He 100 vs. Bf 109

[AndersJ]

@sienar , Thanks for posting the data on the He 100 airfoil. To be honest, it does not look like a very efficient design, almost symmetrical and with a sharp nose. I would be surprised if the Clmax on that is anything more than in the 1.1 to 1.2 range, and the drag properties outside a very narrow Cl range were probably not stellar either. One wonders why Heinkel did this, when almost everyone else was making good use of the new state-of-the-art NACA 4- and 5-digit series profiles?

 

[HoHun]

Hi Anders,

Not sure I make the same interpretation about if the calibration was included or not as you do.

It's a bit vague, since it's not a published paper but an internal document for people who were fully aware of the context and their usual procedures, but I'd read it like this:

v_a = 510 km/h IAS -> +15 to 20 km/h -> ~525 km/h CAS -> ~660 km/h TAS (on 1.32 ata/2550 rpm)

That's not bomb proof though, just what I think they probably implied. They were not yet about intending to get speed measurements, the flight is marked as "Full throttle flight at 4500 m to record the temperatures".

Now 520 km/h IAS is nowhere near 670 km/h at 5 km, and the power at 1.42 ata 2560 rpm is way higher than the “Nennleistung” 1020 to 1030 Ps at 2400 rpm the Heinkel data sheets talk about.

Isn't 520 km/h IAS @ 5000 m pretty exactly 670 km/h TAS in standard atmosphere, if I neglect the compressibility correction? I find test report no. 34 a bit more difficult to interprete, considering that indicated and CINA altitudes diverge, and the Heinkel procedures are not documented.

In addition, since these power values are at a higher FTH and lower power level than the circa 1100 Ps the DB 601 Aa is supposed to deliver, I’m not that sure if they were actually referring to the Aa and not some other A variant.

The DB 601Aa apparently was the engine in the He 100 aircraft delivered to the Soviet Union, the engine Heinkel used is designated as DB 601A in the test report. However, it has a serial number 60008, which I figure might indicate one of the early experimental engines which conceivable wasn't in series trim. The DB 601N for example was expected to run at 2600 rpm, and the DB 601Q even at 2700 rpm.

It's worth noting that the test report marks that 1.32 ata/2550 rpm was used for 10 min, with a 1 min period of throttling down to 1.1 ata/2400 rpm, which might imply that it was considered a 5-minute rating.

Even though they were operating their DB 601 at an astounding 1.42 ata 2560 rpm

That was the ground run, the expectation was to get 1.39 ata/2550 rpm at full throttle height, but the engine was not performing as expected (at least in these tests).

And again: Remember that the spec sheets say they were assuming to get the 670 km/h when operating a DB 601 at 2400 rpm delivering 1020-1030 Ps, which would be at 1.3 ata.

Yes, that's definitely at odds with what they're actually doing. Also odd that they used a full throttle height of 4000 m for the specified DB 601A, so it must have been one with the old supercharger.

Finally, about the surface finish on that tested specimen: I can’t see anything mentioned to conclude that it was "nothing special" and "test-weary" so I'm not sure what you base that conclusion on?

There are way more documents in the cockpitinstrumente.de collection, it's 2 PDFs of a combined 120 MB or something. One page talks about further improvements for the absolute world speed record, and it mentions worthwhile surface quality improvements. Another talks about the fate of the various airframes when the project was closed, and this mentions V2 was, in my words, "test weary". Of course, it probably came out of the shop nice and shiny originally, but they were still cutting a lot of metal to make the prototype work properly, even drilling through the main spars (as mentioned on said page), and as it was never intended as a record breaker, I really doubt it was nicely finished for the test flights that mostly dealt with the functional reliability of the systems.

Regards,

Henning (HoHun)

 

[AndersJ]

Hi Henning,

I’ve made a number of attempts now, beginning with the paper and pen calculations, and even modelled the Heinkel He 100 in my C++ simulation, and yet nothing from this suggests that those two specification sheets from Heinkel pegging the He 100 at 670 km/h are within the realms of the possible. But since I’ve worked in both engineering and marketing in my career, I’m fully aware that some marketing data sheets can be liberally sprinkled with fairy dust, especially if the marketing department has been involved, and I see Tinker Bell’s name written all over those data sheets.

And to me, to see the possibility of 670 km/h TAS as possible from those test reports requires being too creative on many levels, e.g. assuming that the Va in the report actually includes PEC and is really a CAS value, then yet again adding the magic 15-20 km/h BEFORE doing the conversion to TAS? That was creative indeed. Then that the airplane tested was “test-weary” as you call it. Finally, that although they had the engine running at way higher values than the 1.3 to 1.35 ata 2400 rpm in the data specification, i.e. 1.42 ata and 2560 rpm (and no, that was not the ground run: See data at “Horizontal” in table on the left in Bericht 34 beside “Volldruckhöhe”), and even so did not go faster than they did, that this then has to mean that there is something wrong with the engine or supercharger in those tests?

Sorry, all this added up is just a bridge too far for me, especially since Occam’s razor instead suggests a very simple and plausible solution in that the He 100’s airframe was simply draggier than needed to support 670 km/h.

So to sum up: I’ve made my case repeatedly now, and I think we will just have to agree to disagree Henning. In addition, I’ve spent far too much time on this as it is and neglected other duties, so this will have to be my final piece on this subject unless some new information surfaces.

Cheers

Anders

 

[HoHun]

Hi Anders,

And to me, to see the possibility of 670 km/h TAS as possible from those test reports requires being too creative on many levels, e.g. assuming that the Va in the report actually includes PEC and is really a CAS value, then yet again adding the magic 15-20 km/h BEFORE doing the conversion to TAS?

In my opinion, the addition of the 15 - 20 km/h is a correction of the indicated air speed. "Eichung" means "calibration". As I pointed out, I am not positive that this is in fact a calibration of the entire system, including position error, as there just aren't enough details in the report, but that the 15 - 20 km/h have to be added is pretty clear from the German text. I believe it's customary to add corrections to the indicated airspeed, but again, the document is not detailed enough to say what they're actually calculating.

Then that the airplane tested was “test-weary” as you call it.

I didn't say it was test-weary on any of these flights, I pointed out that it was test-weary at the end of the testing. See for yourself:



And here is a document that shows the He 100V3 for a planned record attempt would have aerodynamic improvements over the He 100, which included the "Anstrich" (paint job):



By the way, I just stumbled upon document showing that armament was in being installed in the He 100V2 in 1938 (before Flug Nr. 34):

Finally, that although they had the engine running at way higher values than the 1.3 to 1.35 ata 2400 rpm in the data specification, i.e. 1.42 ata and 2560 rpm (and no, that was not the ground run: See data at “Horizontal” in table on the left in Bericht 34 beside “Volldruckhöhe”), and even so did not go faster than they did, that this then has to mean that there is something wrong with the engine or supercharger in those tests?

Ah, I see the data in no. 34 now. As we have a data point from no. 37 too, which might be a bit slower but where the indicated altitude and the CINA altitude coincede, I thought this would be more solid as we don't have to worry about the data reduction methodology as much. The main problem in my opinion is not the data from the tests, which as Dieterle points out don't show the absolute top speed anyway, but that we are not positive which true air speeds were actually achieved.

So to sum up: I’ve made my case repeatedly now, and I think we will just have to agree to disagree Henning. In addition, I’ve spent far too much time on this as it is and neglected other duties, so this will have to be my final piece on this subject unless some new information surfaces.

I have point out that I don't actually intend to argue that the Heinkel data sheet is fully realistic and thus don't necessarily see me in disagreement with you, but fine with me - it was interesting for sure! I definitely wish there were more information on the He 100 available, for example about the Russian tests.

Regards,

Henning (HoHun)

 

[HoHun]

Hi Anders,

One wonders why Heinkel did this, when almost everyone else was making good use of the new state-of-the-art NACA 4- and 5-digit series profiles?

While I believe some Russian sites mention that this was a "laminar" flow airfoil, I'd speculate the reason probably was that Heinkel was choosing a compromise airfoil that offered a lot of internal volume so the fuel tanks could be housed in the wings.

Heinkel seems to have preferred propretiary airfoils over NACA airfoils as a general rule though ... https://m-selig.ae.illinois.edu/ads/aircraft.html

Regards,

Henning (HoHun)

 

[AndersJ]

Hi Anders,



While I believe some Russian sites mention that this was a "laminar" flow airfoil, I'd speculate the reason probably was that Heinkel was choosing a compromise airfoil that offered a lot of internal volume so the fuel tanks could be housed in the wings.

Heinkel seems to have preferred propretiary airfoils over NACA airfoils as a general rule though ... https://m-selig.ae.illinois.edu/ads/aircraft.html

Regards,

Henning (HoHun)

Hi Henning,

Yes, I actually looked at Lednicer's list as well and noticed that. One wonders what Heinkel thought he would gain by doing an in-house design? TBH, it seems a bit hubristic to me, given the enormous amount of work NACA's Eastman Jacobs put into the 4- and 5-digit series, and which were tried out at very high Re in the VDT tunnel, something no one else was able to do at the time. Takes an awful lot of confidence to pass over all those meticulously tested profiles and think you can do better.

And thanks for the additional He 100 documentation you posted above. Look forward to seeing any more interesting stuff if you find it.

Cheers

Anders

 

[sienar]

@sienar , Thanks for posting the data on the He 100 airfoil. To be honest, it does not look like a very efficient design, almost symmetrical and with a sharp nose. I would be surprised if the Clmax on that is anything more than in the 1.1 to 1.2 range, and the drag properties outside a very narrow Cl range were probably not stellar either. One wonders why Heinkel did this, when almost everyone else was making good use of the new state-of-the-art NACA 4- and 5-digit series profiles?

Per "The German Development of the Swept Wing", Heinkel began testing airfoils in their own high speed wind tunnel in 1937 under the direction of one O. Knappe.

I have no idea why they wen't with such a section, but I'd speculate that moving the max t/c aft was an attempt to get a longer laminar run, and perhaps the sharper nose was to try and get a more favorable pressure gradient to help maintain that laminar flow.

Thought the He-100 had a somewhat different airfoil then those I posted. I haven't come across the actual section used.

In a post-war interrogation Siegfried Gunter told the Americans that the best section for high speed aircraft Heinkel had found was the NACA 0012-0,55-40. This follows the trend of late war German airfoils having a max t/c between 40-50%.

Somewhat related, there is a post on the War Thunder forums that summaries a Japanese test. They found the stall characteristics to be poor though no mention of the speed.

Heinkel 100 D-1 with the wrong weaponry

Several prototype He 100 V series aircraft were sold to the Soviet Union, but according to Soviet documents, these did not have cannons installed in their noses. The Japanese Navy purchased pre-production models of the He 100 D-0 and MG 151 and conducted comparison tests with the Mitsubishi A6M2...

forum.warthunder.com

 

[AndersJ]

Per "The German Development of the Swept Wing", Heinkel began testing airfoils in their own high speed wind tunnel in 1937 under the direction of one O. Knappe.

I have no idea why they wen't with such a section, but I'd speculate that moving the max t/c aft was an attempt to get a longer laminar run, and perhaps the sharper nose was to try and get a more favorable pressure gradient to help maintain that laminar flow.

Thought the He-100 had a somewhat different airfoil then those I posted. I haven't come across the actual section used.

In a post-war interrogation Siegfried Gunter told the Americans that the best section for high speed aircraft Heinkel had found was the NACA 0012-0,55-40. This follows the trend of late war German airfoils having a max t/c between 40-50%.

Somewhat related, there is a post on the War Thunder forums that summaries a Japanese test. They found the stall characteristics to be poor though no mention of the speed.

I'm not familiar with Heinkel's wind tunnels, but for subsonic profile development the problem is not the tunnel airspeed but to attain the same Reynolds number (Re) as the wing section will have in real life when you do the wind tunnel tests. And the only way to do that is either to have a full scale wind tunnel or if you run models to pressurize it, which was what NACA did in the Variable Density Tunnel VDT.

So the Heinkel wing profile testing was most likely done at a lower Re than IRL and that means it's difficult to evaluate how the profile would do IRL since the test Re was simply too low. But today we can look back with close to a century of experience and from that position conclude that no-one today would think of using a close to symmetrical wing profile with such a sharp nose radius on a propeller plane like the He 100 as they did back then.

Sure, on the types of jet aircraft like the Me 262 and He 162, with the state of aerodynamics being what it was in WW2 using symmetrical wing profiles made sense, but not on a propeller plane, and a NACA 22-series, NACA 2R1 or NACA 230-series profile would have been a much better choice.

And for sure, they may with the He 100's wing profile have targeted lower drag. But the thing is, that that profile would have had a very low Clmax. And when you build a plane, you usually target a certain landing speed, and that is determined by the product of the Clmax and the wing area. And since the NACA profiles I mentioned above have a much higher Clmax, you can make the wing smaller and thus get a lower drag overall anyway, even if the drag on profile level is lower on the He 100 section.

 

[HoHun]

Hi Anders,

I'm not familiar with Heinkel's wind tunnels, but for subsonic profile development the problem is not the tunnel airspeed but to attain the same Reynolds number (Re) as the wing section will have in real life when you do the wind tunnel tests. And the only way to do that is either to have a full scale wind tunnel or if you run models to pressurize it, which was what NACA did in the Variable Density Tunnel VDT.

The section in your new book covering the impact of the NACA research was quite fascinating, by the way!

I have no idea why the German designers thought they could improve on the NACA profiles. Junkers also used proprietiary sections, and Bölkow mentions that one of the designers of the Me 410 screwed up the wing profile calculations and lost his reputation at Messerschmitt as a result. He also relates that he defined the profile for the Me 262, and was a bit embarrassed when at a post-war visit to North American, his colleagues there enquired, with great expectations, for his methodology ... whereupon he had to admit it was a bit of NACA research, a bit of intuition, and some lucky "that looks about right"

The Japanese also seem to have used their own profiles, apparently going for "laminar" flow profiles pretty early.

It's difficult to judge the effectiveness of the various choices from historic data, I'd say. I'd guess the efforts in "cleaning up" general airframe drag might have been more important, considering that the profiles had such a limited impact on top speed.

Regards,

Henning (HoHun)

 

[TomcatViP]

The He-100 used an unusual airfoil for its time with the maximum thickness near 40%.

There are an alarming number of false assertion in this Thread but this one is too much for a silent reader like me to not raise his voice.

Heinkel He 100 airfoils: root: NACA M-6 12% mod Tip: NACA M-6 8% mod

I would like all here to remember that the Karman fairing that makes the junction b/w the fuselage and the wing in order to equilibrate the pressure differentials is not to be accounted as being part of the airfoil.

Here is a popular site, free and easy to-access, data on this airfoil:



12% is the same thickness as the Spitfire's wing, which is quit thin for a fighter of this era*.

NACA M6 AIRFOIL (m6-il)

Details of airfoil (aerofoil)(m6-il) NACA M6 AIRFOIL NACA/Munk M-6 airfoil

airfoiltools.com

*The thickness values reported on top of this page are from the He-112 that has a gull-wing with elliptical planform.

 

[HoHun]

Hi,

There are an alarming number of false assertion in this Thread but this one is too much for a silent reader like me to not raise his voice.

Heinkel He 100 airfoils: root: NACA M-6 12% mod Tip: NACA M-6 8% mod

Well, "mod" means modified, which allows for some deviation from the standard M-6.

Perhaps @Aeroweanie knows more about this?

Regards,

Henning (HoHun)

 

[AndersJ]

There are an alarming number of false assertion in this Thread but this one is too much for a silent reader like me to not raise his voice.

Well jumping into a thread and making sweeping accusations is never a good start. But maybe you can share some of your wisdom and improve the impression you make by giving us a concise list of all these "alarming number of false assertion"?

 

[TomcatViP]

Isn't 3 (three) enough in a single post?!

 

[AndersJ]

Isn't 3 (three) enough in a single post?!

OK, so your big words about "There are an alarming number of false assertion in this Thread" is really just a lot of hot air since in reality it was all about a single post?

 

[AndersJ]

Hi Anders,



The section in your new book covering the impact of the NACA research was quite fascinating, by the way!

I have no idea why the German designers thought they could improve on the NACA profiles. Junkers also used proprietiary sections, and Bölkow mentions that one of the designers of the Me 410 screwed up the wing profile calculations and lost his reputation at Messerschmitt as a result. He also relates that he defined the profile for the Me 262, and was a bit embarrassed when at a post-war visit to North American, his colleagues there enquired, with great expectations, for his methodology ... whereupon he had to admit it was a bit of NACA research, a bit of intuition, and some lucky "that looks about right"

The Japanese also seem to have used their own profiles, apparently going for "laminar" flow profiles pretty early.

It's difficult to judge the effectiveness of the various choices from historic data, I'd say. I'd guess the efforts in "cleaning up" general airframe drag might have been more important, considering that the profiles had such a limited impact on top speed.

Regards,

Henning (HoHun)

Hi Henning,

Well I would not be surprised if it turns out that Heinkel used a modification of the NACA M-6 given that that would make much more sense since that profile looks much more sensible than the more or less symmetrical profiles you can see in the fuselage cross sections we have been looking at so far.

Glad you liked the section in the book about the development of the NACA 4- and 5-digit series. I learned a lot myself from writing them, and Eastman Jacobs who led the work seems to have been an exceptionally gifted engineer. Too bad he left NACA so early, since he probably could have contributed so much more seeing all that he managed to do during his years there.

Cheers

Anders

 

[TomcatViP]

OK, so your big words about "There are an alarming number of false assertion in this Thread" is really just a lot of hot air since in reality it was all about a single post?

Kindly saying, you are not reading.

My point is that I already corrected 3 mistakes in my single post. I think I did my share. Thank you.

 

[sienar]

There are an alarming number of false assertion in this Thread but this one is too much for a silent reader like me to not raise his voice.

Heinkel He 100 airfoils: root: NACA M-6 12% mod Tip: NACA M-6 8% mod

I would like all here to remember that the Karman fairing that makes the junction b/w the fuselage and the wing in order to equilibrate the pressure differentials is not to be accounted as being part of the airfoil.

Here is a popular site, free and easy to-access, data on this airfoil:

View attachment 800338

12% is the same thickness as the Spitfire's wing, which is quit thin for a fighter of this era*.

NACA M6 AIRFOIL (m6-il)

Details of airfoil (aerofoil)(m6-il) NACA M6 AIRFOIL NACA/Munk M-6 airfoil

airfoiltools.com

*The thickness values reported on top of this page are from the He-112 that has a gull-wing with elliptical planform.

Kindly saying, you are not reading.

My point is that I already corrected 3 mistakes in my single post. I think I did my share. Thank you.

What is the source of your information?

I have posted a facsimile of an original Heinkel drawing, a copy of the Soviet fuselage drawing of the He-100 and information on airfoils known to have been in use by Heinkel at the time. Those peculiar Heinkel airfoil sections are a close match to the drawings posted.

Furthermore Soviet TSAGI documents state that the airfoil had a very rear max t/c, as does Erwin Hoods well researched book on the He-100.

This drawing is from Erwin Hood;


Then lets do a comparison. Munk M-6 is a poor match to the original Heinkel side view;

However the Heinkel 16.8% tc 2% camber does show a near match in contour. I'd guess that the real root airfoil was 14% or so thick.


Now the Soviet side view. Again the Munk M-6 does not match well.

The Heinkel airfoil section is a close match, but here the camber looks like a bit much and the nose LE is a touch too sharp.


I think it is very clear that the airfoil on the He-100, at least at root, is something like the Heinkel family known to exist. I'll note that the He-176 and He-178 are also known to have used in-house Heinkel airfoils, and these aircraft are shortly after the He-100 design wise.

I'll speculate that the actual root section is something like HE 1 37 14-0.85 36.6 or maybe HE 1.5 .........

Hi Anders,



The section in your new book covering the impact of the NACA research was quite fascinating, by the way!

I have no idea why the German designers thought they could improve on the NACA profiles. Junkers also used proprietiary sections, and Bölkow mentions that one of the designers of the Me 410 screwed up the wing profile calculations and lost his reputation at Messerschmitt as a result. He also relates that he defined the profile for the Me 262, and was a bit embarrassed when at a post-war visit to North American, his colleagues there enquired, with great expectations, for his methodology ... whereupon he had to admit it was a bit of NACA research, a bit of intuition, and some lucky "that looks about right"

The Japanese also seem to have used their own profiles, apparently going for "laminar" flow profiles pretty early.

It's difficult to judge the effectiveness of the various choices from historic data, I'd say. I'd guess the efforts in "cleaning up" general airframe drag might have been more important, considering that the profiles had such a limited impact on top speed.

Regards,

Henning (HoHun)

Have you read "The German Development of the Swept Wing" by Hans-Ulrich Meier? It sporadically talks about the manufacturers own airfoil testing and development.

There is also this; https://www.cia.gov/readingroom/document/cia-rdp78-02646r000400190001-3

pg.103 is where the airfoil summary starts. It even has the equations and design rational for some of them.

I'm not familiar with Heinkel's wind tunnels, but for subsonic profile development the problem is not the tunnel airspeed but to attain the same Reynolds number (Re) as the wing section will have in real life when you do the wind tunnel tests. And the only way to do that is either to have a full scale wind tunnel or if you run models to pressurize it, which was what NACA did in the Variable Density Tunnel VDT.

So the Heinkel wing profile testing was most likely done at a lower Re than IRL and that means it's difficult to evaluate how the profile would do IRL since the test Re was simply too low. But today we can look back with close to a century of experience and from that position conclude that no-one today would think of using a close to symmetrical wing profile with such a sharp nose radius on a propeller plane like the He 100 as they did back then.

Sure, on the types of jet aircraft like the Me 262 and He 162, with the state of aerodynamics being what it was in WW2 using symmetrical wing profiles made sense, but not on a propeller plane, and a NACA 22-series, NACA 2R1 or NACA 230-series profile would have been a much better choice.

And for sure, they may with the He 100's wing profile have targeted lower drag. But the thing is, that that profile would have had a very low Clmax. And when you build a plane, you usually target a certain landing speed, and that is determined by the product of the Clmax and the wing area. And since the NACA profiles I mentioned above have a much higher Clmax, you can make the wing smaller and thus get a lower drag overall anyway, even if the drag on profile level is lower on the He 100 section.

I'm aware of the Re# issue and how its impossible to match mach and Re# and subscale.

I was just explaining what I think the design logic was, not that it actually worked.

For whats its worth Soviet sources give;
Landing speed of 159km/h
To run of 310m
Landing run of 325m

No weights given so who knows the Cl, but I don't think that points to an impressive Clmax.

 

[TomcatViP]

I think you are attaching too much credence to a single drawing. What appears to be a general arrangement sketch would not have mandatorily the airfoil exact geometry for something irrelevant, especially when the model 100 was a derivative of an earlier design, the 112.
Copy pasting was not invented with Windows OS.

You would need to find the right drawing where the section location for the airfoil is indicated. Again also, a Karman fairing is not any indication of a wing airfoil.

 

[sienar]

I think you are attaching too much credence to a single drawing. What appears to be a general arrangement sketch would not have mandatorily the airfoil exact geometry for something irrelevant, especially when the model 100 was a derivative of an earlier design, the 112.
Copy pasting was not invented with Windows OS.

You would need to find the right drawing where the section location for the airfoil is indicated. Again also, a Karman fairing is not any indication of a wing airfoil.

How do you know they used a Munk M-6?

Why does the drawn section in two separate, contemporary drawings match known Heinkel airfoils?

 

[Apophenia]

... especially when the model 100 was a derivative of an earlier design, the 112.
.

Other than the design involvement of the Günter brothers, there was zero relationship between the He 112 and the He 100. Indeed, Walter Günter began designing the much simplified P.1035/He 100 because he was convinced that the He 112 airframe had run its course.

 

[TomcatViP]

@sienar : because the 100 is an evolution of the 112. They used an earlier design and adapted the new wing design to it.*

Think 109 210 410 for example.

Or 108 109

Or BT-1, BT-2, SBD...

Or Vought V166 XF-4U

Other examples escape me tonight but you know better.

*you want to minimize airframe changes and having to swap all your jigs and tools.

 

[Apophenia]

... because the 100 is an evolution of the 112. They used an earlier design and adapted the new wing design to it...

No. The He 100 fuselage was an entirely new design emphasising speed of production.

 

[TomcatViP]

And speed of production comes with what? Derivation, adaptation, re-use of proven sub components... This is old like the Wright Brothers.

 

[Apophenia]

And speed of production comes with what? Derivation, adaptation, re-use of proven sub components... This is old like the Wright Brothers.

Tell it to Siegfried Günter. He's dead, of course, but unlikely to intentionally miss the point.

 

[HoHun]

Hi,

And speed of production comes with what? Derivation, adaptation, re-use of proven sub components... This is old like the Wright Brothers.

From Heinkel's autobiography "Stürmisches Leben", there is no doubt that the He 100 was a clean-sheet design, especially regarding production aspects, with a dramatical reduction in the number of subcomponents and unique parts.

Regards,

Henning (HoHun)

 

[AndersJ]

Kindly saying, you are not reading.

My point is that I already corrected 3 mistakes in my single post. I think I did my share. Thank you.

I did read what you wrote which was: "There are an alarming number of false assertion in this Thread". But this just seems to fizzle down to 1 issue and that is the wing profile. But good to know that for you 1-3 things constitutes an “alarming number”. In addition, no one here is making “false assertions”. What we are doing here is called speculating. I hope this clear it up for you.

 

[AndersJ]

What is the source of your information?

I have posted a facsimile of an original Heinkel drawing, a copy of the Soviet fuselage drawing of the He-100 and information on airfoils known to have been in use by Heinkel at the time. Those peculiar Heinkel airfoil sections are a close match to the drawings posted.

Furthermore Soviet TSAGI documents state that the airfoil had a very rear max t/c, as does Erwin Hoods well researched book on the He-100.

This drawing is from Erwin Hood;
View attachment 800374

Then lets do a comparison. Munk M-6 is a poor match to the original Heinkel side view;
View attachment 800377
However the Heinkel 16.8% tc 2% camber does show a near match in contour. I'd guess that the real root airfoil was 14% or so thick.
View attachment 800380

Now the Soviet side view. Again the Munk M-6 does not match well.
View attachment 800381
The Heinkel airfoil section is a close match, but here the camber looks like a bit much and the nose LE is a touch too sharp.
View attachment 800382

I think it is very clear that the airfoil on the He-100, at least at root, is something like the Heinkel family known to exist. I'll note that the He-176 and He-178 are also known to have used in-house Heinkel airfoils, and these aircraft are shortly after the He-100 design wise.

I'll speculate that the actual root section is something like HE 1 37 14-0.85 36.6 or maybe HE 1.5 .........

Have you read "The German Development of the Swept Wing" by Hans-Ulrich Meier? It sporadically talks about the manufacturers own airfoil testing and development.

There is also this; https://www.cia.gov/readingroom/document/cia-rdp78-02646r000400190001-3

pg.103 is where the airfoil summary starts. It even has the equations and design rational for some of them.

I'm aware of the Re# issue and how its impossible to match mach and Re# and subscale.

I was just explaining what I think the design logic was, not that it actually worked.

For whats its worth Soviet sources give;
Landing speed of 159km/h
To run of 310m
Landing run of 325m

No weights given so who knows the Cl, but I don't think that points to an impressive Clmax.

OK fair enough. My mentioning the Re was more because we were talking about airfoils characteristics, and you mentioned that Heinkel had his own high speed wind tunnel, so I just wanted to point out that that would not be the best tool for airfoil design, and why the VDT was so groundbreaking.

Regarding the He 100 profile question, I think you are right to overlay the profiles like you do, since if you scale the drawn profile with the fuselage length, you get the wings root chord length. And another way to see that is that the trailing edge ends at the rear canopy frame if you look at a top view drawing, and that the wing fairing or fillet, extends more rearwards.

Finally, it’s intriguing that there is such a good fit between the He profiles and the fuselage drawing you posted, and that certainly would be an argument for it actually being a correctly drawn profile in the fuselage study. On the other hand, the wing root profile in the fuselage drawing looks very poor from a design perspective as we talked about earlier, and a NACA M-6 derivate would for sure make more sense. But I don’t think I’ve seen any solid proof that it was one or the other yet. So I would say it’s a bit premature to say that “false assertions” are being made here as some would have it.

What was it Bertrand Russel used to say? “The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts"........

 

[Aeroweanie]

Hi,



Well, "mod" means modified, which allows for some deviation from the standard M-6.

Perhaps @Aeroweanie knows more about this?

Regards,

Henning (HoHun)

The He airfoils discussed previously appear to be using the AVA's expanded NACA 4-digit series. This is defined as:

• The first number indicates the maximum value of the mean-line ordinate (also called the "camber"), in percent of the chord.
• The second number indicates the distance from the airfoil leading edge to the location of the maximum camber in tenths of the chord.
• The third number indicates the section thickness in percent of the chord.
• The fourth number indicates the leading edge radius parameter. The normal NACA 4-digit leading edge radius is designated by a value of 1.1.
• The fifth number indicates the position of maximum thickness in tenths of the airfoil chord.
• The sixth number indicates the trailing edge angle parameter.

An airfoil designated "NACA 1.8 25 14-1.1 30/.50" has 1.8% camber, at 25% of the chord from the leading edge and is 14% thick. The leading edge radius is 1.1 times the thickness to chord ratio squared, the position of maximum thickness is now 30% of the airfoil's chord and the trailing edge angle is 2 * arctangent(.5 * t/c). A designation of "0012-.55" indicates that the camber is zero, so the remaining terms are not listed. You can find all of the relevant equations in "The Theory of Wing Sections"

The He airfoil shown are missing the sixth number, which controls the trailing edge angle. I haven't done an overlay, but it looks like it should be 1.0


I seem to remember finding the airfoil used on the He 100 wing designated as the M-6 in a document - I'll have to dig it out again. If someone can prove the designation is otherwise, I'll revise the listing.

 

[Scott Kenny]

Since it looks like we've beaten the airfoil section thing into the ground, can we loop back to the evaporative cooling setup?

I'm trying to understand how that works out, without cooking the engine.

 

[HoHun]

Hi Scott,

Since it looks like we've beaten the airfoil section thing into the ground, can we loop back to the evaporative cooling setup?

I just found this reference to the archive of the Deutsches Museum in Munich:

Deutsches Museum Digital

Deutsches Museum Digital: Das Portal für Digitalisate aus Sammlung, Archiv und Bibliothek sowie alles rund um die Digitalisierung am Deutschen Museum.

digital.deutsches-museum.de

No digital access, though. It seems Heinkel's son provided two batches of surviving company documents to the museum some 25 years ago, so conveivably, they might have something we don't find in older books.

They also have some documents on airfoil design and wind tunnel testing in other references.

Regards,

Henning (HoHun)

 

[sienar]

Hi Scott,



I just found this reference to the archive of the Deutsches Museum in Munich:

Deutsches Museum Digital

Deutsches Museum Digital: Das Portal für Digitalisate aus Sammlung, Archiv und Bibliothek sowie alles rund um die Digitalisierung am Deutschen Museum.

digital.deutsches-museum.de

No digital access, though. It seems Heinkel's son provided two batches of surviving company documents to the museum some 25 years ago, so conveivably, they might have something we don't find in older books.

They also have some documents on airfoil design and wind tunnel testing in other references.

Regards,

Henning (HoHun)

I suspect these documents may have more about Heinkel airfoils

Details zu: Beiträge zur Profilforschung : Theorie des Singularitätenverfahrens › Zentrales Archiv des DLR - Katalog

dlr-archivkatalog.bsz-bw.de

Details zu: Beiträge zur Profilforschung : 2. Gemoetrie der Profilsystematik › Zentrales Archiv des DLR - Katalog

dlr-archivkatalog.bsz-bw.de

Details zu: Beiträge zur Profilforschung : 3. Berechnung der Geschwindigkeitsverteilung in erster Näherung, mit einer Korrektur in der Umgebung der Profilnase › Zentrales Archiv des DLR - Katalog

dlr-archivkatalog.bsz-bw.de

Details zu: Beiträge zur Profilforschung : 6. Teil: Zweite Näherung zur Berechnung der Geschwindigkeitsverteilung nach dem Singularitätenverfahren › Zentrales Archiv des DLR - Katalog

dlr-archivkatalog.bsz-bw.de

There are many other interesting documents there, unfortunately while many of them say "Digitalisat" and even give the size of the pdf, there is no apparent way of downloading any of them