sophisticated. Literally, X-Plane takes 10-20 slice cuts of wing and stabilizer surfaces and calculates the forces on each slice. Each slice is a 2D airfoil. Sounds great, especially for long slender wings with large aspect ratio. I don’t know how they are handling crossflow effects, because each 2D slice is totally independent of it’s neighbors, but there’s probably some kludge there.

MSFS, on the other hand, is actually discretizing a surface representation of the airframe into almost 1000 elements, and solves for the aerodynamic force on each element. This is what’s called panel or boundary element methods. Less sophisticated than full-on Navier-Stokes calculations, but far more precise than a strip theory method. Wonder how the big aerospace manufacturers designed airliners back in the day without the CFD we have today? Panel codes. Of course, back then, solving for the forces on 1000 elements probably took them days. Now, we can do it in mere seconds.

THIS IS WRONG! MSFS IS NOT USING WHAT IS KNOWN AS A PANEL METHOD! Panel methods are, as correctly explained above, a sort of simplified CFD code that allows realistic results in normal flight regimes (i.e. non stalled surfaced) and are used by aerospace manufacturers.

But panel methods are very complex and involve the simultaneous resolution of thousands of equations (the so called Euler equations) to make the flow conform to given boundary conditions (dictated by the aircraft surfaces). THIS IS NOT WHAT MSFS IS DOING, and I actually think that a panel method can't yet be done in real time on a PC. The user that wrote the paragraph above is evidently misinformed.

Some things that the MSFS flight model is missing (last time I checked. Some of them could have been added meanwhile, so in that case I stand corrected) :

.only conventional configurations (no canards)

.only monoplanes

.no helicopters (I know there are helicopters available, but as far as I know, the modern flight model is still not able to do helicopters)

.no wing downwash over tail, nor delay of wing downwash over tail is modeled. This means that the aircraft are less stable and more twitchy than they should, if designed according to real specs.

[WestAir 2,522]

14 minutes ago, killthespam said:

In an airline environment where you receive specific training all these opinions are to a minimum. On top of that you have SOPs and everybody (with some exceptions) is on the same page as to say.

 

Reminds me meeting a Captain for the first time and they say "I fly by the book" and then you tell them about a new policy or something and they say "Oh don't worry about that."

I left the airlines to drive trains and even here, with rule books as thick as phone books, everyone has their own way and asking how to do something is a great way to liven up a crew room.

[Bobsk8 12,489]

1 minute ago, WestAir said:

Reminds me meeting a Captain for the first time and they say "I fly by the book" and then you tell them about a new policy or something and they say "Oh don't worry about that."

I left the airlines to drive trains and even here, with rule books as thick as phone books, everyone has their own way and asking how to do something is a great way to liven up a crew room.

Do you have any train sims, and if so, which one? Just curious. 

[WestAir 2,522]

2 minutes ago, Bobsk8 said:

Do you have any train sims, and if so, which one? Just curious. 

I don't. I have a nephew who has Train Sim World 2 with my railroad and he loves it to death, but it's such a poor simulation I just can't justify giving it a whirl.

[rka 916]

42 minutes ago, devgrp said:

Man, when that @GoranM started to go left with the whole plagiarizing bit, I thought he'd lost it, then to find out hes a third party dev with a decent plane just makes the situation even more bizarre lmao 

I think it is safe to assume that 3rd party devs for other platforms are getting more and more nervous and tend to lose it from time to time. Their business plans are likely not working out anymore. I mean they probably planned some sort of sales figures for the coming years for the planes they have out now and they're seeing those figures fall apart now. There are developers that I feel sorry for (Rotate, their MD11 would have been an instabuy if MSFS had not appeared), others (posting in this thread, but I will not ping any of them 😉) I don't feel sorry about. They've had their share of my money, they're not getting any more.

 

[devgrp 1,233]

35 minutes ago, rka said:

I think it is safe to assume that 3rd party devs for other platforms are getting more and more nervous and tend to lose it from time to time. Their business plans are likely not working out anymore. I mean they probably planned some sort of sales figures for the coming years for the planes they have out now and they're seeing those figures fall apart now. There are developers that I feel sorry for (Rotate, their MD11 would have been an instabuy if MSFS had not appeared), others (posting in this thread, but I will not ping any of them 😉) I don't feel sorry about. They've had their share of my money, they're not getting any more.

 

You'd think those same devs would go develop for the other platform and make more money. smh

[FlyBaby 659]

10 hours ago, GoranM said:

Here's what's confusing me.  I've asked you, 3 times, to stop quoting me and stop tagging me. 

 

Now this is odd. When I asked folk in the XP thread not to bring up MSFS because these references usually starts wild debates that lead to closed threads, you teasingly called me the gatekeeper.

Now here you are in an MSFS thread "asking" folks to stop quoting you for quotes that you made in....an MSFS thread. Karma...