“Invisible” Aircraft (Stealth: The Early Years)

[Kevin Renner]

I recall from an article in Analog about Henri Coandă that discribed his work with the British engine maker Bristol on routing exhaust systems for radial engines through Coanda Effect mufflers that reduced the engine noise enough to allow the valve train to be heard while increasing power. In a pre radar environment this could be a big contributor to night time stealth

 

[robunos]

It was always my understanding that the pink spitfires were painted that colour to fly photo-recon. sorties at dusk.
Approaching occupied Europe from the west, they would be hidden in the sunset, at the same time, the long shadows at that time of day would reveal more detail on the ground below.

cheers,
Robin.

 

[Sundog]

What I've read is the "pink" Spits were that color because they found it blended best when flying just under the cloud cover. If there wasn't any cloud cover they aborted their missions.

As for the Ho-229 built for the documentary, the latest issue of Aviation History has an article on it that is quite interesting.

 

[Flitzer]

It was always my understanding that the pink spitfires were painted that colour to fly photo-recon. sorties at dusk.
Approaching occupied Europe from the west, they would be hidden in the sunset, at the same time, the long shadows at that time of day would reveal more detail on the ground below.

cheers,
Robin.

That is my understanding too.
;D

 

[joncarrfarrelly]

Ho 229 replica built for a National Geographic TV special mounted for radar tests.

The show is rather unfortunately (and incorrectly) titled Hitler's Stealth Fighter. :

They claim it is built of "only 1940s materials", in the construction photos I don't see the steel tube
framework that formed the basis of the aircraft structure.
http://channel.nationalgeographic.com/episode/hitler-s-stealth-fighter-3942/Overview#tab-Photos/1

Jon

 

[red admiral]

The show is rather unfortunately (and incorrectly) titled Hitler's Stealth Fighter

Especially when the results indicated it wasn't particularly stealthy....

 

[AeroFranz]

I have my own opinion on how stealthy the 229 supposedly was, but it would have been nice to have actual tests results. I am not sure that the way the model was made we'll get a meaningful answer. If they are not reproducing an internal structure, I guess then they must be assuming that the OML was not permeable to radar waves. Any other explanation ???

 

[Pelzig]

What do they plan on doing with the full scale model? Would be nice to see it in genuine colors and put on display somewhere. After all, doubtful we will see the original ever restored.

 

[AeroFranz]

After all, doubtful we will see the original ever restored.

fingers crossed...I started volunteering at the Udvar-Hazy museum, and once a year the staff is given a tour of the Garber facility. Can't wait to see the real thing. I can't think of a more eagerly awaited restauration. Maybe the documentary will be a catalyst and raise interest in this project?

 

[red admiral]

I have my own opinion on how stealthy the 229 supposedly was, but it would have been nice to have actual tests results.

The results seem to indicate similar results to the Bf 109 which is not a "stealth fighter". Of course, a lot of the accuracy of the results depends on how the aircraft was constructed (I don't see any large metallic jet engines there) and what radar was shone at it. Its not really possible to design an aircraft that is effective against the wide range of radars in use from the high metric CH to low centimetric AI radars.

 

[AeroFranz]

given the maniacal attention to detail that is required to reduce RCS to useful levels (the famed fourth power in the radar-range equation), I would be surprised by stealthy-claims. Where does the comparison to the -109 come from?

 

[Norcrafter]

I’m an advanced projects engineer/manager at Northrop Grumman Aerospace Systems. I was the guy who introduced producer/director Michael Jorgensen to the Northrop Grumman team and helped convince our management to pursue and fund the Ho-229 documentary project. I’ve been directly involved with this project from start to finish and I appear in the show. I’d like to address some of the concerns you guys have raised in this forum.

A number of you have expressed concern that the radar cross section (RCS) testing of the constructed Ho-229 full-scale model is invalid for various reasons, including that fact that the model does not have an internal tubular truss structure, metallic engines, control surfaces, etc. This assertion is simply not true. I’m assuming that most of you are not low observables engineers, but please forgive me if any of the following is tutorial.

At this point in time, the aerospace industry’s low observables (LO) engineering community has considerable experience under its collective belt. Over the decades, countless structures have been illuminated across all possible radar frequency ranges. This includes full-up aircraft and models, down to individual parts, representing all forms of aircraft construction methods and material utilization developed since the Wright Brothers. LO computational techniques have been considerably refined and validated in comparison to empirical testing results.

Before we started the build, we were able to inspect the actual Ho-229 in the Smithsonian Garber facility (an awesome experience!). We were also able to do some testing of the actual aircraft’s surfaces to determine their electromagnetic properties, which you’ll see in the show. In addition, we had at our disposal a comprehensive package of wonderful Ho-229 layout drawings prepared by Arthur Bentley, and Mr. Bentley himself was a consultant to the project.

So, my point is that when we sat down to figure out how to build the Ho-229 RCS test model, we already had an excellent detailed technical understanding of this aircraft and how to effectively simulate it for the purpose of determining its electromagnetic properties.

We discussed the possibility of reconstructing the truss structure, but that would be cost prohibitive and our senior LO engineers determined that it wasn’t really necessary. To obtain the kind of first-order results we were looking for, it would be sufficient to build the model from high-grade plywood with carefully targeted applications of various conductive coatings internally and externally to simulate the interior configuration. Specialized paints and coatings are the key!! We have proven on various projects that this technique works, and that’s the way we proceeded with the Ho-229.

Another key aspect in making the construction method decisions was radar frequency. We studied the British Chain Home air defense radar systems used throughout WW II. We concluded that the use of VHF, UHF and L-band frequencies would be representative for our testing. At these relatively low long-wavelength frequencies, small details on the test model would not be visible or contribute significantly to the overall signature, including the gaps in control surfaces. Also, the coating methodology described above would be very effective at accurately simulating this aircraft at these frequencies without the need to recreate the interior features in detail. To keep things simple, we tested the aircraft in a nominal straight and level flight configuration, which would represent its best radar signature. It would have been nice to include moveable control surfaces on the model, but that was beyond the available budget.

Keep in mind that we built a test model for a one hour TV documentary, not for developing and deploying a real combat aircraft! All we needed in this case was enough engineering fidelity to achieve first order results enabling us to reach some top-level conclusions. I believe our project priorities were properly balanced with this goal in mind, and of course, within the available budget.

As you all know, the Ho-229 was not designed with stealth as a primary design goal. The aircraft has a few obvious stealth “Achilles’ Heels” such as the exposed engine faces. However, a flying wing configuration can nonetheless have inherently stealthy properties compared to conventional aircraft even if LO was not a primary design consideration. This was amply demonstrated by Northrop’s YB-49A. Regarding the Ho-229’s RCS performance, we chose to not get into radar signature reduction specifics in the documentary. Rather, we describe the Ho-229’s capabilities in terms of the resulting reduction in detection & warning time against the Chain Home radar system.

I agree that the show’s title “Hitler’s Stealth Fighter” is somewhat misleading and was certainly not my first choice. The show was produced under a different working title, but the Nat Geo Channel had the final say. Bear in mind that a show like this is created for the general public, not specifically for aviation enthusiasts. Nat Geo is in business to stay in business and I can understand why they chose this title. After more than half a century, anything “Hitler” still sells. All that said, there’s plenty of good stuff in this documentary and I think you guys will enjoy it.

As someone pointed out, the Nat Geo website for this show does state that the Ho-229 RCS model was constructed using “materials only available in the 1940’s”, and that is incorrect. They misinterpreted our statements that we used materials that are, from the RCS standpoint, representative of what was used in the 1940’s. I’ll see what I can do to get that corrected.

By the way, the full scale Ho-229 RCS model is being donated to the San Diego Air & Space Museum. We recently had a great meeting with the museum’s team and we are making plans to get the model down there and on display in time for the documentary’s debut.

All things considered, this has been a fun project. I appreciate everyone’s interest and I hope you enjoy the show!

 

[AeroFranz]

Norcrafter,

I appreciate your informative post, and i am even more pleased that from what you wrote care was taken by the Northrop people to do this right (within reason). As mentioned elsewhere, the 'sensationalistic' vibe that forum members got checking out the Nat Geo website kind of worried us for a second that results would be less than accurate. There are many unresolved myths and curiosities in aviation history, and it's not often that you get to find out the truth.
It's really cool that the model will have a home in Balboa park. I can't wait to see the documentary.

 

[Norcrafter]

Hello AeroFranz,

Thanks for your thoughtful comments. The sensationalistic vibe will probably continue to build over the next few weeks. That's the reality of media marketing in the 21st century, as I'm sure you well know. And some of you guys may not agree with all of the statements made in the documentary. But as I said, I think there is plenty of good stuff in this show that will appeal to aviation enthusiasts, and I think our core methods and conclusions are sound.

I'm looking forward to hearing everyone's reaction to the documentary. And I believe it was you who mentioned that perhaps the documentary will be a catalyst for increased interest in the Smithsonian's restoration of the real Ho-229. That would be the best possible outcome!

Norcrafter

 

[windswords]

Well, whether it was truly stealthy or not, it was definately the "coolest" looking aircraft the Germans ever made in WWII! B) Every time I see an illustration, or diagram, or pic of a model of this bird I save it.;D

There are two aircraft at Garber that I hope are restored before I die. One in Ho-229. The other is the Kyushu J7W Shinden. Would love to see it restored with that 6 bladed pusher prop.

 

[red admiral]

Thanks for your description of the work carried out.

Was there any particular reason for using Chain Home radar as the illuminator? It wasn't being used a great deal by 1945 apart from long range spotting of V-2 launches. The radar signature against later war radar types would be rather different, e.g. 1.5m GCI, 10cm AI, 3cm AI...

 

[Norcrafter]

Hello red admiral,
Good question. We specifically mention Chain Home in the show because of its great historical significance and pivotal role in the early air war. Its many variants were in service throughout the war performing the Early Warning (EW) role. The only reason it wasn't being used much in 1945 other than V-2 detection was obviously because THERE WERE NO German air assaults against the UK at that point. If there were, you can be sure it would have been used extensively. Despite the existence of more advanced individual radars at that point, the Chain Home Low and other variants still constituted an entire integrated network, essential to the adequate defense of the UK.

From a strategic standpoint, the most important aspect of the Ho-229's radar signature is it's performance against EW radars, not Ground Controlled Intercept (GCI) and Airborne Intercept (AI) radars. If the Germans were hypothetically able to field the Ho-229 in significant numbers and initiate offensive operations, The EW radar network is the first line of defense and would have been used to cue the defensive response to the attack. This is the reason we chose to test the Ho-229 against VHF, UHF, and L-Band, which covers the characteristic operating frequencies for EW radars during this period of time. These bands cover wavelengths from about 0.9 meters down to about 30 cm.

Of course, we would have loved to test the Ho-229 at higher frequencies as well. We had neither the time nor the budget. I believe that the percentage improvement in radar signature compared to conventional aircraft would be approximately the same order of magnitude at GCI and AI frequencies.

Keep in mind that we have a complex story to tell in about 42 minutes, which is the length of the show without commercials (those of you in Europe and Canada will get a 50 minute version!). We told the radar story as best we could in the time available, in balance with the rest of the story.

 

[spaced_monkey]

Hello AeroFranz,

Thanks for your thoughtful comments. The sensationalistic vibe will probably continue to build over the next few weeks. That's the reality of media marketing in the 21st century, as I'm sure you well know. And some of you guys may not agree with all of the statements made in the documentary. But as I said, I think there is plenty of good stuff in this show that will appeal to aviation enthusiasts, and I think our core methods and conclusions are sound.

I'm looking forward to hearing everyone's reaction to the documentary. And I believe it was you who mentioned that perhaps the documentary will be a catalyst for increased interest in the Smithsonian's restoration of the real Ho-229. That would be the best possible outcome!

Norcrafter

I wonder with the success of this show if there may be a possibility for other such shows to be produced in cooperation with the two companies, maybe a Do 335 or A HE 112 show. (I find that generally speaking when American do WW2 Documentaries there are mostly pro Allied this one was truly a pleasant change from the norm )


the other thing i would like to ask about is why do historians fail to comprehend that the German Nuclear program fail because the German scientists were unable to prove on paper to their higher ups the actual size of a nuke bast. (the heavy water they produced in northern Europe was for their experiment power generators IE nuclear reactor)

 

[Wingknut]

Hi folks,
Haven't been back to this thread for years but I just found these sites on the Kozlov 'transparent aircraft' experiment and other early 'stealth' ideas :
http://alternathistory.com/samolet-nevidimka-3-net-stels-po-russki
http://www.telenir.net/transport_i_aviacija/aviaarhiv_1/p3.php
Please note that the names of the image files attached are mine so I apologise right now if the names / transliterations are hopelessly wrong - my bad, not the web-sites.

Anyway, I really appreciate the detail in the replies above (especially from Norcrafter) re: the use of the Ho 229 as a test-bed for RCS reduction and of course I accept that the flying wing layout has RCS advantages - I still wonder though: is there any evidence that plausibly dates from the 1940s that suggests that reducing RCS was any sort of priority for designing or building any version of the Ho 229 / Go 229? In other words, armed with hindsight we can see that the layout has stealth advantages but did anybody see that at the time?

Thanks and all best, 'Wingknut'

 

[igor-mich]

http://www.airwiki.org/enc/law1/ps.html
http://airfield.narod.ru/yak/air-4/air-4_color.html

 

[Wingknut]

Thanks, Igor-mich.
Couple more images from http://www.telenir.net/transport_i_aviacija/aviaarhiv_1/p3.php, showing the Kozlov test-aircraft in flight accompanied by a Polikarpov U-2.
All best, 'Wingknut'

 

[Wingknut]

Hi again, folks,
Just to tie-up some loose ends from earlier postings I made:

i) Years after I mentioned it, here is the image I had in mind of a British WW1 fighter fuselage in skewed-perspective paint for putting enemy gunners off their aim:
http://www.iwmprints.org.uk/image/743586/experimental-camouflage-on-the-fuselage-of-a-sopwith-camel-developed-during-the-first-world-war-to-disguise-the-aircrafts-direction-of-flight

Clearly not a Bristol Monoplane or Sopwith Pup as I wrongly remembered but in fact a Sopwith Camel. See also:
http://www.sas1946.com/main/index.php?topic=34602.0

http://www.flashpointmag.com/blast_dazzleships_wadsworth.htm


ii) Article on American illustrator McClelland Barclay’s work as a camouflage artist:
http://camoupedia.blogspot.co.uk/2011/04/camouflage-artist-mcclelland-barclay.html


Note though that the ‘upside-down’ aircraft shown at the bottom of the 'McClelland Barclay Composite' image below is not by Barclay:
“Pictured above (in the bottom photo) is an earlier example of dazzle-like airplane camouflage (unrelated to Barclay's work), as published in the New York Herald in 1919, in which it was described as "an upside down flyer" and "a weirdly camouflaged airplane that was a feature in the recent aerial pageant at Hendon, England. Note the dummy landing carriage atop the upper plane and silhouetted pilot's head beneath the fuselage designed to puzzle the spectators as to whether or not the plane is flying rightside up."”

See also McClelland Barclay patent here, filed 16th February 1939:
http://www.google.com/patents/US2190691

iii) Finally, while I’m here, pigeons selectively bred for ‘disruptive’ camouflage patterns:
http://camoupedia.blogspot.co.uk/2010/03/camouflaged-pigeons.html

Cheers, ‘Wingknut’

 

[hesham]

Nice find Wingknut.

 

[Wingknut]

Thank you, Hesham.

Maybe these should go under 'Patent Pending' but here's another pair of finds possibly relevant to early stealth - hope (as always) that they're not old news:

i) 'Radio wave absorption device', US 2464006 A
Publication date: March 8th 1949; Filing date: April 28th 1944; Priority date: April 28, 1944; Inventor: John W. Tiley.

"The present invention relates to an absorption device, and more particularly to a device against which a beam of ultra high frequency radiant energy may be directed for absorption thereby."
http://www.google.com/patents/US2464006

ii) 'Method of minimizing reflection of radio waves', US 2527918 A
Publication date: October 31st 1950; Filing date: September 11th 1946; Inventor: John Collard.

"Application September 11, 1946, Serial No. 696,134 in Great Britain August 26 1943".
“This invention relates to reducing the intensity of electro-magnetic waves reflected from reflecting objects which are normally detectable by radar.”
http://www.google.com/patents/US2527918

EDIT: see also this thread here: http://www.secretprojects.co.uk/forum/index.php/topic,27085.0.html

Thanks again and all best wishes,
from the all-too-visible 'Wingknut'

 

[Wingknut]

Sorry to belabour Horten / Gotha Ho 229 / Go 229 alleged 'stealth' point but here are some quotes from the 'Horten Ho 229 Reconstruction Project':

i) "There are multiple reasons why we want to rebuild Ho 229. One of the reasons is the historic significance which can be linked to our modern stealth fighters Lockheed F-117 Nighthawk & Northrop Grumman B-2 Spirit Stealth Bomber. Both aircrafts used stealth technologies that made them less susceptible to radar detection which was initially used in Horten 229. Horten brothers saw the opportunity to militarize stealth technology in their early attempts to create an aircraft that can not be detected by early radars. In their initial efforts they established the development of more advanced techniques which are now an important part of our modern fighters."
http://www.hortenwings.com/

I've added the italics but everything else is as in the original. What are the sources for these claims?

ii) The site also makes clear that recreating the Ho 229's (again alleged) stealth qualities is not part of the mission:

"What we are not looking for:​​ We are not planning to rebuild stealth capabilities of this airplane. Stealth technologies are outside of our scope. In addition, current FAA rules prohibit operating aircraft without transponder, therefore rendering any stealth technology implemented useless. Bottom line, we want to be very visible to all aircraft traffic and radar operators, so all FAA rules apply."

iii) Re: materials used: "Our Goals:​​ The main idea is to rebuild Horten 229-V3 fighter from the modern materials such as aircraft grade aluminum alloys, and vacuum molded carbon fiber reinforced polymer using the original production approved drawings. The aircraft will be powered by two General Electric CJ610 jet engines which are a non-afterburner turbojet engine derived from the military J85s."

http://www.hortenwings.com/#!goals/c6in

iv) Some quotes from the FAQ page:
"Are you planning to make it out of the wood just like the original? - No, this aircraft will be made from the modern aluminum alloys and other materials. The only reason why Horten brothers used wood to manufacture this aircraft was the fact that they could not find enough aluminum which was simply unavailable (and way too expensive to produce) during World War II.


Are you planning to reproduce center frame from the steel tubing? - No, steel and aluminum does not mix very well, combining both will eventually lead to a galvanic corrosion. In addition, steel frame require extensive welding which will surely weaken joints and make them susceptible to cracks & deformations after numerous operation cycles of the aircraft.


Are you planning to fly it supersonic? - We are not planning to test this aircraft above supersonic speeds. Horten 229 was not designed to go supersonic in the first place. Attempting to do so will jeopardize aircraft, pilot and people below.


Are you planning to make it invisible? Will it have any stealth technology? - We are not planning to rebuild stealth capabilities of this airplane. Stealth technologies are outside of our scope. In addition, current FAA rules prohibit operating aircraft without transponder, therefore rendering any stealth technology implemented useless. You should keep in mind that our current radars operate at much higher frequencies than the first World War II radars, so even if we rebuild this aircraft from wood using the original technology, it will still create a significant radar signature.


How long will it take to finish Ho 229? - our estimated time to completion is 12,000 man-hours or approximately 12 to 18 months.
​
​What make you think you would be able to finish this project in 12 months? - During World War II Horten brothers were able to test Ho 229 V2 in just 6 months. They worked in a harsh condition employing furniture makers without any aircraft building experience and had severe shortages in every material you can imagine. In some cases they had to strip downed aircrafts for needed parts or even "borrow" supplies at night when no one was looking. On the other hand we have an abundance of all materials needed including reliable jet engines, access to laser cutters, CNC milling machines and other computerized equipment used for rapid development, prototyping and testing, FAA certified workers, luxury of the CAD design and simulation, and a professional production environment.

How are you going to manufacture complex parts that require production of unusual shapes like jet intakes? - The majority of complex shapes will be vacuum molded from the carbon fiber reinforced polymer"
http://www.hortenwings.com/#!faq/c172h

So (yet again) I have still to see anything like hard evidence that the Horten brothers or anyone else in WW2 Germany had any ideas aimed at reducing aircraft radar cross-section.

v) The only (possibly relevant) patent I can find is this one:
'Method of eliminating reradiation', US 2103358 A
Publication date: December 28th 1937, Filing date: March 13th, 1935; Priority date: March 26th, 1934
Inventors: Albrecht Gothe, Original Assignee: Telefunken Gmbh,
http://www.google.com/patents/US2103358

vi) And to conclude with an example of the sort of misunderstanding this 'Horten stealth' business can lead to, a little item from one of the things we call newspapers in the U.K.:
http://www.dailymail.co.uk/news/article-1198112/Sleek-swift-deadly--Hitlers-stealth-bomber-turned-tide-Britain.html

 

[Jemiba]

Well, puff is part of the trade and the supersonic capabilities of the Ho/Go 229 fortunately
not theme of this thread (Am I wrong, or do the FAQs somehow suggest, that it would have
been able to do so ? : ), but about the stealth characteristics :
Is there any contemporary and approved authentic document or mention, that the Ho/Go 229
was actually designed with stealth in mind ?
Maybe I've missed something, but all I've heard still yet, are postwar analyses or claims, that
it was. Well, after the war, many Germans swore, that "they didn't do anything", but the Horten
brothers, that they did ...

 

[Wingknut]

Thanks, Jemiba.

I suppose if I had been looking for funds to build a replica Horten Ho 229, no doubt I'd be plugging it as the "world's first stealth" too. (I don't know where the 'supersonic' question comes from - nobody, surely, ever claimed that the Ho 229 could go supersonic? Even if you dropped it from a very great height ...)

All the searching I've done re: Horten aircraft and stealth thus far has revealed only this:
"After the war, Reimar Horten said he mixed charcoal dust in with the wood glue to absorb electromagnetic waves (radar), which he believed could shield the aircraft from detection by British early-warning ground-based radar that operated at 20 to 30 MHz (top end of the HF band), known as Chain Home", https://en.wikipedia.org/wiki/Horten_Ho_229

The Wikipedia article in turn cites the documentary above as source:
http://web.archive.org/web/20090627133554/http://channel.nationalgeographic.com/episode/hitler-s-stealth-fighter-3942/Overview24

The site also includes a timeline, which doesn't actually link Horten and stealth explicitly, saying only this:
"Dec. 1944–– The Horten brothers' jet-powered prototype, the Ho IX V2, flies in Germany. World War II ended before the plane could be built, and the project was abandoned. Many doubted that the plane could fly successfully, because of its tailless design."
http://web.archive.org/web/20090627133554/http://channel.nationalgeographic.com/episode/hitler-s-stealth-fighter-3942/Overview24#tab-time-line

The same site has a Horten Brothers primer that says "In researching the books he’s written about the Horten brothers, author David Myhra visited with Walter numerous times at his home in Germany, and spent several months with Reimar in Argentina", http://web.archive.org/web/20090625043311/http://channel.nationalgeographic.com/episode/hitler-s-stealth-fighter-3942/Overview26#tab-facts

A quick search for David Myhra reveals this: http://www.luft46.com/Myhra/dmyhra.html

Which says: "David Myhra is currently writing Uncovering the Stealth Secrets of the Ho 229 chronicling the entire build and the results of its radar testing."

And also announces another project: "The Nazi Plan To Bomb New York City. Written by David Myhra, this one hour TV documentary features Oberst Siegfried Knemeyer's plan to obtain a flying machine capable of exploding a 5,000 pound conventional bomb over New York City which would have blankets of radioactive silica (sand) wrapped around it. The radioactive silica would have fallen on New York City like snow flakes causing radiation sickness and death leading the Nazi leaders to believe that they might then obtain a cease fire or some sort of condition surrender from the Allies."

This sort of claim may not exactly inspire confidence - and nor may the Google Books preview of our author's 'Conversations with Walter Horten Volume 1'.

https://books.google.co.uk/books?id=Kb2_AAAAQBAJ&pg=PP3&lpg=PP3&dq=%22conversations+with+walter+horten%22&source=bl&ots=6n7Y4NLmTu&sig=hRtXSpg80GJGNm5VtXVuKn8YE7w&hl=en&sa=X&ved=0ahUKEwj02_Hz6ZDMAhWFPBoKHWCXDuMQ6AEIJjAC#v=onepage&q=%22conversations%20with%20walter%20horten%22&f=false

See also: https://dwtr67e3ikfml.cloudfront.net/bookCovers/6df8f8a5707086b87c5d99f5878e1412acae3317

So while I could of course be totally wrong and no disrespect to the Ho 229 reconstruction team but I can imagine someone equally undertaking to make 'stealth' versions of e.g. the Baynes Bat, the Northrop XP-56 or XP-79, the McDonnell XP-67 or the Kalinin K-15 with modern materials. So yeah, the Ho 229 was a flying wing and yeah the B2 is a flying wing but that seems to be about it, resemblance-wise ...

(No one seems to mention that the F117 is not exactly a flying wing though and the XB-35 / YB-49 weren't terribly stealthy ...)

All best, still sceptical, 'Wingknut'

P.S. I suspect some forum-members work with David Myhra and I wish you (and him) well but the occasional piece like this I confess I find a bit off-putting:

"Saqqara Bird By David Myhra Attention all you ancient alien believers! Here's a replica of what our friends way out in the Cosmos gave the early Egyptians over 2,300 years ago. But for now all we have left is a 7 inch wooden scale model. Who knows what maybe still buried under the sands near the Pyramids. A full sized exotic flying machine? This ebooks answers some of these questions and poses a few more! Enjoy! " https://www.smashwords.com/books/view/509718

"The 1,000 Year Old Flying Machines of Pre-Modern Columbia, South America
By David Myhra Ancient Alien Theorist's wild belief that a three inch gold trinket represents a larger exotic flying machine...designed by Extraterrestrials" https://www.smashwords.com/books/view/426091

Now I grant that Dr. Myhra does not seem to endorse the 'alien astronaut' stuff himself but still, it's not the train I'm travelling on ...

 

[Wingknut]

Hi folks,
Sorry, don’t want to give anyone (least of all our fine moderators) a headache and I know I risk flogging a dead horse here, but it seems like every Horten reference I find these days lists them as designing "stealth bombers" or "stealth fighters", and I am still trying to get some sense of what sources and chronology there might be behind these claims.

For instance: "The Ho XVIII A was to be built mainly of wood and held together with a special carbon based glue. As a result, the huge flying wing should go largely undetected by radar", http://www.luft46.com/horten/ho18a.html citing (again) Dr. David Myhra.

Dr. Myhra met the Hortens several times 1982-88 but the 'stealth' claims are all c. forty years after the war and seem to rest on the unsupported word of Reimar Horten.

I think key sections are as follows - often not about the Ho 229 but the Ho XVIII instead:

a) CD 23b, Reimar Horten #10, side 2 of 2, no date
"… why not use metal, aluminum for H IX parts? Reimar: reduce radar reflectivity, 9 centimeter radar wavelength, use of coal to reduce radar reflectivity on aluminum"

b) CD 27b, Reimar Horten #14, side 2 of 2, no date
"Reimar on H XVIIIa replacing H XVIIIb, … Reimar on stealth qualities, mix coal dust with glue ..."

c) CD 45b, Reimar Horten, n. d.
"Reimar continues to talk about Horten IX V3 … special glue used with wood and composite construction … adding coal to glue to reduce radar cross-section, "camouflaged" the radar cross-section of 90% of the IX" according to R, low radar cross-section useful if attacking ships or bombing."

d) CD 51a, Reimar Horten #12, 30 August 1986, side 1 of 2
"...also had to reinforce Horten IX V3 but hide metal strips from radar."

All quoted from the list of interviews, and associated CD recordings, here:
National Air and Space Museum, Archives Division - Reimar and Walter Horten Interviews, Accession No. 1999-0065,
https://airandspace.si.edu/research/arch/findaids/horten/horten_print.html

So for me, this is case closed: maybe Dr. Myhra recorded every word said to him by Reimar Horten with complete accuracy and fairness ... and yet I still don’t believe a lot of Reimar Horten’s claims in general and absolutely none of his 'stealth' claims in particular.

Why does this stuff bug me? Well, a patent for ways of reducing aircraft RCS was filed in April 1944 ... in America. Do we see headlines about 'FDR’s Stealth Bomber'? Nope.

In 1936, an aircraft was test-flown that came as near transparency as then-available technology allowed … but it was flown in the USSR. Do we see headlines about 'Stalin's Invisible Plane'? Nope.

To close on a lighter (if silly) note, here are genuine drawings of a 1940s invisible plane – admittedly it belonged to Wonder Woman and was totally made-up but them’s the breaks … http://goodcomics.comicbookresources.com/2012/06/17/when-we-first-met-when-did-wonder-woman-first-fly-her-invisible-jet/
(Reimar Horten did not, as far as I know, claim any credit for it.)

Thanks and all best, 'Wingknut'

 

[Wingknut]

Snapshots below from: 'The first Stealth Aircraft in the World - The Kozlov PS 1935'
https://www.youtube.com/watch?v=r1b7AwSp6rI

 

[Wingknut]

Hi again, folks,
Just found this:
The Flight of the Invisible Airplane, 1915: Innovation and discovery as chronicled in Scientific American
by Daniel C. Schlenoff on December 1, 2015

December 1915 Dreams of invisibility
“Military authorities await with great interest the development of the new French invisible aeroplane, which bids fair to revolutionize aerial warfare. The body and framework are constructed, as in ordinary machines, of aluminum braced with wire. Over the framework, instead of canvas, is stretched a transparent material which looks like a cross between mica and celluloid [see illustration]. It is called ‘cellon,’ and is a chemical combination of cellulose and acetic acid. Of almost the same transparency as glass, it does not crack or splinter and has the toughness and pliability of rubber.”

Text and illustration from: http://www.scientificamerican.com/article/the-flight-of-the-invisible-airplane-1915/
Cheers, 'Wingknut'

 

[Wingknut]

And more on the Cellon-covered Fokker E3.
Plan and profile from: http://www.chmelnice.org/index.php/2013/03/barvy-barvy-a-zase-barvy/?lang=en

Model photos from: http://www.theaerodrome.com/forum/showthread.php?t=55187
And from:
http://www.proctor-enterprises.com/photo_gallery/eindecker/hgrobler549s-w.jpg
http://www.proctor-enterprises.com/photo_gallery/eindecker/hgrobler547s-w.jpg
http://www.proctor-enterprises.com/photo_gallery/eindecker/hgrobler561s-w.jpg

Photos from: http://www.earlyaeroplanes.com/archive/1w/images/fokkerE3cellon_schwerin.jpg
And: http://www.modelbouwforum.nl/threads/sopwith-pup-scale-1-3.218903/page-12

 

[hesham]

Hi,

there was two Romanian designers invented two invisible airplanes,they were Mr, Dimitrescu and Mr. Stanescu,does anyone know anything about them ?.

 

[snark]

Re: “Invisible” Aircraft (Stealth: The Early Years)

I'm surprised that no one here has mentioned the so-called "Yehudi Lights" developed by the USN during WW2. This was an attempt to render an attacking aircraft invisible from the perspective of a surfaced U-boat by using lights positioned along the leading edges, engine cowls, etc. to match the average luminescence of the daytime sky.

To my knowledge, this approach was practical and successful. It may represent the only attempt at "optical stealth" that actually worked!

Regards, Harry

 

[Jemiba]

I'm surprised that no one here has mentioned the so-called "Yehudi Lights"

http://www.secretprojects.co.uk/forum/index.php/topic,1384.0.html
You're right, a cross-refernce certainly is helpful here, thank you for that clue !

 

[snark]

You're quite right.

I was so ecstatic at having recalled the term "Yehudi Lights" that I neglected to use the search feature before posting.

Profuse apologies. Harry

 

[Jemiba]

No problem and as I wrote, it's good, that your question triggered adding a cross reference.
Merging the two threads would be another possibility, but here the more specific thread should be
above the more generic one, I think.

 

[hesham]

VIENOT's SILENT AIRPLANE
1940 project,

The Vienot patent is a new variant of the concept of placing the propeller inside a tube (see ANF-Les Mureaux Stipa 203) Here the main advantage put forward by the inventor is to provide for « rather silently operating flying machine which damps the noises caused by various causes like : engine exhausts, propeller vibrations, air vortexes »

Note that the air nozzles are thin and flat which is supposed to allow the « vortexes of air » created by the propeller to insert themselves more easily into the surrounding air.

A variant of the initial design uses « ventilators » rotating along a vertical axis instead of the vibration-producing propellers.

Advantages of the machine, according to the inventor are :

• Removal of any outside propeller (!)
• Noise reduction (see above)
• Improvement of performance
• Easyness of adapting this design to remote controlled machines (in which way it is « easy » is not explained)

Another advantage just alluded at is the « the vertical component of the pressure inside the Y branches can be used for the sustentation [lift] of the flying machine ». Yes that means VTOL ability.

Modelstories

Modelstories, avions & maquettes.<br>Modelstories, kits & planes

modelarchives.free.fr

 

[edwest4]

Originally posted on this site by newsdeskdan:


I think I can at least cast some doubt on the debunking. In September 1944, Professor Dr Kurt Krüger, director of the Institut für Luftfahrtgeräte der Technischen Akademie der Luftwaffe at Berlin-Gatow and the Messtechnisches Institut, Königshofen im Grabfeld, produced a report entitled Reflexion elektromagnetischer Wellen an Flugzeugbaustoffen - Reflection of electromagnetic waves on aircraft building materials.
The report summary says: "The task is to camouflage planes and other flying objects against exposure to radio measuring devices, i.e. to make the reflection amplitude of the aircraft as small as possible. In the present report, it is proposed to solve this problem by preferably building the aircraft out of electrically permeable substances and by covering those components that must be metallic in nature (such as the engine, landing gear, etc.) with electrical absorbing substances."
The report notes that "through the mediation of the OKL and their own efforts, materials such as Tronal, Atex, plywood and a combination of several building materials were procured and measured by various companies". One of those companies was Gothaer Waggonfabrik, which at the time was engaged in building the Horten 8-229 prototypes. There is a diagram of a generic twin-engine flying wing aircraft included in the report with the caption "Nurfluegler mit schluckstoffverkleideten (schraffiert gezeichnetan) metallischen Bauteilen." - "Flying-wing aircraft with metallic components clad with absorption material (shown hatched)." The hatched area covers where the engines would be, the cockpit and the undercarriage.
Evidently Gothaer was trying different sets of layered material to various thicknesses which included plywood, Moltopren (a sort of plastic foam, I think), cellular rubber (Hartzellkautsch) and what is described as Holzgitter - wooden lattice.
This report doesn't overtly say 'there was a plan to make the 8-229 out of radar absorbing materials', but it does clearly show that radar absorbing materials were being considered for flying wing types and that Gotha was involved in testing those materials. The Hortens were working closely with Gotha and would almost certainly have been aware of Krüger's work. Of course, Krüger, Grimm and the institutes were left out when Reimar Horten mentioned the radar absorbing material to David Myhra during his interview.
Krüger himself was evidently killed before the end of the war, according to a CIOS evaluation report I have. This says that development of his absorbent materials was at an early stage, which may well mean that they hadn't yet been applied to an actual aircraft.
So although Horten wasn't necessarily telling the whole truth, I don't think he was really lying either.

 

[Wingknut Redux]

Wow, thanks for sharing that, edwest2.
As I said to newsedskdan elsewhere on this forum, I was very sceptical about the Horten stealth claims but I am now chastened - here is compelling evidence that yes, there were proposals to test radar-cross section reduction measures on 8-229 designs during WW2. Hence the scepticism I expressed (rather vocally) a few posts / years ago was totally misplaced. How wrong was I?
Thanks and all best wishes,
'The Artist Formerly Known as Wingknut'

 

[Justo Miranda]

hi