# Ki-61 and He-100 related?



## krieghund (Oct 7, 2010)

As promised in another thread I would move the Ki-61 and He-100 related issue here.

There are many sources over the years citing that the Bf-109 was the inspiration for the creation of the Kawasaki Ki-60 and Ki-61 aircraft. I believe most of this association arises from the initial Intel reports from pilots encountering the Ki-61 reporting it as Japanese built (bought) Messerschmitts or Italian fighters hence the name “Tony” for its identifier code name. Also it uses a Japanese built DB-601 further enhancing the similarity. The Heinkel He-113 wasn’t probably in the minds of those pilots making those reports nor had access the Intel files of the He-113.

Next the fact that the Japanese examined and tested the Bf-109E-4 against their own prototypes is well documented adding further weight to those assumptions.
Before continuing on into some evidence that may prove the He-100 was idea into the Ki-61 creation we should look at the timeline of events of this period.

May 1937 – Heinkel Projekt 1035 started
Oct 1937 – RLM informed of Heinkel fighter construction and designation ‘He-100’ officially allocated.
Jan 1938 – He100v1 first flight
Dec 1938 – Japanese delegation to Marienehe given data/plans on “He-113” (Based A-0 section I aircraft). Five He-100 prototypes flown up to this time.
May 1939 – Hitachi Kokuki K. K. establishes plant in Chiba to license-build the He-100 and He-119. Plans underway to possibly build He-177.
Oct 1939 - Japanese engineering delegation to Marienehe to prepare shipment of He-100 and He-119 to Japan.
Dec 1939 - Koku Hombu creates specification for aircraft built around DB-601
Feb 1940 – Koku Hombu instructs Kawasaki to build two fighter types based on DB-601. Priority given to heavy intercepter (Ki60) and design work begins.
Apr 1940 – DB601 blueprint plans and engines received in Japan.
May 1940 – Three He-100 reach Japan at Kasumigaura, one to IJN and two the Army. (Type A-0 Section II aircraft)
Dec 1940 – Designs started for Ki-61
Mar 1941 – *Ki-60 prototype flown with DB601*
Jul 1941 – Ha-40 (DB601) begins bench running --Three Bf-109E4 are delivered to Japan
Sep 1941 – Ha-40 pre-series deliveries begin
Nov 1941 – Ha-40 ordered into production
Dec 1941 –* Ki-61 prototype flown with Ha-40*
Apr 1942 – Lt Umekawa in Ki-61 tries to intercept a B-25 during the “Doolittle raid”
Jun 1942 – Ki-61 Service Trials


The timing of events support the he-100 influence to be more likely than the Bf109


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## davebender (Oct 7, 2010)

Japanese?German pre-World War II industrial co-operation - Wikipedia, the free encyclopedia


> The Messerschmitt company sold the Messerschmitt Bf 109 E-3/4



It appears to me Germany provided Japan with technical data for everything except a formula for brewing proper beer. I had no idea the data exchange was this extensive until I found the Wikipedia article.


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## Civettone (Oct 7, 2010)

It actually proves that the Ki-60 and Ki-61 were planned seperately from possible licence production of the He 100. The design order was given when the He 100 still had to be delivered. That shows that licence production of the He 100 nor Bf 109 was never seriously planned. 

There is no formal link between the He 100 and Ki-60/-61 except for the Kawasaki chief designer cooperation with Vogt. 

I suppose next up are the design plans of He 100 and Ki-61 as well as data on the jigs lost in transit?
Kris


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## krieghund (Oct 8, 2010)

Of course the next point to indicate a link to the He100 and not the Bf109 would be the obligatory 3 view drawings for comparison;


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## krieghund (Oct 8, 2010)

Civettone said:


> It actually proves that the Ki-60 and Ki-61 were planned seperately from possible licence production of the He 100. The design order was given when the He 100 still had to be delivered. That shows that licence production of the He 100 nor Bf 109 was never seriously planned.
> 
> There is no formal link between the He 100 and Ki-60/-61 except for the Kawasaki chief designer cooperation with Vogt.
> 
> ...



I think that the establishment of the factory at Chiba after the delegation returned with observations of European aero activities centered around inline engines and receiving plans for the DB601 and HE100 prototypes they examined I think speak volumes.

I am searching my data for which ship was lost enroute with the jigs and tooling.


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## krieghund (Oct 8, 2010)

I think this next sequence of pictures and drawings will further show a linkage of design features.

The box beam engine mounting integral with fuselage cowling can be found on only two aircraft which used the DB601 engine......The He100 and the Ki-61. The Ki60 used the standard engine bearers used by all the other designs incorporating the DB601.

It was reported that the same 115mm vertical offset of the front engine mounts of the Ki61 are identical to the He100 and the front mount adapters of the He100 are duplicated on the mounts for the Ki61.

The wide large exhaust ejectors are of the same unusual configuration.


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## Civettone (Oct 8, 2010)

I don't know that much about aircraft construction but that does seem to be a direct copy of a German construction method. 

But I think we should set straight what exactly we are talking about. Are we talking about design as an aerodynamical exterior thing or design as how the fuselage was constructed, were the bolts were and how the engine was attached? I did not think about these last things but it seems only natural that Japan had some things to learn from German construction methods. Or from allied construction methods. 

But one more thing, do you think that Japan was planning to build the Ki-60/61 and He 100 at the same time? And if they had the plans of the He 100 why not build a copy? 
And what about He 100 influence in Russian air industry?
Kris


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## krieghund (Oct 8, 2010)

To set this straight even the line drawings show a resemblance between the Ki-61 and He100.

I think the Japanese designers were very much influenced by their pilot's demands for very maneuverable aircraft and as such the He100 would not fill their preference. I believe since the jigs and tooling did not make it they felt they could make their own design to suit their requirements yet incorporate the latest elements of the German design.

It would be a major effort to reverse engineer a design so I feel they used their time and resources to create the Ki-61 utilizing key factors of the He100. One area they probably felt they couldn't duplicate successfully was the evaporator cooling system though they used some steam capture components in the engine bay. 

It will be noted that they did put this system into one Ki-61 as a test bed to perfect the evaporator cooling system for the Ki-64. 35 flights were made and without the ventral radiator and it could do 630 kph.

The fact that the designers switched to the fuselage integral engine mounts from the engine bearers of the Ki-60 shows the influence of the He100 since it was available for testing and examination 7 months before the designs were laid down on the Ki-61.

The DB601 used two mounting bolts per side in all aircraft using the DB601.

In summary my point in this thread is to show the Ki-61 was directly influenced by the He-100 and the only resemblance to the Bf-109 is that it shares the same engine type. 

My book, "Heinkel He-100 Record Breaker" by E. Hood, the author makes reference to the He100 influence into the LaGG-3 design even though the Russians were already experienced with inline engines.


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## Civettone (Oct 8, 2010)

I think it is really nice how you took the effort to lay all this down 

I think you have proven that the designers were influenced by the He 100. But it seems this was more a technical issue, more for the engineers than for the designers. 
What they do have in common seems to be the tail section. The wings and fuselage are definitely different. But again maybe the inner structure of these have common elements between both designs.

One last thing, are you positive that the Germans never gave the plans for the Bf 109 to the Japanese (prior to the war)?

Kris


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## krieghund (Oct 8, 2010)

i will research the Messerschmitt connection further, but if memory serves Heinkel had cornered the market with Japan or Messerschmitt wasn't that interested at the time however I will look further.

As to the fuselage these are not the clearest pictures but the structure design of all three aircraft are similar the Ki-61 and He100 appear to be closer related.


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## davebender (Oct 8, 2010)

Speaking of the Me-109, I'm surprised KMT China didn't license build such an inexpensive German fighter aircraft. They copied a lot of German equipment and the Me-109 would have compared well with fighter aircraft flown by the Imperial Japanese Army.


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## Civettone (Oct 9, 2010)

They copied guns and vehicles. But the Bf 109 was top technology and only cheap in a highly industrialized country. It's like saying to an African 3rd world country to copy the Northrop F-5. 

Kris


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## krieghund (Oct 9, 2010)

Civettone said:


> They copied guns and vehicles. But the Bf 109 was top technology and only cheap in a highly industrialized country. It's like saying to an African 3rd world country to copy the Northrop F-5.
> 
> Kris



Your right, It took Iran all these years to finally develop an F-5 knock-off


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## Civettone (Oct 9, 2010)

True.

About the fuselage. I actually think the Bf 109 is closer to the Ki-61. Just look how their round frames are pierced by the longitudinal beams. Not so in the He 100. When looking at the form of the cross-section I feel that the top part is more like the He 100 but the bottom part (rounder than on the He 100) is more like that of the Bf 109.

Kris


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## The Basket (Oct 9, 2010)

The Hienkel He 118 and the Yokosuka D4Y certailny proves co-operation between Japanese and German engineers.

But inline engines were not the Japanese cup of tea.


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## krieghund (Oct 9, 2010)

Civettone said:


> True.
> 
> About the fuselage. I actually think the Bf 109 is closer to the Ki-61. Just look how their round frames are pierced by the longitudinal beams. Not so in the He 100. When looking at the form of the cross-section I feel that the top part is more like the He 100 but the bottom part (rounder than on the He 100) is more like that of the Bf 109.
> 
> Kris



However, historically the Army had two examples of the He100 seven months prior to the plans for the Ki61 being laid down and no example of Bf109 until seven months after that.

Note that the He100 and Ki61 fuselage formers are the exact same shape and the skinning seam is at the top on both but the Bf109 is at the bottom.

The Ki60 and Ki61 construction methods are different in many areas which still leads to the conclusion that once the He100 was examined many of its features were incorporated. I will post some pics shortly supporting this issue.

Also I still haven't located any evidence of Messerschmitt technology transfer until 1941 but I am still looking...if it is out there I will find it.

There is a mention in W. Green's book about some Bf109E-7s and a BF109G also being sent later on and we know about the well documented voyage of U-234 with the ME262 and ME163 and some other very curious stuff (but then that is for another thread)


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## cherry blossom (Oct 10, 2010)

The He 100 may also have influenced Japanese airfoils. According to an excellent post by Jim Long at B7A Grace: too heavy for most carriers? on the Navy's B7A “...the airfoil section which was an improvement over that of the German Heinkel He lOO fighter plane; ...”. I looked up the Hien in David Lednicer's “The Incomplete Guide to Airfoil Usage” at The Incomplete Guide to Airfoil Usage and found 

Kawasaki Ki-61 Hien, NACA 2R1 16, NACA 24009

but no He 100. However, the wing root is the same as the Me 209V1 but different from the Bf 109.

Messerschmitt Me 209V1, NACA 2R1 16, NACA 23010-64
Messerschmitt Bf 109E Emil, NACA 2R1 14.2, NACA 2R1 11

Does anyone know if the He 100 and Me 209 shared an airfoil? 

Interestingly the Ki 78, which looks like the He 100 at first glance may have a different airfoil.

Kawasaki Ki-78, LB 510216, LB 510312


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## zoomar (Oct 12, 2010)

I see no reason to believe either the Bf-109 or the He-100 played a major role in either (1) the JAAF's decision to develop and introduce a fighter based on the DB 600 series of engines, or (2) the detailed design of the Ki-60 or Ki-61, other than specific techniques associated with adapting the DBs to Japanese production techniques and mounting the engine. Yes, both German planes provided the Japanese with good information on modern European manufacturing and design techniques, but the Ki-61 was as much a Japanese plane as the Macchi MC-202, MC-205, and Fiat G-55 were Italian planes.


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## krieghund (Oct 12, 2010)

The point was trying to make is that the he100 was that influence in the designers of the Ki-61. The are major changes between the Ki-60 (designed prior to the he100 arrival) and the Ki-61 (designed 7 months after). Many He100 features not found on any other DB601 fighter are found incorporated in the Ki-61.

I am not saying that the Ki-61 is a cookie cutter production of the He100 but even I as an aircraft engineer also takes note not to reinvent the wheel.

The Ki-61 is a Japanese design(period). When I was growing up and started my interest in aircraft one of my first comparisons was the Heinkel to the Hein physical characteristics. (Kind of a coincidence about the name though)

And I think they did a great job.


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## krieghund (Nov 12, 2010)

As i was going through my references I came across this drawing with the source referenced. it is very interesting as it includes a ducted ventral radiator semi-buried in the fuselage and gives a more Ki-61 look to the He-100 lines very similar to the P-51A.


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## E Hood (Nov 14, 2010)

Thank you, krieghund, for the photos of the Ki-61 structures. The search for views of an "unskinned" Ki-61 engine cowl - which is to say, views of the completed structure only - continues, but one of your photos, the starboard side view, clearly shows not only one of the longitudinal beams forming the port side of the cowling, but another item similar to that on the He100, the rectangular hatch on the starboard side of the cowling.
A photo in Rene' Francillon's compendium, of a Japanese-built version of a DB 601A, shows the type of front engine mount adapter used in the Ki-61. This object was essentially identical in size and shape to the adapter used in the He100.

By the time the Ki-60 and Ki-61 were being developed, Japan had all but completely stopped building direct copies of non-indigenous airframes. Two of their primary suppliers of foreign technology, Germany and England, were at war, and war with another, the US, had become a distinct possibility. In a word, they'd recognized the need for self-reliance, and as such aircraft as the Zero and Nell will attest, they'd become quite good at it. That they'd stopped building copies of foreign, front-line aircraft does not mean however, that they'd chosen to ignore developments in foreign technology. Nor did Dr. Vogt's relationship with Kawasaki preclude ties with Heinkel.

Not incidentally, I've never found a photo of the engine bay in the Ki-60, but I do have a rudimentary factory drawing showing that the engine mounts were probably identical to those in the Bf 109.


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## krieghund (Nov 14, 2010)

Here is the only picture I could find of the engine mount to the Ki-60 it is rather poor but it is from this book


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## proton45 (Nov 14, 2010)

The one thing that people seem to ignore is that ideas where "borrowed" and influenced and used back and forth across international borders, racers, oceans and businesses. Flush riveting was first used in one place and standardized in another...the same goes for mono wings, enclosed cockpits and retractable landing gear...ect. At that time inline engine fighters where the latest fashion in pursuit planes... Japan wanted one. I believe the idea was to get one into service as quickly as possible...

It seems strange to pick apart the engine mount and its influence...if you are using a DB engine you mount it to the airframe the way it was designed to...seems simple to me. No big mystery.


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## krieghund (Nov 14, 2010)

proton45 said:


> It seems strange to pick apart the engine mount and its influence...if you are using a DB engine you mount it to the airframe the way it was designed to...seems simple to me. No big mystery.



The point I am making is the Ki-61 and He100 are directly related in many respects that are only peculiar to each other.

With regards to the engine mounts this is the most prominent feature they share. Count the number of aircraft which used the DB60x series engines (quite a large number). They all used the bearer mounting style on the left like the Ki60. Why is it then only the Ki61 and He100 used the integral fuselage mount on the right? The Kawasaki followed everyone with regards to mounting the engine until the arrival of the He100 in Japan. Even the other Japanese manufacturers followed the bearer type of mount (Suisei Seiran)


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## K_K (Nov 17, 2010)

krieghund said:


> Here is the only picture I could find of the engine mount to the Ki-60


No, it isn't. The Polish language caption actually says:
_"Daimler Benz DB601A engine *on a test bench at its parent factory*. Exhaust stacks are removed from the engine. These engines were to power Ki-60s."
_So what it actually shows is obviously a Messerschmitt engine mount, and the only connection between this picture and Kawasaki Ki-60 is engine _*type*._


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## krieghund (Nov 17, 2010)

K_K said:


> No, it isn't. The Polish language caption actually says:
> _"Daimler Benz DB601A engine *on a test bench at its parent factory*. Exhaust stacks are removed from the engine. These engines were to power Ki-60s."
> _So what it actually shows is obviously a Messerschmitt engine mount, and the only connection between this picture and Kawasaki Ki-60 is engine _*type*._



Well Nuts, let's try this..still can't find a Ki-60 naked but here is two profile drawings from a book on Japanese X-planes. It shows the standard engine mount bearers on the Ki-60 and the integral mount on the Ki-61. Still looking for a picture to post though....


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