True Altitude?

[Soldier_Fortune]

Good morning.

I've made and attached below a set of 4 printable Manual Targeting Charts. The Readme into the .zip file explains how to use them.

The cons of these charts: they must be used together with an E6-B Flight Computer.
The pros: they are printable and can be used in-flight.

It is very easy to learn how to use an E6-B, and really it is a cool and useful tool... specially if you like to fly without waipoints.
IMHO, Il2 linked to a combo of printed maps and charts, an E6-B, a plotter and a pencil, is the more realistic and historical approximation to the work that made the airmen in the 40's... for pre-flight planning and navigation, at least.
The price of an E6-B ranges from about 15 up to 50 U$D, regarding of its material (metal, plastic fiber or paperboard) and its trademark, and it can be purchased in aviation stores and online.

But perhaps many players would prefere a "digital age" solution instead of the proposed "old analog age" method.
Yesterday I found this thread in the Warbirds of Prey forum, containing a very complete calculator for manual targeting. It does all what we were talking about in this treath in a very fast way.
I used it to compare the BS Elevation Angles obtained with my charts against those obtained with this calculator: within the desirable accuracy limits, the differences are negligible.

The pros of this calculator: very easy to use and the user doesn't need to learn nothing.
The cons: it is an online calculator and therefore it can not be used inflight; the player must pause and minimize the game and then open the calculator.

Well... Now the level bombing fans have two different methods to perform manual targetings. Both are very accurate and replace the old and obsolete charts and tables. So the choice depends on the tastes of each player.

[majorfailure]

Originally Posted by Soldier_Fortune

The cons: it is an online calculator and therefore it can not be used inflight; the player must pause and minimize the game and then open the calculator.

Look further down in the thread you posted a link to, and there you will find a downloadable version.
I'm gonna test this when I've got time, and if it works then there is potential fun in it, now that i've got the basics of level bombing (and the both of you Soldier_Fortune and KG26_Alpha gave me some hints here why I'm not hitting as good as i wished for -so thanks to the both of you)

[Jeremiah_Weed]

Howdy. I noticed and started reading this thread about a month ago. Then got extremely busy at work on some end of fiscal year projects that need to get out and just haven't had time to post anything. I don't want to butt in on your research so I won't say too much...you may be like me and love the challenge of figuring stuff out.
But I will say this....true altitude and indicated altitude are basically the same thing. The difference being true altitude would be what a tape measure placed between sea level and your plane would say and indicated altitude would be what your instruments tell you. With modern laser and radar equipment, the difference between the two could be mere inches. In addition to indicated altitude, there are 2 other altitudes you need to bomb accurately. Here's a list of the different altitudes....

http://www.meretrix.com/~harry/flyin...altitudes.html

Also, you don't need adaptive bombing. There are definite formulas that are used, but some planes use slightly different values. Also, the IAS/TAS chart that's in the game is only giving you the partial equation...so the values for TAS are usually WAY off. That chart shows the aircraft's speed increasing linearly (on a straight line), but it actually increases on a curve. Fortunately, you don't need a differential equation to calculate it...a simple polynomial is all that's needed. In other words, basic mathematics. LOL
And yes, OAT (Outside Air Temperature) is very important for calculating that curve. With OAT in mind, I recently noticed that the Free Air Temperature gauges on the G4M1-11 Betty are bugged. I've reported it to DT so hopefully it will get fixed. Having air temperature gauges that work properly come in quite handy.
Anyway, I've said enough...but if you guys would like some help, just let me know.

[Soldier_Fortune]

Hi Jeremiah. Thanks for your interest.

As I already stated, in this sim there is not difference between Indicated Altitude (the altimeter reading) and True Altitude (altitude affected by local pressure and OAT at a given altitude). But True Altitude is modeled in other sims (i.e., LOMAC Flamming Cliffs 2).

Will True Altitude be modeled in IL2 in a next future? Really I don't know. But if TD decides to model it, True Altitude will affect the level bombing. In any case, it can be easily calculated with an E6-B, as actually TAS and Ground Speed must be calculated for an accurate level bombing.

Also, you don't need adaptive bombing. There are definite formulas that are used, but some planes use slightly different values. Also, the IAS/TAS chart that's in the game is only giving you the partial equation...so the values for TAS are usually WAY off. That chart shows the aircraft's speed increasing linearly (on a straight line), but it actually increases on a curve. Fortunately, you don't need a differential equation to calculate it...a simple polynomial is all that's needed. In other words, basic mathematics. LOL
And yes, OAT (Outside Air Temperature) is very important for calculating that curve.

I was trying to express all those formulas with a set of printable graphic charts for manual release of bombs in level bombing.
I personally am quite skillfull handling the E6-B and I have no difficulty solving all those equations with it while flying. But, at the same time, I know that may be many players would prefer to have something easier to handle, and I've made that set of graphic charts with that goal in mind (you can download it from the post #30 in this thread: I would like you test them, and then let us know your opinion).
But also, in that post, I adress to a link to the 'Warbirds of prey' site where you will find a nice calculator to obtain all relevant data for an accurate manual level bombing, in a more friendly way (for many people, at least) without an E6-B : Ground Speed and bombsight elevation, taking in account OAT and wind.

With OAT in mind, I recently noticed that the Free Air Temperature gauges on the G4M1-11 Betty are bugged. I've reported it to DT so hopefully it will get fixed. Having air temperature gauges that work properly come in quite handy

Yes: I also noticed that during my tests. And I was about to report that issue when I saw it was already reported.
But, until it is fixed, you always can calculate the OAT easily; for 'Betty' it is:

OAT (ºC) = Tmap (ºC) - 0.0065 (ºC/m) * IALT (m)

Anyway, I've said enough...but if you guys would like some help, just let me know.

Well... in these matters is never 'enough', and any help, advise or proposal is always welcome.

[Jeremiah_Weed]

Howdy SOF.
If you enjoy catching someone parked on an airfield 5000 meters below you or just like being able to drop an egg on your target and hit it, then you'll enjoy this. It looks like you already know these maps are somewhat based on ISA (International Standard Atmosphere) and also that temp rises by .0065 deg C per meter. Also, that 15 deg C is the temp at sea level for ISA normal, at least for one, so I don't really need to go into any detail about that. (I believe there is another ISA that starts at 0 deg C, but we'll ignore that one)

So, on to one of the formulas. While looking at the IAS/TAS chart, I was able to derive a formula that came up with their numbers:

(IAS * .0657 * (ALT/1000)) + IAS = TAS

I quickly realized that this formula didn't take into account changes in OAT (Outside Air Temperature) and it wouldn't have been on a curve...so I modified it. What I came up with is this:

((IAS * .066 * (ALT/1000)) + IAS) * (1 + ALT/100,000) = TAS

Using real numbers, let's say you had an IAS of 260kph and an (indicated) altitude of 4850m. The equation would look like this:

((260 * .066 * 4.850) + 260) * (1.04850) = TAS

In operation, you would multiply the 260 by .066 then multiply that by 4.850, then add the 260 to arrive at a temporary airspeed. You would then multiply the temporary airspeed by the 1.04850 to arrive at your TAS.

Now, here's the deal. The .066 factor is only for some planes, like the B5N1 Kate (my favorite bomber). Russian planes like the Pe-8, the IL-4 and some others use .084. The He-111 H-2 uses .026 and the H-6 uses .046. Also, this formula is used on other maps where the temperature is different (above or below ISA), but it's calculated differently. Namely, you'll be calculating for density altitude. But I'll get into that later on.

I tested this formula by using the Gulf of Finland 1 (summer) map, since it was ISA normal. I used the Island of Lavansaari/Moschnyi as a base and put several air starts in grid AV-11 to the east of it, ranging from 1000m all the way up to 6000m. I also put a sizable group of cargo ships in grid AR-11 to the west and also placed a "destroy ground" icon in the middle so I could see it on the map well before I could see the ships.

The distance gives you time to trim your plane (especially the rudder) and get it stable at altitude without any control inputs before kicking in "auto level". I also cut back on power and prop pitch...some planes not as much as others. Also, I found that as altitude increased, accuracy started to suffer, although not as much as you would expect. I'm still able to zero a freighter at 6000 meters alt with that big ole 5000 kilo monster the Pe-8 drops.

Anyway, if you want, get set up on that map and get used to running the numbers on your way to the target. Then, when you're ready for temperature changes, let me know. Additionally, I think a calculator will do you much better than your E6B due to the variations in the velocity factor. (.084, .066, .046, .026, etc)

[Jeremiah_Weed]

Also, I forgot to mention, if you're testing out the Lofte/Norden type bombsights there's a trick to them. Don't try to track your target forever. They aren't designed for that. Only track your target about 3 or 4 degrees at the most. For instance, if you find the bombs release around 35 degrees at a given altitude, manually move the bombsight angle no farther than 38 or 39 degrees. As your sight moves over the target, enter it into auto mode and let it do its job. If you don't try to track your target forever, they're just as accurate as the OKPB-1 sights.

You can also "tweak" it a bit before you enter into auto mode. If the actual TAS is 2 or 3 kph HIGHER than what you entered as the bombsight velocity, you can move the bombsight altitude DOWN 10 or 20 meters in elevation for fine adjustment. The reverse is also true.

Note: The Betty uses this type of bombsight and its velocity factor is .046.

Bombs away!

[Jeremiah_Weed]

As time permits, I'll post a more sophisticated formula. The one I posted starts to become inaccurate above 6000 meters. The last factor needs to have a Delta/Rate of Change factor in it to slow down the rate of increase, which usually requires the use of exponential function. I've purposely avoided that because I'm not sure most players would enjoy having to (or be able to) work the equation.
This one is relatively simple and still allows you to hit your target the majority of the time and have some fun...and fun is what it's all about.