Mystery Soviet Aircraft Skin

[JoeM]

Not certain this is WWII, but the Red Star with no outline suggests pre- or early war. Skin is bare aluminum, interior has cream-ish paint (primer) with a stub of Russian.

AI says
"Construction style
•Riveted aluminum skin, not composite → pre-modern jet era.
•Flush riveting with very regular spacing → aircraft-grade manufacturing, not light GA.
•Internal cut-out with reinforced rivet pattern → likely an access panel or inspection window area.
•Panel thickness and rivet density are typical of WWII–early Cold War aircraft."

The thickness is .762 mm .

AI says
"In early Soviet aviation, aircraft aluminum skin thickness typically ranged between 0.5 mm and 2.0 mm, depending on the specific model and structural location.
Standard Thicknesses and Variations

• General Range: Most Soviet fuselage skins fell between 0.8 mm and 1.8 mm.
• Structural Location:
  • High-Stress Areas: Cockpit sections and wing roots often used thicker skin, sometimes up to 2.0 mm, for increased protection and structural integrity.
  • Low-Stress Areas: Control surfaces and engine covers were typically thinner, often around 0.5 mm to 0.75 mm, to minimize weight."

Got this decades ago from a collector who claimed it was MIG-15 which I didn't really pay attention to because all Soviet jets are MIG-15s and all German tanks are Tigers, according to the general populace.

I've searched endless photos to find a matching rivet pattern and access panel, to no avail.

So here I am, possibly in the wrong forum.

Any thoughts?

 

[SaparotRob]

View attachment 864338View attachment 864339

Not certain this is WWII, but the Red Star with no outline suggests pre- or early war. Skin is bare aluminum, interior has cream-ish paint (primer) with a stub of Russian.

AI says
"Construction style
•Riveted aluminum skin, not composite → pre-modern jet era.
•Flush riveting with very regular spacing → aircraft-grade manufacturing, not light GA.
•Internal cut-out with reinforced rivet pattern → likely an access panel or inspection window area.
•Panel thickness and rivet density are typical of WWII–early Cold War aircraft."

The thickness is .762 mm .

AI says
"In early Soviet aviation, aircraft aluminum skin thickness typically ranged between 0.5 mm and 2.0 mm, depending on the specific model and structural location.
Standard Thicknesses and Variations

• General Range: Most Soviet fuselage skins fell between 0.8 mm and 1.8 mm.
• Structural Location:
  • High-Stress Areas: Cockpit sections and wing roots often used thicker skin, sometimes up to 2.0 mm, for increased protection and structural integrity.
  • Low-Stress Areas: Control surfaces and engine covers were typically thinner, often around 0.5 mm to 0.75 mm, to minimize weight."

Got this decades ago from a collector who claimed it was MIG-15 which I didn't really pay attention to because all Soviet jets are MIG-15s and all German tanks are Tigers, according to the general populace.

I've searched endless photos to find a matching rivet pattern and access panel, to no avail.

So here I am, possibly in the wrong forum.

Any thoughts?

I can't help you but if there's anyplace with the right knowledge, it's this place.

 

[bf109xxl]

View attachment 864338View attachment 864339

Not certain this is WWII, but the Red Star with no outline suggests pre- or early war. Skin is bare aluminum, interior has cream-ish paint (primer) with a stub of Russian.

AI says
"Construction style
•Riveted aluminum skin, not composite → pre-modern jet era.
•Flush riveting with very regular spacing → aircraft-grade manufacturing, not light GA.
•Internal cut-out with reinforced rivet pattern → likely an access panel or inspection window area.
•Panel thickness and rivet density are typical of WWII–early Cold War aircraft."

The thickness is .762 mm .

AI says
"In early Soviet aviation, aircraft aluminum skin thickness typically ranged between 0.5 mm and 2.0 mm, depending on the specific model and structural location.
Standard Thicknesses and Variations

• General Range: Most Soviet fuselage skins fell between 0.8 mm and 1.8 mm.
• Structural Location:
  • High-Stress Areas: Cockpit sections and wing roots often used thicker skin, sometimes up to 2.0 mm, for increased protection and structural integrity.
  • Low-Stress Areas: Control surfaces and engine covers were typically thinner, often around 0.5 mm to 0.75 mm, to minimize weight."

Got this decades ago from a collector who claimed it was MIG-15 which I didn't really pay attention to because all Soviet jets are MIG-15s and all German tanks are Tigers, according to the general populace.

I've searched endless photos to find a matching rivet pattern and access panel, to no avail.

So here I am, possibly in the wrong forum.

Any thoughts?

1. What tool and method were used to measure the thickness with such high precision?
2. Was this skin fragment subject to corrosion?

A certain tolerance was allowed - according to the Soviet standards -0.06...-0.14 mm for a thickness of 0.8 mm depending on the width of metal sheets. The MiG-15 fuselage skin was mainly made of D17 alloy, but only the inner skin of the air duct was 0.8 mm thick, while the outer skin was 1.0 mm or even thicker. The empennage skin was 0.8 mm thick, but I cannot indicate a place with a suitable riveting where the markings were typically painted. And most importantly, the star marking is completely untypical for the Soviet Air Force in 1950-1970s. At least, I have never seen any like it on MiGs. If you provide data on the elemental analysis of the alloy, then perhaps something will become clearer. But for now, I seriously doubt that this is a MiG skin.

 

[JoeM]

bf109xxl ... I used a micrometer and took several readings along the edges where the metal was flat (ie no bends). All the readings I took basically came out to 30/1000 " which I converted to metric .762

Think I'll follow up with a digital vernier caliper to see what that tells me.

No corrosion anywhere, in my opinion.

I never believed it was MIG-15, just a story that came with it.

I agree the star is unusual... I've never found a satisfying explanation for it.

It's definitely something "real" , but a real mystery indeed.

 

[bf109xxl]

bf109xxl ... I used a micrometer and took several readings along the edges where the metal was flat (ie no bends). All the readings I took basically came out to 30/1000 " which I converted to metric .762

I just wanted to make sure that you were specifying the thickness value to three decimal places for a good reason. But the measured value is still within acceptable limits, which means that it alone cannot be used to reject the hypothesis that the metal is of Soviet origin.

I never believed it was MIG-15, just a story that came with it.

I checked various sources, including scans of official technical descriptions—the aluminum alloy used for the skin is still D16. I'm not even sure that elemental analysis would help in this case—the composition of the alloy could vary: (in %) Al 90.9–94.7; Cu 3.8–4.9; Mg 1.2 - 1.8; Mn 0.3 - 0.9; Fe, Si <0.5, Zn <0.25; Cr <0.1. Theoretically, this composition can be measured using a portable X-ray fluorescence analyzer—these are widely used for rapid analysis of metal scrap. But I don't know if it's possible to distinguish the Soviet D16 from, say, the American AA 2024. Most likely not. Perhaps comparing the trace element patterns could reveal something, but this is a complex study requiring very expensive equipment and offering no guarantee of a positive result.

I agree the star is unusual... I've never found a satisfying explanation for it.

As far as I know, templates for national markings in the USSR were strictly controlled and no deviations were allowed. Other countries that had MiGs in service and used the Cyrillic alphabet also had different markings that were not similar to those mentioned.

It's definitely something "real" , but a real mystery indeed.

Part of the Cyrillic inscription is also quite mysterious - there are very few words beginning with "io(n?)" that could be found in inscriptions on aircraft, for example, "ionizing radiation."

 

[JoeM]

Part of the Cyrillic inscription is also quite mysterious - there are very few words beginning with "io(n?)" that could be found in inscriptions on aircraft, for example, "ionizing radiation."

It's also possible the word ends in "on", yes? We have no context.

 

[Wurger]

It's also possible the word ends in "on", yes? We have no context.

No, it is not possible. The Cyrillic letter "И" is the "I" but not the "N". The "N" letter is the "Н" in russian writing. So the word either ends with the "oi" or starts with "io"

 

[bf109xxl]

In addition to what was written in the previous post. The letter combination -ои (usually the suffix -о and the ending -и) at the end of a word is found in Russian, but relatively rarely - in the plural form of masculine nouns/pronouns ending in -ой in the singular. There are abbreviations ending in "ОИ", but they are usually written in capital letters. At the same time, warnings about ionizing radiation could be encountered - radioactive isotope were used in icing detectors.

 

[Wurger]

IMHO the piece of the aluminium plate is an attempt to pull someone's leg. The diameter of the holes at the top left corner may suggest stitching of a fabric cover at the area. Contrary to that the rectangular inspection panel looks like being cut out with the can opener. Also the rivet holes seem to be irregular in the diameter and layout. Secondly if the plate was riveted to an aircraft frame as its skin where are the traces of the stringers/stiffener or bulkheads on the back surface? Usually there are traces of these made as the dark and light lines/areas due to the dirt/moisture gathering differently at the side edges of the stringers etc ... Unfortunately there aren't any of these. What is more it seems that the rivet holes at the side with the red star painted have their edges painted with the red paint. The marking was applied on the surface not before riveting but after that. In the case each of the hole should be clean of the paint at the area. No matter if it was the snap-head rivet or flush-head one. Just my opinion.

 

[bf109xxl]

A small addition. It is unlikely that you will be able to distinguish between the Soviet D16 and the American AA 2024 in terms of composition, because they are one and the same. The Soviets received samples of 2024 along with the B-29 and very quickly mastered the technology for producing this alloy. I cannot understand how this could be forgotten, sorry.

 

[JoeM]

IMHO the piece of the aluminium plate is an attempt to pull someone's leg. The diameter of the holes at the top left corner may suggest stitching of a fabric cover at the area. Contrary to that the rectangular inspection panel looks like being cut out with the can opener. Also the rivet holes seem to be irregular in the diameter and layout. Secondly if the plate was riveted to an aircraft frame as its skin where are the traces of the stringers/stiffener or bulkheads on the back surface? Usually there are traces of these made as the dark and light lines/areas due to the dirt/moisture gathering differently at the side edges of the stringers etc ... Unfortunately there aren't any of these. What is more it seems that the rivet holes at the side with the red star painted have their edges painted with the red paint. The marking was applied on the surface not before riveting but after that. In the case each of the hole should be clean of the paint at the area. No matter if it was the snap-head rivet or flush-head one. Just my opinion.

Excellent observations, especially the paint in the rivet holes. Good eye!

 

[JoeM]

Talked to a friend of mine who has painted aircraft, and he says the paint behaviour in the photos is consistent with rivets being in place when painted. He also notes that paint chipping at the edges is consistent with the piece being painted prior to its violent removal.

One of the photos looks brownish... that's just the camera on closeup. Everything is the same shade red.

 

[JoeM]

All (large) rivets are spaced 25 mm center to center

 

[Crimea_River]

I would expect a lot more tearing of the skin with "violent removal". If indeed the painted holes are consistent with in-situ rivets, and I'm not convinced of that, then it appears that someone has taken great care to drill out each rivet.

 

[JoeM]

In addition to what was written in the previous post. The letter combination -ои (usually the suffix -о and the ending -и) at the end of a word is found in Russian, but relatively rarely - in the plural form of masculine nouns/pronouns ending in -ой in the singular. There are abbreviations ending in "ОИ", but they are usually written in capital letters. At the same time, warnings about ionizing radiation could be encountered - radioactive isotope were used in icing detectors.

You, sir, are a deep well of knowledge / trivia.

AI says...

Soviet aircraft utilized radioisotopes for ice detection.

1. Radioisotope-Based Ice Detection (RIO-3)
Soviet aircraft, such as the Mi-8 helicopter, utilized a radioisotope-based ice detector known as the RIO-3.

• Mechanism: The RIO-3 system uses a small amount of radioactive material (beta source) that emits particles toward a sensor (Geiger-Muller tube).
• Detection: As ice builds up on a probe in the path of the radiation, it blocks the beta particles. When the detected radioactivity drops below a certain threshold, the system triggers an "ICING" signal.

Maybe this is off a helicopter. I've been looking at endless photos of jets.

 

[bf109xxl]

1. Radioisotope-Based Ice Detection (RIO-3)
Soviet aircraft, such as the Mi-8 helicopter, utilized a radioisotope-based ice detector known as the RIO-3.

• Mechanism: The RIO-3 system uses a small amount of radioactive material (beta source) that emits particles toward a sensor (Geiger-Muller tube).
• Detection: As ice builds up on a probe in the path of the radiation, it blocks the beta particles. When the detected radioactivity drops below a certain threshold, the system triggers an "ICING" signal.

Maybe this is off a helicopter. I've been looking at endless photos of jets.

The RIO-3 sensor with beta emitters (Sr-90 + Y-90) was widely used in Soviet aviation - both military and civil - until the late 1980s. Apart from helicopters, it was certainly installed on the Yak-40, Tu-154, An-24/-26, early series of Su-24, and possibly others - it's too tedious for me to dig through the manuals. Later, apparently due to general radiophobia caused by the Chernobyl disaster, they were replaced en masse with the SO-121.

 

[bf109xxl]

I conducted a brief search on the production of D16 alloy in the USSR. The version involving the B-29 copying, although appealing, seemed questionable to me from the very beginning. It was presented by Joseph Fridland in his memoirs - he was the leading expert on aluminum alloys in the USSR and one of the inventors of the widely used V95 alloy. Nevertheless, D16 appeared in the USSR no later than 1940 - it was mentioned in a Soviet monograph on the annealing of Alclad aluminum alloys. But even more interesting is the question about the metal supply for the planned licensed production of the Vultee V-11 (A-19) and DC-3 in the USSR (the latter began in 1939) - these certainly required alloy 2024 (i.e., D16). The first 50+ PS-84 aircraft (licensed copies of the DC-3) were assembled mainly from American metal - perhaps some small parts were made from Soviet alloys, but their share was negligible. In 1940, production of D16 was clearly established in the USSR - the first designs with parts made of D16 appeared (Su-2 & Pe-2 prototypes). It is not easy to find any information about the development of D16 in Soviet sources - it seems that the Soviets clearly were not interested to cover this issue in detail. I assume that the chemical composition of 2024(24S) was studied by the Soviets as early as the mid-1930s, but the development of the technology continued until 1940. It would be interesting to see the planning documents for the production of the Soviet copy of the Vultee in terms of metal supply.

 

[pb43]

Helicopter?

 

[Truffle Pig]

As someone who has been building stools and cabinets from old aircraft and helicopter metal sheets for over 15 years (aero-1946.com), I have seen a lot of metal scraps over the years. Usually, they had already been riveted out, or we had to do it ourselves. Some had also been torn out due to damage to the rivet points.
My experience mainly relates to Bell helicopters and some European and American aircraft.

1. Three years ago, we received a damaged original sheet metal panel from a Yak 52 from the USA to build a stool for a pilot. Compare for yourself:

Photo Yak 52

2. The "inspection opening." Usually, there are traces of rivet nuts and a reinforced edge...
3. Shadows from stringers, etc. are almost always visible, especially on painted surfaces:

Photo Stringer

4. After riveting, only traces of primer remain in the rivet holes. The top coat usually appears torn off.

Photo: Detail P-38, shot down in 1945.

Photo: Bell Helicopter with drilled-out rivet heads.

5. The dimpling seems far too imprecise to me.

6. Of course, rivets were and are drilled out perfectly to remove sheet metal. But then I don't expect any deformation of the former dimpling.

7. Traces of riveting, DC-3, still visible after removing the rivets

In this respect (and because the pictures available are not very sharp), I don't feel confident enough to make a final judgment. But I am still very skeptical overall and do not consider the part to be authentic.