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Yokosuka D4Y1/2 'Suisei", Projects & Variants

windswords

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According to Wikipedia this was a proposed variant of the D4Y dive bomber (allied code name Judy) with a Nakajima Homare radial engine, a four-blade propeller, and more armor protection. It appears to have been a plan only with no prototype or mock up being built.

Does anyone have an image of this model? I'm am curious to see the difference in the nose shape since the Nakajima Homare was a smaller diameter engine than the Mitsubishi Kinsei radial used in the D4Y3 version. The Homare was however longer than the Kinsei. I imagine it would have looked very sleek.

Thanks!
 

Stargazer2006

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

windswords said:
Does anyone have an image of this model?
I have never seen it, and have just checked Famous Airplanes of the World #69 entitled Navy Carrier Dive-Bomber 'Suisei' (D4Y Judy) (a series which is likely one of the best resources on the subject of Japanese aircraft) but it's not in there.
 

hesham

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Hi,
 

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blackkite

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Of course I will check Japanese sources about your question. ;)
 

windswords

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Just to give you an idea on the size difference (and in case anyone wants to do a speculative drawing - hello Justo!), here are the size specifications of the two engines, according to Wikipedia:

Mitsubishi Kinsei (used in the D4Y3 and D4Y4)
Length: 1,646 mm (64.8 in)
Diameter: 1,218 mm (48.0 in)

Nakajima Homare (proposed for the D4Y5)
Length: 1,778 mm (70 in)
Diameter: 1,180 mm (46.5 in)
 

blackkite

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Hi!
Aichi(愛知)B7A2 Ryusei(流星)had a Homare(誉)12 engine.
Source : as usual

Only Justo can treat this information speculatively based on D4Y4 drawing. ;)
Kinsei 62 weight : 675kg, Length : 1675mm?
Homare 12 weight : 830kg, Length : 1785mm
So perhaps D4Y5 nose is little short compared with D4Y4 to adjust the position of C.G.(Around 1~1.4m short?)
 

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windswords

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

blackkite said:
So perhaps D4Y5 nose is little short compared with D4Y4 to adjust the position of C.G.(Around 1~1.4m short?)
The Homare has a greater length as well as greater weight than the Kinsei (but smaller diameter than Kinsei).

How would you account for the longer length of the Homare engine (Wikipedia - Length: 1778 mm, your source - 1785 mm) from the original Kinsei 62 (Wikipedia - Length: 1,646 mm, your source - 1675 mm?)?
 

Justo Miranda

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Source
"Axis Suicide Squads: German and Japanese Secret Projects of the Second World War"
by Justo Miranda
Fonthill Media F040310
 

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Justo Miranda

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Yokosuka D4Y5 Model 54 technical data
Engine Nakajima JK9C Homare 12 rated at 1,825 hp.
Propeller four-blade metal constant-speed
Wingspan 11,5 m.
Lenght 10,237 m.
Height 3,74 m.
Wing area 23,60 sq. m.
Empty weight 2,750 kg.
Max take-off weight 4,630 kg.
Payload 1,450 kg.
Max.speed 563 kph at 5,900 m.
Cruising speed 370 kph at 3,000 m.
Landing speed 145 kph
Climb to 5,000 m. 7' 30''
Service ceiling 9,000 m.
Standard range 1,400 km.
 

blackkite

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Justo Miranda said:
Yokosuka D4Y5 Model 54 technical data
Engine Nakajima JK9C Homare 12 rated at 1,825 hp.
Propeller four-blade metal constant-speed
Wingspan 11,5 m.
Lenght 10,237 m.
Height 3,74 m.
Wing area 23,60 sq. m.
Empty weight 2,750 kg.
Max take-off weight 4,630 kg.
Payload 1,450 kg.
Max.speed 563 kph at 5,900 m.
Cruising speed 370 kph at 3,000 m.
Landing speed 145 kph
Climb to 5,000 m. 7' 30''
Service ceiling 9,000 m.
Standard range 1,400 km.
Hmmm.......Length is almost same as D4Y4!!! Hmmm....... :-[

How to calculate center of gravity.
http://www.wikihow.com/Calculate-Center-of-Gravity
 

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blackkite

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

windswords said:
blackkite said:
So perhaps D4Y5 nose is little short compared with D4Y4 to adjust the position of C.G.(Around 1~1.4m short?)
The Homare has a greater length as well as greater weight than the Kinsei (but smaller diameter than Kinsei).

How would you account for the longer length of the Homare engine (Wikipedia - Length: 1778 mm, your source - 1785 mm) from the original Kinsei 62 (Wikipedia - Length: 1,646 mm, your source - 1675 mm?)?
Hmmm.........little different. :-[
 

blackkite

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

I assume that the distance between Kinsei 62 engine C.G. and D4Y4 aircraft C.G. is about 2.44m.
The distance between propeller C.G. and D4Y4 aircraft C.G. is about 3.0m.(3.0-2.44=0.56])
To keep aircraft C.G position, it's necessary to keep the value 2.44×(675+50)(Kinsei engine weight+engine cowling weight) +3.0×150(propeller weight)constant.(2219kg-m)
In case of D4Y5, engine weight is 830kg.
So (830+50)×L+150×(L+0.56)=2219, L=2.07m, (L : the distance between Homare 12 engine C.G. and D4Y5 aircraft C.G.)
2.44m-2.07m=0.37m
So I think D4Y5 nose length is about 0.4m shorter than D4Y4 nose length.
(If D4Y5 had a more heavy 4 blades propeller(The weight is around 190kg), I think D4Y5 nose length is about 0.5m shorter than D4Y4 nose length. )
 

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Yes, the D4Y5 was to have a 4 bladed propeller. Since the Homare engine is longer than the Kinsei, if the nose of the airplane is to be shorter to correct the center of gravity (CG), what happens to the space just behind the engine? That area is used for things like the oil tank, bracing and electrical connections. That area would have to be much shorter to fit a longer length Homare in a nose that is overall shorter than the nose of the D4Y4.
 

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Hi! Never mind. D4Y nose was almost engine space.
I think that D4Y3/Y4 Kinsei 62 engine position was determined by C.G.position. Don't you think so? ;)
 

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blackkite

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Please enjoy my very poor patch work for D4Y5 side view. Nose shape little looks like XP-47J ;D
Bomb bay is little small, so I must move oil cooler toward forward direction.
 

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blackkite

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Please enjoy my poor image for D4Y5. Maximum speed was over 600km/h, almost same as F6F?
Thanks a lot windswords-san. Your question is very interesting for me. Is this sleek? ;D
Thanks a lot justo-san. Your source is excellent.
I enjoyed very much. ;)
Please compare original D4Y1 and speculative D4Y5 side view.
I must move oil cooler toward front direction little bit again?
Hmmm...Perhaps I made a mistake again. :'(
 

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blackkite

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Hi! I correct my mistake. Almost Reppu. ;D
I imagine that D4Y5 overall length was 0.487m shorter than D4Y3 overall length(10.237m).
 

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windswords

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Blackkite,

Fantastic job! Yes I do think it looks more sleek than the D4Y3 & 4.

I see that the propeller spinner is very big on your D4Y5. Do you think they would have used a cooling fan similar to the J2M Raiden?

Thanks again for all your work.
 

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Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

windswords said:
Blackkite,

Fantastic job! Yes I do think it looks more sleek than the D4Y3 & 4.

I see that the propeller spinner is very big on your D4Y5. Do you thin they would have used a cooling fan similar to the J2M Raiden?

Thanks again for all your work.
Thanks a lot windswords-san.
Homare type 12 engine did not have a forced cooling fan.
Kugisho Ginga also used Homare type 12 engine.
Homare type 22, 24, 24RU,31, 41, 42, 44, 52,61 had a force cooling fan.
 

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Re: Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Justo Miranda said:
Source
"Axis Suicide Squads: German and Japanese Secret Projects of the Second World War"
by Justo Miranda
Fonthill Media F040310
Hi Justo,

Was just wondering about the D4Y4 Kai you posted about with the clipped wings. Do you know anything more about this model at all?

Thanks
 

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Re: Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Justo Miranda said:
Thats interesting,

How many variants of the D4Y4 were there? Its been on my mind for a short time now, as in the following pictures, all D4Y4s are different...

I also do not think, based on assumption of the aircraft layout, that the initial batch of D4Y4s were purpose built special attack aircraft. Can anyone clarify this?
 

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Re: Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Thank you Justo !
Can you tell us the source for the drawings and tables, that aren't from you, please ?
 

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Re: Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Posted in pic USN361
 

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Re: Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

Yes, thank you Justo! We appreciate your time and effort to bring us these images.
 

blackkite

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Re: Yokosuka D4Y Suisei "Judy" Model 54 unbuilt variants

windswords said:
Yes, thank you Justo! We appreciate your time and effort to bring us these images.
Me,too. Excellent information!! :D
 

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D4Y1/D4Y2 with turbo supercharger

In the discussion about the D4Y5 Model 54, Justo posted an image that showed a D4Y2 with a bulge in the lower fuselage (see pic 1).

This caused me to remember another image of this aircraft with the same characteristic bulge (see pic 2). That second image shows a turbo supercharger installed in the D4Y. Note that both images have the same tail code. None of the references I have say that there was ever a turbo supercharger installed in a D4Y. Does anyone have any further info?
 

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blackkite

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Re: D4Y1/D4Y2 with turbo supercharger

https://dic.pixiv.net/a/%E5%BD%97%E6%98%9F%28%E7%88%86%E6%92%83%E6%A9%9F%29

"他にも高高度性能の向上の為に一二型にターボチャージャーを搭載した試作機も存在したようだ。

It seems that there was also a prototype equipped with a turbocharger for the twelve types to improve the high-altitude performance."

But bomb bay??
 

blackkite

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Re: D4Y1/D4Y2 with turbo supercharger

http://www21.tok2.com/home/tokorozawa/faq/faq08p06e01b.html

"【質問】
 過給器付「彗星」について教えられたし.

 【回答】
 これは「彗星」12型を改造した排気タービン過給器型で,12戊型(夜間戦闘機型)の強化を目指すもの.
 改造は空技廠/第1技術廠の飛行部と発動機部が担当.
 排気管から,爆弾倉内に置いたタービンへ排気を送るためのダクトや,翼根部に新設された過給器用空気吸入口などがとりつけられた.
 写真では,横須賀航空隊の「ヨ-257」号機が確認できる.
 実験準備中に敗戦を迎えたという.

 詳しくは『世界の傑作機69 海軍艦上爆撃機「彗星」』(文林堂,1998.3.1),p.20,33を参照されたし.

【Question】
Please teach me about "Suisei" with supercharger.
【Answer】
It is the modified"Suisei" 12-type with turbocharger(D4Y2-S), which aims to strengthen the 12-type night fighter..
The modification was in charge of the flight technology department and the engine department of the Kugisho.
This type had exhaust pipe which send the exhaust to the turbine placed in the bomb bay, and the air inlet which was newly established in the wing root.
In the photograph, the "yo-257" of the Yokosuka Air Corps can be confirmed.
The defeat was received during the experiment preparation.
The effect of the modification is still unknown.
For more information, see the FAMOUS AIRPLANES OF THE WORLD Vol69 Suisei. (1998.3.1), p20 and 33."

I hope someone has this book. ;)
 

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windswords

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Re: D4Y1/D4Y2 with turbo supercharger

Blackkite,

Thank you for the information. Now it makes sense. This experiment was only done for the D4Y2-12 version. One of the drawings I posted says it is a D4Y1-11. That is incorrect. They never tried it on the later radial engine D4Y. The Yokosuka tail marking makes sense also as that was location of the navy's air technical center.

The English version of Wikipedia does not mention this. I wonder if I could add it and cite this forum as a source? :)
 

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Re: D4Y1/D4Y2 with turbo supercharger

It's a very good idea. :D Anyway windswords-san's this topic is very interesting and sharp.
windswords-san's second drawing has no exhaust pipe. ???

彗星一二戊型(Suisei type 12-bo), base of turbocharged Suisei night fighter.
https://twitter.com/IJNAS_aircrafts/status/814066973843726336
 

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blackkite

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Hi! Turbo charged D4Y2 night fighter.

Explanation for these pictures. Please try auto translator. ;)

これらの写真は、これまでどんな文献にもほとんど触れられていなかった、排気タービン過給器付きの彗星12型の写真である。飛行機の機首がシートで包まれ、月光夜間戦闘機のの垂直尾翼がじゃましているのは残念だが、翼の根元の部分に、過給器用の空気吸入口が新設され、爆弾搭載部分が改造されているのが分かる。この写真は、敗戦後の追浜飛行場で撮影された。

この写真は、上の写真のヨー257と同一の飛行機の前半部の写真である。船舶に搭載してアメリカへ持ち帰ろうとしたのか、この飛行機には保護用に黒く防錆処理(?)が施してある。この写真には、排気管から爆弾搭載部分に置いた、タービンへ空気を送るダクトが見える。この飛行機は、空技廠/第1技術部の飛行機部と発動機部によって改造されたのは確実だが、排気タービンに三菱、日立、石川島のいずれの製品を使ったのか、またその効果はどうだったのかなどは一切不明である。

For example,
"These photographs are the twelve types of comets with exhaust turbine supercharger, which have hardly been mentioned in any literature. The nose of the airplane is wrapped in a seat, and the vertical tail of the Moonlight Night fighter is in the way, it is regrettable, the air inlet of the supercharger is new to the base portion of the wing, it is understood that the bomb mounting part has been remodeled. This picture was taken at the Oppama airfield after the defeat.

This photo is a photo of the first half of the same plane as the yaw 257 of the above photo. Whether it was printout to the United States to be equipped with the ship, this plane has a black rust prevention treatment for protection (? I have been subjected. In this photo, you can see a duct that sends air to the turbine, placed in a bomb-mounted part of the exhaust pipe. It is certain that this plane was remodeled by the airplane part and the engine part of the Aero Factory/The first engineering department, whether the product of Mitsubishi, Hitachi or Ishikawajima was used in the exhaust turbine, and the effect was not known at all."

Source : https://www.secretprojects.co.uk/forum/index.php?action=dlattach;topic=25914.0;attach=585600;image
 

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