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CaptainDoggles 11-30-2011 03:22 AM

Quote:

Originally Posted by ACE-OF-ACES (Post 365676)
Actully PCs have been capable of calculating a 6DOF FM in real time for some time now.. As noted the first that advertised a 6DOF FM was PAW 1942 by Microprose back.. Gezzz.. I want to say 15 years ago?

You are mistaken.

First of all the equations governing fluid flow, the Navier Stokes equations, have no known solution. Modern mathematics does not have a method for determining the solution unless certain simplifying assumptions are made. The only way to get an approximate solution is to use a numeric solver, and these are very computationally expensive. I guarantee that Cliffs of Dover is not running numerical solutions to the fully viscous Navier Stokes equations.

There are certain assumptions that are "good enough" for the consumer flight sim market, and these are in use in all flight sims.

You can keep using the term "6DOF FM" which I assume means that the aircraft are free to move in all six degrees of freedom. That is not the same as a flight model that corresponds 1:1 with reality.

6S.Manu 11-30-2011 10:14 AM

Quote:

Originally Posted by CaptainDoggles (Post 365678)
You are mistaken.

First of all the equations governing fluid flow, the Navier Stokes equations, have no known solution. Modern mathematics does not have a method for determining the solution unless certain simplifying assumptions are made. The only way to get an approximate solution is to use a numeric solver, and these are very computationally expensive. I guarantee that Cliffs of Dover is not running numerical solutions to the fully viscous Navier Stokes equations.

There are certain assumptions that are "good enough" for the consumer flight sim market, and these are in use in all flight sims.

You can keep using the term "6DOF FM" which I assume means that the aircraft are free to move in all six degrees of freedom. That is not the same as a flight model that corresponds 1:1 with reality.

Yep, the same for target visibility: there are still unknown variables in the equation.

IMO the road to take is still the "table based" as Tag says, both for the mandatory approximations and CPU usage.

Think about real time weather: I hope they really didn't take this road because it's madness. I think the good way is to have external CPU greedy applications who provide simplified tables, and then use these tables ingame.

I don't know very well the methods XPlane use to calculate FMs: IIRC the plane developer needs to use some external applications were the data are processed to result in the final plane package.

Have anyone tested their WW2 planes?

ACE-OF-ACES 11-30-2011 02:45 PM

Quote:

Originally Posted by CaptainDoggles (Post 365678)
You are mistaken.

Interesting.. So your saying that that all the PC flight sims since the mid 1990s who claim to have implemented a 6DOF FM were lying to us?

Emmmmm.. don't take this personal, but we will have to agree to disagree on that, sorry

Quote:

Originally Posted by CaptainDoggles (Post 365678)
First of all the equations governing fluid flow, the Navier Stokes equations, have no known solution. Modern mathematics does not have a method for determining the solution unless certain simplifying assumptions are made. The only way to get an approximate solution is to use a numeric solver, and these are very computationally expensive.

Interesting, but fluid flow equations and navier stokes equations are not used in a 6DOF FM

Quote:

Originally Posted by CaptainDoggles (Post 365678)
I guarantee that Cliffs of Dover is not running numerical solutions to the fully viscous Navier Stokes equations.

Hence me stating 6DOF and not fluid flow or navier stokes

Quote:

Originally Posted by CaptainDoggles (Post 365678)
There are certain assumptions that are "good enough" for the consumer flight sim market, and these are in use in all flight sims.

Not only is 6DOF good enough for PC game flight simulation, but it is good enough for most if not all military flight simulations.

On that note, don't confuse flight simulation with aircraft design technics (which you appear to be doing)

Where fluid flow and navier stokes equations are used a lot in aircraft design, and yes the last time I check the full up fluid flow FMs were too CPU intensive to be run in real time.

Granted there have been a few PC flight sims that claimed to be using fluid flow (real-time computational fluid dynamics (CFDs)) for their FM, as was the case back in 1995 with Flight Unlimited. But the equations had to be stripped down (dumb down) to run in real time on a PC such that all the benefits of a fluid flow FM were lost

Quote:

Originally Posted by CaptainDoggles (Post 365678)
You can keep using the term "6DOF FM" which I assume means that the aircraft are free to move in all six degrees of freedom.

You assume correctly

Quote:

Originally Posted by CaptainDoggles (Post 365678)
That is not the same as a flight model that corresponds 1:1 with reality.

I got news for you, no simulation is 1:1 with reality

TomcatViP 11-30-2011 04:44 PM

it's very good comments Ace.

Just remember tht "compressibility" related interferences with "normal" flows regime start to occurs well bellow the 0.5 Mach regime and non potential flows are to be preeminent once AoA increase.

With WWII planes you are both dealing in most of the flight regime with both this problem and simplified equation are hardly accurate. Just hve a look of the drag coeff in a high subsonic flight regime ;)

For GA simulation like in Flight Unlimited or even RoF (the early Flight models where really good until stupid EGO plane where introduced), simplified equation related to design coeff are accurate enough for builiding a good sim. Cleverness of the FMder will do teh trick once the plane depart from the range of parameters where simplified equation are not good enough.

IN WWII flight sim, things are more complicated with most of the flight regime in combat being at the edge where simplified eq simply does not do anymore the trick. It's then IMHO a matter of assessment of what will have a predominant effect and what won't. There of course it's all debatable and really sensitive to the accuracy and honesty of the historical materials submitted for building the flight models :(.

Modern studies could be done in some arrowing section of the FM to assess a specific behavior. That's what I wld hve done perso like building a generic high speed/highG model with, let's say a 23015 wing section AR of 5 straight trezoidal wing etc... etc..

But I am sure those guys there in the Moscow suburb had more in mind and done alrdy plenty :rolleyes:

Tht's what plsd me with CoD is both the honesty and the willingness do things good

CaptainDoggles 11-30-2011 04:51 PM

Quote:

Originally Posted by ACE-OF-ACES (Post 365846)
Interesting.. So your saying that that all the PC flight sims since the mid 1990s who claim to have implemented a 6DOF FM were lying to us?

No, that's not what I'm saying at all. Re-read what I wrote.

Quote:

Interesting, but fluid flow equations and navier stokes equations are not used in a 6DOF FM


Hence me stating 6DOF and not fluid flow or navier stokes


Not only is 6DOF good enough for PC game flight simulation, but it is good enough for most if not all military flight simulations.
So you agree it's an approximation to reality then, as I said earlier?

Quote:

On that note, don't confuse flight simulation with aircraft design technics (which you appear to be doing)
The ideal simulation will follow principles of aircraft design and accurately reproduce reality.

Quote:

I got news for you, no simulation is 1:1 with reality
No kidding, this is the point I was trying to make from the beginning.

ACE-OF-ACES 11-30-2011 05:06 PM

Quote:

Originally Posted by CaptainDoggles (Post 365890)
No, that's not what I'm saying at all. Re-read what I wrote.

Ok lets re-read it..

Quote:

Originally Posted by CaptainDoggles
Quote:

Originally Posted by ACE-OF-ACES
Actually PCs have been capable of calculating a 6DOF FM in real time for some time now.. As noted the first that advertised a 6DOF FM was PAW 1942 by Microprose back.. Gezzz.. I want to say 15 years ago?

You are mistaken.

Hmmm.. Sorry but even after the re-read it appears you are under the impression that no PC flight sim has ever implemented a 6DOF FM, which is just not true.

Granted you did not come out and say they are lying, you just implied it.

As for mistaken..

In light of the fact that many PC flight sims have implemented a 6DOF FM, it appears that you are the one that is mistaken, not I

Quote:

Originally Posted by CaptainDoggles (Post 365890)
So you agree it's an approximation to reality then, as I said earlier?

First thing to note I never said a 6DOF is reality, hence the name 'simulation'

What worries me about what you said is that you seem to think a CFD FM is equal to reality, which is just not the case.

I have this saying, no sim ever was, is, or will be perfect (read equal to reality)

Kind of sums it all up don't it?

Quote:

Originally Posted by CaptainDoggles (Post 365890)
The ideal simulation will follow principles of aircraft design and accurately reproduce reality.

Depends on your definition of ideal..

I think it is safe to say that most people here would agree that a simulation that takes 3 hours to simulate 3 minutes of flight time is NOT ideal..

Your mileage may vary?

Quote:

Originally Posted by CaptainDoggles (Post 365890)
No kidding, this is the point I was trying to make from the beginning.

So you agree a CFD FM like a 6DOF FM is an approximation to reality then, as I said earlier?

ACE-OF-ACES 11-30-2011 05:18 PM

Quote:

Originally Posted by TomcatViP (Post 365885)
it's very good comments Ace.

S!

Quote:

Originally Posted by TomcatViP (Post 365885)
Just remember tht "compressibility" related interferences with "normal" flows regime start to occurs well bellow the 0.5 Mach regime and non potential flows are to be preeminent once AoA increase.

With WWII planes you are both dealing in most of the flight regime with both this problem and simplified equation are hardly accurate. Just hve a look of the drag coeff in a high subsonic flight regime ;)

For GA simulation like in Flight Unlimited or even RoF (the early Flight models where really good until stupid EGO plane where introduced), simplified equation related to design coeff are accurate enough for builiding a good sim. Cleverness of the FMder will do teh trick once the plane depart from the range of parameters where simplified equation are not good enough.

IN WWII flight sim, things are more complicated with most of the flight regime in combat being at the edge where simplified eq simply does not do anymore the trick. It's then IMHO a matter of assessment of what will have a predominant effect and what won't. There of course it's all debatable and really sensitive to the accuracy and honesty of the historical materials submitted for building the flight models :(.

Modern studies could be done in some arrowing section of the FM to assess a specific behavior. That's what I wld hve done perso like building a generic high speed/highG model with, let's say a 23015 wing section AR of 5 straight trezoidal wing etc... etc..

It is true..

All simulations have limits.. Thankfully most of the errors due to the limits are smaller than what most humans can precive.

The good news is the 6DOF FM code has been around for years.. 30+ easy! I have a copy of an old F16 FM writen in FORTRAN from the late 70s early 80s. The math of it all has not changed much, just the code that it is implimented in and the PC it runs on. What use to take a super computer can no be done on a low end PC

Quote:

Originally Posted by TomcatViP (Post 365885)
But I am sure those guys there in the Moscow suburb had more in mind and done alrdy plenty :rolleyes:

Tht's what plsd me with CoD is both the honesty and the willingness do things good

Agreed!

41Sqn_Stormcrow 11-30-2011 05:25 PM

Quote:

Originally Posted by ACE-OF-ACES (Post 365659)
Bingo!


Sure I can.. Or should I say.. Thus far NO ONE has provided anything that would be considered proof there is an error in the FM! Which is not to be confused with me saying there is no problems, only that no one (on the user side, i.e. not someone from 1C) has provided anything that would be considered proof! Look at most if not all of the threads in this forum, for every person that says the PLANE A is too slow, there is another that says PLANE A it is too fast! So what does that say about the users?


Which is why my first question to anyone making a claim of any sort is Got Track?©®. Because most of these so called claims can be put to rest by simply watching the track file, in that most of the time it is clear that it is pilot error! At least that is what I have found after years of viewing IL2 track files people provided as 'proof' of this or that


Oh, there is abundance of proof that the 109 for instance is too slow. Please look up again the corresponding threads.

I guess that there has been similar data posted for other planes as well.

EDIT: On the how to do a sim: I have a couple of years experience in the aerospace business as an engineer and I work for a research institute in this field. One field of our research are hypersonic planes. As any hypersonic plane has to accelerate through the subsonic velocity range (and deccelerate later for landing) we put some effort in studying subsonic aerodynamics. From all experience we have collected I can say one thing: there is not ONE single simplified method that can predict accurately the aerodynamic forces in the subsonic region (but some adequate approximations) for low and medium subsonic speeds. When the speed approaches transsonic speeds it basically gets guesswork.

Only halfway trustworthy aerodynamic results by calculation would be to do the fully viscous NS-equations (provided they can be solved correctly) but this is not at all practicable for a flight sim as the calculation for one flight point only (Ma, altitude, angle of attack, sideslip angle) would take a lot of time and we would need an enormous number of flight points in order to create a sufficiently large data base. And again, as a researcher who respects himself, I would request to verify some calculated points by wind tunnel tests ...

And we yet have not even talked about the damping coefficients which are even more difficult to assess by wind tunnel tests let alone determine by calculations ...

ACE-OF-ACES 11-30-2011 05:53 PM

Quote:

Originally Posted by 41Sqn_Stormcrow (Post 365907)
Oh, there is abundance of proof that the 109 for instance is too slow.

Abundance.. Really? Well if there is an 'abundance' of 'proof' than it should be a simple task for you to 'pick one' and provide the link to it for review.. Right?

Quote:

Originally Posted by 41Sqn_Stormcrow (Post 365907)
Please look up again the corresponding threads.

I have a beter idea..

As noted, I have 'looked' and have yet to see 'one' that would quality as 'proof'

But maybe I missed the one your refering to?

So since you seem to think there is an 'abundance' of 'proof', please pick the best one and provide the link to it for review, that way we are both on the same sheet of music

Quote:

Originally Posted by 41Sqn_Stormcrow (Post 365907)
I guess that there has been similar data posted for other planes as well.

I like to avoid guess work

Quote:

Originally Posted by 41Sqn_Stormcrow (Post 365907)
EDIT: On the how to do a sim: I have a couple of years experience in the aerospace business as an engineer and I work for a research institute in this field. One field of our research are hypersonic planes. As any hypersonic plane has to accelerate through the subsonic velocity range (and deccelerate later for landing) we put some effort in studying subsonic aerodynamics. From all experience we have collected I can say one thing: there is not ONE single simplified method that can predict accurately the aerodynamic forces in the subsonic region (but some adequate approximations) for low and medium subsonic speeds. When the speed approaches transsonic speeds it basically gets guesswork.

Only halfway trustworthy aerodynamic results by calculation would be to do the fully viscous NS-equations (provided they can be solved correctly) but this is not at all practicable for a flight sim as the calculation for one flight point only (Ma, altitude, angle of attack, sideslip angle) would take a lot of time and we would need an enormous number of flight points in order to create a sufficiently large data base. And again, as a researcher who respects himself, I would request to verify some calculated points by wind tunnel tests ...

And we yet have not even talked about the damping coefficients which are even more difficult to assess by wind tunnel tests let alone determine by calculations ...

Agreed 100%

As I allready noted, no sim is perfect!

And no sim ever was, is, or will be equal to reality!

Hence the name 'simulation' in place of 'reality' ;)

41Sqn_Stormcrow 11-30-2011 06:22 PM

I knew that you would ask other ppl to do the search work for you.

Instead I now ask you to provide a proof that there is no data. I have not enough time to do this work for you. Remember: you brought up this whole: leave-it-as-it-is-because-there-is-no-proof thing. And please spare me anything like: "So you don't have proof". I know this argumentation strategy too well and it just bores me. You just look up the threads by yourself or proove that there is no data available. Otherwise I would just take you as of the same kind as all the others that you blame for making unfounded assertions.

Furthermore I come to believe that even if I or anybody else provided proof you would just call it to be no proof. You're a man on a mission. So any effort would be wasted on you imho.

TomcatViP 11-30-2011 06:28 PM

Quote:

Originally Posted by 41Sqn_Stormcrow (Post 365907)
Oh, there is abundance of proof that the 109 for instance is too slow. Please look up again the corresponding threads.

I guess that there has been similar data posted for other planes as well.

EDIT: On the how to do a sim: I have a couple of years experience in the aerospace business as an engineer and I work for a research institute in this field. One field of our research are hypersonic planes. As any hypersonic plane has to accelerate through the subsonic velocity range (and deccelerate later for landing) we put some effort in studying subsonic aerodynamics. From all experience we have collected I can say one thing: there is not ONE single simplified method that can predict accurately the aerodynamic forces in the subsonic region (but some adequate approximations) for low and medium subsonic speeds. When the speed approaches transsonic speeds it basically gets guesswork.

Only halfway trustworthy aerodynamic results by calculation would be to do the fully viscous NS-equations (provided they can be solved correctly) but this is not at all practicable for a flight sim as the calculation for one flight point only (Ma, altitude, angle of attack, sideslip angle) would take a lot of time and we would need an enormous number of flight points in order to create a sufficiently large data base. And again, as a researcher who respects himself, I would request to verify some calculated points by wind tunnel tests ...

And we yet have not even talked about the damping coefficients which are even more difficult to assess by wind tunnel tests let alone determine by calculations ...

Very interesting Storm.

But you don't always hve to go trough the full range of NS eq even in RL. Hopefully You can use simplified form and some fair assumptions to get a valid result.

ACE-OF-ACES 11-30-2011 06:37 PM

Quote:

Originally Posted by 41Sqn_Stormcrow (Post 365928)
I knew that you would ask other ppl to do the search work for you.

As I knew you were talking out your A when you said there is an abundance of proof

ACE-OF-ACES 11-30-2011 06:44 PM

Quote:

Originally Posted by TomcatViP (Post 365930)
But you don't always hve to go trough the full range of NS eq even in RL. Hopefully You can use simplified form and some fair assumptions to get a valid result.

Exactally

svend 12-18-2011 11:22 AM

Quote:

Originally Posted by SEE (Post 364993)
I love this sim but the FM......:rolleyes: Here's a quote from Adolf Galland taken from an interview with him regards the allied ac during the BoB.

"the Hurricane was hopeless, nice to shoot down though!"

But changes are afoot (I hope!) and spare a thought for those of us (in Spits) who are yelling ' throttle back - can't keep up with you!' :grin:


1. Galland was a damn good pilot he had it in his blood :grin:
2. Alot of the allied pilots where new and untestet in combat (which Galland wasnt).

svend 12-18-2011 11:26 AM

Quote:

Originally Posted by cheesehawk (Post 364980)
Biggest thing you were doing wrong is climbing at a constant speed (unless its either way lower or way higher). 300kph is like cruising speed for a 109, if you think climbing at cruising speed is enough to get away, you're mistaken. Either go into a all out climb (250kph or less), or get your engine management down and climb at 400kph. The Hurri will have a hard time maintaining that speed at the same angle climb as you, it might take 10 minutes, but you will eventually end up with higher alt than him, or if he tries to match your angle, he'll drop a bit of speed, and you'll slowly pull away. Pick one end of the spectrum or the other, but never pick the in-between. That's well within a Hurri's flight envelop, so you're not gaining anything on him. At that speed, you shouldn't have to use full throttle, so you were wasting your engine power but flying at that speed with that rpm.

+1

svend 12-18-2011 01:45 PM

Quote:

Originally Posted by ACE-OF-ACES (Post 365662)
Funny.. but while reading this I was struck with how much it sounded like an actual WWII account.. Which to me says the FMs are not as bad as some would have us belive! Long story short, you fly it like it is real and chances are you will get a real feeling experience! Fly it like it is a game where you are not worried about dying, thus you jump into a fight that a real pilot would not, and chances are you will NOT get a real feeling experience!


Bingo!

As my sig suggest! Most sim pilots are missing one key component in their personality that real WWII pilots had in spades.. The ability to look in the mirror and realize the source of the mistake! ;)


Agreed 100%

To both of you. Agree 100%! Learn, adapt, take your time and do not get your self into trouble :grin: To apply real tactics here would be rather boring for most simmers I think - or? :-P

In rl pilots in WWII would do everything to live another day to se their love ones again - that fear is someting we do not have to deal with when online or offline. Infact we only have our pride to deal with, when something goes wrong and we get shotdown or whatever "we push our luck too much perhaps" do the same mistakes over and over again because, that damn plane should be much more superior than my counter part. Knowing your plane and applying tactics in the true spirit of the aircraft we are flying is a big part in how to survive - and survive! :)

Aces who survived the war do not talk alot about luck and if they do you can se the serious look in their face or grin/smile, that pushing your luck can go realy bad! They for sure know :) We all know alot about Hartmann and you can be damn sure he wasnt one who played with luck, the tactic he he used has alot about to do with survival and have a escape plan if needed (part of his tactic). Sticking our neck out is not about pushing your luck it`s about beeing in an environment that can get you killed if you dont know, what you are doing.

It scares me, when FM is put into focus, as you will never know if the goal is to adapt the plane to the player and not the other way around ;) Im saying this in a rather human and friendly way AND! not ment to bash anyone ;)

If I get any holes in my plane or bullets are directed at me it`s damn sure it`s my own fault simply because I pushed my luck to fare and getting into a situation that wasnt good for me and my plane.

jf1981 01-03-2012 05:02 PM

Quote:

Originally Posted by reflected (Post 364953)
Just now I shot up a Hurricane head on, then I started climbing away (I had E advantage) . I trimmed my E-3 perfectly, 2400 RPM, full throttle, climbing at 300 kph. By the time we were over France the Hurricane got within firing distance and shot me down.

What was I doing wrong? I obviously made a mistake, because the Hurricane was notorious for being slow, and sluggish, like a grand-piano with a Merlin.

Thanks in advance.

Hurri's vertical speed is quite good. Its top speed is'nt.

I've measured in actual state of CoD some 2600 ft/min and BF109 E3 700 m/min (2300 ft/min), therefore Hurri may catch you in a vertical climb at reduced speed.

How accurate the models are compared to reality, this needs to be checked and it might change.

TomcatViP 01-03-2012 07:10 PM

Actually it's completely normal. It's all about thick wings.

In a slow speed climb :
Thicker airfoil -> less AoA -> less drag - > higher climb rate for a given horizontal speed.

You need to spiral up to get away with the 109 or the hurri will catch you.

As a side note, Hurri with boost cut out can be slightly over modeled in certain situation. You need to be keep yourself alerted in that situation. Anyway if you are in the front sector of any opponents, it's time to have a close look at what you are doing ;)


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