Thursday 12 December 2019

Army Prop and Spinner Colours

Some recent correspondence on the subject of late war Army propeller and spinner colours raised interesting points and prompted this summary. 

At the start of the Pacific War Army propellers were generally of polished metal with only their rear faces painted dark brown as an anti-glare measure. The colour standard for the dark brown paint has not been confirmed but was referred to as Azuki iro (小豆色 - literally red bean colour from the Azuki bean but meaning reddish brown). The current JIS (Japanese Industrial Standard Z 8102: 2001 Object Color Color Name) conventional colour value for Azuki iro is given as Munsell 8R 4.5/4.5, significantly lighter than the typical appearance of the wartime propeller paint which was a rich chocolate brown with a maroon or reddish undertone. This may be the reason that some aircraft models are finished with spinners and props closer to a brick red colour. The closest colour in the Army KouKaku (航格 for 航空機規格 - aircraft specification) 39 to the actual appearance of the propeller paint is # 37 An Kasshoku (暗褐色 dark brown colour). Thorpe's A11 Dark Brown is comparable. The (infamous?) 'tea colour', Cha Kasshoku # 31 is a colour of slightly different character, more an earth brown in appearance and related to camouflage, although the two have been frequently confused and some of the extant prop and spinner artifacts exhibiting fading begin to approach it in appearance.

The front face of each blade had a red warning stripe painted 5 cm from the tip and 5 cm in depth Spinners were either painted aluminium or more usually painted to match the standard hairyokushoku (ash green) colour of the aircraft. Reportedly regulations of that time required aircraft in the multi-colour camouflage finishes adopted in the China theatre to have the entire propeller assembly and spinner painted Azuki iro, but photographs suggest that this practice was by no means consistent.  The Fine Molds Ki-15 kit instructions (FB23) suggest Mr Color 526 (Japanese Army AFV Early Camo described as 'Japanese Army Brown') for the spinner of the camouflaged 18th Independent Flying Company subject, which matches the brown of the upper surface camouflage, whilst the prop colours are suggested as silver (polished metal) for the front of the blades and Mr Color 191 Propeller Color for the rear of the blades.  Such a combination cannot be ruled out. The whole or partial painting of spinners to identify Chutai or Shotai was not general practice at that time but was not unknown in some cases.

After mid-1942 it became general practice for propellers and spinners to be wholly painted in Azuki iro which was not matt but had a lustrous or satin finish. There are indications that this paint became duller and faded with exposure to a lighter brown appearance. The warning stripes at the tips were painted yellow instead of red and a rectangular yellow data stencil was also applied to the front face of each blade near the root. Dimensions were unchanged except that the warning stripes on Ki-61 prop blades were generally 7 cm in depth. The colour standard for the yellow was # 14 Ki iro (黃色) a strong chrome yellow towards orange-yellow, close to FS 33538 and also approximate to RAL 1033 Dahliengelb (Dahlia yellow) which is slightly darker. Thorpe's A17 Deep Yellow is comparable whilst his A16 Medium Yellow probably documents a faded paint colour. A less frequently seen warning stripe variation was for a 5 cm yellow stripe bisected by a white stripe, the three stripes being each of equal depth and the whole also 5 cm from the tip.  In some units spinners were painted in distinguishing Chutai or Shotai colours, either the whole spinner of just the forward half. Spinners painted in a different colour to the Chutai colour used for the unit insignia on the tail are rare but not unknown.

After mid-1944 propellers were painted in a new green colour, the colour standard for which is unknown. However it is apparent that dark brown propellers continued in use on many aircraft until the end of the war. Former Tachikawa employee Noboru Shimoune prepared a colour sample of the green, assessing the late war prop color for the Ki84, Ki-87, Ki-43 III, Ki-94, Ki-100, Ki-102 & Ki-106 as 5GY 3.5/2.3 (reported match FS34094 ~ actual digital match FS 34082 good). Model Art # 28 on the Ki-84 has a colour chip which shows the prop colour as closer to Munsell 10GY 3/2 (reported match FS 34092 ~ actual digital match FS 34094 poor). This was recorded by the author Ichiro Hasegawa from the recollections of Tadamitsu Watanabe. However, another researcher Kenji Ishikawa, who provided input to Model Art # 329, disagrees with that colour. The Model Art book does not present a colour chip for the green.  FS 24172 has also been given for the greyish green props on the Tachikawa built Ki-43 III Ko but has a significantly more greenish appearance with the closest Munsell match being 10GY 4/2. 

The well respected Gakken book series colour researcher (and animation film director) Sunao Katabuchi has presented a colour which appears close to RAL 7009 Grüngrau (Green grey) but which is darker and greyer than the closest FS value 14159. This colour is perfectly consistent with the appearance of an extant Hayate prop blade.  Katabuchi-san also asserts that this new green colour was the same colour being applied to Ki-45 and Ki-84 cockpit interiors. Propellers painted in the new green colour had a 5 cm yellow tip instead of the previous warning stripe. 

The colour of propeller blades and spinners on the Ki-100 is contentious with Aero Detail 32 asserting that they were delivered to Kawasaki pre-painted (dark) brown (shown in the book in Japanese as 暗褐色 - An Kasshoku), contrary to Shimoune-san's data, but conceding that late production aircraft had spinners painted 'green' (presumably to match the airframe colour). The Gakken book on the Ki-61/Ki-100 series displays the prop and spinners of the Ki-100 and late production factory painted Ki-61-I Tei in the # 7 yellow green (olive brown) colour of the airframes and an extant Tei spinner in a Japanese museum appears to be painted in a similar colour but applied over a previous faded (?) brown on the exterior which is visible as a darker brown at the rear edges and on the rear mounting plate. The interior of the spinner appears to be matt black except for the central frame which is dark brown. The prop  blades on the University of Illinois Ki-100 appear from colour photographs taken in 1949 to be dark brown with yellow tips (not warning stripes) but it is unknown for certain if they were original to the airframe and/or re-painted (more on the subject of the UoI Ki-100 colours in a future blog). Spinner colour is unknown as it was missing from the aircraft in the photos. It is worth mentioning here that in some colour photographs the prop blades can be taken for black or dark grey but the recent FAOW Special Edition Vol.7 Army Type 2 Two-sear Fighter 'Toryu'  has a useful colour photo (on page 14) showing a collection of props in the rich and lustrous dark brown colour - and clearly a dark brown prop on the Ki-61 (with yellow roundels!) in the background. However, care must be taken as a close-up colour photograph of a Nakajima Ki-115 strongly suggests that it has black-painted prop blades!     

Who Did The Painting?

It has been asserted that prop and spinner assemblies were delivered pre-painted but it seems unlikely that this was done by the propeller manufacturers. Sumitomo Metal Industries Propeller Division (Sumitomo Kinzoku Kogyo K.K. Puropera Seizosho) manufactured nearly 40% of the propellers used by the Army but the production flow charts within the United States Strategic Bombing Survey (USSBS) report for this company give no indication of a painting process and no mention of spinners as manufactured products. The report also mentions that completed propellers were delivered to Army depots and not direct to aircraft manufacturers. 

The Japan Musical Instrument Manufacturing Company (Nippon Gakki Seizo K.K.) manufactured under licence from Sumitomo 28% of the propellers used by the Army, including those for the Ki-43 and Ki-48, averaging 241 and 120 a month respectively for those two types in the last three months of 1943. The USSBS report on the company gives a stronger indication that the manufacturing process did not include painting. Although the main plant did have a paint shop it is clear from the production flow charts that this was used only in the manufacture of plywood droptanks and not for propellers. Again there is no mention of spinners as a manufactured product and the report mentions that all propellers were delivered to the 'Munitions Ministry' (軍需省- Gunjushō) and again not direct to aircraft manufacturers. 

It would seem logistically clumsy for props to be painted at Army depots (but which would explain why they were painted to the same colour standard as the spinners) and then shipped to aircraft manufacturers. However post war photographs of newly manufactured Ki-84 Hayate at Ota and Utsunomiya show rows of prop-less aircraft with no indication of props on the ground as might be expected if they had been removed in conformity to surrender terms. The answer may lie with the Army Air Depots (Rikugun Kôkû Shô) responsible for equipping and supplying complete new aircraft and which were subordinate to the Department of the Director of Field Air Ordnance (Yasen Kôkû Heiki Chôkambu). In terms of ferrying replacement aircraft there was a depot to depot arrangement. Lt Shuho Kurita's 1943 photograph (below, from Ken Arnold's Home Page) of a Ki-43-I being ferried from Sadohara, Japan to Peitung (Heito?), Formosa (now Taiwan) reveals a natural metal aircraft with anti-glare panel and dark painted prop and spinner. Heito was an important Army Air Depot so it is not unreasonable to conclude that natural metal finish Ki-43-1 aircraft were subsequently camouflage painted there before delivery to units (which will be explored further in a future blog). Indeed after the fall of the Netherland East Indies the 64th Sentai collected some new Ki-43-I aircraft from Formosa which were completely and proficiently camouflaged with lacquer-type paint on all surfaces.   

This selection of rendered chips for the brown propeller and spinner colours from extant artifacts are based on Munsell comparisons provided by Japanese researcher Katsushi Owaki and the late Jim Lansdale. The closest FS and where appropriate RAL colours are displayed adjacently and as usual a value of 2.0 or less denotes a close match. The colours should not be taken as precisely indicative of the original paint colour as the paint appears to have been prone to fading towards lighter shades (and as mentioned above towards the # 31 Cha Kasshoku colour), but they do provide a guide as to the general dark reddish brown character of the colour - and not a brick red (Methuen 7D7) which is a much lighter colour closer to the Army # 4 Seki Kasshoku (red brown colour), the IJN red-brown primer paint and the modern JIS Azuki iro!

Suitable and specific hobby paint colours are available from Gunze (GSI Creos) as Mr Color C131 Propeller Color and Sovereign Hobbies Colourcoats ACJ23 Propeller Brown. In standard ranges Humbrol 98 Matt Chocolate is an approximate match but just a little too greyish, Revell 84 ‘Leather Brown’ being a better and reasonable match. Xtracolor X807 ‘Schokoladebraun’ (RAL 8017) is also acceptable. Vallejo Model Color 822 ‘German Camouflage Black Brown’ matched to RAL 8019 is a little too dark and 985 ‘Hull Red’ matched to FS 30059 is probably a better alternative for smaller models. Other more recent acrylic contenders have not been assessed or measured yet so suggestions are welcome!

Image credit: Heading image of RAF Museum Ki-100 © 2019 Ronnie Olsthoorn; All rendered colour chips © 2019 Aviation of Japan; Ki-43-I photo © Shuho Kurita via Ken Arnold.


Francesco Borraccino said...

pure gold...thanks Nick!

Danilo said...

Extremely interesting and exhaustive as usual. Many thanks, Nick for such a precious research!

Alex said...

Very useful and interesting. Thank you, Nick!

Ken Glass said...

Thanks for taking the time and effort on this one, Nick,

Dan Salamone said...

Nick, you have outdone yourself on this one. Thank you!


Michael Thurow said...

Excellent Nick! Just at the right time because I have begun the research for my Ki-61/Ki-100 project hopefully starting the next coming summer. Yes, that sounds strange but I need to finish the current production line first.

WD said...

Excellent post sir!


Andorka said...

Thanks for your investigation, really useful learning!

Young Ian said...

Once again, I am stunned at the amount of information you've assembled and synthesized! Thank you!

Anonymous said...

Another great piece of research.
Thanks Nick


Fabien L said...

Hi Nick,
Wonderful work as usual! Just one question : Does it exit photos of last Ki-43 III Ko with yellow propeller tips from the top to 5cm down...
Fabien from France

Straggler 脱走兵 said...

Hi Fabien
Photos of 19th Shinbu-tai show props with painted tips and tip stripes but Gakken 52 illustrates the tip-striped props as dark brown and makes the case that early production III Ko were painted by the Army after roll out. It is also possible that dark brown replacement props were retro-fitted to factory painted III Ko.


Fabien L said...

Thanks a lot Nick !

Fred Boucher said...

Nick, thank you for this comprehensive research.

Gianluca Manissero (Giangio) said...

thank you for this research Nick