Luftwaffe: Secret Designs of the Third Reich

[Wurger]

Dan, the lesser known german aircraft manufacturers/design bureaus aren`t well represented in literature. Do you have material on AGO, Fieseler, Siebel, Bücker, Hütter Klemm, Gotha, Skoda-Kauba or Zeppelin?

 

[newsdeskdan]

Dan, the lesser known german aircraft manufacturers/design bureaus aren`t well represented in literature. Do you have material on AGO, Fieseler, Siebel, Bücker, Hütter, Klemm, Gotha, Skoda-Kauba or Zeppelin?

I have a lot from Gotha and scraps from Fieseler, Hütter, Skoda-Kauba and Zeppelin (which worked almost exclusively on other people's projects). AGO, Siebel and Bücker were all captured by the Soviets and therefore 'lost'. This has resulted in large gaps in our knowledge of German WW2 'projects'. While the western Allies got most of the major manufacturers' material, Heinkel's projects material almost all went to the Soviets (though Ernst Heinkel was initially under the impression that he'd made sure the western Allies would get it) along with the likes of Henschel and the others mentioned. Anecdotally, most of Skoda-Kauba's documents were burned, and there does seem to be some truth in that. A lot of Focke-Wulf material survived but mostly from Flugmechanik L under Wolff and (to a lesser extent) Flugmechanik E under Mathias. Documents from the actual Focke-Wulf projects office under Mittelhuber are conspicuous by their absence. Robert Forsyth has said that these were destroyed and it seems as though that might indeed have been the case.
Klemm ought to have been captured by the western Allies but if that was the case I've no idea what happened to their documents. Junkers is interesting because all of that company's documents ought to have been captured by the Americans but if that is the case then very few 'projects' documents seem to have survived for some reason. Messerschmitt and Arado material was, again, captured by the western Allies but as with Focke-Wulf there are plenty of gaps in the projects material.

 

[steelpillow]

I suppose there weren't enough designs of helicopters and other rotorcraft to fill up an entire issue?

There were, and that might be one for the future.

The not too distant future I trust. B) ;D

 

[sienar]

Personally I'd like to see the Focke Wulf 159 design studies and the late 30s Arado radial fighter you mentioned. The 309 would be nice too, especially details on the radiator installation.

 

[newsdeskdan]

Personally I'd like to see the Focke Wulf 159 design studies and the late 30s Arado radial fighter you mentioned. The 309 would be nice too, especially details on the radiator installation.

The 159 design studies are a candidate for the next one, thanks to Jemiba's efforts in transcribing and translating the accompanying notes for me. The Arado fighter's still on the shelf. There appears to have been a huge amount of work done on the 309's radiator and I could certainly expand a great deal on that. One of the potential options for the next Luftwaffe: Secret was piston-engined fighters, but I decided against it because the Ta 153 vs Me 209 and Me 409/Me 155/Me 109 H/Me 309 H/Me 209 H/P 1091/BV 155 stories are proving too complex to pull together in the short term. I need more time on those.

 

[steelpillow]

I need more time on those.

Luftwaffe: Secret Rotorcraft of the Third Reich should buy you that time, while the current popularity of VTOL drones and "flying car" autogyros would make it an excellent eyecatcher. Only problem is, you already used the <i>Triebflûgel</i> cover art.

 

[newsdeskdan]

I need more time on those.

Luftwaffe: Secret Rotorcraft of the Third Reich should buy you that time, while the current popularity of VTOL drones and "flying car" autogyros would make it an excellent eyecatcher. Only problem is, you already used the <i>Triebflûgel</i> cover art.

I doubt helicopters will follow the next 'unknowns' but we'll see.

 

[gatoraptor]

I guess the Triebflugel is technically a rotorcraft.

 

[newsdeskdan]

I guess the Triebflugel is technically a rotorcraft.

Yes. I think I have at least one design drawing of the Triebflugeljager that's not been in print before (discovered after I wrote about it in Luftwaffe: Secret Jets). The Heinkel Lerche and Wespe are also technically rotorcraft.

 

[sienar]

Personally I'd like to see the Focke Wulf 159 design studies and the late 30s Arado radial fighter you mentioned. The 309 would be nice too, especially details on the radiator installation.

The 159 design studies are a candidate for the next one, thanks to Jemiba's efforts in transcribing and translating the accompanying notes for me. The Arado fighter's still on the shelf. There appears to have been a huge amount of work done on the 309's radiator and I could certainly expand a great deal on that. One of the potential options for the next Luftwaffe: Secret was piston-engined fighters, but I decided against it because the Ta 153 vs Me 209 and Me 409/Me 155/Me 109 H/Me 309 H/Me 209 H/P 1091/BV 155 stories are proving too complex to pull together in the short term. I need more time on those.

Do you know what type of airfoil the 309 used? Lots of books claim it was a laminar section but I'm pretty sure that is not the case.

Have you uncovered anything on the swept wing 309 development?

 

[steelpillow]

I guess the Triebflugel is technically a rotorcraft.

Yes. I think I have at least one design drawing of the Triebflugeljager that's not been in print before (discovered after I wrote about it in Luftwaffe: Secret Jets). The Heinkel Lerche and Wespe are also technically rotorcraft.

There's a bit of a grey area between rotorcraft on the one hand and hybrids like convertiplanes, stop-rotors and powered lift aircraft on the other. Is the V-22 Osprey tiltrotor a "rotorcraft"? Boeing think so, but I am not sure that everybody would agree. The French FAI would at one time have classified it as a Convertiplane, though I don't know if they still do. The American FAA would probably classify ducted prop/rotor types such as the Heinkels as Powered Lift.
Mostly everybody is pretty vague until a design actually flies and the regulatory bodies have to start making their minds up. To some extent one can distinguish between customary engineering terminology and local regulatory terminology. Engineers usually agree that it doesn't matter as long as you know what you are talking about, until somebody writes an overly-dogmatic textbook. National regulators usually disagree until somebody writes an international standard.
At the end of the day, you can be pretty flexible about it and everybody will just be glad that you included their favourite weird stuff.

 

[newsdeskdan]

Personally I'd like to see the Focke Wulf 159 design studies and the late 30s Arado radial fighter you mentioned. The 309 would be nice too, especially details on the radiator installation.

The 159 design studies are a candidate for the next one, thanks to Jemiba's efforts in transcribing and translating the accompanying notes for me. The Arado fighter's still on the shelf. There appears to have been a huge amount of work done on the 309's radiator and I could certainly expand a great deal on that. One of the potential options for the next Luftwaffe: Secret was piston-engined fighters, but I decided against it because the Ta 153 vs Me 209 and Me 409/Me 155/Me 109 H/Me 309 H/Me 209 H/P 1091/BV 155 stories are proving too complex to pull together in the short term. I need more time on those.

Do you know what type of airfoil the 309 used? Lots of books claim it was a laminar section but I'm pretty sure that is not the case.

Have you uncovered anything on the swept wing 309 development?

I must admit to not being particularly au fait with the different NACA airfoils but some drawings I have show NACA 13012, others NACA 15014.5, and tests appear to have been done using variations on NACA 0012. There are references to it having a 'symmetrical airfoil'. Does any of that mean anything to you? There is at least one document I've seen on tests of a 309 model with a 'thin wing' in September 1943 - three months before all work on the 309 apparently ceased.
I've never seen anything on a swept wing development of the 309. However, I wouldn't rule it out. The 309 was in development from mid-1941 to the end of 1943 - plenty of time to try different arrangements. The key characteristics that Messerschmitt hoped to build into its design were a sliding canopy, pressure cabin (it's been suggested that it would have an ejection seat too), wide-track inwards-retracting tricycle undercarriage, retractable radiator, reversible pitch propeller - and the capability to accept much larger engines than the 109 could. Wing, tail and radiator shapes appear to have been fairly fluid, much like those of the Me 209. I have an AVA report on wind tunnel tests of 22 different radiator shapes for the 309 and I've no doubt that there were many more.
Early on, it was intended that it should take the DB 603 A or Jumo 213, but other potential powerplants included the DB 622, DB 627 and DB 628 (an Allied report also suggests the DB 609). The DB 603 G was only brought in towards the end of the development cycle. I have an Allied intelligence report which suggests that Messerschmitt had worked on a version of the 309 with tandem engines, A DB 605 in front of the cockpit and a second behind it, with the extension shaft running under the pilot's seat and a contra-rotating propeller. The way the report is written seems very authoritative but I've seen nothing from Messerschmitt itself to support this idea. The same report mentions the 309 as having a thin aerofoil section, making it difficult to install cannon in the wings.
I've also seen material suggesting that the 309's characteristic tricycle undercarriage was actually abandoned towards the end in favour of a conventional tail-sitter layout.
Again, research on the Me 309 is a work in progress.

 

[Wurger]

The Arado fighter's still on the shelf

Sorry, please explain: do you have it? I mean Rudiger Kosin`s answer to the I-16.
Kranzhoff also tell us about an alternative single engined carrier based Arado torpedo bomber, as opposed to the twin engined E310.

 

[newsdeskdan]

The Arado fighter's still on the shelf

Sorry, please explain: do you have it? I mean Rudiger Kosin`s answer to the I-16.
Kranzhoff also tell us about an alternative single engined carrier based Arado torpedo bomber, as opposed to the twin engined E310.

No, I don't think the radial-engined fighter design I have is what you mean. It's not a torpedo bomber.

 

[steelpillow]

I must admit to not being particularly au fait with the different NACA airfoils but some drawings I have show NACA 13012, others NACA 15014.5, and tests appear to have been done using variations on NACA 0012. There are references to it having a 'symmetrical airfoil'. Does any of that mean anything to you?

Of the aerofoils cited, the first two are broadly conventional while NACA 0012 is both laminar-flow and symmetrical.

Most aerofoils have a "hump" at the front, thickest around say 25% back from the leading edge, where they curve the most and then straighten out towards the rear. This hump causes turbulence, roughly speaking backwards from its highest point, and that causes drag.

A laminar design keeps the smooth front airflow for longer, by moving the thickest point further back to say 40%. It is only "laminar" in a nominal kind of way because at least 60% of the flow is still turbulent. It gives you less drag at high speeds, the penalty being slightly higher drag at low speeds.

The centre line of a conventional aerofoil curves upwards underneath the hump. This is called camber. A symmetrical aerofoil is the same above and below and therefore must have zero camber. It is less efficient than a cambered equivalent, so is not normally used. However in violent manoeuvring when the aeroplane is all which ways up, its inverted flight characteristics are as good as ever, while a cambered aerofoil is seriously disadvantaged. So symmetrical aerofoils are common on aerobatic specials and are - or were - sometimes considered for air-to-air combat dogfighters.

Because both features tend to "smooth out" the hump a bit, they can also give good transonic properties, with a higher critical Mach number (i.e. a delayed shock buildup) compared to the conventional cambered equivalent of the same thickness.

NACA 0012 must have been a promising candidate for a fast jet fighter. The variations on it would have been in thickness-chord ratio, its "thinness".

Hope this helps.

 

[Wurger]

No, I don't think the radial-engined fighter design I have is what you mean. It's not a torpedo bomber.

I mean the 1938 radial engined Arado fighter project submited by Rüdiger Kosin and Van Nes to Walter Blume and then to the RLM. They made their proposal after inspecting a Polikarpov I-16 captured in Spain. The very short story can be read at Kosin`s book "The German Fighter Since 1915", originally printed as "Die Entwicklung der Deutschen Jagdflugzeuge".

The torpedo-bomber I mentioned is refered in Jörg Armin Kranzhoff`s book "Die Arado-Flugzeuge. Vom Doppeldecker zum Strahlflugzeug". He tells about the carrier-borne Arado E310 and states its 5 (known) versions: a 1940 single engined (DB601) project, and 4 twin engined (DB 601, Jumo 210, As 402 and BMW 132). We know the As 402 version, and another with BMW 800 posted by me some years ago in our forum.

 

[gatoraptor]

This publication is now available at the Barnes & Nobles in the Atlanta area, one week later than Huntsville. As with the prior issues in this series, more "book" than "zine".

 

[sienar]

Personally I'd like to see the Focke Wulf 159 design studies and the late 30s Arado radial fighter you mentioned. The 309 would be nice too, especially details on the radiator installation.

The 159 design studies are a candidate for the next one, thanks to Jemiba's efforts in transcribing and translating the accompanying notes for me. The Arado fighter's still on the shelf. There appears to have been a huge amount of work done on the 309's radiator and I could certainly expand a great deal on that. One of the potential options for the next Luftwaffe: Secret was piston-engined fighters, but I decided against it because the Ta 153 vs Me 209 and Me 409/Me 155/Me 109 H/Me 309 H/Me 209 H/P 1091/BV 155 stories are proving too complex to pull together in the short term. I need more time on those.

Do you know what type of airfoil the 309 used? Lots of books claim it was a laminar section but I'm pretty sure that is not the case.

Have you uncovered anything on the swept wing 309 development?

I must admit to not being particularly au fait with the different NACA airfoils but some drawings I have show NACA 13012, others NACA 15014.5, and tests appear to have been done using variations on NACA 0012. There are references to it having a 'symmetrical airfoil'. Does any of that mean anything to you? There is at least one document I've seen on tests of a 309 model with a 'thin wing' in September 1943 - three months before all work on the 309 apparently ceased.
I've never seen anything on a swept wing development of the 309. However, I wouldn't rule it out. The 309 was in development from mid-1941 to the end of 1943 - plenty of time to try different arrangements. The key characteristics that Messerschmitt hoped to build into its design were a sliding canopy, pressure cabin (it's been suggested that it would have an ejection seat too), wide-track inwards-retracting tricycle undercarriage, retractable radiator, reversible pitch propeller - and the capability to accept much larger engines than the 109 could. Wing, tail and radiator shapes appear to have been fairly fluid, much like those of the Me 209. I have an AVA report on wind tunnel tests of 22 different radiator shapes for the 309 and I've no doubt that there were many more.
Early on, it was intended that it should take the DB 603 A or Jumo 213, but other potential powerplants included the DB 622, DB 627 and DB 628 (an Allied report also suggests the DB 609). The DB 603 G was only brought in towards the end of the development cycle. I have an Allied intelligence report which suggests that Messerschmitt had worked on a version of the 309 with tandem engines, A DB 605 in front of the cockpit and a second behind it, with the extension shaft running under the pilot's seat and a contra-rotating propeller. The way the report is written seems very authoritative but I've seen nothing from Messerschmitt itself to support this idea. The same report mentions the 309 as having a thin aerofoil section, making it difficult to install cannon in the wings.
I've also seen material suggesting that the 309's characteristic tricycle undercarriage was actually abandoned towards the end in favour of a conventional tail-sitter layout.
Again, research on the Me 309 is a work in progress.

Yes, the airfoil info is interesting. Messerschmitt at some point moved over to preferring symmetrical sections, doing quite a bit of work with modified NACA sections having an elliptical nose.

The swept wing 309 was worked on by caudron and there was an expected 20% or so increase in top speed. But I wouldnt be surprised if this was purely a test article for figuring out the low speed handling of swept wings rather than an honest attempt at a swept piston fighter. Its also possible that caudron was lied to and the swept wing work was for a non-309 project.

There is a drawing of an ejection seat for the 309 in Willy Messerschmitt: Pioneer of Aviation Design.

Bulges for wing canons were allegedly test installed in the 109 V-31, being necessary due to the thinness of the wing, but I've never seen photos of it. Testing showed that these bulges actually reduced drag slightly, possibly being the first instance of kuchemann carrots, albeit accidentally.

With all those engine variants they looked at I'm kinda surprised that the 222 wasnt considered.

 

[Wurger]

Here is the link:

https://www.secretprojects.co.uk/forum/index.php/topic,4771.msg37651.html#msg37651

 

[newsdeskdan]

Here is the link:

https://www.secretprojects.co.uk/forum/index.php/topic,4771.msg37651.html#msg37651

Ah, you mean this (attached - column on the extreme right)? No I don't have a drawing of that. I do have all five 'entwurf' drawings but Entwurf 1 is 2 x DB 601, Entwurf 2 is 2 x BMW 800, Entwurf 3 is 2 x DB 601 with tail turret, Entwurf 4 is 2 x BMW 800 with tail turret and Entwurf 5 is 2 x As 402.
Interesting that the five 'entwurf' drawings all depict the later Ar 240 cockpit, whereas the seven other drawings (side view, side with wings folded, front, front with wings folded, top, top with wings folded, pair of see-through side views - Kranzhoff's designer seems to have chopped the front section off the lower one and put a box around it for some reason) show the E 310 with the Ar 240 V1 cockpit.

 

[newsdeskdan]

With all those engine variants they looked at I'm kinda surprised that the 222 wasnt considered.

Doesn't seem to have been but again I wouldn't rule it out.

There is a drawing of an ejection seat for the 309 in Willy Messerschmitt: Pioneer of Aviation Design.

And here's (attached) the non-cleaned up version of the Me 309 ejection seat drawing and a second closer-up one - from a large file consisting entirely of different Messerschmitt seat designs bizarrely. I don't know that it was always specified as standard equipment for the 309 though.

 

[Wurger]

Ah, you mean this

Exactly right, that`s the single-engined "multi-purpose" carrier-borne aircraft. I didn`t know about the tail turrets. Can you please publish that or do you intend to do it in a future "Luftwaffe/Marineflieger" bookazine?

What about the 1938 radial-engined fighter? Do you have it? Kosin stated that it would have a 14 cylinder BMW radial (certainly the BMW 139). Proposed speed at 600-650 Km/h.

 

[newsdeskdan]

Ah, you mean this

Exactly right, that`s the single-engined "multi-purpose" carrier-borne aircraft. I didn`t know about the tail turrets. Can you please publish that or do you intend to do it in a future "Luftwaffe/Marineflieger" bookazine?

What about the 1938 radial-engined fighter? Do you have it? Kosin stated that it would have a 14 cylinder BMW radial (certainly the BMW 139). Proposed speed at 600-650 Km/h.

I do have a quantity of unpublished Arado material that I think people will be interested to see but I can't say exactly what will be in the next bookazine at this stage. Definitely something from Arado. At this stage I can't see myself doing a Luftwaffe/Marineflieger bookazine but who knows? It'd probably be mostly be Blohm & Voss and Dornier projects.

 

[Wurger]

Okidoki, Dan B).

 

[steelpillow]

a Luftwaffe/Marineflieger bookazine but who knows? It'd probably be mostly be Blohm & Voss and Dornier projects.

Gets my vote!

 

[Antonio]

My vote

 

[Justo Miranda]

My vote

 

[athpilot]

My vote

Me too! ;D B)

 

[newsdeskdan]

My vote

Me too! ;D B)

There's certainly a few interesting flying boat/floatplane projects out there which I don't think have been published before. The floatplane versions of the Ar 232 and Fw 189 spring immediately to mind. Anyone ever seen anything much on those elsewhere? The Seefernaufklarers chapter in Luftwaffe: Secret Designs has plenty of 'new' flying boat/floatplane designs in it. Although for me perhaps the most interesting aspect of working on it was how much everybody, especially its own crews, truly hated the BV 138. Even Blohm & Voss must have been heartily sick of it by about 1943.

 

[steelpillow]

And they certainly proposed enough upgrades/replacements. I have seen some 13 mentioned on the Internet, of which I have been able to verify nine (from secondary sources):
P 61
P 94
P 108-113 (6 in all)
P 122-125 (4 in all)
And, bizarrely, a landplane version the P 187.
The P 61, 108. 109 and 117 remain unverified, though most if not all are reputed to be listed by Nowarra.

 

[newsdeskdan]

And they certainly proposed enough upgrades/replacements. I have seen some 13 mentioned on the Internet, of which I have been able to verify nine (from secondary sources):
P 61
P 94
P 108-113 (6 in all)
P 122-125 (4 in all)
And, bizarrely, a landplane version the P 187.
The P 61, 108. 109 and 117 remain unverified, though most if not all are reputed to be listed by Nowarra.

The P 187 is the landplane version of the BV 238 - later known as the BV 238 Land, then the BV 250. Sorry, my mistake, the BV 238 Land is the P 161 as you point out below. I've amended this entry after the fact to avoid any confusion. The P 187 is the BV 222 Land. I have the full original BV project list - I thought I'd posted a fragment of it on the forum somewhere, although exactly where now escapes me.

Note: Having now looked up the entries for the projects you mention, the P 13 is original twin-engine Ha 138. The P 61 is the first attempt at a three-engine version, with 3 x DB 601, and the P 94 is what actually became the production Ha 138 with 3 x Jumo 207 A. P 108-113 are indeed attempts to improve the BV 138. P 122-125 appear to be nothing to do with the BV 138. Each had 4 x Jumo 208 and a starting weight ranging from 33,000kg to 41,000kg - quite a way above what the BV 138 airframe was ever likely to be able to handle. The P 117 is a version of the BV 222.

 

[steelpillow]

And they certainly proposed enough upgrades/replacements. I have seen some 13 mentioned on the Internet, of which I have been able to verify nine (from secondary sources):
P 61
P 94
P 108-113 (6 in all)
P 122-125 (4 in all)
And, bizarrely, a landplane version the P 187.
The P 61, 108. 109 and 117 remain unverified, though most if not all are reputed to be listed by Nowarra.

The P 187 is the landplane version of the BV 238 - later known as the BV 238 Land, then the BV 250. I have the full original BV project list - I thought I'd posted a fragment of it on the forum somewhere, although exactly where now escapes me.

I have that down as the P 161, again an Internet meme. Thanks for the corrections.

Have to say, I'd kill for a copy of that list. Any chance you can either publish it somewhere or PM me a private copy? In fact, how about a "B&V Special" spinoff issue with the list included?

 

[newsdeskdan]

And they certainly proposed enough upgrades/replacements. I have seen some 13 mentioned on the Internet, of which I have been able to verify nine (from secondary sources):
P 61
P 94
P 108-113 (6 in all)
P 122-125 (4 in all)
And, bizarrely, a landplane version the P 187.
The P 61, 108. 109 and 117 remain unverified, though most if not all are reputed to be listed by Nowarra.

The P 187 is the landplane version of the BV 238 - later known as the BV 238 Land, then the BV 250. I have the full original BV project list - I thought I'd posted a fragment of it on the forum somewhere, although exactly where now escapes me.

I have that down as the P 161, again an Internet meme. Thanks for the corrections.

Have to say, I'd kill for a copy of that list. Any chance you can either publish it somewhere or PM me a private copy? In fact, how about a "B&V Special" spinoff issue with the list included?

Sorry, my mistake. You're right, the P 161 is the BV 238 Land. The P 187 is the BV 222 Land. I think I said previously that I'd publish the original projects list somewhere - maybe in the next bookazine.

 

[steelpillow]

I think I said previously that I'd publish the original projects list somewhere - maybe in the next bookazine.

 

[sienar]

Have you found anything to confirm that the floatplane 109 was a real project?

 

[newsdeskdan]

Have you found anything to confirm that the floatplane 109 was a real project?

No - but then I haven't been specifically looking for it. It'd be great if someone did find something on it though!

 

[Wurger]

Dan, the projected Fw189 V7/8 floatplane versions are already abridged in Hans-Peter Dabrowski's "Focke-Wulf Nahaufklärer Fw 189 >Uhu<, pages 192 to 194, 1 origal Fw 3-view, a lateral detailed plan and a nice foto of a float and the full bird under construction.

 

[newsdeskdan]

Dan, the projected Fw189 V7/8 floatplane versions are already abridged in Hans-Peter Dabrowski's "Focke-Wulf Nahaufklärer Fw 189 >Huh<, pages 192 to 194, 1 origal Fw 3-view, a lateral detailed plan and a nice foto of a float and the full bird under construction.

This one?

 

[Wurger]

I'm afraid that's the one B).

 

[newsdeskdan]

I'm afraid that's the one B).

Well, I guess it's not yet appeared in an English language publication... or has it?