Two planned new models.

Hello folks,
There are two Russian airplanes that have caught my attention to build models
of in the near future: The Il-2 Shturmovik and the Petlyakov PE-2.

IL-2 Shturmovik
---------------
The Il-2 Shturmovik fighter seems to have been quite a remarkable WWII fighter,
tuned for low-altitude ground attack. It was difficult to shoot down and posed
a strong rival to the Luftwaffe. There is only one fying example nowadays,
but several are displayed in museums.
36,183 units were built making it one of the most produced fighters in history.
At a MTOW of 10300 lb, its armoured shell was 15% of this weight.

A two-seater prototype flew in 1939, and went through several improvements.
In 1940 a high-altitude version came out with original Mikulin AM-35 1,370 hp.
improved versions of the Hispano Suiza Y12.

However, it was decided to have a lighter, single-seat design, with the more
powerful 1,680 hp Mikulin AM-38 engine, optimised for low level operation.

It proved devastating for ground attack missions, against road convoys, railways
and tanks, but was vulnerable against air-attacks, so the two-seater version was
re-instated in 1943, with an aft-firing machinegun, and an upgraded Mikulin AM38F
engine that conferred a Max. speed of 257 mph.

This engine had a geared supercharger, working at 53.54 in. Hg for take-off,
giving 1720 Hp at 2350 RPM, whereas for normal maximum continuous operation it
operated at 47.24 in. Hg, giving 1500 Hp at 2050 RPM at 2500 ft.

Petlyakov PE-2
--------------
The Petlyakov PE-2 was a twin-engined fighter/dive-bomber, remarkably fast,
manoueverable and durable. It started out as a high-altitude fighter-escort. The
prototype had a pressurized cabin, superchargers and many electrically actuated
systems. Because a tactical bomber was deemed more necessary, the design was then turned
into a heavy fighter/dive bomber, and production started in 1941.
11427 units were built.

The most-produced version was the PE-2FT, with 2×1210 hp Klimov M- 105PF liquid-
cooled V-12 engines, which had a 2-stage supercharger:
(Data for the M-105R)
> 1,100 hp at 2,700 RPM for take-off, boost rated at 1.27 Atm (38.00 MP)
subsequent variants had 43.3 and 47.2 MP
> 1,050 hp at 2,700 RPM at 13,123 ft, boost rated at 1.21 Atm (36.22 MP)
subsequent variants had 43.3 MP
> 500 hp at 2,700 RPM at 31,168 ft (9,500 m)
>Emergency boost (maximum 2 minutes): 1,100 mm Hg (43.30 MP) at 2,800 RPM.
subsequent variants ??
>Critical altitude: 2,000 m (6,561 ft) at 1st speed, 4,000 m (13,123 ft) at 2nd speed.

(I still have to see which variant is the M-105PF, which had 100 Hp more, but it seems
to have been a maximum of 43.3 MP for the engine in question.

As CFS1 only allows single-speed superchargers, for the moment I have decided to
put take-off and emergency power into WEP, totalling 43.3 MP, leaving altitude boost
power within normal operation at max. throttle - 36.22 MP.

In my opinion, these would be two very interesting models to make for CFS1!
Cheers,
Aleatorylamp

Hello Folks,
The two stage supercharger on the Klimov VK-105PF engine of the Petlyakov PE-2
is certainly a headache, as it is impossible to make such a thing for CFS1.

The corresponding graph on the chart attached is the one marked in red.
It would continue downwards as the black line does for the M-105P.

Translated into numbers, altitudes/Hp are the following:
_S.L. ...: 1210 Hp
_2300 ft: 1260 Hp
_3280 ft: 1225 Hp
_5500 ft: 1140 Hp
_6500 ft. 1160 Hp
_8850 ft: 1180 Hp
_9840 ft: 1160 Hp
12467 ft: 1060 Hp
16404 ft: 980 Hp
19685 ft: 825 Hp
23000 ft: 720 Hp

In order to achieve the best possible performance equivalent for this engine
using a single speed supercharger, the first thing to do would be to try and
bend the graph into a convenient shape, but this is easier said than done.

The problem is that too much power around the medium altitudes comes out.
It appears that the low and high altitudes will be a little easier to do...

For the moment my efforts have produced the green graph line - one can
recognize a single-engine supercharger pattern, with the obvious deformation
at mid altitude.

This is for WEP. In this case, with the adjustments, the Manifold pressure settings
do not coincide with the WEP MP on the specs and is 3 in. Hg lower, at 40.3 in. Hg.
Also, Boost Gain and WEP Pressure Change rate had to be lowered so much that
critical altitude is no longer at 13120 ft, but much higher.
Problems, problems...

Cheers,
Aleatorylamp

Hello Folks,
The "small" issue of Critical Altitude being altered by entering
values lower than 0.528 into "WEP Pressure Change Rate" was
solved by simply leaving this field at Zero - it did not impair
the functioning of WEP. In effect, it made it more understandable!

So, it seems that this parameter does not need to be zero only
for non-WEP .air files, contrary to what I´d thought before.

Anyway, with a Zero entry here, it is easier regulate Boost and
WEP with the usual parameters. I also noticed entering different
low values here had a strange effect on Boost Gain, and not only
Critical Altitude.

The comment in Air Ed that the minimum entry for this parameter
is 0.528 seems to mean that a smaller value will have the same
increase effect as 0.528.

Cheers,
Aleatorylamp

Hello Aleatorylamp,

I was wondering if you would figure this out or remember what we did earlier.

If you check the last post on this thread (The infamous "Engine Performance Tuning Tutorial"):
http://www.sim-outhouse.com/sohforum...Tutorial/page2

You will find that there is a description of these parameters in greater detail.
We (actually you) came across some weirdness with this parameter back when working on the Martin Baltimore and I took it quite a bit further in testing with my P-40N to see exactly what it was doing. Afterwards, I wrote up what I had found during the testing.

This is what you posted at the time (Post 77 on the Martin Baltimore thread):
http://www.sim-outhouse.com/sohforum...altimore/page4

Quote:

---

Originally Posted by Aleatorylamp

Update:
The main problem with F10 WEP is that in order to get the right Manifold Pressure readings at altitude, WEP and NON-WEP require different Boost Gain entries in the .air file!
Rather frustrating, I must say! I´ll have to see if there´s a way round this... That´s why it worked so much better with the WEP-Within-Throttle-Lever.
At the moment I´m drastically reducing Emergency Power Press Change Rate parameter, which seems to be doing something. I wonder...

---

There was a lot more discussion after that.

It seems like most of the issues you are currently asking about or running into were covered in pretty good detail in that thread.

Using the stock AIR files as examples isn't always a good idea. Many of them are not very well behaved.

It seems like the designers of the AIR file system created a useful feature but the authors of the stock CFS AIR files didn't really understand what the parameters were used for. We have already had plenty of discussions about other places where the stock AIR files are broken.
The comments in the AIR file editors were probably based on guesses and are often not entirely accurate.

Coincidentally, the relevant post in the Engine Performance Tuning Tutorial was on May 16, 2016 -- EXACTLY Two Years ago and it was about a week or so after the discussion in the Martin Baltimore thread.

- Ivan.

Hello Aleaorylamp,

Here is another useful conclusion from the Martin Baltimore thread on Post 79:
http://www.sim-outhouse.com/sohforum...altimore/page4

Quote:

---

Originally Posted by Aleatorylamp

Halving Emergency Power Pressure Change Rate value had produced no satisfactory results, and leaving it at one tenth was better, although I didn´t understand what was happening very well, so I left it at zero, discovering that above critical altitude, WEP falls off very rapidly! This seems to point towards a possible solution.

---

This was on May 9, 2016 or about a week before I posted to the Engine Performance Tuning Tutorial.
I had figured from your posts that you understood the basic concept.

The entire section on Page 4 is worth reading because it covers in great detail what it appears you are trying to do now with ta different aeroplane.

- Ivan.

Hello Ivan,
Yes indeed!
My memory is not very good anymore. In fact, it was always quite mediocre...

Anyway, yesterday evening I remembered both the Baltimore WEP issue
and the WEP extension to your tutorial, looked that up and I saw what you
are mentioning. It says exactly what I´m finding again right now!

So it´s not strange that now, it turns out that the performance envelope is
overall better as I already had it on the graph I posted, using small values in
WEP Pressure Change Rate and adjusting Boost Gain a little.

Note: The small glitch about the change in Critical Altitude, is in fact rather a
benefit than a bother, because as WEP still works above Critical Altitude, it
compensates very nicely for the low non-WEP performance there!

Well, at least we CAN use this feature to our benefit, contrary to what one
is lead to believe from the vague AirEd indications.

Leaving it at zero at first seemed promising, and lowered the unwanted peaks
between 6000 and 9000 ft a bit. However, it did so at the expense of lower
and higher altitude performance - both came out low. Hence, I´m reverting
back to using the WEP Pressure Change Rate with small values.

It IS a quirky issue, isn´t it, this busines of trying to figure out how to use a
single-speed supercharger because a 2-speed one isn´t to be got.

So... What do you think of the green line in Post #2?
I´m still trying different things but so far, it´s the nearest I´ve got.

OK, then! Cheers,
Aleatorylamp

Hello Smilo,
Perhaps it would be a good idea to change the name
of this thread to Petlyakov PE-2 Dive-Bomber.
If you think so too, perhaps you could do it,
as I haven´t got the capability.
Thank you for your kind attention!
Cheers,
Aleatorylamp

hello Stephan,
i don't believe i have the capability
to edit a thread title.
i would suggest just starting a new thread.

Hello Smilo,
OK, thanks. I´ll do so as soon as I start building the model!
Cheers,
Aleatorylamp

Hello Rami,
I will not be building these models, so it may be a good idea to delete this thread.
Thank you for your attention,
Aleatorylamp