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View Full Version : Comparing Il-2 speed tests with real-life figures.



XyZspineZyX
09-09-2003, 04:25 PM
I decided to place this topic on this forum because of a few posts I've read.

When comparing speed tests with aircraft in Il-2 FB, with real-life figures, it must be taken into account that the real life figures where:

A: TAS
B: sometimes, factory figures


A: The speed you see on your dial in the cockpit or the speedbar, are Indicated airspeed (IAS) only. The True airspeed (TAS) changes with the altitude. When you are close to the ground, IAS and TAS are almost the same but, when altitude increases, the TAS also increases. The speed you see on the dial in the cockpit is only the relative speed of the aircraft. It is not the real speed at wich you travel trough the air. The formula for IAS--->TAS is fairly simple, up to 400 km/h. below 400 km/h the air is supposed to be non-compressible. Above 400 km/h, compressablility has to be taken into account. Undoubtedly, the diffrent formula's can be obtained form the internet. Search for it with google.com.

B: If you have overcome the problems with IAS/TAS, then, your obtained speed graph/figures might still be factory figures. Factories still had a product to sell and often there wher competitors. So, a certain factory could be messing with figures to make their airplane look more attractive. (this also includes roll-rate or, any other figures from any kind)



okay, i hope that i have informed you on the matter of testing the il-2/FB planes and compare them with figures from their real-life counterparts.


Happy flying!

1 Judge not, that ye be not judged.
2 For with what judgment ye judge, ye
shall be judged: and with what
measure ye mete, it shall be
measured to you again.

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XyZspineZyX
09-09-2003, 04:25 PM
I decided to place this topic on this forum because of a few posts I've read.

When comparing speed tests with aircraft in Il-2 FB, with real-life figures, it must be taken into account that the real life figures where:

A: TAS
B: sometimes, factory figures


A: The speed you see on your dial in the cockpit or the speedbar, are Indicated airspeed (IAS) only. The True airspeed (TAS) changes with the altitude. When you are close to the ground, IAS and TAS are almost the same but, when altitude increases, the TAS also increases. The speed you see on the dial in the cockpit is only the relative speed of the aircraft. It is not the real speed at wich you travel trough the air. The formula for IAS--->TAS is fairly simple, up to 400 km/h. below 400 km/h the air is supposed to be non-compressible. Above 400 km/h, compressablility has to be taken into account. Undoubtedly, the diffrent formula's can be obtained form the internet. Search for it with google.com.

B: If you have overcome the problems with IAS/TAS, then, your obtained speed graph/figures might still be factory figures. Factories still had a product to sell and often there wher competitors. So, a certain factory could be messing with figures to make their airplane look more attractive. (this also includes roll-rate or, any other figures from any kind)



okay, i hope that i have informed you on the matter of testing the il-2/FB planes and compare them with figures from their real-life counterparts.


Happy flying!

1 Judge not, that ye be not judged.
2 For with what judgment ye judge, ye
shall be judged: and with what
measure ye mete, it shall be
measured to you again.

http://acompletewasteofspace.com/forum/templates/subSilver/images/logo_phpBB.gif (http://acompletewasteofspace.com/forum/index.php)

XyZspineZyX
09-09-2003, 04:27 PM
Good points.



"Tis better to work towards an Impossible Good, rather than a Possible Evil."

SeaFireLIV.
(Escape Whiner Member - The need to return home!)

XyZspineZyX
09-09-2003, 04:57 PM
Not only that, different examples of the same aircraft (even if built at the same time using identical parts) will often have slightly different performance numbers.

Overall, they'll match, but one example may climb better or fly faster than another seemingly identical aircraft. A difference of a few MPH/KPH in top speed or fpm in climb is not uncommon, and that's right from the factory.

Once they get into the field and start accumulating wear and damage, especially from combat, things can change even more. Major repairs may restore the functionality of an airframe, but they often add some extra weight and sometimes a little extra drag because they're not quite "ideal" fixes.

The gross performance of the plane will still be the same (top speed around XXX, climb rate of about XXX), but the chances of it being identical to published numbers or even the numbers that specific plane produced in the past are slim. It's generally accepted that every few years planes should have their weight and balance rechecked and recomputed, since a few years of use can cause a measurable change in the original calculations.

In most cases, if you took a reasonable sample from real aircraft and compared them to the published numbers, you'd probably find some that did better and some that did worse, and very few that were exactly the same.

If something is off by a huge amount (e.g. 50%), I can see complaining about it, but for small differences (5%-10%) it falls well within the acceptable variation that you'd find in the "real world".

For the best possible realism, I'd expect a simulated aircraft to be modeled on performance data from as many actual examples of the aircraft as possible, and then have its in sim performance based on the average of all the aircraft sampled. It'd be the most reasonable way to simulate the average combat aircraft encountered during the war. It's also the method likely to produce aircraft models that don't exactly match the two or 3 published tests that people like to look at.

XyZspineZyX
09-09-2003, 07:06 PM
IAS isn't a speed at all - its simply a measure of the pressure in the pitot head, if your flying at 300k TAS into a 20k headwind the IAS will show 320k, if your flying at 300k with a 20k tailwind the IAS will be 280k.



Tedious unoriginal wooly philoshophical statement the pith of which is lost in repetition.

XyZspineZyX
09-09-2003, 09:21 PM
flapbuster wrote:
- IAS isn't a speed at all - its simply a measure of
- the pressure in the pitot head, if your flying at
- 300k TAS into a 20k headwind the IAS will show 320k,
- if your flying at 300k with a 20k tailwind the IAS
- will be 280k.
-

My point but, english is not my native language so, I couldn't find the right words in a short time.


Thanks /i/smilies/16x16_smiley-wink.gif

1 Judge not, that ye be not judged.
2 For with what judgment ye judge, ye
shall be judged: and with what
measure ye mete, it shall be
measured to you again.

http://acompletewasteofspace.com/forum/templates/subSilver/images/logo_phpBB.gif (http://acompletewasteofspace.com/forum/index.php)