Exhaust Thrust ????

[Kurfürst]

So maybe its at this point you go start your own sim company and make your own FM, because its getting tired that you some how "demand" proof of FM making abilities when he has created so many quality FMs already. He can only answer your questions so many times, and this is a copy of a thread that got locked once already, and this one is headed that way as well...

 

To expand, Yo-Yo has been researching this FM for some time, he works hard to get it as accurate as humanly possible, but dont take any evidence you can find on the internet at face value, and dont assume because you found a couple test on some random website that you are now an expert in the flight characteristics of any aircraft. If he believes something is missing of a particular document based on his research, then that is his/ED's interpretation... and should be respected based on his/their proven history at FM creation.

 

:thumbup:

 

Spared me a warn point, too. :music_whistling:

[NineLine]

Yeah, like Messersmitdh's extremely pessimistic calculated performance of the Me 209, Me 309. The Bell charts that I've shown were also for buyers btw.

 

And if Focke Wulf's estimation is so accurate (less than 0.5% variance) why should you think there should be such a large disparagement of the D9's calculated performance versus real product.

 

In fact, by march 1945 there were plenty of flying D9s in combat already, it would make no sense for Focke Wulf to keep the same test figure in their march 1945 test document if it wasn't accurate.

 

Documents in March of 1945... yes, couldn't possible have any mistakes, omissions or errors, Germany was so well off in the war a this time... they must have been perfect ;) I am sure it was a major concern to get test reports perfect then...

[GrapeJam]

Documents in March of 1945... yes, couldn't possible have any mistakes, omissions or errors, Germany was so well off in the war a this time... they must have been perfect ;) I am sure it was a major concern to get test reports perfect then...

Oh you might wanna read Hans-Werner Lerche's book on that ;)

[NineLine]

Oh you might wanna read Hans-Werner Lerche's book on that ;)

 

Point is, much of this is open to interpretation, the 40's were some time ago, and there are big gaps in much of this history. This is Yo-Yo's professional interpretation of the data, he has been more than open when he find an error or something that needs to be corrected, but the bottom line is this is ED's Fw 190D-9 FM, based on data they have available to them. Going on and on about the same thing is not going to change that. And honestly, I dont see why it would, nothing has been presented to justify it.

[Crumpp]

Yeah, like Messersmitdh's extremely pessimistic calculated performance of the Me 209, Me 309.

 

You mean the racing prototype that held the world speed record for 30 years?

 

Not exactly a production machine built for a customer.

 

See the attached article below.

 

The Bell charts that I've shown were also for buyers btw.

 

And what happened with that? Bell never mass produced another fixed wing aircraft. They never got another mass production contract from the Department of Defense.

 

And if Focke Wulf's estimation is so accurate (less than 0.5% variance) why should you think there should be such a large disparagement of the D9's calculated performance versus real product.

 

Grapejam,

 

Read the NOTES ON THE USE OF PERFORMANCE ESTIMATE

 

The margin of error is always much smaller for level speed performance prediction vs climb performance. It is simply easier to predict level speed performance.

 

Please read the information presented in the thread, the answers to all of your posted questions are in it and nothing new is being presented.

 

A Yo-Yo explained, not all engines develop exhaust thrust to the same extent.

 

It very much depends on the design of the exhaust system. On the first page of this thread, it talks about the changes made to the BMW801 series to improve the exhaust thrust of the engine.

 

So maybe its at this point you go start your own sim company and make your own FM, because its getting tired that you some how "demand" proof of FM making abilities when he has created so many quality FMs already. He can only answer your questions so many times, and this is a copy of a thread that got locked once already, and this one is headed that way as well...

 

To expand, Yo-Yo has been researching this FM for some time, he works hard to get it as accurate as humanly possible, but dont take any evidence you can find on the internet at face value, and dont assume because you found a couple test on some random website that you are now an expert in the flight characteristics of any aircraft. If he believes something is missing of a particular document based on his research, then that is his/ED's interpretation... and should be respected based on his/their proven history at FM creation.

 

:thumbup::thumbup::thumbup::thumbup::thumbup:

 

 

Yo-Yo knows what he is doing and is delivering great products. That is why I bought DCS.

High Speed Feud.pdf

High Speed Feud part II.pdf

[Kurfürst]

Documents in March of 1945... yes, couldn't possible have any mistakes, omissions or errors, Germany was so well off in the war a this time... they must have been perfect ;) I am sure it was a major concern to get test reports perfect then...

 

In my experience, many of these calculations were just quick and dirty estimates to get an idea of the feasibility of installing a certain engine or using a certain configuration. It was cheaper than actually spending money of building prototypes. How much will it be faster with a certain increase in power? Which one will be better at high altitudes for bomber interception, one existing design in production if we add extra weapons, or a new design in standard config? Often preliminary questions like this had to be answered with some rough estimate before proceeding.

 

Plus, it was often made by the same guys working on the project, so many times not all data was recorded, as everyone knew that for example that the No. 6. plane had a missing intake or another non-standard feature - things that you can only figure out when your read between the lines of other reports. They are also riddled with typos - the 109G's Rechlin datasheet for example lists 10 km/h higher speed at an altitude due to a typo, and you have to cross-check it with the corresponding speed graph to find this error, and there is one Messerschmitt AG document at the 'Lair that uses both Bf and Me for the 109 in the same document...!

 

Not to mention the atmospheric and testing standards varied from company to company, nation to nation. The British usually gave speed figures for 95% load, the Germans for 100%, for example. British Standard Summer was different from German Standard Summer, or Soviet Standard Summer etc. Direct comparison is often meaningless without some brain work on these things first...

Edited March 11, 2015 by Kurfürst

[Crumpp]

This is Yo-Yo's professional interpretation of the data, he has been more than open when he find an error or something that needs to be corrected, but the bottom line is this is ED's Fw 190D-9 FM, based on data they have available to them. Going on and on about the same thing is not going to change that. And honestly, I dont see why it would, nothing has been presented to justify it.

 

The right education makes a world of difference.

[GrapeJam]

You mean the racing prototype that held the world speed record for 30 years?

 

Not exactly a production machine built for a customer.

 

No, I meant the Me 209 fighter in 1943.

 

And what happened with that? Bell never mass produced another fixed wing aircraft. They never got another mass production contract from the Department of Defense.

Other than being warded the contract to develope the P63(the P39 underperformed than estimated performance), then the Soviets bought a couple of thousands P63s from them, and then went on to build and produced the UH1 Iroquois Helicopter (Also known as the Huey), the V22 Osprey, just a few examples on top of my head, no.

 

 

 

 

Grapejam,

 

Read the NOTES ON THE USE OF PERFORMANCE ESTIMATE

 

The margin of error is always much smaller for level speed performance prediction vs climb performance. It is simply easier to predict level speed performance.

 

Please read the information presented in the thread, the answers to all of your posted questions are in it and nothing new is being presented.

 

A Yo-Yo explained, not all engines develop exhaust thrust to the same extent.

 

It very much depends on the design of the exhaust system. On the first page of this thread, it talks about the changes made to the BMW801 series to improve the exhaust thrust of the engine.

 

 

 

:thumbup::thumbup::thumbup::thumbup::thumbup:

 

 

Yo-Yo knows what he is doing and is delivering great products. That is why I bought DCS.

Like I've said before, tests were still being run up to the end of the 3rd Reich, read Hans Lerche's book.

 

It makes no sense for Focke Wulf to retain the same climb figure in march 1945 when more than 1 thousand D9 were already produced, fly tested and sent into combat. if it wasn't accurate.

[Crumpp]

No, I meant the Me 209 fighter in 1943.

 

Never a production machine, always a new type fighter.

 

 

Other than being warded the contract to develope the P63(the P39 underperformed than estimated performance), then the Soviets bought a couple of thousands P63s from them, and then went on to build and produced the UH1 Iroquois Helicopter (Also known as the Huey), the V22 Osprey, just a few examples on top of my head, no.

 

 

Fixed Wing...United States Department of Defense...

 

:music_whistling:

 

Like I've said before, tests were still being run up to the end of the 3rd Reich, read Hans Lerche's book.

 

It is a good book and is on my shelf.

 

It makes no sense for Focke Wulf to retain the same climb figure in march 1945 when more than 1 thousand D9 were already produced, fly tested and sent into combat. if it wasn't accurate.

 

It does if you read the title of the graph.

 

Climb Rate over Altitude at Climb and Combat Power.

 

Nothing about reporting performance at Special Emergency Power. That is why curves 1, 2, and 3 include aircraft condition information.

 

The curve you refer too has no aircraft condition information nor is it even labeled in the legend. It matches the Flugmechanik data.

[GrapeJam]

Fixed Wing...United States Department of Defense...

 

:music_whistling:

 

Right, missed anything about the part where they got the funding for the P63, and the P59 at that?

 

And if you think lobbyism and corruption didn't exist in the 3rd reich, you might wanna look at the issue about Messersmidth, Focke Wulf and the DB engine ;)

 

 

It is a good book and is on my shelf.

Right.

 

 

It does if you read the title of the graph.

 

Climb Rate over Altitude at Climb and Combat Power.

 

Nothing about reporting performance at Special Emergency Power. That is why curves 1, 2, and 3 include aircraft condition information.

 

The curve you refer too has no aircraft condition information nor is it even labeled in the legend. It matches the Flugmechanik data.

And you think that your "SWAG" is more accurate than Focke Wulf's own estimation based on what's available, ok.

 

And this game engine certainly does not emulate real life condition as well as, well, real life. Meanwhile the P51's missing 20 km/h at SL while having correct climb rate, probably a look at the game's engine is needed.

[NineLine]

 

Like I've said before, tests were still being run up to the end of the 3rd Reich, read Hans Lerche's book.

 

It makes no sense for Focke Wulf to retain the same climb figure in march 1945 when more than 1 thousand D9 were already produced, fly tested and sent into combat. if it wasn't accurate.

 

 

Regardless of how long the test were run, or how close to the end of the war they were run does not speak to how accurate they were, what info was on them or left off of them. Having seen a few raw testing reports (not just a graph or 2 neatly displayed on a website) I can only imagine what could happen in the process of preparing a final report for whomever... far as I can tell on the ones I have seen, the data was recorded on a worksheet of sorts, and then later transferred to a fancy graph. The thought that something could be left off, or transferred incorrectly is so very believable...

 

But it keeps coming back to collecting as much data as you can (not just from one or two websites) and then making an educated interpretation of that data. Also note that I believe ED uses the data in a way not seen in other FMs so the comparison to other FMs can fall apart there as well...

[NineLine]

 

And you think that your "SWAG" is more accurate than Focke Wulf's own estimation based on what's available, ok.

 

This is what got the other thread locked, and this is the misconception some of you have. It doesnt matter what I think, or you think or anyone else. ED/Yo-Yo collects data he/they need and they determine what they have and how to use it... so attacking another users data is really pointless and only stands to send this thread back into the toilet... you guys have to stop getting so hung up on trying to disprove each other...

[Crumpp]

And you think that your "SWAG" is more accurate than Focke Wulf's own estimation based on what's available, ok.

 

Who said that? The purpose of running the math is to let you know if the performance is plausible. When it does not agree, it is time to start looking for answer's as to why.

 

That reason has been found.

 

The aircraft performance math that estimate is based on is designed to give good agreement with actual flight. Just because it is a convenient method does not mean it is not an accurate method. It has been around for ~60 years and works well.

 

 

Meanwhile the P51's missing 20 km/h at SL while having correct climb rate, probably a look at the game's engine is needed.

 

Present the evidence. Obviously Yo-Yo looks at it. If it makes sense then I am confident Yo-Yo will make the right call. His track record speaks for itself.

 

I can tell you it would help if you knew more about the science of flight so you can pick out good data and know how to set the conditions to compare performance. Otherwise, it becomes difficult to see your point.

 

I do not see an issue with the P-51 climb rate from what I have checked out but would extend an offer to help you compare some of the data to confirm or deny your assumption.

 

That is the good thing about math.... it does not care about anyone's opinion.

Edited March 11, 2015 by Crumpp

[Pilum]

I agree completely with what Solty, Grapejam and Kwiatek have been saying: All logic and evidence combined points to that the the Focke-Wulf chart showing 22 m/s climb at 1.8 ata for the Dora is with exhaust thrust included.

 

Attached is also a C++ simulation showing that a correctly modeled Dora will fulfil both the Steig&Kampfleistung flight measurements and the Kennblatt and the calculated 1.8 ata chart by Focke-Wulf: As can be seen in the figure there is no contradiction at all between the flight tests and the calculated values by Focke-Wulf when looking at the delta between Steig&Kampfleistung and 1.8 ata and that it would be wrong to add the exhaust thrust resulting in a climb rate of 28 m/s since this is already included.

 

In addition, if the reason for the 6 m/s climb difference between DCS and the Focke-Wulf chart was that exhaust thrust was not included in the Focke-Wulf calculations and that when this is added we get the 28 m/s we see in DCS where does that leave the DCS Me1094? Since the DCS K4 is climbing 30 m/s at 1.8 ata does that mean that the climb charts calculated by Messerschmitt showing around 24 m/s are also without exhaust thrust?

 

So in order for all this to make sense we have to assume that both Focke-Wulf and Messerschmitt left exhaust thrust out of their estimates? I find this quite unlikely and more plausible explanation being that the climb figures of 28 and 30 m/s for the Dora and K4 in DCS are just too optimistic.

Fw190D9climbexhausttcomp.bmp

[Kurfürst]

Is there something similar for 605? :)

 

I will take a good look.. certainly not direct power graphs I can recall, but sometimes such data may be hidden amongst other papers on different subject.

 

Also, thank you for your time you have put into trying to explain things on Dora 9 flight model.

[NineLine]

Ok Pilum and all, I suggest you send all your logic and evidence to Yo-Yo in PM and let him decide (which I believe he already has). This thread is just more redundancy again.

 

Edit: Re-opened at Yo-Yo's request, but I stress, bring something new and constructive, I reserve the right to close it again if it turns into redundant crap and attacks ;)

Edited March 11, 2015 by NineLine

[Yo-Yo]

I agree completely with what Solty, Grapejam and Kwiatek have been saying: All logic and evidence combined points to that the the Focke-Wulf chart showing 22 m/s climb at 1.8 ata for the Dora is with exhaust thrust included.

 

Attached is also a C++ simulation showing that a correctly modeled Dora will fulfil both the Steig&Kampfleistung flight measurements and the Kennblatt and the calculated 1.8 ata chart by Focke-Wulf: As can be seen in the figure there is no contradiction at all between the flight tests and the calculated values by Focke-Wulf when looking at the delta between Steig&Kampfleistung and 1.8 ata and that it would be wrong to add the exhaust thrust resulting in a climb rate of 28 m/s since this is already included.

 

In addition, if the reason for the 6 m/s climb difference between DCS and the Focke-Wulf chart was that exhaust thrust was not included in the Focke-Wulf calculations and that when this is added we get the 28 m/s we see in DCS where does that leave the DCS Me1094? Since the DCS K4 is climbing 30 m/s at 1.8 ata does that mean that the climb charts calculated by Messerschmitt showing around 24 m/s are also without exhaust thrust?

 

So in order for all this to make sense we have to assume that both Focke-Wulf and Messerschmitt left exhaust thrust out of their estimates? I find this quite unlikely and more plausible explanation being that the climb figures of 28 and 30 m/s for the Dora and K4 in DCS are just too optimistic.

 

Our discussion must be split in two: the first one is about the reference and the second one is about climb rate in DCS current version.

Starting from the second one I must say that I examined the current version and noticed that MW-50 power rate gives 2300 hp instead of right 2100 hp value That gives about 28-29 m/s for 4300 kg. I have no idea when did it appear after our internal tests... and it will be fixed soon.

 

But the first discussion must be proceed... do you see that your estimation with exhaust thrust suffers in comparison with the REAL TEST that gives about 18-19 m/s for 3000 rpm?

So, please, share the main data you operate with for SL conditions - engine power and thrust (hope you use the same chart), prop efficiency and L/D polar coefficients.

[Pilum]

Our discussion must be split in two: the first one is about the reference and the second one is about climb rate in DCS current version.

Starting from the second one I must say that I examined the current version and noticed that MW-50 power rate gives 2300 hp instead of right 2100 hp value That gives about 28-29 m/s for 4300 kg. I have no idea when did it appear after our internal tests... and it will be fixed soon.

 

But the first discussion must be proceed... do you see that your estimation with exhaust thrust suffers in comparison with the REAL TEST that gives about 18-19 m/s for 3000 rpm?

So, please, share the main data you operate with for SL conditions - engine power and thrust (hope you use the same chart), prop efficiency and L/D polar coefficients.

 

Ok Yo-Yo good to hear that you found the source to the high climb rates. Such an adjustment of the power would be welcome and could very well be an explanation for what we are seeing.

 

I would gladly share my simulation results and also the methodology behind them with you but I would prefer to do that via PM and mail if that is OK with you? :smilewink:

[Yo-Yo]

Ok Yo-Yo good to hear that you found the source to the high climb rates. Such an adjustment of the power would be welcome and could very well be an explanation for what we are seeing.

 

I would gladly share my simulation results and also the methodology behind them with you but I would prefer to do that via PM and mail if that is OK with you? :smilewink:

 

Yes, it would be OK.

[Crumpp]

2300 hp

 

Yes, please fix that!

 

It should be at sea level ~2250 hp with the worlds lowest 1st gear FTH of ~800 meters.

 

Any idea Yo-Yo why Junkers did that?

Edited March 11, 2015 by Crumpp
added power chart

[Yo-Yo]

Yes, please fix that!

 

It should be at sea level ~2250 hp with the worlds lowest 1st gear FTH of ~800 meters.

 

Any idea Yo-Yo why Junkers did that?

 

I prefer this one

 

http://www.wwiiaircraftperformance.org/fw190/Jumo_213A_power_graph.jpg

 

because the graph you mentioned has very strange match to the table data from Jumo.

[Kurfürst]

I wonder why that Janus face of the Jumo 213A exist. The first graph by Crumpp has definite MW-50 injection, and slightly higher powers, the second one from YoYo is from AIR 40/74 series does not note MW-50 and has very slightly higher altitude ratings, but lower low altitude ratings.

 

My take is that the second Jumo 213A graph is actually for the increased compression ratio version of the Jumo 213A, with C-3 fuel but no MW-50 which was probably not used in the end for serial production.

Edited March 11, 2015 by Kurfürst

[TAGERT]

I have no idea when did it appear after our internal tests... and it will be fixed soon.

That is great news!

[Yo-Yo]

I wonder why that Janus face of the Jumo 213A exist. The first graph by Crumpp has definite MW-50 injection, and slightly higher powers, the second one from YoYo is from AIR 40/74 series does not note MW-50 and has very slightly higher altitude ratings, but lower low altitude ratings.

 

My take is that the second Jumo 213A graph is actually for the increased compression ratio version of the Jumo 213A, with C-3 fuel but no MW-50 which was probably not used in the end for serial production.

 

Just compare the graphs to the Jumo 213a.

http://www.forum.lockon.ru/attachment.php?attachmentid=88144&d=1379528179

Edited March 11, 2015 by Yo-Yo

[Crumpp]

because the graph you mentioned has very strange match to the table data from Jumo.

 

I agree, the chart does not match the table below.

 

[/url]

 

While this chart does match:

 

http://www.wwiiaircraftperformance.org/fw190/Jumo_213A_power_graph.jpg

 

However, allow me to explain the reason why I used the power chart previously posted.

 

During the restoration of White 1, we did not start out with a good core engine to rebuild. We proceeded in the beginning of the project with the understanding we would have to resurrect the BMW801D2. That meant buying up wrecked motors in order to acquire examples of the parts we would have to reproduce.

 

We had quite a few wrecked BMW801D2's. When we started to disassemble the engines we began to notice details between the various wrecks were not always the same. Different magneto's, ignition harness some where even pressurized, plugs, and even different pistons. Puzzling but not unexplained. Lycoming for example makes numerous models of the O-360 and not all of them are created equal. The engine is tuned and set up for the specific installation/application based on the different missions the aircraft is expected to perform.

 

In fact, some of this was reflected in the BMW801D2 Ersatzteilliste.

 

Digging through the archives at the Smithsonian, we came across this report:

 

 

When you get ready to make an FW-190F8, I will give you a copy of the report. It has a nice matrix of what was interchangeble with what. It was done to educate the Luftwaffe supply chain that there were 6 different BMW801D2's that were designed to go into different radial engined FW-190 variants.

 

We finally found an overhaulable core in the form of a BMW801G2 engine. Theoretically, the same engine as the BMW801D2 but set up for bomber installation. All we thought it was missing was the synchronization gear. It even had the housing for it on the block. We were wrong and ended up having to resurrect pistons, magnetos, and other peripherals.

 

You can see that the Jumo 213 series also had various set ups and was tuned for the installation and mission it was expected to perform.

 

 

The Jumo213A1 that was installed in the FW-190D9 was a specifically tuned fighter engine.

 

I came across this power graph as part of the investigation comparing the Jumo 213A1 as installed in the FW-190D9 to the DB603 series engines. As you know, the DB603 was a major contender and a favorite of Kurt Tank.

 

 

That power curve is clearly labeled for a fighter engine variant as found in the FW-190D9.

 

That curve matches this power chart.

 

 

The clear connection to the fighter engine variant is why I use it.

 

Just food for thought.