[REPORTED] K-4 level speed

[rel4y]

Lets be reasonable here guys. There are certainly people who feel the need for an advantage in a comparison of airplanes.. that equates to dong size comparison stuff and is plain stupid. And please dont mix all sorts of topics into one, this thread here should be concerned with level speed of the BF 109 K4.

 

The real point here is, we have a simulation of what is supposed to be as close to the real deal as it gets. Problem being if your using drag model data of a G14 mostly and neglecting the aerodynamic changes that were made due to inconsistency of historical data you are essentially creating a a visual K4 model with G14 flight model, which in my oppinion should not be an option in top notch flight simulation. IIRC there were two different german flight tests which incorporate data on tailwheel drag. The complete retraction of the long tailwheel definitely causes a level speed increase above of the 3-4 km/h mentioned by YoYo. If russian sources state differently there is no reason to assume them being more accurate, as german engineers would have no reason to cheat themselves. Furthermore to state 2% lower speed values fits a certain margin of error maybe theoretically correct, but should not resemble what should be the goal and also the interpretation is off. The stated performance figures are going to be reached with well-built serial production machines for certain. Emphasis being on for certain here. Also I dont see how relative performance to another aircraft matters if were trying to simulate the Bf 109 K4. Not everybody buys a module to dogfight something, some people might be just happy to fly the sim of a legend perfectly reproduced.

 

Ill be looking out for the second report on drag reducing measures, meanwhile please dont derail this thread.

Edited December 26, 2015 by rel4y

[rel4y]

http://kurfurst.org/Performance_tests/109G1-6_datasheet/109G_perftable_EN.html

 

This document YoYo posted as we guessed earlier states the difference between half retracted tailwheel and fully retracted tailwheel as 3-4 km/h.

 

Conditions of the aircraft as of current state, i.e.

Without wheel well covers, MG 131 installation with blisters on engine cowling, on the G-5 and similiarly on G-6 tailwheel 1/2 retracted.

Speed tolerance +/- 4 km/h. All performance values are understood for ,,Steig-Kampfleistung".

Possibilities for increasing performance Airframe-wise

 

Wheel well covers, ca 11-14 km/h

Improved MG 131-installation, 7-9 km/h

Fully retractaible tailwheel, 3-4 km/h

Edit: picture of a half retracted tailwheel on an 109 F4 model (same as early G).

 

 

Edit2: here you can see the clear difference in size/length of G2 - G10 tailwheels. K4 tailwheel was the same as G10.

Edited December 26, 2015 by rel4y

[Anatoli-Kagari9]

I really get completely LOST over this threads....

 

Please help me finding out what are your points:

 

1) Is there a lower than expected level speed of the K4, near MSL, or a higher than expected one ?

 

2) Is it just right the way it is, given the structural optimizations of this version of the 109 ?

 

Who's on 1) and who's on 2).... ?

[rel4y]

The MSL speed atm is roughly at the level of a higher drag late G14, so it it somewhat slower than depicted in the charts. That may be due to drag modeling of parts which where actually aerodynamically improved in the K4 model. Main focus being on retracted tailwheel, wheel covers, (possibly engine hood) and resulting reduction in drag.

[Anatoli-Kagari9]

The MSL speed atm is roughly at the level of a higher drag late G14, so it it somewhat slower than depicted in the charts. That may be due to drag modeling of parts which where actually aerodynamically improved in the K4 model. Main focus being on retracted tailwheel, wheel covers, (possibly engine hood) and resulting reduction in drag.

 

 

:thumbup:

 

Thx rel4y ! On track again now :-)

[Kurfürst]

2 Kurfurst

 

What is the source of this data? I mean calculations, WT test or they were taken from the level speed flight?

 

One of the Russian official handbook of the same period gives quite close value of drag area for the half-opened wheels but very different value for a fixed tailwheel... and both sources based on somewhat like tests. :)

 

They are obtained from real life flight test. Wheel well drag from multiple tests (I even have picture of aircraft - a true xmas tree with sand filter, gondolas, new engine cover etc. - all attached at once!).

 

I am 99% sure the tailwheel drag figures come from flight test in that table since I was able to track back all the other figures to real life flight tests.

 

The most of tetsts at 1.3 ata give not more than 17 m/s generalised for 3400 conventional GW.

THis Finnish test gives almost 22 m/s average ROC for the first 150 s of climb.

 

3400 kg GW is a bit much for fully loaded G-2... weight was 3037 kg with ammo and fuel.

 

Otherwise Finnish figures match

Soviet [ame]http://kurfurst.org/Tactical_trials/109G_Soviet/109G_NIIVVS_1944.pdf[/ame]

and Rechlin trials http://kurfurst.org/Performance_tests/109G_Rechlinkennblatt/R_G1_Datenblatt.jpg

 

quite nicely, except for the first 2500 meter, where Finns admitted of having the radiators closed.

 

Noway... the best climbing speed is calculated as 1-2-3 and this procedure does not require highest math to do it. Radiators can give +- 1 m/s at the speed of climb but not more. Keep in mind that you can not deliberately close or open radiators as you do not wish to kill the engine.

But - as you perform your tests at -30C you will have radiators shut and if you perform tests at +25C they will be open, so, even if you recalculate your results to MSA regarding lift, drag and engine power there will be a difference due to radiators left out of count. I can agree with this test only if it was performed at -25C and was not recalculated at all.

 

Finn trials were conducted At airfield :

Atmospheric pressure = 747,6 mm Hg

Temperature = +11,2° C

Atmospheric pressure

measured with onboard

manifold pressure gauge =

= 1,018 ata

 

Read trial, that is why I link ;)

 

Also pay attention to notes of pilot.

 

Notes of pilot:

 

"At 2500m coolant radiator flaps open fully for the first time.

After that varying between open and closed position.

Above 5500m manifold pressure dropping during climb.

Practical ceiling 10 500m.

Climbs were executed with greater than optimal climbing speed, in order to improve cooling.

Opening of the radiator flaps noticably decreases the rate of climb."

 

They climbed at 300 kph instead of 260-270.

 

Now as to effect of radiator flaps on climb, German trials of w. G-6 WNr 16550 in June 1944 showed climb influence of radiator opening from 360 mm closing to 180 mm is already +1,7 m/sec...

 

Full closed radiators is something like 40 mm.

 

So full open to full closed there must be considerably gain, much more than +/- 1 m/sec.

 

THe last FM had higher engine power by mistake - so it was. :) As far as I can see, the current model is very good corresponded with 109G with the DB 605D engine... possible, if some valuable real test data is found, the drag can be reduced regarding the differences between G and K.

 

Good! :thumbup: So basically now we have G-10 instead of the K-4.

 

So I suppose all model needs to be done is to shave off -0,0540 m2 drag for the long tailwheel and -0,0265 m2 for the main wheels, and voila! Its a K-4.

[Anatoli-Kagari9]

Precious Kurfurst !!!!

[Echo38]

They are obtained from real life flight test.

 

I am 99% sure the tailwheel drag figures come from flight test in that table since I was able to track back all the other figures to real life flight tests.

 

How can we confirm this? Was this in one (or more) of the documents, and I overlooked it?

[rel4y]

How can we confirm this? Was this in one (or more) of the documents, and I overlooked it?

 

Well if Kurfürst says he has pictures of this test run, I would say that could be used as proof?

[Echo38]

Well if Kurfürst says he has pictures of this test run, I would say that could be used as proof?

 

Is there a way that the two can be definitively linked? The pictures to the document(s), I mean.

[Kurfürst]

How can we confirm this? Was this in one (or more) of the documents, and I overlooked it?

 

Here all the tests used to establish drag figures are listed in the same docement.

http://kurfurst.org/Performance_tests/109G_Leistungzusammenstellung/Leistungzusammenstellung109G.html#testdetails

 

Main wheel well doors test is no. 3

[Crumpp]

Lets be reasonable here guys. There are certainly people who feel the need for an advantage in a comparison of airplanes.. that equates to dong size comparison stuff and is plain stupid. And please dont mix all sorts of topics into one, this thread here should be concerned with level speed of the BF 109 K4.

 

The real point here is, we have a simulation of what is supposed to be as close to the real deal as it gets. Problem being if your using drag model data of a G14 mostly and neglecting the aerodynamic changes that were made due to inconsistency of historical data you are essentially creating a a visual K4 model with G14 flight model, which in my oppinion should not be an option in top notch flight simulation. IIRC there were two different german flight tests which incorporate data on tailwheel drag. The complete retraction of the long tailwheel definitely causes a level speed increase above of the 3-4 km/h mentioned by YoYo. If russian sources state differently there is no reason to assume them being more accurate, as german engineers would have no reason to cheat themselves. Furthermore to state 2% lower speed values fits a certain margin of error maybe theoretically correct, but should not resemble what should be the goal and also the interpretation is off. The stated performance figures are going to be reached with well-built serial production machines for certain. Emphasis being on for certain here. Also I dont see how relative performance to another aircraft matters if were trying to simulate the Bf 109 K4. Not everybody buys a module to dogfight something, some people might be just happy to fly the sim of a legend perfectly reproduced.

 

Ill be looking out for the second report on drag reducing measures, meanwhile please dont derail this thread.

 

Relative performance is the everything in these games and the key parameter you are trying to simulate. It is the only way you will get things as "real as it gets".

 

All specific aircraft is a percentage range over a guarantee mean under specific atmospheric conditions. It is not absolute.

 

Absolute specific performance is an impossibility.

 

 

http://www.spitfireperformance.com/spittest.html

 

 

Our Bf-109K4 falls within that spectrum for specific performance. More importantly, it falls were it should for relative performance within the aircraft line up.

 

It is a realistic simulation of the design, that is a fact.

 

Could it be "closer to a production machine"?

 

Sure....

[Crumpp]

They are obtained from real life flight test. Wheel well drag from multiple tests (I even have picture of aircraft - a true xmas tree with sand filter, gondolas, new engine cover etc. - all attached at once!).

 

I am 99% sure the tailwheel drag figures come from flight test in that table since I was able to track back all the other figures to real life flight tests.

 

 

 

3400 kg GW is a bit much for fully loaded G-2... weight was 3037 kg with ammo and fuel.

 

Otherwise Finnish figures match

Soviet http://kurfurst.org/Tactical_trials/109G_Soviet/109G_NIIVVS_1944.pdf

and Rechlin trials http://kurfurst.org/Performance_tests/109G_Rechlinkennblatt/R_G1_Datenblatt.jpg

 

quite nicely, except for the first 2500 meter, where Finns admitted of having the radiators closed.

 

 

 

Finn trials were conducted At airfield :

Atmospheric pressure = 747,6 mm Hg

Temperature = +11,2° C

Atmospheric pressure

measured with onboard

manifold pressure gauge =

= 1,018 ata

 

Read trial, that is why I link ;)

 

Also pay attention to notes of pilot.

 

Notes of pilot:

 

"At 2500m coolant radiator flaps open fully for the first time.

After that varying between open and closed position.

Above 5500m manifold pressure dropping during climb.

Practical ceiling 10 500m.

Climbs were executed with greater than optimal climbing speed, in order to improve cooling.

Opening of the radiator flaps noticably decreases the rate of climb."

 

They climbed at 300 kph instead of 260-270.

 

Now as to effect of radiator flaps on climb, German trials of w. G-6 WNr 16550 in June 1944 showed climb influence of radiator opening from 360 mm closing to 180 mm is already +1,7 m/sec...

 

Full closed radiators is something like 40 mm.

 

So full open to full closed there must be considerably gain, much more than +/- 1 m/sec.

 

 

 

Good! :thumbup: So basically now we have G-10 instead of the K-4.

 

So I suppose all model needs to be done is to shave off -0,0540 m2 drag for the long tailwheel and -0,0265 m2 for the main wheels, and voila! Its a K-4.

 

Good job finding the flat plate area!

[rel4y]

Relative performance is the everything in these games and the key parameter you are trying to simulate. It is the only way you will get things as "real as it gets".

 

All specific aircraft is a percentage range over a guarantee mean under specific atmospheric conditions. It is not absolute.

 

Absolute specific performance is an impossibility.

I think you misinterpreted what I said. Lets take it to an extreme and say our 109 flys at 800 km/h levelflight MSL and the P51 model has a maxspeed which would relative to these 800 km/h be perfectly correct. That would make them balance wise still perfectly viable, but it doesnt change the fact speedvalues per se are historically incorrect. Just an example.

 

That there is a variance in factory model performance is perfectly correct and normal. But why use >2% deviaton of mean to the worse when german documentation shows random sample analysis of production line aircraft to be well within mean. (That is for G models at least.)

 

Do you know what Im trying to say?

[Kurfürst]

I don't care how fast the 51 flies. I want to fly a correctly modelled 109K. That's why I bought the module, at full price to support devs who will give us a correct, deep model.

 

As far as I am concerned, the 51 could fly 2 Mach I do not care.

[Crumpp]

I think you misinterpreted what I said. Lets take it to an extreme and say our 109 flys at 800 km/h levelflight MSL and the P51 model has a maxspeed which would relative to these 800 km/h be perfectly correct. That would make them balance wise still perfectly viable, but it doesnt change the fact speedvalues per se are historically incorrect. Just an example.

 

That there is a variance in factory model performance is perfectly correct and normal. But why use >2% deviaton of mean to the worse when german documentation shows random sample analysis of production line aircraft to be well within mean. (That is for G models at least.)

 

Do you know what Im trying to say?

 

I agree with you. In any variable enviroment, some will be behind and others ahead of the mean.

 

As they say somebody has to loose!!

 

I don't care how fast the 51 flies.

 

Obviously ED does.....

 

And they are not wrong from an aeronautical science POV once you understand all aircraft performance is percentage variation over a mean.

[Echo38]

I agree with what Rel4y said: it should be modelled as accurately as possible, regardless of what its opponent aircraft's accuracy-of-modelling is. "Two wrongs don't make a right," and all that. If the relative balance is thrown off by making one aircraft more correct, then the correct solution is to then make the other aircraft more correct, too. The relative balance will then take care of itself.

 

Which doesn't mean I believe that there's an error, in this case. Again, if there is, then it should be corrected, regardless of what that does to the 109 vs. P-51 relative balance. (And then the P-51 amended, too, if it has an error as well.) However, it remains to be determined whether there actually is an error in the 109's modelling. Looking at the links, I'm not seeing an unbroken connection between documents and conclusions.

 

Although I disagree with the statement that relative balance is all that matters, Crumpp raises a valid point: if the aircraft are both within their historical range, then relative balance becomes more important than getting each aircraft exactly to the mean of its performance range. For example, if both aircraft are on the slow side of their historical averages, but by the same approximate percentage, then there is no real problem. Preserved relative balance, check; within historical range of individual variation, check. Good to go.

 

Would it be nice to have both firmly within the exact average? Yeah, but consider what you're asking for, then, and for what gain. If they're already within historical range of individual variation, then that's a miracle by itself. By definition, being within that range makes the sim accurate, and there isn't much to be gained by splitting hairs (and demanding that Yo-Yo move more mountains) to push them more towards that "perfect mean," if there isn't already a relative balance problem.

 

(Now, the more aircraft there are, the more likely it's going to be that relative balance is thrown off for at least one pair of them, if various examples are at opposite extreme ends of their historical range. But, we don't have enough birds for that to be a problem, at this point, and it hasn't been established that some aircraft are at extreme low end, and others at extreme high end, of historically-accurate individual variation.)

Edited December 26, 2015 by Echo38

[rel4y]

Which doesn't mean I believe that there's an error, in this case. Again, if there is, then it should be corrected, regardless of what that does to the 109 vs. P-51 relative balance. (And then the P-51 amended as well, if it has an error as well.) However, it remains to be determined whether there actually is an error in the 109's modelling. Looking at the links, I'm not seeing an unbroken connection between documents and conclusions.

 

I think it comes down to if or if not YoYo accepts the data presented by Kurfürst as viable. As I understood it he already acknowleged our concerns about the drag difference between G and K models. I think it is in our all interest to model an as close to real life 109 as we (well actually YoYo :thumbup:) can.

 

THe last FM had higher engine power by mistake - so it was. As far as I can see, the current model is very good corresponded with 109G with the DB 605D engine... possible, if some valuable real test data is found, the drag can be reduced regarding the differences between G and K.

I would argue the data is legit, since it says Leistungsmessung "Messung" = measurement, so I would guess german engineers to be competent enough to measure flat area drag correctly. Now that this is just my humble assessment which noone cares for im totally aware! :smilewink:

[Echo38]

I would argue the data is legit, since it says Leistungsmessung "Messung" = measurement, so I would guess german engineers to be competent enough to measure flat area drag correctly.

 

Problem is, I don't see all the referenced document scans where they're supposed to be. I see a web page with transcriptions, but no way to know that those are true to the originals. I can't take one forum-goer's word for it, and I don't think Yo-Yo will, either.

[rel4y]

Problem is, I don't see all the referenced document scans where they're supposed to be. I see a web page with transcriptions, but no way to know that those are true to the originals. I can't take one forum-goer's word for it, and I don't think Yo-Yo will, either.

 

Thats quite reasonable, but as YoYo said earlier the flat area drag for main wheel covers match other (I think soviet?) sources well, so I would argue the others to be correct as well. Somewhere I have seen a level flight test which included the tailwheel, but I cannot for the life of me find it anywhere...

 

Edit: Didnt he post the original document to the transcript?

Edited December 26, 2015 by rel4y

[Kurfürst]

Problem is, I don't see all the referenced document scans where they're supposed to be. I see a web page with transcriptions, but no way to know that those are true to the originals. I can't take one forum-goer's word for it, and I don't think Yo-Yo will, either.

 

Yoyo already has that paper in full. Its some 40 pages...

[Echo38]

Yoyo already has that paper in full. Its some 40 pages...

 

It includes original documentation listing the conditions of the test(s)? All I could find on that, from the links you posted in this thread, was your statement. If I overlooked a relevant link, my apologies.

Edited December 26, 2015 by Echo38

[javelina1]

a very informative thread. (thank you for keeping to the topic). I've learned quite a bit already.

[ArkRoyal]

Where is the aisle and who are the sides??

 

Thanks but no need to answer.

 

Your post is simply irrelevant, off topic, and trying very hard to be inflammatory without cause.

 

But I DO need to answer. :lol:

 

My post was very relevant, for reasons I spelled out above. You apparently didn't read it, in the future please try to keep up with the conversation :D

 

Oh and there is no need for inflammation. If you are getting inflamed, you might want to work on that.

 

 

The current 109 IS too slow. I don't disagree with that. The issue here is that once again we are being fed the same old nonsense. Every time a flight model is disputed with historical documentation, "problems" are found in that documentation. And like I said before, those "problems" have no evidence to support their insinuation outside of the fact that the ED flight model doesn't agree with them.

Edited December 26, 2015 by ArkRoyal

[NineLine]

The current 109 IS too slow. I don't disagree with that. The issue here is that once again we are being fed the same old nonsense. Every time a flight model is disputed with historical documentation, "problems" are found in that documentation. And like I said before, those "problems" have no evidence to support their insinuation outside of the fact that the ED flight model doesn't agree with them.

 

Yo-Yo doesnt lay all is cards on the table either, so dont assume he is going to explaining every bit of data out for you every time someone questions the validity of his FMs, and nor should he, I mean most of these documents cost money, it also his time in translating, cleaning and building these FMs. So now he should just lay it all out for free because someone doesnt agree with something because of one or two documents they found on the interwebs?

 

So Mr Royal, unless you have something useful to add to the thread, instead on insulting anyone and everyone with groundless accusations, I suggested you sit quietly and read, or move along. I am trying to keep an open mind, but this stuff just sends these threads into the mud, and I am not 100% sure that wasnt you intention anyways. Yo-Yo does this for a living, if he find issues with given info, then that is well within his right as the creator of the FM, you are well in your right not to purchase the software if you dont think ED is capable of creating an FM.

 

Next post that doesnt add to the discussion will get a 1.5, with associated bonus points, if that thread consists of insulting remarks to EITHER side of this coin, count on more points. It may seem I am getting a little tired of the drama that ensues in these threads... you are not wrong.