Hi all!:)

Jeremiah: I am an experienced engineer also, but that is not relevant here. However, since we have the same profession, we certainly must share the basic concepts about Mathematical Calculation.

1) The calculation rules are rigid and do not allow exceptions.

2) It is not allowed to transform arbitrarily an absolute amount into another relative: for such a transformation to be valid, the absolute amount must be refered to another which can be considered as a basis or reference in a consistent manner.

Thus, you are not free to transform "4850 meters" into "0.0485 p.u." (or "4.85%"), because always you will must answer the immediate question: "0.0485 p.u. (or 4.85%) of WHAT?"

And, why are you using a chart which returns TAS for (roughly) 25 ºC @MSL, with a map of 15 ºC @MSL? :confused:

If you are looking for a good method to find the in-game IAS/TAS relationships with any map, I could suggest you to fly a B-25J: it has IAS/TAS and OAT gauges, and altimeter. These three instruments are all you would need to see differences and matches of TAS for different altitudes and thermal conditions. This aircraft perfectly could serve as the control case for your research.

Waht the wiki's article shows about E-6B are the equations to solve the 'triangle of speeds' in order to find Ground Speed and True Heading when there is any wind. Those equations may be solved mathematically (applying the Theorem of the Sins), or geometrically (drawing the vectors of a/c's and wind's speeds in a given scale, and then measuring the modulus of the resulting vector with a ruler, and the angles with a protractor).
The back side of the E6-B returns GS and TH in few seconds, solving the triangle of speeds in only two steps, and avoiding to use complicated equations.

The front side of the wizz wheel is designed to obtain TAS from IAS (among many other calculations), regarding of the OAT and altitude, in one step and no need to solve all and each of the ISA equations.

Perhaps it's needed to define what the E6-B really is: It is an Analog 'Flight Computer'.
An Analog Computer (it is not the matter if it is an electronic or mechanical analog computer) is programmed by hardware. Therefore, it can only do that for which it was designed and built, and it must be considered a "specialized" tool.
The E6-B basically is a circular slide ruller, but specially designed to perform flight calculations in the easiest and fastest manner as possible.

Of course, today we can find apps like 'Pilotwizz' (this is only for iPhone), or 'FlightTools E6-B' (it is for Android and iPhone). But the usage of a smartphone or a programmable calculator while I'm flying an IL-4 over Eastern Prussia in 1944, is not realistic (and therefore funny) for my taste.:)

Mate: I've been testing all sort of bombers, maps (my lattest tests were performed just with both Finland maps), and winds. The result is expressed in the charts I've attached to the post #30.
I've achieved accurate hits using manual targeting & drops.

I don't think that TD have taken such "special liberties" with Physics. If they were done something like that, it should affect in-game all what is related with the flight, in the same way: take-off, landing, cruising... and level bombing.
But if you hit the Autopilot during one of your bombing missions, and then watch how the AI does the task, you will see it is not able to perform a decent level bombing, even an AI pilot with the best skills.

IMHO, many improvements were introduced since the 4.09 patch until today: FM, beacons, temperatures, winds... And it seems something was missed or forgotten about level bombing and bombsights, along the patches.
The fact is neither the Norden/Lofte type BS nor the OKPB-1 type work as it is supposed to do... as if they were uncalibrated.:rolleyes:

Thus, IMO, if I must do calculations by myself to get certain accuracy, then I prefere to calculate directly the BS elevation angle for manual drop, instead of calculating how to compensate for a poorly calibrated automatic bombsight.


As I said earlier, and as I've said in every post of this thread, I've tested many maps, with all the actual level bombers, at diffeerent altitudes. Taking in account the historical accuracy of pin-point high level bombing during the WW2 (less than 20% of bombs fell on their intended targets along the war), I've obtained a more than acceptable accuracy, always using manual targeting.
The most of data for my calculations were gathered in-game: altitude, IAS, heading, OAT. And, with the B-25J, the TAS was read, not calculated.

My tests included:
1) The lapse rate of OAT measured with different OAT gauges (The ISA model was confirmed in-game for all the tested maps).

2) The TAS regarding OAT and altitude (This was calculated with the E6-B and with the ISA equations, and measured with the TAS gauges of Me-262 and B-25J. Measurements match calculations, for different maps).

3) The accuracy of level bombing using manual targeting, in differents maps with all the bombers, but with no wind.

4) The accuracy of level bombing using manual targeting, in differents maps with all the bombers, but with winds: tail wind, nose wind, cross wind, any wind direction and any wind speed. (This confirms: the need of to calculate the Ground Speed and True Heading to mantain the True Course approaching to the target; the need of to use the + or - side slip angle of the bombsight to compensate the angle between True Course and True Heading; if not, the bomb will fall far from the target confirming the effect of the cross wind on the free fall bombs. True Heading, Ground Speed and Compensation Angle were calculated with the back side of the E6-B).

The atmosphere now is better mdeled, but humidity and true altitude are not included (by now). Anyway the atmospheric model involves the aircrafts' behavior: take-off, landing, flight, engines heating and endurance, max payload, speed, fuel consumption, trimming, altitude to engage/disengage superchargers, altitude to change the air/fuel mix... and a long etc.:cool:

Would you like to see one more test with the Gulf of Finland_summer map, anyway?
OK: when I return home next week, I'll do that test, and then I'll try to do a .ntrk to show how accurate may be the manual targeting.:cool:

Hello Soldier_Fortune,

I am trying to find the formula IL2 uses for TAS calculation.

I spent the whole morning searching and reading the web and so far I can calculate temperature, pressure and density at the altitude, but I found no equation which would plug these to the TAS calculation.
(They always included other factors which circularly used TAS for their calculation)

Based on you example:

I suppose you have the ISA equation for TAS handy?
Would you be so kind and share it?

Hi FrankB. :)

Yes: I use ISA for all my above calculations, because the E6-B Flight Computer is based on that standard and, as far as I can see, also the atmosphere model in IL2 is based on ISA.

The equation to calculate manually TAS is:

TAS = IAS* SQRT(AD@MSL / AD_ALT) [1]

Where:

AD@MSL: Air Density @ MSL = 1.225 kg/m3
AD_ALT: Air Density at a given altitude

Surely already you've found the AD_ALT equation. But if not, that is:

AD_ALT = AD@MSL* [(Tmap - ALT*0.0065)/Tmap]^4.25 [2]

Where Tmap is the outside air temperature @MSL of the chosen map.

If you combine both equations, you can calculate TAS directly as an E6-B does it:

TAS = IAS*[Tmap / (Tmap - ALT*0.0065)]^2.125 [3]

WARNING:All the above temperatures are expressed in Kelvin (ºK = ºC + 273), and altitudes in meters. If you prefer to use feet for altitude, then you must change 0.0065 for 0.002 in all the above equations.

The eq. [3] clearly shows the link among TAS, IAS, actual altitude, and OAT at such altitude.
Being (Tmap - ALT*0.0065) the OAT at a given altitude, the eq. [3] allows you to calculate TAS directly with your altitude, speed and OAT gauges readings. And the best is that you can use any speed units: km/h, m/sec, MPH or knots, without a previous conversion. :cool:

I.e: The "Betty's" altimeter returns the altitude in meters but the IAS is read in knots (the G4M1-11 has an OAT gauge but it doesn't work; therefore you must calculate OAT by yourself... but you know how to do it.:D).
No problem: use altitude and IAS into eq. [3] as you read them..!:cool:

I hope this help you. Anyway, don't hesitate to ask me. :wink:

Thanks Soldier, you are da man!.

The math is quite simple once you have the missing link, which, for me was your equation [1].

Reviewing my research I saw the equation before, but

1. In a different form: TAS = EAS*SQRT(AD@MSL / AD_ALT) and then the definition of EAS introduced dynamic pressure or Mach number and I never got results at least close to yours.
2. With a remark it is valid only for low-speed flight (~0.3 Mach)

Hi again!:grin:

Your remarks are right: at low speeds the difference between EAS and IAS is negligible.
For TAS close to the sound speed the equation is quite different and a bit more complex.
Always you can check your TAS calculations with the in-game TAS for a given map and any altitude, flying a Me-262 or a B-25J. :wink:

Just FYI.............
After some more thought, I realized that bomb flight paths could be manipulated during flight between aircraft and target, and any manipulation could therefore remain unnoticed. I realized that rather than having several planes try to drop at the same time, just use a stopwatch and time the drop from plane to target from altitude. Any falling object, so long as no other force like drag or thrust is acting on it, will follow set rules...rules set by classical mechanics.

I dropped several bombs from altitude and the results were interesting. For instance, a 1000kg bomb (with zero delay) dropped from an IL-4 at 7650 meters took 41.77 seconds to impact. It should have only taken 39.49 seconds. Another drop from the same plane with the same bomb, but at 7850 meters, took 42.38 seconds to impact. It should have only taken 40.01 seconds. Other drops from other aircraft using different types of bombs resulted in very similar results. All time-of-flights from this altitude took 2+ seconds longer than would be expected.

Other drops from other planes at lower altitudes achieved similar results, with all drops taking longer than expected. A drop from a Ju88 at 4820m took 32.74 seconds and it should have only taken 31.35 seconds. A drop from a B5N2 at 4950m took 32.58 seconds and it should have only taken 31.77 seconds. Another drop from a B5N2 from 4890m took 32.39 seconds and it should have only taken 31.57 seconds.

Conclusion: YES...flight paths from bombs ARE being manipulated in IL-2 and are NOT following the rules of classical mechanics.

What I tested seems correct then JW :(

ok.........

I found this not sure how applicable/correct it is and might explain what TD have done.

"v= v(initial) + at works in a vacuum in which WWII bomber did not fly. v=obviously velocity. a= acceleration

D= 1/2 CpAv^2 Where C=Drag Coefficient, p= rho=air density, A=crossectional area v= obviously velocity.

However at some some value of v Drag will equal mg this point is called terminal velocity. m=mass, g=gravity

so, 1/2CpAv^2 = mg

v= (2mg/CpA)^(-1/2)

This is only a rough formula to calculate the terminal velocity of the bomb because aerodynamics get very complicated, but this should get you somewhat close.
All you need is the mass of the object, gravity which is 9.8 m/s^2, the drag coefficient,
air density at the point that you want to know presumably fairly close to sea level, and the cross sectional area."


Might be rubbish.............


Chart monkeys apply within :)





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Hi J_W!:smile:

May be you have discovered a more elemental game's feature: the in-game's time would pass more slowly than IRL.

Don't worry: this has nothing to do with Stephen Hawking or the Theory of the Relativity. :mrgreen:

But there would be some practical reasons for such delay.
In any case, we should apply the following basic rules of thumb:

- Never use other than a sim's in-game clock to measure their internal times.
- Never use other than a sim's in-game ruler to measure their internal distances.
- Never use other than a sim's in-game protractor to measure their internal angles.
- Never use other than a sim's in-game guages to measure their internal magnitudes and quantities.

Because a sim is an approximate model of a part of Reality, but it is not Reality.

In order to the above, before making a jugdment about whether the bombs' flight path are being internally manipulated or not, we should check if the game's clocks are sinchronized with those of the real world or not.

The delays you've observed are +6% over the calculated theoretical time, and that percentage remains almost constant regardless of the altitude.
That means adding 0.06 s (or 60 ms) every elapsed second. It's like as if an in-game electromagnetic wave of 60 Hz was seen as a wave of 13 Hz IRL.
And the same could be applied to every physical magnitude within the sim... if the developers have decided to apply it.

It is easier to establish an intencional delay (for whatever technical reason), than to introduce specific constants which in turn depend of certain conditions. The last demands many more calculations and resources, and it's more difficult to tune: this would be the case for such "bombs' path manipulation".
But the time must be the same for each "universe", and it would be easier to handle for a "fine tunning of the IL-2 universe" by their developers.

I would like to do an experiment about your data, but I can't come home yet. Thus I'll beg you to do the following test, please:

1) Design any bomb mission, and place a static camera near to the target.

2) You must use the onboard clock (instead an external stop watch) to measure the time it takes for the bomb to hit the ground (the He-111 would be a good choice: this aircraft has a clock just in front on the player offering them a complete and clear view of it. This clock counts seconds).

3) Play the mission. Drop your bomb when you're ready, and immediately pause the game.

4) Read the drop instant with the aircraft's clock, and hit the "camera view", and gather all the in-flight data with the gauges (not the speedbar): altitude, IAS, OATs, variometer, how much elevator trim is applied if the autolevel is engaged.

5) Unpause the game and be ready to pause the game again when the bomb hits the ground.

6) Jump to the cockpit and read the clock again.

7) The difference between the two readings is the bomb's flying time within the IL2 universe.

With the onboard clock you cannot measure times shorter than 1 second; but it should be sufficient to measure differences of 2 seconds.

Other experiment might be to measure a longer lapse (i.e.: 2 or 3 minutes) simultneously with both the aircraft clock and your stop watch, to see how long is that "IL2 universe" lapse when it is compared with the RL.

It's not relevant if that time matches or not the RL time, while all the other variables are consistent with that. If that consistency was verified, the Mechanical Laws would remain applicable within IL2.

But if not... Then I should review all my calculations to find why the laws of Classical Mechanics seems to work well for manual targeting. :rolleyes:

Please: if you carry on such experiment, let me know your data, outcomes and what map you've used. ;)

Hi KG.:)

That equations are interesting. But as far I could see, drag is not included into the bombs' FM.

I've tested all sort of bombs (German, Russian, Japanese and American) in my level bombing tests, with masses ranging from 60 up to 2000 kg; and I didn't see drag effects.

Basically the manual targeting is a BS Elevation Angle calculation using the classical equations for parabolic motion, and utimately that depends of the falling time. If there would be a different drag effect for every bomb's weight and shape (like it is IRL), such BS Elevation Angle should be dependent of the bomb type, and therefore it would be different for each one. But it is not the case.
And, of course, I used the classical equations for parabolic motion you've posted several posts above.

What I observed is the wind effect over the free fall weapons. But all bombs are affected in same way. And this should be sufficient to guess that we've a simple and newtonian FM for all bombs in IL-2, with the crosswind component (when it exists) as the only force vectorially combined with vertical and horizontal velocities acting on a bomb, and determining its path. ;-)

That does not explain the inconsistency with bombs falling long or short when the correct inputs are made into the bombsites.

Whats is consistent is the above happening on all maps at different OAT's alts and speeds, the Russian bombs fall long and the German fall short.

This can only mean that there is a different non real world calculation for the bombs in IL2 1946.





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