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eastriverman

Bf-109K-4 lacking high altitude performance in BoBP career

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HiHo!

 

I stumbled over a weird effect while playing die Bodenplatte single player career.

 

On missions regarding the interception of an allied recon plane, always a Spit IXe, there's a problem with the high altitude performance of the Bf-109 K-4.

 

While on the way to the mission point everything is fine and I can use the throttle in a normal way. In particular, I can employ any power from 0% to 100% (emergency)

 

To conserve combat und emergency power I make my approach with permanent power around 60% throttle and do a shallow climb to approx. 7000 meters to have an initial altitude advantage.

But when the target is sighted and I push the throttle to 100% to make a fast approach and dispose the Spit with a short squirt, nothing happens.

 

Even with full throttle I get only 80% power, emergency power would only be engaged above 85% throttle.

 

From the technical data, the K-4 should go like stink at that altitude.

 

More detailed: With the DB605C engine combat power gives 684 kph between 6200 and 8000 meters end emergency adds another 20 kph to this.

 

But I end stumbling around with 450 kph.....not amused.

 

My K-4 wingman obviously don't have this problem and so they overtake me and munch up the Spit.

 

So, for me it looks like a bug or is it a feature to make this type of mission more difficult?

 

If so: It's not a good idea to fiddle with the original technical data of planes.

 

Can anybody explain what's happening here?

 

As far, I noticed this strange power loss only in Bodenplatte and only with this type of mission.

 

Any help is strongly appreciated.

 

best regards

eastriverman

 

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Your display is showing indicated speed, so your speed compared to your local air pressure, while the specs page shows ground speed, or TAS. At high altitudes you will always see a lower indicated speed than your ground speed. 684kph indicated at 7km altitude would be almost 1000kph ground speed and Mach 0.88

 

https://www.wolframalpha.com/input/?i=684+kph+ias+at+7000m

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450kph indicated at ~7000 meters in standard atmospheric conditions is about 706kph true (faster than pretty much any Merlin engined Spit, and basically dead on with the tech specs).  Every engine of the era had what is called a critical altitude, which is the maximum altitude at which it could produce full boost.  At this altitude the supercharger (or turbo for P-47s and P-38s etc) is spinning at full output and so above that it can no longer continue to produce full power as the air continues to get thinner.  For a DB605D this should be right around 7000 meters.  It's worth noting that ram air can play a factor in this as well - if you are very slow (in a climb or turn for instance) your critical altitude will occur lower because you don't have the benefit of as much additional ram air pressure.

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do you use throttle assistance (can't remember it's exact name)?  Figured that's why you said it will only go to 80% when you hit full throttle.  

 

Also I think the manual says emergency power is prohibited past a certain altitude, like 6000m?

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Hello, below is the data from IL-2 compare for the 109 K4 DB engine vs the fastest spitfire i could find at that altitude. The data for this came from in-game testing by CountZero in his thread here. As KW mentioned above if 450 kph IAS is around 700 TAS then the K4 looks to be just fine. 

image.thumb.png.7a9ac51aa80eb327dbf68cfd12eafe9d.png

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Sound like a difficulty setting ,as FeuerFliegen already mentioned.

Disable Throttling Assistance , or check if the trottling assistance is enabled.

However keep in mind you got to configure an own key to enable MW50 Boost.

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14 minutes ago, 1./JG42Nephris said:

Sound like a difficulty setting ,as FeuerFliegen already mentioned.

Disable Throttling Assistance , or check if the trottling assistance is enabled.

However keep in mind you got to configure an own key to enable MW50 Boost.

 

you sure about your last sentence? In the G-14 MW50 automatically kicks in in emergency power.

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39 minutes ago, Sybreed said:

 

you sure about your last sentence? In the G-14 MW50 automatically kicks in in emergency power.

It works the same way in the K4. Additionally, as FeuerFliegen also mentioned, the use of the MW50 boost was forbidden above 6k. You can read these two things in the Specifications.

Reading educates:P

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22 hours ago, Yogiflight said:

It works the same way in the K4. Additionally, as FeuerFliegen also mentioned, the use of the MW50 boost was forbidden above 6k. You can read these two things in the Specifications.

Reading educates:P

HiHo again!

 

First, let me thank you all for spending some thoughts upon my problem.

 

I investigated that issue further and now I'm even more convinced that this is a bug.

 

Outing myself as a german, I read through the german version of the K-4 technical data as presented by the game itself of which I made a screenshot.

 

Here, "Notleistung" is emergency power (between 85% and 100%) and "Kampfleistung" is combat power (between 64% and 84%).

 

Regarding the use of emergency power at altitudes of 6000 meters and above the correct translation into englisch language is as follows:

 

The plane is equipped with a water-methanol mixture ("MW50") injection system which prevents a destruction of the engine at emergency power. It's automatically activated when
the throttle is set to maximum (i.e.100%). The mixture lasts for 25 to 30 minutes. However, the engine can only work in this mode for 10 minutes an after that one has to wait
for 10 minutes at combat power before emergency power can be used again.

 

Attention: Operating the engine at emergency power without the water-methanol mixture is forbidden in altitudes above 6 kilometers.

<skipped rest of text>

 

 

 

This means emergency power is very well allowed and possible at altitudes above 6 km as long as there is MW50 in the tank !!!

 

So, I tested that and indeed, at 5900 meters everything was fine and I could go to 100% and emergency power.

 

Climbing to 6100 meters, no emergency power anymore. Power is limited to 80% and with level auto pilot switched on, the K-4 has a maximmum speed of 434 kph, which is shockingly low.

 

I then was, let's say, somewhat surprised that the K-4s emergency power system was properly described in the german localization of the game but improperly implemented in the game itself....

 

This makes the K-4  completely useless in high altitude combat situations like those recon intercept missions which it was meant for (ceiling > 13.000 meters!).

 

From the above decription, having a full tank of water-methanol mixture ("MW50"), one should be able to use emergency power 3 times for 10 minutes each under optimal conditions with a 10 minutes break between subsequent uses. This would then be the correct modelling of the K-4s emergency power system.

 

Probably the described bug was overseen because Great Battles up to now is a low altitude flight simulator. Free hunt and bomber intercept missions take place at around 2000 meters, while ground attacker intercept missions are at 500 meters and in this range of altitudes everything works fine.

 

Even with additional underwing gun pods the K-4 can outrun, outclimb, outturn and outgun the P-47, the P-51 and the Tempest as well with emergency power. The same is true for the Spit IXe, except you cannot outturn it. Cannot say anything about the P-38, since I never saw one in der BoBP career.

 

Could be worthwile to check the high altitude performance of the other german fighters, too.........

 

I can only hope for that this will be fixed as soon as possible because correctly modelled the K-4 will be the ultimate killer machine among all piston engine fighters in GB.

 

Again, thanx a lot for all answers which inspired me to investigate this issue thoroughly.

 

best regards
eastriverman  

 

 

Bf-109K-4 MW50.jpg

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On 1/26/2020 at 3:03 PM, eastriverman said:

 

But when the target is sighted and I push the throttle to 100% to make a fast approach and dispose the Spit with a short squirt, nothing happens.

 

Even with full throttle I get only 80% power, emergency power would only be engaged above 85% throttle.

 

This is the telling point here. The fact that the simulation is limiting you to 80% means you have automatic throttle limit selected in the game difficult (realism) settings as others have already stated.

 

I, and everyone else who has disabled this option, can command 100% throttle and emergency power at all altitudes. . . . . no bug

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2 hours ago, eastriverman said:

HiHo again!

 

First, let me thank you all for spending some thoughts upon my problem.

 

I investigated that issue further and now I'm even more convinced that this is a bug.

 

Outing myself as a german, I read through the german version of the K-4 technical data as presented by the game itself of which I made a screenshot.

 

Here, "Notleistung" is emergency power (between 85% and 100%) and "Kampfleistung" is combat power (between 64% and 84%).

 

Regarding the use of emergency power at altitudes of 6000 meters and above the correct translation into englisch language is as follows:

 

The plane is equipped with a water-methanol mixture ("MW50") injection system which prevents a destruction of the engine at emergency power. It's automatically activated when
the throttle is set to maximum (i.e.100%). The mixture lasts for 25 to 30 minutes. However, the engine can only work in this mode for 10 minutes an after that one has to wait
for 10 minutes at combat power before emergency power can be used again.

 

Attention: Operating the engine at emergency power without the water-methanol mixture is forbidden in altitudes above 6 kilometers.

<skipped rest of text>

 

 

 

This means emergency power is very well allowed and possible at altitudes above 6 km as long as there is MW50 in the tank !!!

 

So, I tested that and indeed, at 5900 meters everything was fine and I could go to 100% and emergency power.

 

Climbing to 6100 meters, no emergency power anymore. Power is limited to 80% and with level auto pilot switched on, the K-4 has a maximmum speed of 434 kph, which is shockingly low.

 

I then was, let's say, somewhat surprised that the K-4s emergency power system was properly described in the german localization of the game but improperly implemented in the game itself....

 

This makes the K-4  completely useless in high altitude combat situations like those recon intercept missions which it was meant for (ceiling > 13.000 meters!).

 

From the above decription, having a full tank of water-methanol mixture ("MW50"), one should be able to use emergency power 3 times for 10 minutes each under optimal conditions with a 10 minutes break between subsequent uses. This would then be the correct modelling of the K-4s emergency power system.

 

Probably the described bug was overseen because Great Battles up to now is a low altitude flight simulator. Free hunt and bomber intercept missions take place at around 2000 meters, while ground attacker intercept missions are at 500 meters and in this range of altitudes everything works fine.

 

Even with additional underwing gun pods the K-4 can outrun, outclimb, outturn and outgun the P-47, the P-51 and the Tempest as well with emergency power. The same is true for the Spit IXe, except you cannot outturn it. Cannot say anything about the P-38, since I never saw one in der BoBP career.

 

Could be worthwile to check the high altitude performance of the other german fighters, too.........

 

I can only hope for that this will be fixed as soon as possible because correctly modelled the K-4 will be the ultimate killer machine among all piston engine fighters in GB.

 

Again, thanx a lot for all answers which inspired me to investigate this issue thoroughly.

 

best regards
eastriverman  

 

 

Bf-109K-4 MW50.jpg

I mean, most combat in the sim in MP does take place below 6000 m. But people fly K4s at full throttle above 6k all the time. Trust me, people kill me with them quite frequently

Maybe test your throttle device to make sure that you are actually reaching 100%? my throttle, for example, only reaches 99% when I push it all the way forward, I have to give a smal dead zone at either end to make it read 100%

 

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Should be easy to reproduce if this is a bug.

 

a) Fly above 7.000 metres and set throttle to 100% (emergency power) using no auto motor mangement and measure IAS

b) Fly above 7.000 metres and set throttle to 100% (emergency power) using auto motor management and measure IAS

 

If there is a big difference then, there is a bug. Propably in auto motor management which needs fixing

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2 hours ago, eastriverman said:

This means emergency power is very well allowed and possible at altitudes above 6 km as long as there is MW50 in the tank !!!

The purpose of MW50 is to cool down the charged air. As higher as you fly the cooling effect will be lowered as well. This means the boost effect of MW50 will be reduced to zero at a certain altitude. And above the engines full throttle height for war emergency power, wich in this case, is well below 7000 meters you can't expect any increase in engine performance.

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3 hours ago, eastriverman said:

Attention: Operating the engine at emergency power without the water-methanol mixture is forbidden in altitudes above 6 kilometers.

The german text is:

Vorsicht: der Betrieb des Motors bei Notleistung ohne Wasser-Methanol-Gemisch oder in Höhen größer als 6km ist verboten!

Correct translation to english:

Attention: Operating the engine at emergency power without the water-methanol mixture or in altitudes above 6km is forbidden!

The important thing here is the oder (or), so it means you may not use emergency power without water-methanol mixture and you may not use emergency power above 6km.

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1 hour ago, RedKestrel said:

I mean, most combat in the sim in MP does take place below 6000 m. But people fly K4s at full throttle above 6k all the time. Trust me, people kill me with them quite frequently

Maybe test your throttle device to make sure that you are actually reaching 100%? my throttle, for example, only reaches 99% when I push it all the way forward, I have to give a smal dead zone at either end to make it read 100%

 

Well, as I noted, pushing my throttle "pedal to the metal" at 5900 meters it shows 100% , emergency power kicks but doing the same at 6100 meters it shows 80% which is even % below the maximum combat power an

 

3 hours ago, sevenless said:

Should be easy to reproduce if this is a bug.

 

a) Fly above 7.000 metres and set throttle to 100% (emergency power) using no auto motor mangement and measure IAS

b) Fly above 7.000 metres and set throttle to 100% (emergency power) using auto motor management and measure IAS

 

If there is a big difference then, there is a bug. Propably in auto motor management which needs fixing

 

Greetings to all!

 

Thanx a lot again for your interest in this topic.

 

First I can confirm that I use the advanced automatic engine control system of the K-4 and this is the single reason why I chose to be a german fighter pilot in the BoM-, BoS-, BoK-, and BoBP-singleplayer careers since it allows me to concentrate on what these machines where made for: air combat.

 

Switching off the automatic motor management and fiddle with the engine manually would then be counterproductive for me.

 

To make things easier without musing about the known differences between IAS and TAS, my problem is the following:

 

Refering to the TAS vs. altitude diagram in this topic kindly provided by  Kataphrakt, the K-4 should be considerably faster than the Spit IXe at almost any altitude though I don't know what the designations 100% and MAX mean in this diagram.

 

So, if this diagram reflects the flight models of the K-4 and the IXe in Great Battles I should have no problem at all to close on a Spit IXe while chasing it with a K-4.

 

But  what's happening is that the IXe runs faster than the K-4 and gains distance during the chase even if I push my throttle "pedal to the metal" which then gives me 80% power.

 

Below 6000 meters the world is OK again and I can outrun any allied fighter with the K-4s emergency power and I can still hold my ground using "only" combat power (84%) during the MW50 breaks.

 

So, is either the diagram wrong or the are the flight models wrong? Who knows.....

 

Until this issue is sorted out somehow I have decided to go the practical way and send my squadron mates on those chases which then fail also while I stay in the idyllic world of low altitude air combat and collect my kills 😀

 

best regards
eastriverman  

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aahhh

just wondering, are u confusing the realism setting with the auto/manual prop pitch management?

 

just checking

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13 minutes ago, eastriverman said:

First I can confirm that I use the advanced automatic engine control system of the K-4

It is as simple as that. With this engine control you can't go above 80%, if you turn it off, you can go higher, but as soon as you reach 85%, you'll get the message 'Achtung! Zu niedriger Einspritzdruck! (Attention! Too low injection pressure!). If you stay above 84%, your engine will get damaged pretty fast (less than half a minute, when I tried)

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42 minutes ago, eastriverman said:

First I can confirm that I use the advanced automatic engine control system of the K-4 and this is the single reason why I chose to be a german fighter pilot in the BoM-, BoS-, BoK-, and BoBP-singleplayer careers since it allows me to concentrate on what these machines where made for: air combat.

 

Leave engine control at automatic and try to disable throttle auto limit. I guess that does the trick for you. K4 should run at 475 km/h IAS with that on 100% throttle at 7000 metres.

Unbenannt.jpg

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10 minutes ago, sevenless said:

Leave engine control at automatic and try to disable throttle auto limit. I guess that does the trick for you. K4 should run at 475 km/h IAS with that on 100% throttle at 7000 metres.

Why did I destroy my engine at 85% throttle, when you can run it with 100%?

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32 minutes ago, Yogiflight said:

Why did I destroy my engine at 85% throttle, when you can run it with 100%?

 

Simple answer. For test purposes I set the plane to unbreakable.

 

Edit for further tests:

 

Rechecked with vulnerability and breakability and that doesn´t blow the engine, at least not after 5min. Didn´t test longer in QMG. See the screenies:

Unbenannt1.jpg

Unbenannt2.jpg

 

With throttle auto limit activated you will max out at 450 IAS at 7000 metres and it will limit you to 80% throttle. So you can gain 30 km/h IAS by deactivating that auto throttle feature and the K4 runs up to 480 km/h IAS at 7k. Spit IX with Merlin 70 will max out at 445 km/h IAS at 7k btw.

Edited by sevenless
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On 1/27/2020 at 4:59 PM, Kataphrakt said:

Hello, below is the data from IL-2 compare for the 109 K4 DB engine vs the fastest spitfire i could find at that altitude. The data for this came from in-game testing by CountZero in his thread here. As KW mentioned above if 450 kph IAS is around 700 TAS then the K4 looks to be just fine. 

image.thumb.png.7a9ac51aa80eb327dbf68cfd12eafe9d.png

Merlin 70 is the High alt engine for the spit, not the M66

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16 hours ago, sevenless said:

 

Simple answer. For test purposes I set the plane to unbreakable.

 

Edit for further tests:

 

Rechecked with vulnerability and breakability and that doesn´t blow the engine, at least not after 5min. Didn´t test longer in QMG. See the screenies:

Unbenannt1.jpg

Unbenannt2.jpg

 

With throttle auto limit activated you will max out at 450 IAS at 7000 metres and it will limit you to 80% throttle. So you can gain 30 km/h IAS by deactivating that auto throttle feature and the K4 runs up to 480 km/h IAS at 7k. Spit IX with Merlin 70 will max out at 445 km/h IAS at 7k btw.

That's it!!

 

Explains pretty much everything that I've described formerly.

 

With auto throttle limit active on the K-4 the SpitIXe has a 12 kph IAS speed avantage allowing it to gain distance during the chase...

 

I think I don't need the throttle auto limit anymore since I learned on my very first K-4 mission the hard way that it is a very stupid idea to go into a dive with full throttle, ending up hanging from a parachute watching my formerly so shiny K-4 going on an oil drilling mission  :o:

 

So, time to rejoin my mates for another chase and check out how long I can go how fast after a Spit without ruining my engine. Will check my K-4 against other allied fighters at the weekend for scientific reasons.....

 

Could be useful if there once will be another great battle: BoR = battle of Reichsverteidigung (defense of the "Reich")  ....... well, only kidding.

 

Thanx a lot for the crucial info on this topic!

 

best

estriverman

 

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The throttle limit issue is interesting because the DB 605 D  , unlike all the other 601s and 605s before, had an automatic supercharger bleed system, so throttling back to avod over pressure was probably unneccessary.

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On 1/28/2020 at 7:55 PM, -[HRAF]Roland_HUNter said:

Merlin 70 is the High alt engine for the spit, not the M66

I used the 66 because at 25 lbs it's faster than the 70 is at 7000m according to IL-2 compare. image.png.a14c69fbd9a314d81edf88dbaeabad7b.png

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3 hours ago, -[HRAF]Roland_HUNter said:

Wow 😄


Makes sense, the normal +18 boost Merlin 66 is also faster at 7000 meters than the Merlin 70. 

7000 meters is the top speed for the Spit LF Mk IX.  The Merlin 70 has a really high altitude optimized second stage, critical altitude at around 8700 meters for +18 boost. At around 7500 meters is where the Merlin 70 Spit becomes faster than the Merlin 66 one regardless of +18 or +25 boost since it's above Merlin 66 critical altitude.

unknown.png

Edited by -=PHX=-SuperEtendard
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16 minutes ago, -=PHX=-SuperEtendard said:

Makes sense, the normal +18 boost Merlin 66 is also faster at 7000 meters than the Merlin 70. 

 

Hmm, 446 km/h IAS is the maximum what I can get from the Merlin 66 with 150 oct at 7300 metres in the game. That is about the same as the Merlin 70 delivers at the same altitude. Did I miss something?

 

 

merlin66.jpg

Edited by sevenless

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3 minutes ago, sevenless said:

 

Hmm, 446 km/h IAS is the maximum what I can get from the Merlin 66 with 150 oct at 7300 metres in the game. That is about the same as the Merlin 70 delivers at the same altitude.

 

 

Yes, I didn't test in between 7000 and 8000, excel interpolation line makes them meet at around 7500 but 7300 could well likely be the point at which they are equal. Below it the Merlin 66 is faster, above it the Merlin 70 is faster. At this alt 150 oct doesn't really matter, you are at +16 boost anyway at that altitude.

 

Edited by -=PHX=-SuperEtendard
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2 minutes ago, -=PHX=-SuperEtendard said:

 

Yes, I didn't test in between 7000 and 8000, excel interpolation line makes them meet at around 7500 but 7300 could well likely be the point at which they are equal. Below it the Merlin 66 is faster, above it the Merlin 70 is faster. At this alt 150 oct doesn't really matter, you are at +16 boost anyway at that altitude.

 

 

Ah I see. What is the max altitude for +25 boost?

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16 minutes ago, sevenless said:

Ah I see. What is the max altitude for +25 boost?


+25 boost crit alt is around 4800 meters but above that it's still offering more power until it drops down to +18 boost at around 6700 meters where it would equalize with the 100 oct Merlin 66.

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On 1/30/2020 at 7:48 AM, VO101Kurfurst said:

The throttle limit issue is interesting because the DB 605 D  , unlike all the other 601s and 605s before, had an automatic supercharger bleed system, so throttling back to avod over pressure was probably unneccessary.

Greetings,

 

to add to the topic I tested the performance of the Bf-109 K-4 with the DB 605 DC engine in clean configuration (no gunpods etc.) and with 100% fuel at 7000 meters.

 

Pushing the throttle to 100&% in level fligth gives you 483 kph IAS which is a 40 kph IAS speed advantage over the Spitfire IXe.

 

After 9:35 Minutes you get a warning "duration of emergency power exceeded" but the speed stays at 483 kph IAS.

 

Continuing with100% gives you after 11:41 a warning "engine damaged"  and from then on the speed slowly decreases.

 

After 13:50 minutes the warning "engine overheated" is diplayed and at that time the speed has decreased to 434 kph IAS.

 

At 14:37 the engine stops working. No fire, no explosion, the propeller just stops spinning.

 

So, being on the safe side, you can go with 100% emergency power approximately 10 Minutes at that altitude before throttling back to keep the engine healthy.

 

That will be the time window in which one has to get rid off the Spit.

 

But it's still diffcult to do so since sharp turns and abrupt maneouvers to get a  quick lead for shot, which work fine at low altitude, will cause an immediate stall and a significant loss of altitude due to the thinner air and the reduced lift of the wings.  Moreover, the Spit can do tighter turns at 7000 meters without stalling than the K-4 can.

 

The recipe that worked out for me in the end was to employ a zoom and boom tactic:

 

Start the fight with an altitude advantage.

 

Dive down when the Spit approaches, do a careful turn to get the proper lead for a shot and pull up again.

 

If you are a good shot, the fight will be over already, otherwise turn back and try again.

 

Did 6 of these intercept missions in the meantime and it worked well every time.

 

best

eastriverman

 

 

 

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Help me understand why the turn radius or turn rate would be affected by altitude if IAS is equal? IAS is basically a function of air mass over the wing. I fully understand engine performance drops off and high alt turns are affected when the engine can't keep the aircraft above its IAS stall speed. But if IAS is the same at 500m vs 7000m the turn performance should be the same.

At least that's what Greg from Greg's airplanes seems to say. Or did I miss something?

:salute:

skud

 

 

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If you are pulling the same g at the same IAS up high as you do down low, you're pulling a larger radius at a higher true air speed (TAS) at the same drag. Not only will you require more power to sustain it (drag * TAS), you'll also go through a larger circle (g ~ TAS² / radius), which will take longer.

 

Assume TAS to be 30% higher at the same IAS up high (roughly 5km), and at the same g your turning circle is 69% larger (1.3²). It also means you'll need 30% longer to go around this 69% larger circle once (1.69 / 1.3), so obviously your turn rate is down by just as much. And you'd still need 30% more power to achieve all that.

 

Now if you're saying "I'll just pull more g" - given that the best turning speed usually is near the stall speed, you can't really do that while going "at the same IAS". Maximum g at the same IAS is not higher at high altitude. And you'd need an even more powerful engine on top of everything else.

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 Ok I thought TAS had something to do with it and I remember some discussion about induced vs. parasite drag at high alt.  I understand how to convert IAS to TAS but I'm not sure I understand why they are different from an ideal gas law perspective. I guess I'll do some studying unless you want to give me the short version😀

:salute:

skud

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