Different maximum temperature at high altitude for water cooled engines

[TAIPAN_]

Sorry again I ask about cockpit gauges, twice in the same week

 

MiG-3 water temperature max is 120c, and this works fine at sea level.

 

However when at 5000m+ I get overheat message much earlier at about 100c.

There was a discussion on reddit that confirmed it also happens with the Yak and Bf109 (all water cooled engines).

 

Is this due to modelling different boiling points of water at altitude, meaning the specs max temperature is only for sea-level? We need to adjust temperatures lower as we get higher?

Or does the gauge read incorrectly due to altitude affect and there is not actually any risk of overheat (technochat message would be wrong in this case)?

Or something else going on?

 

Screenshot below shows:

• water (green gauge) at 100 (max is  120)
• Oil intake (red gauge) at 60 (max is 85)
• Out output (above intake) at 90 (max is 120)
• Technochat "Engine overheat"

 

 

Edited May 27, 2020 by Dan_Taipan

[II./SG.1-MarkWilhelmsson]

4 hours ago, Dan_Taipan said:

Sorry again I ask about cockpit gauges, twice in the same week

 

MiG-3 water temperature max is 120c, and this works fine at sea level.

 

However when at 5000m+ I get overheat message much earlier at about 100c.

There was a discussion on reddit that confirmed it also happens with the Yak and Bf109 (all water cooled engines).

 

Is this due to modelling different boiling points of water at altitude, meaning the specs max temperature is only for sea-level? We need to adjust temperatures lower as we get higher?

Or does the gauge read incorrectly due to altitude affect and there is not actually any risk of overheat (technochat message would be wrong in this case)?

Or something else going on?

 

Screenshot below shows:

• water (green gauge) at 100 (max is  120)
• Oil intake (red gauge) at 60 (max is 85)
• Out output (above intake) at 90 (max is 120)
• Technochat "Engine overheat"

 

 

 

Boiling point of fluids is a function of pressure. I believe these of are fully sealed systems so I'm not entirely sure altitude should effect the boiling point. It likely is something more to do with the air density at higher altitudes. There is a point where volume of air passing through the heat exchanger is more important than the temperature of that air.

[TAIPAN_]

2 hours ago, II./SG.1-MarkWilhelmsson said:

 

Boiling point of fluids is a function of pressure. I believe these of are fully sealed systems so I'm not entirely sure altitude should effect the boiling point. It likely is something more to do with the air density at higher altitudes. There is a point where volume of air passing through the heat exchanger is more important than the temperature of that air.

Wouldn't the supercharger bring the air density up? I think in the MiG it's optimised for 7200m.

Unless it affects the gauges and not the engine.. maybe I should have tested with HUD mode difficulty on then I could see the actual values instead of the gauges..

[Lusekofte]

3 minutes ago, Dan_Taipan said:

Wouldn't the supercharger bring the air density up? I think in the MiG it's optimised for 7200m.

Unless it affects the gauges and not the engine.. maybe I should have tested with HUD mode difficulty on then I could see the actual values instead of the gauges..

Is this supercharger a user of coolant? Or does it heat up environment around the engine?

I am not trolling, I never really pushed engines up high, I want to learn

[Yogiflight]

You can see it on the temperature gauge of the 109s, which temperature was allowed at what altitude. The altitudes are written over the scale, so easy to see for the pilot.

From my understanding it works like in a pressure cooker. The higher pressure inside the system compared to the pressure of the surrounding air, makes the coolant boil at lower temperature.

Another example would be, if you would be in space without a protecting suit. Your blood would start boiling in a few seconds, because of the much higher pressure inside of your body, compared to the vacuum of the space.

EDIT: But as far as I am aware, this is not modelled in game.

Edited May 27, 2020 by Yogiflight

[Lusekofte]

Thanks @Yogiflight spent all my reactions of the day. You get one tomorrow

[TAIPAN_]

1 hour ago, Yogiflight said:

You can see it on the temperature gauge of the 109s, which temperature was allowed at what altitude. The altitudes are written over the scale, so easy to see for the pilot.

From my understanding it works like in a pressure cooker. The higher pressure inside the system compared to the pressure of the surrounding air, makes the coolant boil at lower temperature.

Another example would be, if you would be in space without a protecting suit. Your blood would start boiling in a few seconds, because of the much higher pressure inside of your body, compared to the vacuum of the space.

EDIT: But as far as I am aware, this is not modelled in game.

 

Thanks! Let's hope we never get shot into space without a suit then..

 

I'll have to keep things a bit cooler as I get higher, I wonder if there's a formula somewhere we can figure out the right temps.

 

In terms of being modelled in game - are you sure it's not modelled? Because technochat does say it's overheating...

 

 

[216th_Jordan]

2 hours ago, Yogiflight said:

You can see it on the temperature gauge of the 109s, which temperature was allowed at what altitude. The altitudes are written over the scale, so easy to see for the pilot.

From my understanding it works like in a pressure cooker. The higher pressure inside the system compared to the pressure of the surrounding air, makes the coolant boil at lower temperature.

Another example would be, if you would be in space without a protecting suit. Your blood would start boiling in a few seconds, because of the much higher pressure inside of your body, compared to the vacuum of the space.

EDIT: But as far as I am aware, this is not modelled in game.

 

I'm not sure I get you correctly but from my knowledge its not the relations of pressue that matter because inside a closed system they would not matter anyways. AFAIK its a pure function of pressure/density. In space, without outside pressure the pressure inside your body also decreases because your body allows expansion, hence the lower boiling point.

 

In a pressure cooker you get a higher boiling temperature not a lower one. (Or did I missunderstand you?)

 

I'd think that the overpressurization in airplane systems was defined by how much higher the system pressure can be against the outside pressure. So lets say system pressure can be 0.5 bar higher than the outside pressure to function safely: At sea level you would have 1.5 bar in the system but when you get higher up and the outside pressure is at 0.5 bar the system pressure will be at 1 bar and boiling starts sooner. Also this is easy to implement with a very simple valve system.

 

I'd be happy to learn more if I am wrong though.

Edited May 27, 2020 by 216th_Jordan

[RedKestrel]

I pulled this from the pilot's notes of the Spitfire Mk. IX, as I was able to find it quickly online:

7. Engine coolant system.—On early aircraft only, circulation of the coolant through the underwing radiators is thermostatically controlled, the radiators being by-passed until the coolant reaches a certain temperature. The header tank is mounted above the reduction gear casing and is fitted with a relief valve. On all aircraft the radiator flaps are fully automatic and are designed to open at a coolant temperature of 115°C. A pushbutton is fitted on the electrical panel for ground testing; and there is a coolant temperature gauge (16) on the instrument panel.

 

So for the Spitfire it doesn't look like the engine would overheat below 115 coolant temperature. If it did, the spitfire's automatic radiator system doesn't make sense, especially since they operated frequrently at relatively high altitudes. A while back there were some issues with this after a patch, where the spitfire was overheating and venting coolant before the radiator shutters would even open. 

@216th_LuseKofte in regards to the supercharger, it does appear that operating the supercharge introduces heat into the system, and at least in the Spitfire IX, looks like it has an automatic system to turn the supercharger to a lower stage when it overheats.

8. Intercoolcr system.—On all aircraft the high temperatures resulting from two-stage supercharging necessitate the introduction of an intercoolcr between the supercharger delivery and the induction manifolds, particularly when S (high) gear is used. An auxiliary pump passes the coolant from a separate header tank to a radiator underthestarboard wing, and thence through the supercharger casing to the intercooler, where the charge is cooled by loss of heat passing to the coolant. On early aircraft a thermostatically operated switch in the induction pipe is connected to the supercharger operating ram and causes it to change the supercharger to M (low) gear in the event of the charge temperature becoming excessive. This change of gear ratio is indicated to the pilot by a pushbutton, which springs out on the instrument panel. The supercharger will change back to high gear after the temperature of the charge has returned to normal and the pushbutton has been pushed in. If, however, the excessive temperature is of a permanent nature, due to failure of the intercoolcr system, the pushbutton will continue to spring out and the flight should be continued in low gear.

[Yogiflight]

1 hour ago, 216th_Jordan said:

In space, without outside pressure the pressure inside your body also decreases because your body allows expansion, hence the lower boiling point.

 

In a pressure cooker you get a higher boiling temperature not a lower one.

Yes, you are right, my fault.

 

1 hour ago, 216th_Jordan said:

from my knowledge its not the relations of pressue that matter because inside a closed system they would not matter anyways

 

1 hour ago, 216th_Jordan said:

I'd think that the overpressurization in airplane systems was defined by how much higher the system pressure can be against the outside pressure. So lets say system pressure can be 0.5 bar higher than the outside pressure to function safely: At sea level you would have 1.5 bar in the system but when you get higher up and the outside pressure is at 0.5 bar the system pressure will be at 1 bar and boiling starts sooner

These two statements are pretty much the same. Maybe I didn't express good enough, what I meant. With the relation of pressure, I meant the difference of the pressure inside the system and of the surrounding air.

 

1 hour ago, 216th_Jordan said:

Also this is easy to implement with a very simple valve system.

You mean implement in the game? Would be nice, if it was implemented in the game, but with the career missions usually being very low altitude, I don't see a big interest by the Devs doing so.

[216th_Jordan]

3 hours ago, Yogiflight said:

 

You mean implement in the game? Would be nice, if it was implemented in the game, but with the career missions usually being very low altitude, I don't see a big interest by the Devs doing so.

 

I meant IRL, but I also think that the simulation is implemented ingame if water starts boiling at a lower tamperature ingame, as was written in the post by the OP. But I do not know if the overheating message and simulation necessarily correspond.

Edited May 27, 2020 by 216th_Jordan

[Yogiflight]

24 minutes ago, 216th_Jordan said:

 

I meant IRL, but I also think that the simulation is implemented ingame if water starts boiling at a lower tamperature ingame, as was written in the post by the OP. But I do not know if the overheating message and simulation necessarily correspond.

I don't think it is simulated, as I often have higher water temperatures in high altitude, than the numbers on the gauge would allow me and never had any issues. Plus I don't see any differences in water temperatures in higher altitudes, which should be lower, but as I wrote above, it isn't neccessary for the low alt missions we have in the career mode. For MP or PWCG, however, it would be interesting.

[TAIPAN_]

I found this interesting document from 1920

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930091123.pdf

 

It's a very short paper but a bit too much maths/physics for me, I wasn't able to gather an appropriate estimate for how to estimate the max temp as I climb.

 

I think I'll just take the ratio the 109 uses on the gauge and apply it to all. From the 109 gauge it looks like a rule of thumb would be:

• Reduce by 30% at 5,000m
• Reduce by 60% at 10,000m

 

Another question is - do we apply this reduction to only the max temperature? Or also to the rated/optimal temperature?

I'd say probably both, because at 10,000m the max temperature is going to be lower than the normal rated temperature...

Edited May 28, 2020 by Dan_Taipan

[JtD]

WW2 aircraft may have closed, pressurized cooling systems, but they all have some sort of relieve valve, which typically is set at a relative over-pressure (German designation would be atü). Meaning that at 1ata pressure down low the system blows off steam at 1.5ata, but up high, at 0.7ata, it blows off steam at 1.2ata already, assuming you're using an 0.5atü relief valve. As boiling points (temperature at which water becomes steam) go down with pressure, the boiling points of the cooling systems typically go down with altitude.

 

One should also note that while the boiling points and thus the maximum water temperatures go down, so do the air temperatures at altitude, and with pressurized systems, the decrease in air temp is larger than the decrease in maximum water temp. The difference between these temperatures is very important for the maximum cooling effect, so that in the end, a lower boiling point at altitude doesn't necessarily mean less cooling than at sea level.

 

This is modelled in game since the 3.006 update in September 2018.

 

"36. The water in all water cooled engines boils at different temperatures depending on the altitude;"

 

https://forum.il2sturmovik.com/topic/12826-game-updates/?tab=comments#comment-673733

 

Edited May 30, 2020 by JtD

[Yogiflight]

50 minutes ago, JtD said:

"36. The water in all water cooled engines boils at different temperatures depending on the altitude;"

This might well be, but it is not modelled correctly. See screenshot below.

109 G6 flying for 15minutes in 10km altitude with max combat power (2600RPM, ATA pretty low in that altitude).

Temperature 90°C, but according to the temperature gauge it should not be above 40 or 50°C in 10km altitude.

 

 

[unreasonable]

19 minutes ago, Yogiflight said:

This might well be, but it is not modelled correctly. See screenshot below.

109 G6 flying for 15minutes in 10km altitude with max combat power (2600RPM, ATA pretty low in that altitude).

Temperature 90°C, but according to the temperature gauge it should not be above 40 or 50°C in 10km altitude.

 

 

 

I always wondered about that myself. 

 

When we had the introduction of the cooling/pressure system to the game, it was obviously incorrect in the Spitfires, which were simply unable to fly at high altitudes because of boiling coolant, we think because the developers had set the pressurization of the system at far too low a level.  We got that fixed with reference to technical data for the cooling systems and the manuals - which (seem to) make clear that the temperature limits are unaffected by altitude in the Merlin powered planes over the actual operation range of heights.

 

So I wondered about these markings and notes in the 109 manuals - not yet seen a satisfactory explanation.

 

 

 

 

 

  

[[CPT]Crunch]

Cabin pressurization systems are also a closed system, but generally they're going to raise cabin altitude as you climb due to aircraft skin psi limits, it's a safety issue if the skin or a hatch ever were to give way.  A few psi makes a huge difference when your talking a large surface area.  Otherwise the airlines would keep sea level and sell you unlimited booze, make more in the bar tending than pax hauling end.

[TAIPAN_]

1 hour ago, Yogiflight said:

This might well be, but it is not modelled correctly. See screenshot below.

109 G6 flying for 15minutes in 10km altitude with max combat power (2600RPM, ATA pretty low in that altitude).

Temperature 90°C, but according to the temperature gauge it should not be above 40 or 50°C in 10km altitude.

 

 

My MiG-3 would be dead with that temp at 10k, according to technochat... I haven't pushed it to kill it for science yet though.. hopefully somebody who knows what's going on will stumble across this topic.

[JtD]

1 hour ago, Yogiflight said:

This might well be, but it is not modelled correctly. See screenshot below.

 

Of course, it's always the model that's wrong...it's never possible that it's just a wrong texture or anything else.

The limits are modelled about right:

 

Interestingly enough, the 1942 Bf109G instruments section of the manual contains information about markings that are to be applied on the gauges. For the temperature gauge it states:

As with other markings that are supposed to be made according to this manual, it actually states the limits for the 1939 Bf109E/DB601A.

[unreasonable]

14 minutes ago, JtD said:

 

Of course, it's always the model that's wrong...it's never possible that it's just a wrong texture or anything else.

 

Bit grumpy today...    

 

Well that does explain it but I wonder where the game cockpit markings came from.  Could it be the limits if your pressurization is compromised? 

Not that it matters - 109s clearly should not be boiling over all the time at high altitude any more than Spitfires.    

[JtD]

6 minutes ago, unreasonable said:

Bit grumpy today...

 

Guilty as charged.

 

I'd suppose the markings come from the reference I gave, plus some artistic freedom. The boiling point of pure water at 10km altitude is around 75°.

 

The way I read the MiG-3 manual, the MiG radiator ran at 1.4atü with (pure) water, which should be good for 125° at sea level and 110° basically in vacuum. This agrees with the manual which states 120° on take off and 110° in flight, with the pressure gauge at 1.2-1.5at. So operational limits slightly below the physical ones. The water temperature is being measured at the engine outlet, so it is the hottest point and no hidden reserve is needed. Imho, the MiG-3 should not "overheat" at 100° at altitude.

[Yogiflight]

2 hours ago, JtD said:

 

Of course, it's always the model that's wrong...it's never possible that it's just a wrong texture or anything else.

The limits are modelled about right:

 

Interestingly enough, the 1942 Bf109G instruments section of the manual contains information about markings that are to be applied on the gauges. For the temperature gauge it states:

As with other markings that are supposed to be made according to this manual, it actually states the limits for the 1939 Bf109E/DB601A.

Thanks for correcting me, I am always pleased to learn something new.

To affirm what you wrote, here a screenshot of the temp gauges of the 110 E2

[-=PHX=-SuperEtendard]

 @JtD talking about radiator efficiency and coolant pressurization, do you have some information on how the Macchi C.202 cooling system worked?

Since the update that modelled the coolant loss because of overpressure the 202 has quite some trouble not having it's coolant overheat, looks like it doesn't have much pressurization in the system and also the radiator is quite innefficient. Sounds strange given this plane opearted in the hot mediterranean and north africa theaters.

For example in game in a Summer map with "just" 25ºC (compared to the temps in the MTO) the 202 can't sustain a climb in combat settings (1.35 ata, 2400 RPM) even with full open radiators, it will start losing coolant at 2500 meters of altitude, 250 km/h, with around 105ºC water temperature at the radiator intake, and 101ºC at the radiator exit point.

[Raven109]

 

The water/oil temperature gauge from the 109G2 "Black 6". So at least the texture does seem to be correct.

 

Another one from a 109G6 instrument panel:

 

 

The 109E/DB601 limits were:

 

 

Real-life altitude/temperatures placard in the 109E.

 

 

The 109E placard matches the manual. I can't find any reason why the 109G series temperature limits shown on the temp gauge do not match the manual.

Edited May 30, 2020 by Raven109

[LukeFF]

2 hours ago, Raven109 said:

The water/oil temperature gauge from the 109G2 "Black 6". So at least the texture does seem to be correct.

 

Thanks, I've made a report about it.

[Voyager]

Dumb question but, have you tested to see if the engine actually fails when run in that condition? 

 

I've encountered an issue with the Techno chat on the P-47D where, once you get past around 7km the technochat does not report engine overheat situations until much hotter than the actual failure point is. The engine will still overheat and fail if the cylinder head temp is past the red line for too long, but the tech chat wouldn't go off until something like 10-15C hotter. 

 

So question is, when the tech chat is reporting an overheat condition below the listed red line, it is worth testing if the engine will actually fail, or if it will only fail at a higher temperature. We may need to treat tech chat more like the D2 character sheet, than ground truth. 

[JtD]

11 hours ago, Raven109 said:

Another one from a 109G6 instrument panel:

 

This is interesting. The Bf109 manual states at Fl20343 switchable temperature gauge is to be used. It goes to 160° and can display oil inlet temp when the button on the top right is being pressed (as with the Black6 picture you posted). The data sheet below states it is not supposed to be used for new models. There also is a Fl20342 non-switchable temperature gauge, which goes to 130°, and says is supposed to be used as a replacement for the Fl20343 switchable gauge.

Now the interesting bit is, that in your picture, the gauge is ending at 130° and is missing the switch-button in the top right corner. It's not a 20343, likely a 20342. But the frame still says "press the button", and I wonder if the markings put on the green-red bar on top of the gauge still come from an original 20343. Interestingly enough, the in game version is also a mix, but a wrong one, as it is missing the switch button.

 

https://www.deutscheluftwaffe.com/downloads/Dokumente/Geratezeichnungen/20000-22000/Blatter/Fl20343.gif

 

https://www.deutscheluftwaffe.com/downloads/Dokumente/Geratezeichnungen/20000-22000/Blatter/Fl20342.gif

 

Please also note that on the 109 the radiator was automatic and set to control the coolant temperature at 102°, independent of altitude. Any markings below that temperature can't really have operational meaning to the pilot. The DB605A cooling system ran at 1atü and was good for 106° at 15km altitude, according to the DB605 manual.

 

Edit: I found the figures for the markings of 78° at 10km and such already in a May 1941 Bf109F manual, it's exactly the same text. Which is wrong already there, and definitely a leftover from earlier versions. The correct version for a Bf109G would probably look like this, which corresponds to the figures from the compact flight manual:

https://upload.wikimedia.org/wikipedia/commons/9/96/Messerschmitt_Bf_109_G-6R3_Cockpit.jpg

 

 

Regarding the Mc.202, I found that it used a "special Aer. Macchi valve" that weighs 620grams. No information about pressure. Please note that even closed systems running without over-pressure would need some sort of pressure valve, otherwise an overheating coolant would simply blow a line or a joint and never seal for the rest of the flight if the coolant temperature drops again. I've also read that the temperature should not exceed 95° E and 103° U in a climb, which I'd wager are engine in and engine out temperatures.

The Mc.202 uses a licence built DB601Aa, which, afaik, used the temperature limits given by Raven109 and me before. These values supposedly are "6° below the boiling point", fwiw. The DB601Aa had an pressure valve rated at 0.3atü, according to a Bf109E export description. I suppose the devs went with the same figures for the Mc.202. I have no data that explicitly says otherwise, might be a good idea to ask our Italian community members. At the very least they speak Italian, which I don't. It's possible the cooling system on the Mc.202 was upgraded to later DB601/DB605 standards, we'd just need some more info on that.

Giving 103° as a limit in a climb does not make sense if that's higher than the physical maximum already at 2km altitude...but that's no hard data, just an indication.

Edited May 31, 2020 by JtD

[Raven109]

Unfortunately, older pictures are not clear enough to see the temperature values on the gauge or the placard (so by looking at them we could at least avoid making mistakes based on new, restored 109 models). But you can still see that the placard is there and the temperatures are on the placard (even in the manuals). The gauge and the placard are different objects, and as far as I can tell, the gauge can be installed without the placard. So, if it wasn't necessary, why did so many planes have it? As I see it, it could certainly lead to confusion - but perhaps, these values were not that important to pilots (as we make them to be), since the radiator was automatic, and most of the time it was hands off.

 

Interesting to note is that there are G6 models which have just the gauge without the placard. And the late 1944 models seem to have removed it (e.g the K4). This could indicate that the placard was not that important. 

 

I agree that the manuals should be the ones that should be followed, I can see the values both in the 109G manual, and the DB605 manual, but still can't help myself being curious as to why the placard shows something else.

 

In the cockpit below (G2) if you zoom in, you can clearly see that a FL20342 is being used. Seems to have no switch button. The limits are still present though. If the gauge itself could not be switched between showing 2 temperatures (oil and coolant) and the placard values were irrelevant, why go through all the trouble of adding the placard? (as a side note, see the ATA gauge limited to 1.3)

 

 

3 hours ago, JtD said:

Edit: I found the figures for the markings of 78° at 10km and such already in a May 1941 Bf109F manual, it's exactly the same text. Which is wrong already there, and definitely a leftover from earlier versions. The correct version for a Bf109G would probably look like this, which corresponds to the figures from the compact flight manual:

https://upload.wikimedia.org/wikipedia/commons/9/96/Messerschmitt_Bf_109_G-6R3_Cockpit.jpg

 

Later edit: I just noticed you updated your post. Good find, so it seems that there were at least multiple scales for the placard. The values from your pic correspond (at least for the 8k value) to the what the DB605A manual lists. For the "over 8k" setting the placard shows 95*C, while the manual lists 98*C @ 9k, 97*C @ 10k. The 605 values are given for 0,75 atue.

 

From my point of view, the conclusions regarding the 109 temperature gauge are these:

a. The game models one type of placard. The texture doesn't seem to be wrong, and it could be that some aircraft had the wrong placard installed. It could also be that the texture is wrong in that it's missing the 3 lines which correspond to the 10 5 0 km values, and so players assume that the actual position of the 10 5 0 values along the temperature tape are the max temp values that they should follow at the different altitudes.

b. The 109 does have an automatic radiator system, however we cannot ignore the fact that automatic systems still fail, so then the pilot does need some guidance regarding the temperatures the engine can be run safely at a given altitude.

c. Later 109 models (mid 1944 onwards) don't have the placard anymore, which might indicate that it wasn't that important to begin with. This becomes more evident if we consider the models that had the wrong placard and no one bothered to update it.

 

Here's a crop from a ww2 cockpit:

 

 

Full image here:

Spoiler

The numbers on the placard could be 10 5 0 , in the top right corner (as we've seen in the other pictures). Now, I don't know if it's just me, but you can also notice faint lines on the tape above the actual temperatures scale (you can also see these red lines in the pics I've posted before). All lines seem to correspond to values between 80*C and 120*C (which is what we get from the 109G manuals). So this, in my opinion, double confirms that the placard modeled in-game is not the one which corresponds to the actual temperatures for the 109G, or at least, that its missing these lines that we see on the tape (In game we do have the white-red-white lines, but these seem to be centered around the 110*C value, and could indicate a maximum allowable value).

Edited May 31, 2020 by Raven109

[JtD]

Totally agree with you, that placard is a placard of many questions. I found a parts number in a Bf109G component list, says 109.954, but that doesn't lead anywhere.

 

I also think that for the most part we should ignore pictures of restored 109's, because all too often they are wrong in some details. In the picture you posted last, the placard seems to have been added at a later date, it looks much more fresh than everything else. I also note the screws are painted in a glossy black, while most other (probably original) screws are painted in a matt grey. Doesn't really add trust.

[Raven109]

8 minutes ago, JtD said:

Totally agree with you, that placard is a placard of many questions. I found a parts number in a Bf109G component list, says 109.954, but that doesn't lead anywhere.

 

I also think that for the most part we should ignore pictures of restored 109's, because all too often they are wrong in some details. In the picture you posted last, the placard seems to have been added at a later date, it looks much more fresh than everything else. I also note the screws are painted in a glossy black, while most other (probably original) screws are painted in a matt grey. Doesn't really add trust.

 

Yes, I'm getting more and more the feeling that the restored 109s have that placard just for the sake of completeness, i.e. to look the same as seen in WW2 pictures, but since the pictures are not that detailed, the finer details are missing or are not correct (i.e. the small lines which map the 10 5 0 values to the temperatures values on the gauge).

 

It's interesting to note that we can distinguish 3 types of placard:

a. One has the 10 5 0 values spread along the whole width of the placard;

b. One that has the 10 5 0 bunched up at the top right corner of the placard;

c. One with just two values (the one you posted);

 

I think all the above types can be used, so long the lines on the tape are drawn to match the actual values on the temperature scale.

 

 

This is what we're missing from the game texture.

 

From my tests the temperatures which are actually indicated by the in-game gauge seem to be correct. Apparently it's just a markings error.

[JtD]

A Bf110C cockpit image shows another type of placard. I'd say it says "km 10-5-0" and that there are markings corresponding to the temperature limits of the manual. These placards aren't present in the poor quality images of the manual. Since these placards are easily made in your local workshop, they may have well been added as an afterthought at any point between the production line and front line squadron activities, and that in many forms. The purpose probably was to indicate the safe operating zones, which are not on the actual temperature gauge. But unless someone finds dozens of high quality images of WW2 Bf109G cockpits, I guess we'll never really know what exactly was done how back then, and if they indeed painted wrong limits on some of them.

 

Bf110C image (temp gauges labelled 14 low centre panel):

https://www.deutscheluftwaffe.com/archiv/Dokumente/ABC/e/Ereignisse/bilder/gross/007.jpg

 

Personally I wouldn't use them at all, because of the performance impact of the added weight.

[TAIPAN_]

On 5/31/2020 at 1:19 PM, Voyager said:

Dumb question but, have you tested to see if the engine actually fails when run in that condition? 

 

I've encountered an issue with the Techno chat on the P-47D where, once you get past around 7km the technochat does not report engine overheat situations until much hotter than the actual failure point is. The engine will still overheat and fail if the cylinder head temp is past the red line for too long, but the tech chat wouldn't go off until something like 10-15C hotter. 

 

So question is, when the tech chat is reporting an overheat condition below the listed red line, it is worth testing if the engine will actually fail, or if it will only fail at a higher temperature. We may need to treat tech chat more like the D2 character sheet, than ground truth. 

 

Sorry I was a bit slow to test this, but finally did it today.

The technochat is perfectly correct in warning of overheat at the lowered temperature (for the MiG-3 at least).

 

I tested at 7,000m putting the oil radiator in a safe range and then water at 100c (20c below the specs max temp). When water gets up to 100c the overheat warning comes up. Hold it at 100c for 5 minutes then engine damage message, and failure very soon afterwards.

To make sure nothing else was the cause I tested the exact same parameters with lower water temps and no failure or warning.

 

So it seems the sim does implement different(lower) maximum water temperatures at altitude. I'm just looking at the differences in the placards of the 109 and others and trying to calculate what it should be for the Russian aircraft as well.. although different engines might have different parameters. I wonder if the way it's implemented is a fixed percentage change for all aircraft or if it's individualised.. don't have time to test more right now.

[JtD]

This is modelled based on (atmospheric) pressure and boiling point physics, and as I've already stated, the MiG-3 apparently ran at 1.4atü. But I've also aready quoted the devs that this is implemented, and still you tested it?

 

Here are tables and charts that give water boiling points over pressure:

 

https://www.engineeringtoolbox.com/boiling-point-water-d_926.html

 

Mig-3 1.4atü -> 2.4ata (2.4bar for ease of conversion) at sea level, 1.4ata in vacuum (or say 1.7ata at altitude). Boiling points: 126°C down low, 110°C in vacuum or 115°C at altitude. Limits in the manual are 5° lower than that (120° for take off, 110° in flight). Makes sense.

 

Different aircraft -> different pressure, different coolant (for instance glycol) -> different boiling points.

 

If I were you, I'd take what you have on the MiG-3 and contact the devs about it (PM Gavrick), or write a bug report in the much ignored bug report section of the forum.

[TAIPAN_]

11 hours ago, JtD said:

 But I've also aready quoted the devs that this is implemented, and still you tested it?

 

I didn't see a quote of the devs from you, only your own statements that it was implemented (and other details which were useful thank you). Although I'm very tired lately maybe I missed the quote..

 

I tested because the only thing I knew for sure was that technochat was telling me something, but did not know if the engine would die. Elsewhere I was told to ignore technochat, the best way to know who to believe was to test it.

 

I'll take your advice and ask the Devs if they think there's an issue that needs adjustment.

 

Thanks

[216th_Jordan]

Don't trust technochat, its known for being unreliable for such info. A20 used to show overheating messages while being far from overheating and Yak-7 or other Yaks were trailing coolant vapor while technochat gave no message about oberheating, slowly depleting the coolant volume and making you stand out.

[TAIPAN_]

3 hours ago, 216th_Jordan said:

Don't trust technochat, its known for being unreliable for such info. A20 used to show overheating messages while being far from overheating and Yak-7 or other Yaks were trailing coolant vapor while technochat gave no message about oberheating, slowly depleting the coolant volume and making you stand out.

 

This is exactly why I tested Technochat is correct about an overheat this instance with the MiG, more correct than the specs.