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The Yak and its radiators

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The current Yak1b s127 is capable of maintaining speeds well in excess of its stat page or any documentation I have been able to find on the aircraft. Closing the rads to 0% on the 1b allows for a little over 4 minutes of what is essentially "war emergency drag." (summer, and much longer in winter)

 

I found that at 4500m I could hit 395mph during summer conditions, which seems extremely optimistic. At 2500m I could hit 367mph. 

 

After running with the rads closed I found that all I had to do to cool down was open them back up....and back to normal. A shrewd pilot can manipulate the rads in such a manner as to allow the Yak to massively perform above what documentation generally says it should be capable of. 

 

4mins of operation with no rad cooling seems a bit absurd. Yefim Gordon's book on soviet fighters states that the maximum allowed for rads shut was only two minutes. And it doesn't specify if this merely allowed the tested top speeds, or something much more than that. 

 

close your rads and bang! 20-30mph more speed. 

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Maybe you should ask the devs. AnPetrovich could be the right contact person

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Tests for top speeds were always done with rads open and temps within normal operating levels. The top speeds listed are not the maximum that can be attained but the maximum that can be sustained. We can run our engines right to the limit of damage and get more performance, but that’s not how they were tested.

 

Actually 4 minutes until engine damage with closed rads sounds about right, if Gordon mentions a maximum allowed time of 2 minutes.

 

Engine heat model doesn’t look wrong to me, but there is a legitimate discussion to be had whether the radiators themselves are too effective. I fly the MiG-3 a lot, and its radiators are extremely effective. I practically never have to open the water rad more than 2/3.

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4mins of operation with no rad cooling seems a bit absurd. 

No saying your necessarily wrong on the Yak, but just because the game says 0% water radiator doesn't mean that there's no cooling. If you look at the flap position on some aircraft there is still a gap to allow airflow over the radiator, even at 0% or fully shut.

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That is defiantly one thing to keep in mind, 0% in game isn't necessarily closed off entirely. If, for example, 0% meant all the way shut then closing down the fuel flow would kill engines much sooner than it does in game.

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The Yak radiators were designed so that the "neutral" or "by airflow" position provided enough cooling so that the plane mantains around 100°C for water and 110°C for oil in the standard 15°C temperature at sea level at maximum speed horizontal flight, according to the devs in the Yak-1B these are 35% for the water radiator and 50% for the oil radiator.  The more you climb the temperature of the air decreases and less radiator openings are needed.

One thing that is said in the manual IIRC is that there was a 10/15 limit for having the water temp above 110°C, but the engine overheat pops up a bit higher than that 115°? So it would be good if we had some sort of time limit simulated there.

Edited by -=PHX=-SuperEtendard

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What i read (different books) Yaks during the war had constantly problem with overheating engines. Cooling wasn't enough. In climbs was recomened in most types radiator full open cause insufficent cooling engine. Of course it decrased maximum climb rate. Dunno about maximum speed but definitly in sustained climbs was a problem even at late state of war.

 

Actually less radiator opening allow BOS Yaks to reach speeds expecially at high altitude which wasn't possible IRL. So Yaks are faster about 30-50 kph TAS at higher alts.

Edited by 303_Kwiatek

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If, for example, 0% meant all the way shut then closing down the fuel flow would kill engines much sooner than it does in game.

Actually, we can’t directly control fuel flow to the engine. The throttle controls the intake of air into the engine, not fuel, which is why it is called “throttle” - closing it deprives the engine of air, not fuel.

What i read (different books) Yaks during the war had constantly problem with overheating engines. Cooling wasn't enough. In climbs was recomened in most types radiator full open cause insufficent cooling engine. Of course it decrased maximum climb rate. Dunno about maximum speed but definitly in sustained climbs was a problem even at late state of war.

And this is where this sim might have a legitimate problem. The cooling seems overly effective on most aircraft.

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Don't forget that we have factory fresh engines, they are usually running pretty well and don't overheat instantly.

 

That being said: the figures given in the stats page are not absolute maximum speeds but determined by specified radiator setting. The series 69 for example uses 50% water, 100% oil for these figures.

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What is the basis for thinking the original flight tests were done for the sustained position? 

 

 

Personally I find it hard to believe that a plane that is supposed to have a significant speed deficit vs its enemies can gain parity by cheesing its radiator to a utterly shut position. Instead of a 360-370mph plane we have a nearly 400mph plane a critical height. Intead of 2 min of max rad closed, we have double this.

 

Its present performance makes is a pseudo Yak-3 in some respects.

 

I question the extreme speed bonus you get for closing the rads 100%, regardless of the time allowed. The airplane more or less gains 20-30mph of airspeed. 

Edited by Fumes

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The current speeds are about the same as a Yak 3 when the Yak1b in game is fully rads shut. 

 

The yak3 has the entire forward radiator scoop removed AND 100 more bbp. Yet somehow our yak1 can do the same speeds with just the rads closed. 

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This is an interesting report. The radiators referenced use plain water in a vented cooling system (plot 3 on page 7 charts the drop in boiling point with altitude, 194F at 10000ft) and the water cooled engines in common use at the time (1918-1920) by the Army, for example the Curtiss D-12, Liberty L-12 and Wright-Hispano E and H series, were not supercharged so their power drop off with density altitude would play a big part in cooling system adequacy.  The raw numbers though are very interesting.  As most know, for comparison with many WW2 aircraft there is always wwiiaircraftperformance.org.

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What i read (different books) Yaks during the war had constantly problem with overheating engines. Cooling wasn't enough. In climbs was recomened in most types radiator full open cause insufficent cooling engine. Of course it decrased maximum climb rate. Dunno about maximum speed but definitly in sustained climbs was a problem even at late state of war.

 

Actually less radiator opening allow BOS Yaks to reach speeds expecially at high altitude which wasn't possible IRL. So Yaks are faster about 30-50 kph TAS at higher alts.

Well, in a way it is Overheating, in that you can barely maintain 100°C with 100% Rads and Power on. At least in the Yak the Thermal Model seems about right, apart from allowing 115°C continuously. The Devs would just have to put a timer on "Combat Temperature", to about 5-10 Minutes and it would fit the Rest of the Game quite well. 

 

I think the Thermal Engine Model Right now either is too efficient at low Airflow, or the Engines produce too little Heat in Idle. Especially in the Fighters, with their far smaller Radiators and Oil and Coolant Amounts. 

Realistic Engine Warm Up on Idle on the Ground starting from Cold is not possible right now because of that. 

 

It's especially noticable in the P-40 and 109s as well.

Edited by 6./ZG26_Klaus-Mann
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I made a couple high speed tests, in the Autumn map, with the plane with neutral radiators and with fully closed radiators:
 

BWLL6YP.png

(Since my "resolution" is 1000 meters, i'm missing the supercharger gear switch between 2000 and 3000 meters).

From the neutral radiators, to fully closed the difference is 15-16 km/h IAS, which in TAS increases with altitude. At mid altitudes the TAS difference is around 20 km/h, at 9000 meters it's 24 km/h.

Edited by -=PHX=-SuperEtendard
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I made a couple high speed tests, in the Autumn map, with the plane with neutral radiators and with fully closed radiators:

 

BWLL6YP.png

 

(Since my "resolution" is 1000 meters, i'm missing the supercharger gear switch between 2000 and 3000 meters).

 

From the neutral radiators, to fully closed the difference is 15-16 km/h IAS, which in TAS increases with altitude. At mid altitudes the TAS difference is around 20 km/h, at 9000 meters it's 24 km/h.

Which program did you use to make this graph just out of curiosity. Me want!

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What is the basis for thinking the original flight tests were done for the sustained position?

Because that’s how such tests are done. No military performance test ever relies on you having to overheat the engine. Why on Earth would you want that?

 

Personally I find it hard to believe that a plane that is supposed to have a significant speed deficit vs its enemies can gain parity by cheesing its radiator to a utterly shut position. Instead of a 360-370mph plane we have a nearly 400mph plane a critical height. Intead of 2 min of max rad closed, we have double this.

Thing is: All the Bf 109s and one of the Fw 190s can do exactly the same, if they so desire.

 

The two minute limit with engine damage happening after four minutes seems perfectly reasonable.

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It's especially noticable in the P-40 and 109s as well.

 

 

The effect is so great that I flew several sorties in the P-40 without noticing that any cooling controls exist.

 

Of course, I eventually realized that this should be impossible. 

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Because that’s how such tests are done. No military performance test ever relies on you having to overheat the engine. Why on Earth would you want that?

 

 

Thing is: All the Bf 109s and one of the Fw 190s can do exactly the same, if they so desire.

 

The two minute limit with engine damage happening after four minutes seems perfectly reasonable.

There is doubt on the testing parameters in the Yaks case because we know the rad wasn't doing it job. Its not hard to imagine that if 2 minutes of closed rads was considered permissible, that the tests may have done this with this in mind. 

 

 

The 109s and 190s cannot do this in game to the same degree. Doing the same results in much faster engine failure and much smaller speed improvements. 

 

I am also not certain where you are getting this idea of 2min limit with 4 min of damage. There is simply a 4min limit in game. There is no two minute anything in the context of the game. 

 

 

 

Even if we accept this sort of rad abuse as realistic behavior, there is still a issue with a degree of benefit that comes from it. The current Yak1b in game might as well be a Yak-3 with a crappy climb rate. Somehow, the Yak1b in game is getting more or less the same top speeds as a Yak3. The Yak3 managed its speeds with complete removal of the front scoop and 100 more horsepower. Our Yak 1 is somehow managing the same benefit from simply by closing its rad from an intermediate position to fully closed. The airplane should not be going from a 360/70mph class airplane to a 400mph class airplane for useful amounts of time simply by closing the rad. 

 

unknown_3.png

Edited by Fumes

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Even if we accept this sort of rad abuse as realistic behavior, there is still a issue with a degree of benefit that comes from it. The current Yak1b in game might as well be a Yak-3 with a crappy climb rate. Somehow, the Yak1b in game is getting more or less the same top speeds as a Yak3. The Yak3 managed its speeds with complete removal of the front scoop and 100 more horsepower. Our Yak 1 is somehow managing the same benefit from simply by closing its rad from an intermediate position to fully closed. The airplane should not be going from a 360/70mph class airplane to a 400mph class airplane for useful amounts of time simply by closing the rad

 

I suspect that there is a error in the drag model of the YAK 1b , where the airframe itself is modeled with way too low drag , making the radiator position this influental.

It was surely a relatively clean airframe , but for sure not ways better then contemporary designs.Especially the bubble canopy is known to be a source of drag and turbulence behind it ,as can be seen in the P47 early models , where the razorback (697 km/h) version was faster then the bubble canopy (690 km/h)one or the P51b (710 km/h with 1490 hp) and P51d (705 km/h with 1590 hp).

 

 

EDIT: Could a Moderator please move this into FM section? Thanks

Edited by Hutzlipuh

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There is doubt on the testing parameters in the Yaks case because we know the rad wasn't doing it job.

 

 

No there is no doubt on the testing parameters and what the heck are you talking about 'the rad not doing its job'?

Test procedures have to be done in a repeatable way. Like when you want sustained turn time you'll not use maximum instantaneous turns to measure it.

 

The current speeds are about the same as a Yak 3 when the Yak1b in game is fully rads shut. 

 

I can assure you the Yak-3 would have gone even faster with closed rads. ;)

 

 

The Yak-1b was very well refined from the older series. While the bubbletop creates more drag than the razorback other refinemenrs helped increase speed quite well.

 

And yes, maybe put this to the fm discussion.

Edited by 216th_Jordan

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Well, I did try OH Damage myself once and actually found the Yak to take Damage a lot more quickly than the 109s. Give me a Sec to dig it up. 


https://forum.il2sturmovik.com/topic/19993-radiator-effectiveness-loss-overheat-bf109g-2f-4-lagg-3-and/


If anyone wants to try again, I  may, but not in the mood right now. 

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The Yak radiators were designed so that the "neutral" or "by airflow" position provided enough cooling so that the plane mantains around 100°C for water and 110°C for oil in the standard 15°C temperature at sea level at maximum speed horizontal flight, according to the devs in the Yak-1B these are 35% for the water radiator and 50% for the oil radiator.  The more you climb the temperature of the air decreases and less radiator openings are needed.

 

One thing that is said in the manual IIRC is that there was a 10/15 limit for having the water temp above 110°C, but the engine overheat pops up a bit higher than that 115°? So it would be good if we had some sort of time limit simulated there.

They were designed that way for the P and PA Engine. The PF is much more powerful and would run hotter, while the Rads weren't modified to compensate for it, and the 1B was only solving that Problem by a increasing the Opening Angle of the Shutters.  

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The Yak-1b was very well refined from the older series

 

What exactly where those modifications then (apart from slightly improved engine with differnt supercharger switch heights)? the only set of modifications i could find are those:

  • Upper decking of the fuselage behind the cabin was lowered, providing pilot all-around view;
  • Windshield side sections and the sliding section sides made flat to reduce optical distortions;
  • Rear view mirror installed;
  • Canopy shape was changed to reduce drag;
  • Armor:
  • Front and rear bullet-proof glass plates;
  • Armored head cover on the sliding section of the canopy;
  • Left arm protection;
  • Armament:
  • Two ShKAS machineguns replaced by single
  • UBS with 200 rounds;
  • Pneumatic system of gun reload was removed, pneumatic-mechanical and mechanical firing system replaced by electro-mechanical.
  • New R-1 control stick was installed. Two firing levers were replaced by two buttons on the stick head - like on Bf-109. Now pilot did not have to move his left hand from throttle control to the firing levers.
  • Disliked by pilots optical gunsight OPB was replaced by VV-1

Source:http://www.ram-home.com/ram-old/yak-1b.html

 

Nothing above suggest such a drastic increase in top speed , when also the radiator opening was widened , as Klaus-Mann suggested?

Edited by Hutzlipuh

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Well, from that same Page: The Radiator Change may still have occured on a Pre-Bubble Canopy series. It is modelled ingame at least. 69 has small Cowling Angle, 127 has the larger Angle. 

 

More scrupulous analysis of modified powerplant revealed number of drawbacks. Even at normal Summer temperatures 18...23°C horizontal flight with full power was possible for only 2 to 3 minutes. After this oil and water temperatures exceeded allowed maximum. Engine also overheated during climb, and it was necessary to level aircraft every 2500 to 3000m. Overheating resulted in increased oil leaks. Oil spills contaminated radiator surface and the windshield, forcing the pilot to fly with open canopy (15km/h speed penalty).

 

When those controversial results reached VVS command, two modified Yak-1s were ferried to the NII VVS for systematic study. Full-scale flight evaluation program confirmed gains in performance, as well as the fact that overheating problems do not allow to utilize those advantages during desired time intervals. Based on trials result, the NKAP ordered the engine modifications together with cooling system changes to be introduced on the series Yaks.

 

Since May 1, 1942 M-105PA was replaced on production lines (Engine Factory N°26) by M-105PF with air pressure boosted to 1050mm.Hg and modified carburetor. This engine was soon renamed VK-105PF for its chief designer V.Klimov. On May 29 1942 GKO ordered production of Yak-1 with VK-105PF engine, and since June 4 all Yak-1s rolled out with new engine and OP-352 oil cooler with increased cooling surface.

 

During Summer and Fall of the 1942 during Stalingrad Battle air combat situation for Soviet Army worsened: Luftwaffe put into action new Bf-109F-4 and Bf-109G-2 with more powerful engines. Those Messerschmitts had substantial advantage over series Yaks in climb and maneuverability and some in speed (specially when 3min boost system was engaged).

Following major efforts were undertaken by A.S.Yakovlev OKB:

  • Installation of modified VK-105PF engine (see Yak-1 VK-105PF);
  • Installation of new VK-106-1sk (see Yak-1 VK-106);
  • Weight saving program (see Yak-1 light);
  • Refinement of the fighter airdynamics, described here.

The GKO order was to increase aircraft speed by 20km/h: 525km/h at ground level and 590km/h at 3750m. Research centers TsAGI and LII recommended, and designers introduced following measures:

  • Fuselage divided by walls into sealed sections;
  • Tailwheel made retractable;
  • Cowling and fairing shape improved;
  • Grid protecting the water cooler removed;
  • Spinner replaced by less pointed;
  • Engine exhaust stacks covered by fairings;
  • Exhaust stacks re-shaped to utilize exhaust reaction force;
  • Cooler tunnels shape changed;
  • Surface quality requirements tightened;

In October 1942 series built Yak-1 N°16-99 was flown before and after airdynamic improvements. Trials took place at LII by test-pilot V.N.Kochenuk (from Factory N°292) and engineer V.Ya.Molchanov (LII). Results were positive - performance of improved Yak matched demands of VVS.

Edited by 6./ZG26_Klaus-Mann

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From Gordon's book concerning the modification that are posted just above:

 

"Work on Yak-l improvements proceeded

throughout 1943, and all of the modifications
were phased on to assembly lines. The excellent
results were evident in the tests of Yak-l
No.46139. At a loaded weight of 6,3131b
(2,864kg) it attained speeds of 334mph (539
km/h) at sea level and 375mph (605km/h) at
13,500ft (4,100m), climbed to 16,400ft
(5,000m) in 5.7 minutes, completed a 360 0
turn at low altitude within 17 to 18 seconds,
and climbed to 3,500ft (1,050m) while performing
an ascending turn. This was apparently
the best performance that could be
attained by a fighter of this type."
 
Something of a similar effect is said on the page that is being quoted above. The best the Yak-1 could pull off with all those refinements was 375mph. It would appear unlikely that simply closing the radiators would yield more performance than major overhauls of the design. What is more, doing the same with the German planes only gives about 10mph. Not 20 or 30. 
 
It should also be noted that neither Yak in game suffers from the climbing issue that the above post indicates, implying even more that the current rad performance is wrong. 

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<snip>

It should also be noted that neither Yak in game suffers from the climbing issue that the above post indicates, implying even more that the current rad performance is wrong. 

 

 

If you mean the overheating in a climb, I disagree. Flying the Yak scripted campaigns on the summer map, on the hot days, I often found that I had to back off from the recommended engine settings and climb speeds to prevent overheating.  Naturally, in colder weather, there was no problem.

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If you mean the overheating in a climb, I disagree. Flying the Yak scripted campaigns on the summer map, on the hot days, I often found that I had to back off from the recommended engine settings and climb speeds to prevent overheating.  Naturally, in colder weather, there was no problem.

I would wonder what parameters those were then, as I have never had this issue. Upon taking off in summer multi matches I simply crack open the rads and climb forever. 

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I would wonder what parameters those were then, as I have never had this issue. Upon taking off in summer multi matches I simply crack open the rads and climb forever. 

 

I believe you. TBH it surprised me as I had read up the contemporary flying instructions and had assumed that this could not happen if I stuck to the recommended climb speed and engine/cooling settings, which I do.  It was SP, some of the "Ivan's War" missions in the summer map. Presumably the SL air temperature was fairly high - maybe over 30 degrees C in summer. I have no idea what temperature the MP servers set for the summer maps, worth checking. If they just stick with standard 15 degrees C it is not surprising that you do not overheat. 

 

It is possible that you climb at a slightly higher speed than recommended, which presumably gives more cooling - a lot of people do, thinking that this is tactically better in some way if surprised. I tend to fly "by the book". 

 

Anyway my point is that you may need to do more extensive, systematic testing before concluding absolutely that the Yak radiators are "wrong". There might be some odd things about the radiators: P-40 gets a lot of comments along these lines, or it may be that the whole way engine heating, wear etc is modeled is a bit basic.

 

Spitfire heats up pretty quickly on the runway....  

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MP Mission Creators tend to set the Temps low to keep the players happy. It's very rare to find MP Servers using realistic Temperatures. 

Edited by 6./ZG26_Klaus-Mann

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Something of a similar effect is said on the page that is being quoted above. The best the Yak-1 could pull off with all those refinements was 375mph. It would appear unlikely that simply closing the radiators would yield more performance than major overhauls of the design. What is more, doing the same with the German planes only gives about 10mph. Not 20 or 30.

 

If you check the graph provided by SuperEtendard above you see that speed increase with fully closed rads is 11-12 mph max.

Also it is true what Klaus says, rarely you'll find temperatures higher than 20°C on servers. In the Stalingrad area you'd get temperatures as high as 40°C in summer.

Edited by 216th_Jordan

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If you check the graph provided by SuperEtendard above you see that speed increase with fully closed rads is 11-12 mph max.

Also it is true what Klaus says, rarely you'll find temperatures higher than 25°C on servers. In the Stalingrad area you'd get temperatures as high as 40°C in summer.

Ive seen his graph. Im getting different results. My tests so far are summer Kuban rads shut auto level. 

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Ive seen his graph. Im getting different results. My tests so far are summer Kuban rads shut auto level. 

 

I did the tests on Kuban map summer and got similar speed differences as SuperEtendard, around 15-16 kph (10 mph) at ground level and around 18 kph (11-12mph) at 4000m.

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Which program did you use to make this graph just out of curiosity. Me want!

 

Nothing special, just taking note of the speeds in game, convert them to TAS with this page http://indoavis.co.id/main/tas.html, which is really good, by taking temperature into account it's rather accurate (I had to gather temperature data with the Bf 110 up to 8k and Pe-2 at 9k), I compared it with a German test of a Bf 109 with both IAS and TAS noted in the report, and I took the IAS and got almost the same results as the real TAS (only a 2-3 km/h difference at the most, and these can be explained by a couple degrees differences in the ambient temperature, which is hard to read since both the Bf 110 and Pe-2 ambient temp gauges have markings each 10°C).

 

The graph was made with Excel.

 

 

What exactly where those modifications then (apart from slightly improved engine with differnt supercharger switch heights)?

 

In the Dev Diary 138 Petrovich talks about the different changes:

 

 

The first news I would like to tell you is that we have completed work on the development of the physics model for the Yak-1b 127 series, and now the aircraft is under internal "factory" testing. We plan to pass it to our beta testers in about a week.

 

Historically, the Yak-1b ser.127 was the result of systematic refinement and improvement of the Yak-1 during its serial production. The main external difference between 127th and the early series is the lack of fairing and a new teardrop-shaped canopy that provides a good view to the rear:

 

A bulletproof visor was installed to the front of the cockpit canopy. The pilot's back was covered by armored plate and a block of armored glass.

 

This aircraft got a new propeller - the VISh-105 instead of the VISh-61, which allowed the engine to develop full RPM at low airspeed. It slightly reduced the takeoff distance of the aircraft. Simultaneously, the propeller control changed; instead of a separate wheel it became a handle located next to the throttle handle so that both handles could be moved together with one hand.

 

To simplify the airframe and speed production, it was decided to abandon the rudder trim and aileron trim. Instead of the trims, adjustment plates were installed. The aircraft became a little lighter and its pressurization was improved [Note from Super: I think this means the air tightness of the fuselage was improved, by decreasing the gaps of the panels in the construction, the Yak wasn't a pressurized plane] . The shape of intake collector was changed. The exhaust pipes were covered by additional plates and the tail landing gear could now be raised in flight. All these changes reduced the aerodynamic drag of the aircraft and increased its top speed by 15-20 kmh. However, the climb rate and the turn time remained almost the same.

 

Also, the engine cooling system was modified. Now the radiator shutters were able to open wider than the previous Yaks shutters could. The downside of this refinement was an increase of the drag when the radiator shutters are fully open.

 

In addition, a new scheme of the tail wheel locking was implemented. The manual lock control was removed, and the wheel automatically became free when pushing the pedals more than three-quarter deflection. It simplified taxiing, but the plane became "stricter" on the takeoff and landing.

 

The aircraft’s armament was also improved: instead of two small ShKAS guns, a large-caliber UBS gun with 220 rounds of ammunition was installed. However, installing rockets into the plane was refused, and only aircraft ordered by the Air Defense Forces were equipped with the landing light.

 

Lots of minor improvements which appeared in the Yak-1 serial production all together significantly improved its fighting qualities. We hope that as soon as our beta-testing is finished, all the pilots who have already pre-ordered it will come to see that.

 

 

 

 Somehow, the Yak1b in game is getting more or less the same top speeds as a Yak3.

Yak-3's top speed is a bit too much though, it's top speed at sea level was around 567 km/h  (1B without rads is 544 km/h) and at altitude was around 640 km/h at 4000 meters (1B without rads does 616 km/h).

 

They get similar at high altitudes though, as the performance loss with altitude is less than the real plane.

 

mzfcYwF.png

 

 

There is technical manual/report about the Yaks radiators translated to Spanish in the rkka.es website  http://www.rkka.es/Manuales/001_manuales_vuelo/Manual_Yak-X/2002.htm In which it is said that from the neutral to full closed position they give around 12 km/h increase in top speed, I translated the graph with the different radiator positions:

 

 

MmHejBh.gif

 

Thing with this report is that I don't know to which particular Yak variant it applies, it mentions the PF engine but I don't know if it applies to the Yak-1, Yak-1B, Yak-7B or Yak-9.

 

Currently the speed gains for closing the rads is 15-16 km/h, which would be 3-4 km/h more than what the report says, it isn't that much of a difference, in TAS at 6000 m it would only 5 km/h slower.

 

 

So I think the speed effect of closing the rads themselves isn't much of a problem imho, I think it's more about the smaller performance decrease with altitude, also the lack of a more strict overheat damage implementation (15 mins over 110°C as a timer limit).

 

The 109 F-4 is still faster than the 1B at high altitudes, but the margin gets diminished.

 

RPaR02Z.png

Edited by -=PHX=-SuperEtendard
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Is the difference in the 109 speed at sea level really that big between 1.37 and 1.42 ata? From 525 to 545kph?

No, sorry that particular point got mixed up with one from another plane in the notes, it should be 534 km/h at sea level at 1.37 ata.

 

Updated the graph with the correct speed, thanks for noticing :)

Edited by -=PHX=-SuperEtendard

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Nice work Etendard.

 

 

So I think the speed effect of closing the rads themselves isn't much of a problem imho, I think it's more about the smaller performance decrease with altitude, also the lack of a more strict overheat damage implementation (15 mins over 110°C as a timer limit).

Reminds me of this:

https://forum.il2sturmovik.com/topic/29459-440kmh-ias-6k-yak-1b/

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Nothing special, just taking note of the speeds in game, convert them to TAS with this page http://indoavis.co.id/main/tas.html, which is really good, by taking temperature into account it's rather accurate (I had to gather temperature data with the Bf 110 up to 8k and Pe-2 at 9k), I compared it with a German test of a Bf 109 with both IAS and TAS noted in the report, and I took the IAS and got almost the same results as the real TAS (only a 2-3 km/h difference at the most, and these can be explained by a couple degrees differences in the ambient temperature, which is hard to read since both the Bf 110 and Pe-2 ambient temp gauges have markings each 10°C).

 

The graph was made with Excel.

 

 

 

In the Dev Diary 138 Petrovich talks about the different changes:

 

 

 

 

 

Yak-3's top speed is a bit too much though, it's top speed at sea level was around 567 km/h  (1B without rads is 544 km/h) and at altitude was around 640 km/h at 4000 meters (1B without rads does 616 km/h).

 

They get similar at high altitudes though, as the performance loss with altitude is less than the real plane.

 

mzfcYwF.png

 

 

There is technical manual/report about the Yaks radiators translated to Spanish in the rkka.es website  http://www.rkka.es/Manuales/001_manuales_vuelo/Manual_Yak-X/2002.htm In which it is said that from the neutral to full closed position they give around 12 km/h increase in top speed, I translated the graph with the different radiator positions:

 

 

MmHejBh.gif

 

Thing with this report is that I don't know to which particular Yak variant it applies, it mentions the PF engine but I don't know if it applies to the Yak-1, Yak-1B, Yak-7B or Yak-9.

 

Currently the speed gains for closing the rads is 15-16 km/h, which would be 3-4 km/h more than what the report says, it isn't that much of a difference, in TAS at 6000 m it would only 5 km/h slower.

 

 

So I think the speed effect of closing the rads themselves isn't much of a problem imho, I think it's more about the smaller performance decrease with altitude, also the lack of a more strict overheat damage implementation (15 mins over 110°C as a timer limit).

 

The 109 F-4 is still faster than the 1B at high altitudes, but the margin gets diminished.

 

RPaR02Z.png

Thanks for the data collection, the rad document is particularly useful. 

 

 

 

Im going to publish my own tests later, probably today at some point when i decide how to format it all. 

 

I am definitely getting different results. In my tests the G-2 is on par at 3500m with Yak1 rads shut. The F4 is slightly faster. All are withing a few mph of each other at 3500m. 

 

With rads shut I am getting yaks that hit anywhere from 371mph top end to 407mph. Using your TAS calc is how I got 407mph. Most testing hits max speeds at 4500m summer conditions of 395mph. This is using tacview to get TAS. For some reason there is variation between tests in speeds, which i think it leading to the different between our testing as well. 

 

Rad shut vs rad open speed differences are consistent however. Fully shut gave me 360mph at 4500m, and 395mph closed. So about 35mph. 

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