Il-2 Sturmovik

Hello folks,
I prefer to separate the Il-2 Sturmovik thread from the other Russian aircraft I´m
planning to build, so I´ll use this thread for it as soon as I start building it.

At the moment I´m preparing the .air file, and I seem to be having trouble with
the single speed supercharger, probably because of the information quoted in
the source I found may not be exact, or my interpretation of it may be wrong.

For non-WEP values of 47.2 inches of mercury, the model´s performance curve
tallies acceptably with specifications, even with the lower performance of
900 Hp at 16000 ft.

However, as soon as I enter the extra 6.3 in. Hg WEP boost, for the full 53.54 MP
that the supercharger gave, the model´s performance goes way above realistic
values, by more than 50 Hp at S.L. and more than 300 Hp at 16000 ft.

At 2500 ft there should be 1720 Hp at 2350 RPM, with full boost, but far too much
comes out. Then, with 47.2 in. Hg boost, I get the correct 1500 Hp, but not at
2050 RPM - that stays at 2350 RPM, but I recall it´s difficult to deal with.

At the moment I´m trying out different Boost values to see where the correct
boost-perfomance lies. Correcting WEP Boost MP to get rid of the 50 Hp difference
at low altitude, still leaves it at over 200 Hp too fast at altitude. This doesn´t sound
new, and I seem to remember something similar happening before on some older work,
and in some posts it was mentioned that a compromise must be reached.

I wonder how complicated it will get with the other Russian plane, with the 2-speed
supercharger. That will probably be even more difficult, but I´ll deal with it when
the time comes.

Anyway.... more later!
Cheers,
Aleatorylamp

Hello Folks,
The obscure Emergency Power Change Rate parameter does have some useful effects.
There is a comment in AirEd that it should be set to a minimum of 0.528, but in some
cases it can be completely misleading, probably for low Boost Gain values.

Max. Manifold Pressure is set at 47.2, WEP Manifold Pressure is set at 6.3, and normal
Supercharger Boost Gain is at 1.835.

This gives me the desired non-WEP power of 900 Hp at 16000 ft, the desired non-WEP 1500 Hp at 2500 ft and the desired WEP 1720 Hp at 2500 ft.

Now, if the Parameter in question is set to the commented minimum of 0.528, it causes an ever growing undesired increase in WEP power at altitude. At 10000 ft I was getting an excess of 360 Hp for WEP!

It appears that this Parameter exists to avoid this.
Trying out different values, I´ve got it at 0.178 now, and I am getting a much more realistic 16000 ft WEP power of 1017 Hp. It has also corrected the excess WEP power at most of the lower heights, down to 6500 ft. Further below values remain expectedly closer to the 1500 non-WEP and the 1700 WEP Hp.

I thought this was very interesting indeed!
Cheers,
Aleatorylamp

Hello all!
I was fine tuning the Mikulin AM38F engine this morning, and
came up with some very satisfactory results:

Aim:
S.L. : 1720 Hp at 2350 RPM and 53.53 in. Hg MP
2500 ft: 1500 Hp at 2050 RPM and 47.24 in. Hg MP

Reference:
Mikulin engine power chart. The orange lines refer to the AM38F engine.
The WEP line overlaps with the red line of the AM38 engine.

Performance results, all at 2348 RPM:
S.L.:
1718 Hp 248 mph 53.5 MP Hp OK!
1472 Hp 238 mph 47.2 MP Hp OK!

2460 ft:
1747 Hp 259.5 mph 53.5 MP Hp +2.5 mph
1498 Hp 242.2 mph 47.2 MP Hp v.g!

3280 ft: (1000 m)
1708 Hp 258.4 mph 52.2 MP +88 Hp
1509 Hp 244.0 mph 47.2 MP +59 Hp

6560 ft: (2000 m)
1509 Hp 252.3 mph 46.1 MP +209 Hp
1343 Hp 242.1 mph 42.2 MP +183 Hp

10000 ft: (3000 m)
1316 Hp 247.1 mph 40.3 MP Hp OK!
1167 Hp 238.8 mph 36.8 MP Hp v.g!

13100 ft: (4000 m)
1156 Hp 242.4 mph 35.7 MP Hp v.g!
1021 Hp 235.3 mph 32.5 MP Hp v.g!

15800 ft: (4800 m)
1029 Hp 238.2 mph 32.0 MP Hp v.g!
906 Hp 206.5 mph 29.2 MP Hp v.g!

19000 ft: (5800 m)
890 Hp 222.3 mph 28.2 MP Hp OK
781 Hp 192.2 mph 25.7 MP Hp OK

Probably not too bad...
Cheers,
Aleatorylamp

Hello Folks,
This time I started at the nose, and am working backwards, just for a change.

One interesting aspect of this plane, perhaps a bit complicated to build and
quite component-hungry, is the number of air intakes it has.
I find they give the model a lot of charisma.

Just behind the propeller, there are two on the sides and one underneath.

Then, there´s a large one at the top, about 2/3 of the way towards the cabin.
This one needed that section done in 2 components: Left and right halves, with
a flat bit in the centre.

And there´s yet another to come, seemingly the oil cooler, under the wing in the
centre.

Anyway, here´s a picture of the flying nose... and a photo of the resotred, flying
Sturmovik.
Cheers,
Aleatorylamp

Hello Aleatorylamp,

As with other warbirds from the Great Patriotic War, you need to be very careful about what you see in a modern example, especially a flying example. Many times, LOTs of changes have been made to get a SIMILAR airframe flying with modern fuels, and aviation regulations and of course Parts and Engine availability.

As a general rule, modern flying examples are great eye candy but not very good references for equipment on war time examples.

- Ivan.

Hello Ivan,
OK, thanks for the warning! - My logical thought was that this photo
was the best example. I was taking for granted that the only flying
example would be restored to the original state.

I´ll check with other photos, and also double-check with the 3-view
drawings I found just in case - they have dotted lines showing some
inner details otherwise invisible from outside.

This one is a cut-away without the landing-gear, its housing and the
outer wings. It shows the lower radiator scoop (not oil-cooler after all)
and the upper engine air-inlet duct.
Cheers,
Aleatorylamp

Hello Aleatorylamp,

Priorities and what is considered acceptable during war time are quite different from what is acceptable with the last surviving examples.
As I see it, many of the current flying "warbirds" really are just full sized replicas and their emphasis is on safety rather than performance.

Example 1: Of all the flying A6M Japanese Type Zero fighters, only one has the original Sakae engine.
The rest use the Pratt & Whitney R-1830 which is a larger engine and changes the shape of the cowling a bit.

Example 2: Of all the currently flyable FW 190As, only one has the BMW 801 engine. The rest are an assortment of mostly Shvetsov M-82 / ASh-82 engines or even a Pratt & Whitney R-2800.
The modern reproductions may use the engine cooling fan, but the drive ratio is different and the oil cooler has been relocated from an armoured ring at the front of the cowl to the upper cowl where the synchronized cowl machine gun used to live.
One other small detail is the bolt pattern on the windshield frame is slightly different....

Example 3: The current flyable Yak-3 are all either new production or conversions of the Yak-11 Trainer and all use the Allison V-1710 engine with an opposite rotation propeller and a little carburetor scoop just in front of the cockpit. The Yak-11 was actually derived from the Yak-3, so it isn't THAT different, but it really isn't quite the same either, especially with the Allison installation.

Airworthy examples of the original engines are pretty hard to come by, so
For reference photographs, I am very careful what the subject is. I much prefer museum examples for authenticity.

As for the Sturmovik, where did you get your drawing from? I might have some pretty good references if you need additional drawings.

- Ivan.

Hello Ivan,
I see the point. I understand the precautions needed for air-show examples!
There are about 12 museum examples around, so I´ll look for pictures of those.
Despite so many of these planes having built, survivors are not as abundant as
one would expect, which is an indication of how savage the war was on the
Eastern Front.

Then, I suppose pictures of plastic models can be quite illustrative too, especially
if the author mentions painstaking efforts to maintain authenticity.

What I´m using now is a large 2261x2295 pixel blueprint from The Blueprints.com.
They have several on their site, in several sizes, so it took me quite a while to sort
out one I thought was the most convenient.

Anyway, it seems to be going OK now, after the usual head-banging at the beginning
due to unrealiable source drawings. Thanks for your offer anyway!

Cheers,
Aleatorylamp

Hello Rami,
As I will not be building this model, it may be a good idea to delete this thread.
Thank you very much for your attention.
Aleatorylamp