Spit/109 sea level speed comparisons in 1.08 beta patch

[ACE-OF-ACES]

Originally Posted by 5./JG27.Farber

Which from the minute amount of this information I followed before - I thought as much...

Shame.

Agreed

Originally Posted by 5./JG27.Farber

However hopefully we can come to some kind of accord and present the data to 1c:MG...

When it comes to calculating data.. I am sure 1C can do it as well if not better than any member of this forum.. The math is the math! The only time the math comes into question is when it does not match reality.. And in this case, where we have no reality to compare to, no one can say one way or the other how good the math is doing in simulating the aircraft.

Originally Posted by 5./JG27.Farber

This is the part where we must choose what I would call "Folklore" (eye witness accounts) and "facts" actual graphs... I don't see how you can truly have purely one or the other and I think this is where the real nitty gritty arguments break out...

Considering the fact that people can find a way to argue about the hard data (graphs) it is no wonder they can argue about the folklore.

Originally Posted by 5./JG27.Farber

So with an open mind I am finding myself more in the "feeling" group than the facts but with a balance of both.

The difference is the hard data (graphs) can be reviewed such as to minimize the errors..

Which is not the case with folklore!

There are just too many unknowns associated with the folklore to make it useful. Some people think they can do some statistically analysis of all the folklore and come up with some sort of consensus.. But it is just not the case.. Or should I say that in the past 20 years of flight simming, I have seen many make that claim, but no one has yet do pull it off.

Which is not surprising, in that we are NOT talking about gathering up folklore statements that somewhat agree..

For example, assume 3 WWII pilots said they could climb to 20kft in 9.2min, 10.2min, 9.8min.. And we say, hey that is great, we will just take the average of those three staments and call it good. NOPE! What we have is folklore that is many cases is 180 out! Fore example, there are WWII Spitfire pilots that said they could easily out turn or turn with a Bf109.. At the same time we have WWII Bf109 pilots who say they could easily out turn or turn with the Spitfire.

What do we do in that case?

Flip a coin?

I think not!

That is why most if not all folklore (pilot accounts, pilot action reports, etc) are so useless! In that they typically never provide enough information to even recreate the scenario in the game.

For example, a P51 pilot reports says he got behind a Bf109, closed in on it, and shot it down.

Ok..

Did he dive down from above to get on the 109s six? Or did he climb up to the Bf109? Or was he at co-alt and got in behind the 109? Did the 109 even know the P51 was behind him? Was the 109 pilot wounded and just trying to make it home, was the 109 engine damaged from a previous dog fight that just ended..

The list of un-knows is ENDLESS!

Which is why most if not all folklore is useless when it comes to tweaking the FM! IMHO your better off relying on the math and leaving it at that!

Long story short, typicall folkloare (pilot accounts and reports) tell us alot about the 'men' and thier 'tatics' but they tell us very little about the 'performance' of the planes.

Originally Posted by 5./JG27.Farber

We can have all the facts nailed on the head like ROC and TAS

Most but not all.. In that as I noted above, even with hard data like graphs, there are some unknowns associated with it that can cast doubt on the data..

The funny ones are the folks with double standards that will cast doubt on a test of a plane they don't like but at the same time accept lesser data for the planes they love as proof positive! It would be funny if it was not so sad!

Originally Posted by 5./JG27.Farber

but as you say we are still guessing the rest which is where "folklore" fills the gap...

Disagree

There may be a handful of folklore accounts that are 'useful'

But as noted above, most if not all folklore is useless!

Just to many unknowns!

Not to mention the fact that most if not all pilot reports are ONE SIDED STORIES!

That and they typicall dont include enough info to re-produce the scenario in the game to see if the plane the pilot was flying can do what he said, let alone the fact that we have absolutely no idea of what the state of the other plane and pilot was!

Originally Posted by 5./JG27.Farber

However then we are down to the spit always out turns the 109 and vice versa... - from pilot accounts...

Bingo!

Originally Posted by 5./JG27.Farber

So, its a mine field...

Should we try to get 1c:MG nail the "fact" figures as close as possible and then the "pilot account" things like turn and roll?

No not in my honest opinion, best to rely on the math when there is no real world data to compare to

Originally Posted by 5./JG27.Farber

This is my first forray into a FM debate... So forgive the open mindedness and lack of direction.

No worries!

[swift]

The results of a calculation (what you call maths) is only as good as its data. Also there are equations and equations. Some are highly approxamtive and only thump rules for quick estimates, others may be closer to reality but also very complicated and requiring a lot of divers input data.

I would agree to use mathematical relationships to deduce aircraft behaviour if we had enough reliable data or data at all for input into the equation and some reliable data to verify the results.

My guess is the data we would need to calculate it is not available. I mean what would be great if we had all the aerodynamic coefficients as a function of Mach number and angle of attack and the corresponding reference area for each plane.

"Equations" deducing turn performance from the wing loading, sorry, this is far from anything near accurate. I would not like to have the fm built on this kind of thump rules. Then I'd rather prefer anecdotical evidence.

[5./JG27.Farber]

AoA, you seem to agree with what I thought before... Folklore is fairly useless except from that particular pilots expericence... and the maths and graphs is what counts...

I am interested in what swift has to say... He makes good points.

In these days, is there surely not computer models that could aid us? - as for 1c:MG doing the maths... they are surley not doing quite a good job?


I state somethings in argument... Like do we use the folklore, maths or combination? I agree with your statement on folklore... Adrenaline, fear and rapid actions can distort the memory... Unless it can be proved just by maths what else can you do?!

[ACE-OF-ACES]

Originally Posted by 5./JG27.Farber

Unless it can be proved just by maths what else can you do?!

In many cases all we have is math to fill in the blanks.. Sad but true!

[5./JG27.Farber]

Originally Posted by ACE-OF-ACES

In many cases all we have is math to fill in the blanks.. Sad but true!

Well this is a proactive thread so get cracking and then show us some results!

[SlipBall]

Originally Posted by 5./JG27.Farber

Well this is a proactive thread so get cracking and then show us some results!

AoA will need some direction and study material...first link Spitfire study 1941

http://ntrs.nasa.gov/search.jsp?R=19...re%2520lateral

http://ntrs.nasa.gov/search.jsp?R=19...e%2520spitfire

http://www.bing.com/search?q=+NATION...ox&FORM=IE8SRC

[ACE-OF-ACES]

Originally Posted by swift

The results of a calculation (what you call maths) is only as good as its data.

Correction..

The 6DOF math (what you call thumb rules) is more than adequate to simulate flight!

And the 'data' that the 6DOF math uses has nothing to do with any of the real world performance data (ROC, TSPA, etc). The 'data' the 6DOF math uses is coefficients only. That is to say the 6DOF math for a P51 is the same as that for a Bf109, what makes a P51 a P51 is the coefficients loaded into the 6DOF equation. That is to say, no where do you 'load' say the ROC or TSPA values from a WWII performance test.

The only time you make use of the WWII performance data is in the validation of the 'outputs' of the 6DOF math and the corsponding coefficients selected.

That is to say the math never changes, only the coefficients.

Basically they can get a good set of coefficients to use based off the geometry of the plane (CL, CD, mass, wing loading, etc). Than they 'tweak' the coefficients until the outputs of the equations match the real world data. As part of all this the power plant (engine) is also simulated and is one of the inputs to the 6DOF (thrust) equation.

Originally Posted by swift

Also there are equations and equations. Some are highly approxamtive and only thump rules for quick estimates, others may be closer to reality but also very complicated and requiring a lot of divers input data.

The more complicated versions were an issue back in the early 90s.. Where games like AOTP made use of fixed point math, in that the floating point processors were just not fast enough to do the complex calculations in real time. Mater of fact back then they were even limited to a 3DOF flight model, but than around 1995 a flight sim called Pacific Air War 1942 came out, that was one of if not the first PC flight sim to implement a 6DOF flight model, it still used fixed point math. These days there is no need for fixed point math and thus no need to use the simplified versions of the 6DOF flight model equations.

Originally Posted by swift

I would agree to use mathematical relationships to deduce aircraft behaviour if we had enough reliable data or data at all for input into the equation and some reliable data to verify the results.

Who wouldn't?

Originally Posted by swift

My guess is the data we would need to calculate it is not available.

Depends on which data your referring too.. As noted above, a good estimate of the 6DOF coefficients can be derived from the planes geometry. Actually the hard part to simulate is the engine! In that many of those records do not exist and no good way to derive them from looking at the dementions of the engine.

Originally Posted by swift

I mean what would be great if we had all the aerodynamic coefficients as a function of Mach number and angle of attack and the corresponding reference area for each plane.

As noted above, if they have enough info to draw the plane in 3D, then they have enough info to derive many if not all the coefficients for the 6DOF FM.. What is lacking in the power plant info (thrust)

Originally Posted by swift

"Equations" deducing turn performance from the wing loading, sorry, this is far from anything near accurate.

Disagree 100%

Originally Posted by swift

I would not like to have the fm built on this kind of thump rules. Then I'd rather prefer anecdotical evidence.

To each his own than

[swift]

Originally Posted by ACE-OF-ACES

Correction..

The 6DOF math (what you call thumb rules) is more than adequate to simulate flight!

And the 'data' that the 6DOF math uses has nothing to do with any of the real world performance data (ROC, TSPA, etc). The 'data' the 6DOF math uses is coefficients only. That is to say the 6DOF math for a P51 is the same as that for a Bf109, what makes a P51 a P51 is the coefficients loaded into the 6DOF equation. That is to say, no where do you 'load' say the ROC or TSPA values from a WWII performance test.

The only time you make use of the WWII performance data is in the validation of the 'outputs' of the 6DOF math and the corsponding coefficients selected.

That is to say the math never changes, only the coefficients.

Basically they can get a good set of coefficients to use based off the geometry of the plane (CL, CD, mass, wing loading, etc). Than they 'tweak' the coefficients until the outputs of the equations match the real world data. As part of all this the power plant (engine) is also simulated and is one of the inputs to the 6DOF (thrust) equation.


The more complicated versions were an issue back in the early 90s.. Where games like AOTP made use of fixed point math, in that the floating point processors were just not fast enough to do the complex calculations in real time. Mater of fact back then they were even limited to a 3DOF flight model, but than around 1995 a flight sim called Pacific Air War 1942 came out, that was one of if not the first PC flight sim to implement a 6DOF flight model, it still used fixed point math. These days there is no need for fixed point math and thus no need to use the simplified versions of the 6DOF flight model equations.


Who wouldn't?


Depends on which data your referring too.. As noted above, a good estimate of the 6DOF coefficients can be derived from the planes geometry. Actually the hard part to simulate is the engine! In that many of those records do not exist and no good way to derive them from looking at the dementions of the engine.


As noted above, if they have enough info to draw the plane in 3D, then they have enough info to derive many if not all the coefficients for the 6DOF FM.. What is lacking in the power plant info (thrust)


Disagree 100%


To each his own than

My point is that you will have difficulties to derive reliable coefficients and you seem to agree on this. I do know a little about flight mechanics and trajectory computation (where the 6dof equations intervene) and about coefficient determinations (it is my daily business).

At work we frequently use a simplified tool to calculate the aerodynamic coefficients for subsonic and transsonic flight conditions and I can tell you I would not trust them for applications such as CoD. We use them for different applications where the impact is minor so we can live with it. But CoD would rely heavily on these coefficients and I'd say to obtain something that is halfway close to reality such a tool is not sufficient. And from experts working for years in the aerospace business using modern and highly sophisticated cfd tools I know that using these methods for subsonic regions is far from trivial. And it would take hours to days to calculate just one flight point for one configuration and probably would take longer if one would take into account the viscious terms instead of relying on simplified Euler calculations.

But what we need in CoD does not stop at the determination of lift, drag and lateral force coefficients and the moment coefficients about the three axis. We also need the derivate coefficients to obtain a believable flight model. Up to now the means with which these are "determined" is more than crude and very little reliable.

This gets even more complicated when one considers that each flap, rudder and aileron movement will have an impact on the aerodynamic coefficients (the 6 static coefficients and the derivates). You'd need a database set for several flap, rudder and aileron deflection combination. Then we have the trimmed and untrimmed flight conditions and other aerodynamic control surfaces such as flaps and airbrakes. Now let's talk about canopy open or closed and radiator and oil cooler openings ...

And these are just the coefficients for the airframe. We'd also need reliable data for the propulsion set.

I really do not believe in being able to obtain a full AEDB that will result in a flight performance that will be close to the real thing anyway, provided we even know where the real thing was. I think it is smarter to take the bottom up approach by tweaking the used coefficients in such a way that they fit to the experienced behaviour including test results and, where values are missing, to anecdotical evidence as long as there is a bunch of anecdotes saying the same.

BTW: CoD is definitely using 6dof. What we are disputing is how they come up with the forces and moments they inject into the 6dof equations.

[David198502]

Originally Posted by swift

My point is that you will have difficulties to derive reliable coefficients and you seem to agree on this. I do know a little about flight mechanics and trajectory computation (where the 6dof equations intervene) and about coefficient determinations (it is my daily business).

At work we frequently use a simplified tool to calculate the aerodynamic coefficients for subsonic and transsonic flight conditions and I can tell you I would not trust them for applications such as CoD. We use them for different applications where the impact is minor so we can live with it. But CoD would rely heavily on these coefficients and I'd say to obtain something that is halfway close to reality such a tool is not sufficient. And from experts working for years in the aerospace business using modern and highly sophisticated cfd tools I know that using these methods for subsonic regions is far from trivial. And it would take hours to days to calculate just one flight point for one configuration and probably would take longer if one would take into account the viscious terms instead of relying on simplified Euler calculations.

But what we need in CoD does not stop at the determination of lift, drag and lateral force coefficients and the moment coefficients about the three axis. We also need the derivate coefficients to obtain a believable flight model. Up to now the means with which these are "determined" is more than crude and very little reliable.

This gets even more complicated when one considers that each flap, rudder and aileron movement will have an impact on the aerodynamic coefficients (the 6 static coefficients and the derivates). You'd need a database set for several flap, rudder and aileron deflection combination. Then we have the trimmed and untrimmed flight conditions and other aerodynamic control surfaces such as flaps and airbrakes. Now let's talk about canopy open or closed and radiator and oil cooler openings ...

And these are just the coefficients for the airframe. We'd also need reliable data for the propulsion set.

I really do not believe in being able to obtain a full AEDB that will result in a flight performance that will be close to the real thing anyway, provided we even know where the real thing was. I think it is smarter to take the bottom up approach by tweaking the used coefficients in such a way that they fit to the experienced behaviour including test results and, where values are missing, to anecdotical evidence as long as there is a bunch of anecdotes saying the same.

BTW: CoD is definitely using 6dof. What we are disputing is how they come up with the forces and moments they inject into the 6dof equations.

really good thread so far, and very good and interesting post!

[ACE-OF-ACES]

Originally Posted by swift

My point is that you will have difficulties to derive reliable coefficients and you seem to agree on this.

Key word being reliable..

Now ask yourself..

How do you prove to yourself they are reliable?

Answer is you compare the results (outputs, such as tas, roc, roll-rates, turn rates, etc) of the 6DOF using these coefficients to the real world data..

Which is pretty easy to do when you have the real world data!

But what do you do when you don't have any real world data?

You guess it.. You rely on, aka trust, the math!

That is my point

That being we do NOT have real world data on each aspect of the WWII plane.. So unless we come up with a time machine, we are going to have to rely on calculated results (the math) for not only simulation but validation.

Originally Posted by swift

I do know a little about flight mechanics and trajectory computation (where the 6dof equations intervene) and about coefficient determinations (it is my daily business).

You too? Here as WSMR we use a lot of trajectory math to calculate the launch to impact site of the missiles we test here. We also have our own flight simulation software that we call RAGE

http://www.csc.com/public_sector/suc...tual_landscape

I work with the guy who wrote that software on a daily bases.. I also write plug-ins for RAGE but he is the true gu-roo of the software. All in all a great job, on my way to work I may see anything from a F22 to a UAV fly by at tree top level (landing or taking off from holloman).. It can be dangerous sometimes.. In that I am always looking up in the blue instead of looking forward at the road!

Originally Posted by swift

At work we frequently use a simplified tool to calculate the aerodynamic coefficients for subsonic and transsonic flight conditions and I can tell you I would not trust them for applications such as CoD. We use them for different applications where the impact is minor so we can live with it. But CoD would rely heavily on these coefficients and I'd say to obtain something that is halfway close to reality such a tool is not sufficient.

Well than I guess we will have to agree to disagree on that point

Originally Posted by swift

And from experts working for years in the aerospace business using modern and highly sophisticated cfd tools I know that using these methods for subsonic regions is far from trivial. And it would take hours to days to calculate just one flight point for one configuration

Note I never said it was easy or trivial.. My only point is it is doable! Many have for many years now.

Originally Posted by swift

and probably would take longer if one would take into account the viscious terms instead of relying on simplified Euler calculations.

I know of only one PC flight sim that implemented a real-time computational fluid dynamics flight model (what you call 'viscious') and that was FLIGHT Unlimited

http://en.wikipedia.org/wiki/Flight_Unlimited

It was done back in 1995.. And was not only overkill IMHO but too much for the PCs of that time. Maybe even today, I don't know in that not many make use of it in that the 6DOF (what you call simple euler) has proven itself to be more than adequate for military applications, thus more than adequate for PC games IMHO.

Originally Posted by swift

But what we need in CoD does not stop at the determination of lift, drag and lateral force coefficients and the moment coefficients about the three axis. We also need the derivate coefficients to obtain a believable flight model.

Key word being believable..

Now ask yourself..

How do you prove to yourself they are believable?

Answer is you compare the results (outputs, such as tas, roc, roll-rates, turn rates, etc) of the 6DOF using these coefficients to the real world data..

Which is pretty easy to do when you have the real world data!

But what do you do when you don't have any real world data?

You guess it.. You rely on, aka trust, the math!

That is my point

That being we do NOT have real world data on each aspect of the WWII plane.. So unless we come up with a time machine, we are going to have to rely on calculated results (the math) for not only simulation but validation.

Originally Posted by swift

Up to now the means with which these are "determined" is more than crude and very little reliable.

Well than I guess we will have to agree to disagree on that point

Originally Posted by swift

This gets even more complicated when one considers that each flap, rudder and aileron movement will have an impact on the aerodynamic coefficients (the 6 static coefficients and the derivates). You'd need a database set for several flap, rudder and aileron deflection combination. Then we have the trimmed and untrimmed flight conditions and other aerodynamic control surfaces such as flaps and airbrakes.

Which has all been done before and done for years!

Originally Posted by swift

Now let's talk about canopy open or closed and radiator and oil cooler openings ...

Better yet..

To drive my point home..

Let talk about you going out and finding the real world test data for each plane in the game of the 'effects' of the canopy open vs. the canopy closed on each aspect of the plane (tas, roc, roll-rate, turn-rate, etc)

Allow me to spare you that effort!

In that you wont find such data!

Thus, back to square one of my point

You will have to trust the math and how it says the canopy open vs. closed will 'affect' the flight

Oh sure you may find some anecdotical evidence for some of the planes.. For example we have all read the stories.. Like the Me262 that was stuck in a high speed dive, until the pilot popped the canopy and started to bail out, at which point he noticed that popping the canopy 'changed something' such that he was able to regain control, and thus didn't bail out. What is not 'clear' about such stories is the parameters to re-create that scenario in the game to see (validate) the flight model. For example..

What was his altitude when he popped the canopy?
What was his speed when he popped the canopy?
What was his dive angel when he popped the canopy?
What was his flap setting when he popped the canopy?
What was his trim setting when he popped the canopy?

The list goes on and that is only for the point in time of when he popped the canopy..

So all we know from that story is that 'something' changed.. For all we know his plane was slowing down and the popping of the canopy had NOTHING to do with it.. It could have just been a coincidence that he popped the canopy at the same time the plane had slowed down enough that he was able to regain control

Originally Posted by swift

And these are just the coefficients for the airframe. We'd also need reliable data for the propulsion set.

Ah, glad to see you agree with what I said in my last post!

So not all is lost, in that we can agree on some things!

Originally Posted by swift

I really do not believe in being able to obtain a full AEDB that will result in a flight performance that will be close to the real thing anyway, provided we even know where the real thing was.

Bingo!

So do we give up?

Or do we trust the math and move on?

Originally Posted by swift

I think it is smarter to take the bottom up approach by tweaking the used coefficients in such a way that they fit to the experienced behaviour including test results and, where values are missing, to anecdotical evidence as long as there is a bunch of anecdotes saying the same.

Which is exactly what I was saying minus the anecdotical evidence (aka pilot combat reports)

Just too many variables involved to make most if not all anecdotical evidence useful

As I noted early on

Many 'feel' the can derive some sort of statistical average of the anecdotical evidence.. Many have tried, all have failed! Which is not surprising when you consider the fact that the anecdotical evidence is not something that varies a 'little' As in one reports says the top speed is 305, another say 307, and another says 302, and another say 310. If that was the case it would be a simple mater of taking the average and calling it good! But that is not the case for anecdotical evidence, what we have there is Spitfire pilots saying they could out turn 109s and 109 pilots saying they could out turn Spitfires. So based on that it is not surprising that those who have tried have failed.

Originally Posted by swift

BTW: CoD is definitely using 6dof.

Ah, glad to see you agree with what I said in my last post!

So not all is lost, in that we can agree on some things!

Originally Posted by swift

What we are disputing is how they come up with the forces and moments they inject into the 6dof equations.

No, we know how they come up with them.. What we are disputing IMHO is how they validate the flight model.. For the aspects of which we have no real world test data to use in the validation. In such situations I am saying we have to trust the math to fill in the blanks, where as your saying we should use anecdotical evidence to fill in the blanks..

In summary

I put more faith in the 6DOF math than you do
You put more faith in anecdotical evidence than I do

Other than that I think we agree