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Author Topic: speed/altitude proper adjustement needed  (Read 5475 times)

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SAS~Storebror

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Re: speed/altitude proper adjustement needed
« Reply #12 on: March 20, 2015, 12:02:05 PM »

you did that first!?))
So that's a joke too I hope.

look at specs..p-40 is mess..
Third time you say the same thing and it still doesn't become true by repeating.
Even if you repeat the same thing a hundred times, the answer given to you before stays valid:
Answered before already, start reading and stop complaining:
current settings for p-40 are complete mess. they specified some brute force hack for engine just to make it flyable.
What? No.
Sounds like you're mistaking the fmd and emd parameters for precise resemblances of real life values?
Usual beginner mistake.

Best regards - Mike
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SAS~GJE52

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Re: speed/altitude proper adjustement needed
« Reply #13 on: March 20, 2015, 12:44:19 PM »


.................. you can lead a horse to water, but you cant make him drink.......  ;)


G;
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bomberkiller

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Re: speed/altitude proper adjustement needed
« Reply #14 on: March 20, 2015, 12:48:52 PM »

Quote
you can lead a horse to water, but you cant make him drink

Words of a wise man  :)
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yak

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Re: speed/altitude proper adjustement needed
« Reply #15 on: March 20, 2015, 02:51:13 PM »

"Third time you say the same thing and it still doesn't become true by repeating."
hear you are wrong!
post specs for p-40e and p-40m to prove your words.
i posted specs from latest buttons.
for p-40f,l,k setting are relatively fine. they use alternative merlin and allison p-40 file. but crafts also does not show their speed (TAS) at all altitudes.
old p-40b,c,e,m are mess!truth for forth time!
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BT~wasted

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Re: speed/altitude proper adjustement needed
« Reply #16 on: March 20, 2015, 03:53:38 PM »

then why you ask?  :)

Do it yourself and show us, how they should perform in your opinion  ;)
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yak

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Re: speed/altitude proper adjustement needed
« Reply #17 on: March 20, 2015, 03:59:58 PM »

exactly! 8)
do you know what happens if to set updated "allison_p40 family" engine on old p-40e? it shows speed close to real but climb goes high. unfortunately! takes less than 5min to climb at 5km...
as you see topic is actual speed/altitude/climb!
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BT~wasted

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Re: speed/altitude proper adjustement needed
« Reply #18 on: March 20, 2015, 04:28:38 PM »

Well did you thought about that fact that alot of people were working on those flight models and maybe they've made lots of tests and researches?

Just make your changes, upload here and people will test and give you feedback, so you will have more data to compare with. Plus you should try different maps and different versions of the game. Lots of factors influence flight model in IL-2. And not only engine horsepower will influence on how plane accelerates, climbs, or how fast it can go. Just keep in mind such values as Cy_0 and Cx_0 in .fmd file, also AoA drag and lift etc etc. Il-2 flight models are quite complex.

You better first try to understand how things work in IL-2. Book values in .emd or .fmd rather will give you wrong results, and you will be forced to test, test, and test again to get right values in order to make the plane perform right.
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SAS~Storebror

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Re: speed/altitude proper adjustement needed
« Reply #19 on: March 21, 2015, 01:41:54 AM »

"Third time you say the same thing and it still doesn't become true by repeating."
hear you are wrong!
post specs for p-40e and p-40m to prove your words.
i posted specs from latest buttons.
for p-40f,l,k setting are relatively fine. they use alternative merlin and allison p-40 file. but crafts also does not show their speed (TAS) at all altitudes.
old p-40b,c,e,m are mess!truth for forth time!
Holy cow...

Should I emboss it on your forehead?

The mistake you make is this:
You think "in real life the P-40E's Allison V-1710-39 engine produces 1150hp, so the corresponding line in IL-2's .emd file must read 'HorsePowers 1150'".

What I'm trying to tell you over and over and over again is that the IL-2 flightmodel files don't work that way.
Sometimes real life values give good figures, often they don't and you have to use different values to get the real life performance right.

So you did a new P-40 engine model to "fix" the top speed?
I gave prove to you already that there's nothing to fix. Apparently you simply failed to get the difference between IAS and TAS, that's all.
Now you've changed the emd to fix something that was right before, just to introduce a massive mess (5min climb to 5km) by doing so.
Great show.
You will have your reasons not to provide download links to your "improved" FMs.

Still I wish you good luck in convincing TD that their FM is "a mess", you know better and, give a f*ck for physics, IAS and TAS are all the same.
I'm sure they'll be happy to listen to your words.
I won't anymore.
You successfully ended up on my "troll" pile.

Best regards - Mike
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Herra Tohtori

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Re: speed/altitude proper adjustement needed
« Reply #20 on: March 21, 2015, 02:53:12 AM »

old p-40b,c,e,m are mess!




The irony is that you're actually right in stating that the "flight model is a mess"... from a certain point of view. It all depends on what criteria are used to evaluate that statement.



In an ideal case, a simulation of a physical thing should work like real world when you insert real life parametres into it.

But since simulators are always approximations, sometimes you need to fib things a little bit. Add some correction factors somewhere, adjust another properties elsewhere, and then the simulation looks like it's working right... which is actually the only thing that really matters to end user gameplay experience.



Looking at things from physics perspective, it actually does look awfully fishy that the aircraft requires such a high engine power value to achieve its performance specification.

For example, if you look at a simple physics simulation where a box with 100 kg weight is lifted to 1 metre of elevation in one second, that requires exactly the power of 981 W.

If the weight of the box is changed to, say, 1000 kg, then to achieve the same elevation in same time, the power must also be increased by 10 to 9800 W.

Now, the mass of the box could be set to any figure and there could always be a power level that results in same lift time, and if you make a video of it, it should look exactly the same in all cases.

But even though the simulation gives the same "lift time" performance in both cases and will look similar in that respect, the higher mass and higher power variants will have other differences in a more complex simulation. Increased inertia and moment of inertia come to mind first. If the object is lifted by a cable or rod, the tension or compression forces are much higher, leading to different amount of deformation, different resonant frequencies, different structural strength requirements etc.

And this is just a simple idealized situation where a device of some vague description lifts a weight to a prescribed elevation in a certain amount of time.


Increased amount of parametres leads to exponential rise in crosstalk effects between each of them. Adjusting one parametre may result in unwanted changes in the behaviour of the simulation elsewhere. Something like a flight model has a lot of parametres, and it is sometimes difficult to adjust them all so that you can insert "real world" values into something like engine power, and actually get correct visual results out of the simulation.


A proper evaluation of why the power needs to be set so high might be interesting, but it would require immense amount of testing and changing FM parametres one by one to see what effects each of them have.

Again from physics perspective, if an aircraft in a simulation requires too high power to reach its prescribed top speed, then it would suggest that the aircraft's drag parametres are set too high (which in itself could be caused by high drag coefficient, low lift coefficient, or high mass, to name a few possible reasons) or that the propeller's thrust efficiency ratio is too low (specifically at high speeds at the altitude you're testing at). That's just a conclusion from the fact that, at top speed (zero acceleration), the thrust and drag forces must be balanced and equal.


But unless you're interested in doing this as an academic exercise or self-flagellation of some kind, there is very little to be gained by actually doing it because the "fixed" flight model should retain almost exactly same flight characteristics and performance as the current flight model.


I would rather see modders and Team Daidalos use their talents for improving the game in a way that is apparent to us players.
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SAS~GJE52

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Re: speed/altitude proper adjustement needed
« Reply #21 on: March 21, 2015, 03:01:16 AM »

It never ceases to amaze me how people still confuse a $10 game with a $10,000,000 flight simulator.

So, as has already been suggested, if you are serious then put your new flight models up for download and let others, who have considerable practical experience concerning the difficulties of flight modelling, evaluate them.

Or in other words.... Be part of the solution, not the problem......  :)


G;
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greybeard

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Re: speed/altitude proper adjustement needed
« Reply #22 on: March 21, 2015, 04:04:59 AM »

It seems that everyone wants to be heard, but no one wants to hear ... is a shame, because I think everyone here has said some useful things, but have also shown the limits of his knowledge.

I would add my pros and cons, hoping that in the end we all learn something.

Samuelson, a professor at MIT and Nobel prize for economics, said that there aren't things true in theory but wrong in reality, there are only wrong theories! A flight model can't require fifty percent more power in reality than in theory. Power required is simply the product of air drag for speed (P = D x S); for a given speed, if P is too high, that means D is excessive.

It matters anyway of a scientifical matter, although reduced to basics (again Samuelson said that theory is reality, cleaned of useless details) and must be approached with principle of shareability: that's to say all people should be provided of all info and tools to reproduce test. Only in this condition errors (like neglecting difference between IAS and TAS) can be detected and corrected, sharing in the end the common thruth.

The alternative is a sterile and destructive fight of egos.
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Herra Tohtori

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Re: speed/altitude proper adjustement needed
« Reply #23 on: March 21, 2015, 05:16:00 AM »

A flight model can't require fifty percent more power in reality than in theory. Power required is simply the product of air drag for speed (P = D x S); for a given speed, if P is too high, that means D is excessive.

That's a bit dodgy. In that equation, "P" stands for the power of the thrust force (equal to drag at top speed) generated by the propeller, rather than engine power. This comes from the definition of work - when a force F acts on an object for a distance s, it does work W = F·s.

In one-dimensional analysis you can get rid of vector notation and handle all the quantities as scalars instead, which simplifies things.

Since power P = W/t and speed v = s/t, you can divide both halves of the equation W = F*s by time and end up with W/t = F * s/t which can be written as P = F * v (although I should note that there's a whole bunch of differentials I've omitted from here for clarity).

But you have to remember that this power describes the work done by a force, in this case the thrust force produced by the propeller. At top speed, this thrust force must be equal but opposite to drag, so it's not incorrect to write as drag, but I personally feel it obfuscates what is actually doing the work that you're measuring the power from. You can't directly translate that to engine power without knowing the propeller's efficiency at any given time. A propeller can never be perfectly efficient, and it depends on propeller's design, airspeed, RPM, pitch, and air density (at least).

Point being, the engine always produces more shaft power than the propeller can convert to thrust power. How much more, depends on the efficiency of the propeller. Should it be 66% or more? I don't know, I'm sure there are flight regimes where the efficiency can be even lower than that, but that would mostly be in the very low speeds or very high speeds (approaching transonic regime).


Like I wrote before: If an aircraft needs more engine power to reach its specified top speed than it should, it can mean two things. Either there's too much drag, or the propeller has bad efficiency and isn't producing enough thrust. Or a combination of the two.

If I had to guess I would be inclined to investigate the latter option first, because if the aircraft's drag coefficient was that much higher than it should, it should lead to poor lift/drag ratio which would noticeably affect the aircraft's non-powered glide performance. I don't recall ever noticing the P-40 to be in any way deficient in this respect, in comparison to other similar aircraft like the Bf 109F or Yak-1, so that would suggest the problem is in the way the engine power is translated into thrust.

But without testing, I wouldn't rely on that being the correct interpretation.
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