109 advice needed (climb)

[ACE-OF-ACES]

Originally Posted by CaptainDoggles

Guys the flight models are an approximation. Even the best gaming PC money can buy could not model the exact equations behind flight fast enough to run at playable speeds.

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?

[CaptainDoggles]

Originally Posted by ACE-OF-ACES

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]

Originally Posted by CaptainDoggles

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]

Originally Posted by CaptainDoggles

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

Originally Posted by CaptainDoggles

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

Originally Posted by CaptainDoggles

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

Originally Posted by CaptainDoggles

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

Originally Posted by CaptainDoggles

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

Originally Posted by CaptainDoggles

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]

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

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

[ACE-OF-ACES]

Originally Posted by TomcatViP

it's very good comments Ace.

S!

Originally Posted by TomcatViP

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

Originally Posted by TomcatViP

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

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

Agreed!

[CaptainDoggles]

Originally Posted by ACE-OF-ACES

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.

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?

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.

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]

Originally Posted by CaptainDoggles

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

Ok lets re-read it..

Originally Posted by CaptainDoggles

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

Originally Posted by CaptainDoggles

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?

Originally Posted by CaptainDoggles

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?

Originally Posted by CaptainDoggles

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?