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  #1  
Old 06-08-2012, 01:59 PM
Z1024 Z1024 is offline
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Default La-7 FM issues and its versions

There are several issues with La7.

1. The 3 cannon version should be moved to 1945

It went into production only in March of 1945:

Quote:
Большинство серийных Ла-7 выпущено с двумя пушками ШВАК, а не с тремя УБ-20. Пушка УБ-20 представ ляла собой переделанный под калибр 20 мм пулемет У Б, и поначалу отличалась низкой надежностью; до конца войны изготовили только 368 трехпушечных Ла-7, их строили с марта 1945 г. на заводе № 381.
Taken from here: http://www.lithub.ru/read/374196/
Looks like a reliable source, lots of references in the back of the book, mostly Russian so they probably know what they are talking about.

2. La7s top speed is too high

According to il2 compare it sits at ~682km/h @6000m (with boost).
Its in game performance is based on the prototype, not on the production units.

From the same book is in above example:
Quote:
При мас совом производстве характеристики са молетов неизбежно снижаются – ни один серийный Ла-7 не развил скорости более 658 км/ч.
It says no production La7 ever exceeded 658km/h.

This apparently triggered an official inquiry/tests in August-September of 1944, and test pilots concluded the production model demonstrated unsatisfactory performance - slower speed, +55C in the cockpit, engine overheating while climbing.
Quote:
Недобор скорости послужил причиной проведения НИИ ВВС в августе-сентябре 1944 г. конт рольных испытаний самолета головной серии и серийного. Летчики-испытате ли выставили серийной машине неудов летворительную оценку: недобор скоро сти, температура в кабине составляла +55° С, при наборе высоты грелся мотор.
This is a link to one such report (max speeds page): http://www.airpages.ru/mn/la7_02.shtml#p3
This is a OCRed version, much easier to read than the scanned (I also found that on the Internet and can provide a copy if need)

More reports attached.

Comparing these reports with Il2 compare figures we can see the that maximum speeds in the game are higher at sea level and 6000m, but sometimes lower than the real thing in between.

3. WEP/supercharger effects.

As we can see in these reports WEP power is never used above 2000m because probably the supercharger can't provide enough air anyway. In il2 compare we can see the effects of WEP throughout the whole range of altitudes.
BTW this also applies to German planes such as FW and maybe others as well.

4. La7 44/45 differences.

As you can see from the attached tables, the 655km/h @ 6000m is actually quite a good figure for a 1944 La7. For example the La-7 #45210150 initially showed only 640km/h. Once they tuned it, enhanced the surface, installed a prototype propeller etc. the top speed figure has substantially improved - 674km/h but this is definitely not a production unit, it is very much "aftermarket tuned" if you know what I mean

In the 2nd report we can see that in 1945 La7s performance significantly improved - the 2 cannon version reached 677km/h and the 3 cannon one - 661km/h.

5. Turn performance @1000m

The 1944 2 cannon La7 shows 20-21sec and in il2 Compare it is 18-18.5sec.
This is closer to the 1945 La7 figures of 18-19.5sec.
Although it is only 1sec - this is still a ~5% difference and can be quite significant. Not nearly as important as top speeds but still.

May I suggest to have 3 versions of La7 instead of current 2?

We would have:
1. a 2 cannon 1944 version with top speed about 660 @6k and turn time of 20s @1000m
2. a 2 cannon 1945 version with top speed about 677 @6k and turn time ~19s
3. a 3 cannon 1945 version with top speed ~ 665 @6k and turn time 18s.
Attached Images
File Type: jpg La-7_pic1.jpg (119.6 KB, 43 views)
File Type: jpg La7_pic2.jpg (60.8 KB, 31 views)
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  #2  
Old 06-08-2012, 02:06 PM
Z1024 Z1024 is offline
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Alternatively if the 2 cannon version differences are deemed insignificant to warrant a new plane entry I suggest we use the
- 1944 2 cannon version for the La7 1944 ,
- 1945 3 cannon version for the La7 3x20mm 1945
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  #3  
Old 06-08-2012, 02:40 PM
[URU]BlackFox [URU]BlackFox is offline
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Good to see that documentation about russian fighters is showing up. I'm not in for nerfing russians, but I want them to be as real as possible, just as the rest of nationalities are getting.
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  #4  
Old 06-09-2012, 10:19 AM
gaunt1 gaunt1 is offline
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Excellent! This again shows that on some aircrafts, FM is based on prototypes. Btw, can you find some detailed info about LaGG-3 and VK-105 powered Yaks? Then we can continue this in the other thread about soviet fighters.
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  #5  
Old 06-09-2012, 09:47 PM
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Treetop64 Treetop64 is offline
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Quote:
Originally Posted by gaunt1 View Post
Excellent! This again shows that on some aircrafts, FM is based on prototypes. Btw, can you find some detailed info about LaGG-3 and VK-105 powered Yaks? Then we can continue this in the other thread about soviet fighters.
If you really got a more realistically modelled VK-105 powered anything, well, you wouldn't be doing much flying at all!
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  #6  
Old 06-10-2012, 02:39 PM
IceFire IceFire is offline
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Solid start Z1024! This is definitely the beginning of some excellent research on such aircraft where you've gone out and dug up some serious resources on it. Rather than just stating it's wrong...you've got some great information. Maybe it can be put to some good use?
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  #7  
Old 06-10-2012, 10:49 PM
Z1024 Z1024 is offline
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Quote:
Originally Posted by IceFire View Post
Solid start Z1024! This is definitely the beginning of some excellent research on such aircraft where you've gone out and dug up some serious resources on it. Rather than just stating it's wrong...you've got some great information. Maybe it can be put to some good use?
Thank you IceFire, I certainly hope so.
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  #8  
Old 06-11-2012, 05:38 PM
EJGr.Ost_Caspar EJGr.Ost_Caspar is offline
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I repeat: Interesting stuff here! Be assured, that it had been recognised.
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  #9  
Old 06-12-2012, 05:35 PM
Z1024 Z1024 is offline
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Quote:
Originally Posted by EJGr.Ost_Caspar View Post
I repeat: Interesting stuff here! Be assured, that it had been recognised.
Great news! thank you
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  #10  
Old 08-05-2012, 11:05 PM
1984 1984 is offline
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Quote:
Originally Posted by Z1024 View Post
Taken from here: http://www.lithub.ru/read/374196/
Looks like a reliable source, lots of references in the back of the book, mostly Russian so they probably know what they are talking about.
ORIGINAL of this very old magazine - with other tables of performance la's and lagg's...


and other test -
Quote:
С 22 февраля по 25 марта 1945 продолжались гос. испытания модифицированного Ла-7 с 3 пушками Б-20 N 38105758 производства февраля 1945 381 завода, которые были прерваны 7 февраля. Самолет выполнил 14 полетов и налетал 8 час. 30 мин. Скорость по сравнению с эталоном 1944 г. упала у земли на 26 км/час и на высоте на 18-38 км/час (743,1).
...
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