The I-15bis Colour Mystery

Of all the aircraft serving in the VVS just prior to the war, the colouration of the I-15bis as finished at Factory No.1 has remained a vexation. Whereas most of the aircraft of this period are well understood, and in some cases have had extensive archaeological evidence gathered (I-16, SB, DB-3, etc) giving a complete picture of the finishes used, neither of these things are the case for the I-15bis. That observation is especially frustrating in that a lot of new documentary material has been unearthed, to include all three books of the Tekhnicheskoe Opisanie (Technical Manual). Moreover, historian and author Mikhail Maslov even found a national markings instruction document from Factory No.1 for the I-15bis, and despite the pedantic accuracy with which it lays out the size and location of all such insignia, and despite referring to itself as a fuselage covering schematic, it does not refer to the surface colouration at all!

We are, therefore, better informed about all aspects of the I-15bis programme... except for it's colouration.

Assembling the Puzzle

Broadly speaking, we may start with the assumption that Factory No.1 (in Moscow) must have finished these aircraft with a paint which was available in quantity, either currently in production or through remaining stocks. The main families of aviation lacquer then being manufactured in the USSR (production of the I-15bis took place during 1938 and 1939) were AE, AEh and AII, the latter two predominating. Obsolete finish 3B (zashitniy), no longer being produced, was available in large quantities. We also know that even older aviation finishes were in stock at a number of factories via their correspondence with the government, and various requests to use up this paint were met rather inconsistently; in cases factories were granted permission to use up stocks, and in other cases to discard them immediately.

Looking at the contemporary and previous behaviour of Factory No.1 as regards production aircraft finish, we can see that their practices were fairly consistent. The immediately preceding project, the I-15, was mainly finished in an early over-all Aluminium lacquer, a scheme which was highly favoured by the government. I-15 examples from Factory No.39 were usually completed in AEh lacquers -4/-15 (Lt. Blue, Dark Green), and while some Factory No.1 examples might also have been so, the majority seem to have been Alum dope. This colouration is, therefore, a fairly reliable method for distinguishing between examples from the two factories across the photographic record.

Prior to the I-15, Factory No.1 shared production of the I-5 fighter with Factory No.21 (Gor'ki). Examples of these machines again can be distinguished in the photographic record by colour. I-5s built in Moscow show a darker looking finish
-- presumably khaki or olive paint-- either over-all, or alternately with unpainted and burnished dural sheet areas (cowling and forward panels). I-5s built in Gor'ki were finished with a lighter green paint, over-all, and a black painted Townend Ring.

I-5 manufactured at Factory No.1 with burnished dural areas

I-5 from Factory No.21, lighter colour and black Townend Ring

I-5 examples seen together in the same photograph, proving the relative differences in appearance

R-5 aircraft built at Factory No.1 around this same time showed an interestingly similar finish. These machines demonstrate un-painted forward dural panels and a darker finish which on film is identical to that seen on the I-5, albeit in most cases a light blue paint was applied to wing under-surfaces (and struts, etc). Some of these aircraft made their way to Spain to serve with Republican forces during the Civil War, and it was most fascinating to discover that on the pieces of Natashas which have been unearthed to date, none of them were re-painted in Spain. Such behaviour was almost unheard of (I-15s, I-16s and SBs were systematically re-painted, for example), and it is a matter to which we will return with the I-15bis.

Now, this finish seen (presumably) on the R-5 and I-5 cannot be a lacquer of the AII family, which was introduced in 1936. It would seem to have appeared too early as well to be a paint of AEh type (~1934), and the date of introduction of aviation finishes of the AE variety is not now known. Prior to 1928, Factory No.1 made use of a wide variety of paints, some of which were automotive finishes, and this situation was rectified only when Factory No.16 was opened in Moscow to produce aviation-specific lacquers. We can therefore surmise that the R-5 and I-5 were painted with specific aviation use finishes, but of which type and formulation we do not currently know. We can also surmise that this paint was available and used in significant quantities at Factory No.1, being the basis for at least two major production programmes.

The Unwanted Child

The full development story of the I-15bis is by far too complicated to detail comprehensively in this article. It is sufficient to highlight certain curiosities of the programme here which could have impacted on the finish and other details of the aircraft during its production history. The I-15bis was basically unwanted, both by the government and by Polikarpov. The NKAP seems to have placed all of its eggs into the basket, so to say, of new versions of the I-16 (including TK high-altitude versions, Ultra-ShKAS armed versions, shturmovik versions, and so on) which it envisioned being manufactured at Factory No.1. None of these projects, however, came to fruition, leaving the government rather red-faced and with no series projects available for the State's premier aviation factory for two years. Polikarpov, on the other hand, hated the "sabotage" of his gull-winged fighter design, and agitated to engage in production of an improved I-15 with an M-25V engine and ShKAS gun armament. This plan was rejected by the government at once.

The government had always been suspicious of Polikarpov's gull wing, claiming that it was "too radical" and hindered pilot visibility during take-off and landing. Even while the TsKB-3 was still a prototype, the No.7 machine was re-built in March 1935 with a conventional, braced central wing section at the insistence of the government, and to the profound irritation of N. Polikarpov. Developmental work on this machine led in a somewhat convoluted way to the DI-6 (TsKB-11), not to mention other projects involving high-altitude fighters, and then to the DIT two-seat trainer prototype. However, with such copious work having been completed on an I-15 with a conventional wing, series manufacture of such a variant would represent an immediate and painless certainty. Thus, after heated and protracted debate, it was decided to manufacture the I-15bis at Factory No.1 until Polikarpov's new 'gull'-- the I-153-- was ready.

Series manufacture of the I-15bis thus began at Factory No.1 in 1938. Even so, the project received the lowest possible priority by the NKAP, even to the point that an improved production standard I-152 prototype (and the desire to change the bis designation to this more appropriate nomenclature) were abandoned to overwhelming disinterest in the aircraft. All attempts, even by the UVVS, to have the obsolete PV-1 guns replaced by ShKAS weapons were rejected by the government. The I-15bis was a stop-gap project-- or indeed not really even a project-- and was not entitled to the newest equipment and fittings (radios, gun sights, etc.).

The I-15bis Production Finish

I-15bis examples built at Factory No.1 with a two-colour finish show that facility's consistent pre-war appearance, that is to say a darker upper surface green (or khaki) and now with light blue under-surfaces. The upper-lower colour demarcation on these examples is quite unique, and absolutely not in keeping with usual Soviet painting practice. This demarcation was ruler sharp, and extended in a straight line aft from the cowl face to the tail skid, even so over the aft wing-root fillet along the mid fuselage.

But, what colour and what lacquer do we see? This colour is similar in tonality to finish AEh-15 Dark Green on most film types, and so for years many observers (myself included) assumed that this was the paint in view. However, subsequent investigations showed that this cannot be true, and so we must find other candidates as possibilities.

Surface Finish

The first major problem with an AEh-15 attribution was the incorrect surface finish of the I-15bis' paint. AEh aviation lacquers had a semi-gloss finish when new, indeed approaching full gloss (the darker colours like Dk Green and Black look very glossy as a result). AII aviation lacquers featured a satin sheen when new, as did AE family finishes. To be an example of any of these lacquers, the I-15bis' paint must agree with these observations.

This lovely photograph, likely taken by a proper photographer, shows the surfaces clearly. The darker upper colour in view is fairly new and has a satin finish. This satin surface finish can be seen in all such photos, but here it is crystal clear. Compare it, for example, to the adjacent light blue areas which are much glossier. Indeed, compare these surfaces to the following photograph showing an I-16 prototype built at Factory No.39 which was finished with AEh-15 Dark Green.

The very gloss surface of AEh lacquer is manifestly evident, and on the I-15bis' 'khaki' paint, completely absent. As a result, this paint cannot be a finish of the AEh family.

An olive green colour is consistent with all of the existing photographic evidence, even images of vastly different properties.
The image below was taken on fairly generic AGFA monochrome stock with the use of a red polarising lens filter (a common choice) by German personnel, the contrasting behaviours of which resulting in a nice image. Had the green colour contained more blue pigment, such as AEh-15, it would have appeared very dark indeed on the image. Moreover, we have evidence corroborating our observed gloss levels in this picture, the over-exposed camera setting eliminating areas of considerable reflected light (propeller, under-surface colour), but preserving it in areas of lesser sheen.

So, What Colour Is It?

Unknown, in a word. IF this mystery paint is indeed the same as found on the I-5 and R-5, then we can say approximately what it looks like by evaluating Natasha bits recovered in Spain. The only other Soviet aircraft to arrive in Spain which was not re-painted was the I-15bis Super Chato. Of course, these aircraft arrived very late in the conflict and barely flew a sortie in anger; perhaps there was no time? But, is it really a co-incidence that it was these two of the Russian aircraft that were not re-painted
(indeed, even the R-Z was)? And noting that French aircraft, delivered in a khaki colour, were also not re-painted? It is also interesting to note that the colour found on R-5s is consistent with the appearance of the khaki paint in all of the photographic evidence.

IF the mystery paint was not the same as seen on the R-5, it could be an example of the AE family of lacquers. We know of AE-2 (Black), -7 (Light Grey) and -10 (Grey-Blue); surely there could be several more colours in this range. Such an identification must await more research.

The use of obsolete aviation lacquers makes absolute sense on the I-15bis programme. In fact, we know that this was done on the bis at least with respect to the under-surface colour. Semi-gloss finish, very light tonality, consistent with light blue on photography... there can only be one candidate, that being AEh-4 Lt Blue. In 1938, this paint was obsolete, out of production, but obviously still in stock at Factory No.1; exactly the properties we would look for on this lowest of priorities programme. The green colour would have been something similar, and it could have been older than AE varnish. One can imagine the giant factory having an older khaki finish, widely used for years over several programmes and therefore held in vast quantity at the facility. This paint disappeared during I-15 production, which made use of the new AII lacquers, but suddenly reappeared two years later when a stop-gap programme was introduced, to be completed with other obsolete finishes. And thereafter, during 1939, disappeared again; and for good.

Not only that, we can also say that this paint was likely not available outside of Factory No.1. Recall the I-5 programme, where Factory No.21 used a different green paint, and indeed a different finishing scheme altogether. I-15bis aircraft which survived into the war years always show comprehensive re-painting, upper and lower surfaces. This would suggest that the original lacquers could not be sourced anywhere. As production of the I-15bis moved into 1939, the mystery green paint was replaced by an over-all scheme of AIl Aluminium, just as the I-153 would usually be finished that year.

I-15bis "White 68" having been comprehensively refinished in AII lacquers Green - Black - Lt.Blue. Virtually all wartime survivors show this type of work.

Curiously, examples of over-all AII Aluminium are less common in the photographic record. Despite that fact, we can be certain that increasingly during 1939 this became the usual finish at Factory No.1


Taking all of the evidence into consideration, it is my own view that the I-15bis' upper khaki colour probably was the same as used on the I-5 and R-5 programmes. We can be certain that Factory No.1 would have accumulated huge stocks of obsolete paints and varnishes over the many years of its operation, and also the breadth of the aircraft types manufactured there. That the government-- always penny-pinching-- would allow the factory to use up these paints on the unwanted I-15bis programme makes perfect sense. We can be sure that this paint was, indeed, a specific aviation use lacquer, but of what family or chemistry we just do not know at this time.

The following profile is an estimation of the I-15bis' factory scheme. The appearance of the khaki green colour is based upon evidence taken from R-5 aircraft, and also impressions from period photography.

 A reminder that I-15bis is the correct nomenclature. For years, many (including myself) had regarded the designations I-152 and I-15bis to be synonymous, but later research by Ivan Rodinov has shown why this was not the case, and that ultimately the term "I-152" was applied only to two prototypes, even if the NKAP had intended to assign this designation to the entire project.