The Yokosuka D4Y Suisei

Allied codename 'Judy'

Japan
Japan

side view front view under view

The Yokosuka D4Y Suisei (Comet) is often compared to the British de Havilland Mosquito due to it's developmental history, excellence and versatility. But this is where the similarities end. Let's go back to 1938, the year in which the first actions were taken that finally resulted in this excellent naval dive-bomber, reconnaissance aircraft and night fighter.
Due to the strong resemblance from a political point of view, Japan had already established a good relationship with Germany. Both powers were rapidly expanding their military potential, both had great plans for domination dictated from their belief in their superiority over other peoples and countries surrounding them. Both for Germany and Japan, as well as for Italy, it was only natural that they would rule over their neighbours, since they were "of a superior race". Or so they believed. It is no surprise then that the cooperation between these countries, even though the racial differences were quite great from each others point of view, was reasonable strong as far as military aspects were concerned. This was abundantly clear when Japan was allowed to buy one of the Heinkel He 118 prototypes, the V4. Together with the actual machine Japan bought the rights to develop and build further on the Heinkel He 118 concept.
The German machine achieved a max level speed of 260 mph (418 km/h) during test flight, powered by 1 × Daimler-Benz DB 601Aa inverted-Vee, rated at 1,175 hp (876 kW). Impressed by the potential the aircraft offered, the Japanese Navy immediately planned for a Japanese carrier-borne version of the He 118.
Redesignated according to the Japanese system, the DXHe1 was used until it broke up in mid-flight. Even so, the Navy was consisting in it's plans for their own high speed carrier-borne dive-bomber version of the DXHe1. For this reason the dai-Ichi Kaigun Koku Gijisusho (1st Naval Technical Air Arsenal) was instructed to design a dive-bomber based on the DXHe1, but smaller. The requirements for this type of aircraft were laid out in the 13-Shi Navy experimental Carrier Bomber requirement of 1938, calling for a max level speed of 322 mph (518 km/h), cruising speed of 265 mph (427 km/h), a range of 1,381 miles (2.222 km) without a bomb, and a range of 921 miles (1.482 km) with a bombload of 551 lb (250 kg).
Headed by Masao Yamana, the Yokosuka design team created a clean design for a single-engine mid-wing monoplane dive-bomber with accommodation for two in a long cockpit under a ‘glasshouse’ canopy, a wing that was more or less comparable with that of the Mitsubishi A6M Reisen in span and area (thereby removing the need for a wing-folding system), a fuel capacity almost as large as that of the Aichi D3A that it was to supplant, and a fully retractable tailwheel landing gear. The basic configuration showed resemblance to the DXhe1 prototype of Heinkel, but this D4Y design was smaller, lighter, stronger, more advanced in its structure and aerodynamics, and possessed internal stowage for the 1,102 lb (500 kg) bomb that was its primary armament. Another proof to the German inheritance was the projected powerplant, being 1 × Aichi AE1 Atsuta inverted-Vee piston engine, which was the Japanese license-built derivative of the DB 601. The navy ordered Yokosuka the production of five prototypes each powered by an imported Daimler-Benz DB 600G engine, rate at 960 hp (716 kW) and driving a three-blade metal propeller of the constant-speed type, pending availability of the Atsuta.
Central in it's design, the airframe was an oval-section fuselage of semi-monocoque construction which carried the engine in the nose with its radiator in a bath set slightly back from the nose on the underside of the forward fuselage. This core structure supported the flying surfaces, comprising a cantilever tail unit of metal stressed-skin construction with fabric-covered control surfaces, and the low/mid-set wing. This wing was slightly dihedraled, tapered in thickness and chord, and carried along almost the full span of its trailing edges the standard combination of outboard ailerons and inboard flaps, the latter with electrically operated three-section dive-brakes ahead of them under each wing. The first D4Y1 prototype made its maiden flight in December 1940, and proved to possess an excellent combination of high performance and good handling.

After the prototype's succesful trials development was sped up, but then the first unpleasant surprise came. During dive-bombing trials the wings of the D4Y started to flutter, so much that it could break up the wing spars. Even though Aichi was already asked to build a construction line for the D4Y, the future was unsure at that time. The task it was designed for, the D4Y was unfit to perform. As an alternative taking into considration it's good performance, ceiling and range, the D4Y was then selected for reconnaissance duties. Therefor the first pre-production batch was adapted for this role, and the Suisei started lifa as a reconnaissance aircraft in stead of a dive bomber

Version list:

Further pictures:

Yokosuka D4Y Suisei 'Judy' in full flight
Yokosuka D4Y Suisei 'Judy' in full flight

 

Technical data on the Yokosoka D4Y1-C Suisei
Powerplant 1 × Aichi Atsuta 12 twelve-cylinder inverted-Vee liquid cooled, rated at 1200 hp (894.59 kW) Role during war
  • Night-Fighter
  • Light Bomber
  • Dive Bomber
  • Reconnaissance Aircraft
Length 33 ft 6.4 inch Height 12 ft 0.6 inch
Empty weight 5379 lb Operational weight 8047 lb typical,
9370 lb max
Wing Span 37 ft 8.75 inch Wing Aspect ratio unknown
Wing Area 254.027 sq ft Service ceiling 32480 ft
Maximum speed 343 mph at 15585 ft Cruising speed 265 mph at 9845 ft
Initial climb rate Climb to 9,845 ft in 5 min 14 sec Range 978 miles typical,
2417 miles max
Fuel capacity internal unknown Fuel capacity external Up to 145 Imp gal (174 US gal) in two 72 Imp gal (87 US gal) drop tanks
Machine guns
  • 2 × 0.30 inch Type 97 fixed forward-firing in the upper nose
  • 1 × 0.303 inch Type 1 trainable rearward-firing
Cannons -
Bomb load Up to 1,234 lb of disposable stores carried in a lower-fuselage weapons bay rated at 1,100 lb and on two underwing hardpoints rated at 66 lb each. General disposables load consisted of:
  • 1 × 551 lb bomb
  • 2 × 66 lb bombs
Torpedoes/rockets -
Crew 2: pilot, radio operator/gunner Naval or ground based Naval
First flight (prototype) December 1945 Operational Service Mid-1942 - 1945
Manufacturer Dai-Ichi Kaigun Koku Gijitsusho, Yokosuka (1st Naval Air Technical Arsenal, Yokosuka) Number produced 2.038 total, unknown this version
Metric system
Length 10.22 m Height 3.67 m
Empty weight 2440 kg Operational weight 3650 kg typical,
4250 kg max
Wing Span 11.5 m Wing Aspect ratio unknown
Wing Area 23.6 m² Service ceiling 9900 m
Maximum speed 552 km/h at 4750 m Cruising speed 426 km/h at 3001 m
Initial climb rate Climb to 3.000 m in 5 min 14 sec Range 1574 km typical,
3890 km max
Fuel capacity internal unknown Fuel capacity external Up to 660 liters in two 330 liters drop tanks
Machine guns
  • 2 × 7,7 mm Type 97 fixed forward-firing in the upper nose
  • 1 × 7,92 mmType 1 trainable rearward-firing
Cannons -
Bomb load Up to 560 kg of disposable stores carried in a lower-fuselage weapons bay rated at 500 kg and on two underwing hardpoints rated at 30 kg each. General disposables load consisted of:
  • 1 × 250 kg bomb
  • 2 × 30 kg bombs
Torpedoes/rockets -

Technical data on the Yokosoka D4Y2 Suisei
Powerplant 1 × Aichi AE1P Atsuta 32 twelve-cylinder liquid-cooled Inverted-Vee, rated at 1400 hp (1043.69 kW) Role during war
  • Night-Fighter
  • Light Bomber
  • Dive Bomber
  • Reconnaissance Aircraft
Length 33 ft 6.4 inch Height 12 ft 3.75 inch
Empty weight 5089 lb Operational weight 8445 lb typical,
10192 lb max
Wing Span 37 ft 8.75 inch Wing Aspect ratio unknown
Wing Area 254.027 sq ft Service ceiling 35105 ft
Maximum speed 360 mph at 17225 ft Cruising speed 265 mph at 6560 ft
Initial climb rate Climb to 9,845 ft in 4 min 36 sec Range 909 miles typical,
2239 miles max
Fuel capacity internal unknown Fuel capacity external Up to 145 Imp gal (174 US gal) in two 72 Imp gal (87 US gal) drop tanks
Machine guns
  • 2 × 0.30 inch Type 97 fixed forward-firing in the upper nose
  • 1 × 0.303 inch Type 1 trainable rearward-firing
Cannons -
Bomb load Up to 1,234 lb of disposable stores carried in a lower-fuselage weapons bay rated at 1,100 lb and on two underwing hardpoints rated at 66 lb each. General disposables load consisted of:
  • 1 × 551 lb bomb
  • 2 × 66 lb bombs
Torpedoes/rockets -
Crew 2: pilot, radio operator/gunner Naval or ground based Naval
First flight (prototype) December 1945 Operational Service Mid-1942 - 1945
Manufacturer Dai-Ichi Kaigun Koku Gijitsusho, Yokosuka (1st Naval Air Technical Arsenal, Yokosuka) Number produced 2.038 total, unknown this version
Metric system
Length 10.22 m Height 3.75 m
Empty weight 2308 kg Operational weight 3831 kg typical,
4623 kg max
Wing Span 11.5 m Wing Aspect ratio unknown
Wing Area 23.6 m² Service ceiling 10700 m
Maximum speed 579 km/h at 5250 m Cruising speed 426 km/h at 1999 m
Initial climb rate Climb to 3.000 m in 4 min 36 sec Range 1463 km typical,
3603 km max
Fuel capacity internal unknown Fuel capacity external Up to 660 liters in two 330 liters drop tanks
Machine guns
  • 2 × 7,7 mm Type 97 fixed forward-firing in the upper nose
  • 1 × 7,92 mmType 1 trainable rearward-firing
Cannons -
Bomb load Up to 560 kg of disposable stores carried in a lower-fuselage weapons bay rated at 500 kg and on two underwing hardpoints rated at 30 kg each. General disposables load consisted of:
  • 1 × 250 kg bomb
  • 2 × 30 kg bombs
Torpedoes/rockets -

Technical data on the Yokosoka D4Y3 Suisei
Powerplant 0 × , rated at 0 hp (0 kW) each Role during war
Length unknown Height unknown
Empty weight unknown Operational weight unknown
Wing Span unknown Wing Aspect ratio unknown
Wing Area unknown Service ceiling unknown
Maximum speed unknown Cruising speed unknown
Initial climb rate unknown Range unknown
Fuel capacity internal unknown Fuel capacity external Up to 145 Imp gal (174 US gal) in two 72 Imp gal (87 US gal) drop tanks
Machine guns unknown Cannons unknown
Bomb load unknown Torpedoes/rockets unknown
Crew unknown Naval or ground based unknown
First flight (prototype) unknown Operational Service unknown
Manufacturer Dai-Ichi Kaigun Koku Gijitsusho, Yokosuka (1st Naval Air Technical Arsenal, Yokosuka) Number produced unknown
Metric system
Length unknown Height unknown
Empty weight unknown Operational weight unknown
Wing Span unknown Wing Aspect ratio unknown
Wing Area unknown Service ceiling unknown
Maximum speed unknown Cruising speed unknown
Initial climb rate unknown Range unknown
Fuel capacity internal unknown Fuel capacity external Up to 660 liters in two 330 liters drop tanks
Machine guns unknown Cannons unknown
Bomb load unknown Torpedoes/rockets unknown

Technical data on the Yokosoka D4Y4 Suisei
Powerplant 0 × , rated at 0 hp (0 kW) each Role during war
Length unknown Height unknown
Empty weight unknown Operational weight unknown
Wing Span unknown Wing Aspect ratio unknown
Wing Area unknown Service ceiling unknown
Maximum speed unknown Cruising speed unknown
Initial climb rate unknown Range unknown
Fuel capacity internal unknown Fuel capacity external Up to 145 Imp gal (174 US gal) in two 72 Imp gal (87 US gal) drop tanks
Machine guns unknown Cannons unknown
Bomb load unknown Torpedoes/rockets unknown
Crew unknown Naval or ground based unknown
First flight (prototype) unknown Operational Service unknown
Manufacturer Dai-Ichi Kaigun Koku Gijitsusho, Yokosuka (1st Naval Air Technical Arsenal, Yokosuka) Number produced unknown
Metric system
Length unknown Height unknown
Empty weight unknown Operational weight unknown
Wing Span unknown Wing Aspect ratio unknown
Wing Area unknown Service ceiling unknown
Maximum speed unknown Cruising speed unknown
Initial climb rate unknown Range unknown
Fuel capacity internal unknown Fuel capacity external Up to 660 liters in two 330 liters drop tanks
Machine guns unknown Cannons unknown
Bomb load unknown Torpedoes/rockets unknown

Here is a quick overview of all different versions, without the full technical specifications:

Different versions of the Yokosuka D4Y  Suisei
Yokosuka D4Y1 Suisei (Comet) Pre-produktion version, identical to the prototype.
Number built: 660 D4Y1 plus unknown out of 215 built by Dai-Juichi Kaigun Kokusho at Hiro
Yokosuka D4Y1-C Suisei This pre-production version was based on the initial (dive-bomber) prototype's but since the D4Y was unfit to perform as such was converted to the reconnaissance role. This version had a K-8 in the fuselage, and were powered by 1 × Aichi AE1P Atsuta 12 inverted-Vee, rated at 1,200 hp (895 kW). Other technical details are: height was 12 ft 0.75 inch (3,68 m), empty weight of 5,379 lb (2.440 kg), normal take-off weight of 8,047 lb (3.650 kg), max take-off weight of 9,370 lb (4.250 kg), max level speed of 343 mph (552 km/h) at 15,585 ft (4.750 m), cruising speed of 265 mph (426.5 km/h) at 9,845 ft (3.000 m), max range of 2,417 miles (3.890 km), typical range of 978 miles (1.574 km), climb to 9,845 ft (3.000 m) in 5 minutes 14 seconds, and service ceiling of 32,480 ft (9.900 m).
Number built: 660 D4Y1 plus unknown out of 215 built by Dai-Juichi Kaigun Kokusho at Hiro
Yokosuka D4Y1 KAI Suisei This dive-bomber sub version of the D4Y1 was fitted with catapult equipment to operate from small Japanese carriers.
Number built: 660 D4Y1 plus unknown out of 215 built by Dai-Juichi Kaigun Kokusho at Hiro
Yokosuka D4Y2 Model 12 Suisei Although the Japanese designers should hav elearned from the fact that their aircraft were too vulnerable, as proven during the 'Great Marianas Turkey Shoot' they failed to do something about it.
Because it was difficult to enhance the structure without too much redesign, they opted to work on the performance of the aircraft. This version therefor was powered by 1 × Aichi AE1P Atsuta 32, rated at 1,400 hp (1.044 kW). Other technical details: empty weight of 5,809 lb (2.635 kg), normal take-off weight of 8,455 lb (3.835 kg), max take-off weight of 10,192 lb (4.623 kg), max level speed of 360 mph (579 km/h) at 17,225 ft (5.250 m), cruising speed of 265 mph (427 km/h) at 6,560 ft (2.000 m), max range of 2,239 miles (3.603 km), typical range of 909 miles (1.463 km), climb to 9,845 ft (3.000 m) in 4 minutes 36 seconds, and a service ceiling of 35,105 ft (10.700 m).
Number built: 326 D4Y2 plus unknown out of 215 built by Dai-Juichi Kaigun Kokusho at Hiro
Yokosuka D4Y2a Model 12A Suisei This version was identical to the Yokosuka D4Y2 Model 12 Suisei, save for one thing: The 1 × 0.303 inch (7,92 mm) Type 1 machine gun in the rear cockpit was replaced by 1 × 0.51 inch (13 mm) Type 2 machine gun
Number built: 326 D4Y2 plus unknown out of 215 built by Dai-Juichi Kaigun Kokusho at Hiro
Yokosuka D4Y2-C Suisei This version was the reconnaissance version of the D4Y2 Suisei
Number built: 326 D4Y2 plus unknown out of 215 built by Dai-Juichi Kaigun Kokusho at Hiro
Yokosuka D4Y2-Ca Suisei This version was the reconnaissance version of the D4Y2a Suisei
Number built: 326 D4Y2 plus unknown out of 215 built by Dai-Juichi Kaigun Kokusho at Hiro
Yokosuka D4Y2 KAI Model 22 Suisei This version was was the catapult-capable attack bomber version of the D4Y2
Number built: 326 D4Y2 plus unknown out of 215 built by Dai-Juichi Kaigun Kokusho at Hiro
Yokosuka D4Y2a KAI Model 22A Suisei This version was was the catapult-capable attack bomber version of the D4Y2a
Number built: 326 D4Y2 plus unknown out of 215 built by Dai-Juichi Kaigun Kokusho at Hiro
Yokosuka D4Y2-S Suisei-E This version was a conversion of the D4Y2, specifically for the night-fighter role. It had the bomb-racks, trainable gun and carrier equipment removed, and the weapons bay was faired over. Fixed forward-firing armament was revised to 2 × 0.303 inch (7,7 mm) Tyoe 97 guns in the upper nose, and 1 × 20 mm Type 99 model 2 cannon was installed in the central fuselage to fire obliquely forward and upward in a 30 dgree angle. This cannon was meant to fire into the belly of target bombers much like the German Schräge musik installation. Under the wings provisions were made to install air-to-air rockets. Although these aircraft entered service, they were not very effective due to the lack of radar and because of the poor climb rate.
Number converted: unknown
Yokosuka D4Y3 Model 33 Suisei In the early versions the Suisei was hard to keep serviceable since the liquid-cooled Atsuta engines were unreliable and difficult to maintain. Already since the beginning there were voices heard that argued the Suisei should be powered by an air-cooled radial, the type of engine Japan had experience with and trusted. As soon as time permitted the Aichi design team therefor looked for a radial engine to mate with the D4Y airframe. The Mitsubishi MK8P Kinsei 62 radial, rated at 1,560 hp (1.163 kW), was selected. Tha fact that the fuselage was quite narrow had te be taken into consideration by the design team. They succeeded in creating a low-drag, close-fitting cowling with a supercharger air inlet in the upper lip. Flight trials showed that performance was rougly the same as the D4Y2, the gain being easier maintenance and greater reliability. You have to take into consideration that reliability of the engine is important for a naval single-engine aircraft with a long range. The drawback was the fact that the forward and downward view of the pilot worsened, hampering carrier operations. Late production aircraft also received provisions for RATO units (Rocket Assisted Take Off) to improve take-off from smaller aircraft carriers.
Number built: 536 D4Y3 plus unknown out of 215 built by Dai-Juichi Kaigun Kokusho at Hiro
Yokosuka D4Y3a Model 33A Suisei This version was identical to the D4Y3, but had it's 0.303 inch (7,7 mm) defensive gun replaced by a 0.51 inch (13 mm) gun.
Number built: 536 D4Y3 plus unknown out of 215 built by Dai-Juichi Kaigun Kokusho at Hiro
Yokosuka D4Y4 Model 43 Suisei This version was the final production version. It was designed in 1944, when Japan was loosing on all fronts. Therefor it might not be surprising that it was designed as a single-seat kamikaze aircraft, armed with 1 × 1,764 lb (800 kg) bomb partly inside the fuselage and provision for three RATO units. These units could either be used for take-off of small carriers, or to boost the final dive onto the target. The type’s gun armament was limited to 2 × 0.303 inch (7,7 mm) fixed forward-firing machine guns, and other details are: empty weight of 5,809 lb (2.635 kg), normal take-off weight of 10,013 lb (4.542 kg), max take-off weight of 10,463 lb (4.746 kg), max level speed of 350 mph (563 km/h) at 19,355 ft (5.900 m), cruising speed of 230 mph (370 km/h) at 9,845 ft (3.000 m), max range of 1,611 miles (2.593 km), typical range of 1,024 miles (1.648 km), climb to 16,405 ft (5.000 m) in 9 minutes 22 seconds, and a service ceiling of 27,725 ft (8.450 m).
Number built: 296
Yokosuka D4Y5 Suisei This version was still under development when Japan surrendered. The powerplant was 1 × Nakajima JK9C Homare 12 radial, rated at 1,825 hp (1.361 kW), driving a four-blade metal propeller of the constant-speed type. Also, more armor protection for the crew and fuel tanks were installed.
Number built: 0
Navy Type 2 Carrier Reconnaissance Aircraft Model 11 Official designation for the D4Y1-C
Redesignated aircraft
Navy Carrier Bomber Suisei Model 11 Official designation for the D4Y1
Redesignated aircraft
Susei Carrier Bomber Model 12 Official designation for the D4Y2
Redesignated aircraft
Susei Carrier Bomber Model 12A Official designation for the D4Y2a
Redesignated aircraft
Navy Type 2 Carrier Reconnaissance Aircraft Model 12 Official designation for the D4Y2-C
Redesignated aircraft
Navy Type 2 Carrier Reconnaissance Aircraft Model 12A Official designation for the D4Y2-Ca
Redesignated aircraft
Susei Carrier Bomber Model 33 Official designation for the D4Y3
Redesignated aircraft
Susei Carrier Bomber Model 33A Official designation for the D4Y3a
Redesignated aircraft
Suisei Special Attack Bomber Model 43 Official designation for the D4Y4
Redesignated aircraft
Suisei-E Night Fighter Official designation for the D4Y2-S
Redesignated aircraft
Susei Carrier Bomber Model 54 Official designation for the D4Y5
Redesignated aircraft

Operational remarks:

The Suisei saw first action during the Mattle for Midway. Two aircraft were embarked and stationed on the Soryu as reconnaissance aircraft, but these were lost when the carrier was sunk.
During the Battle of the Philippine Sea (a.k.a. Great Marianas Turkey Shoot) large numbers of Suisei were shot down, this was also because of the inexperienced aircrews. In June 1944 about 174 Suisei's were embarked on nine Japanese carriers to ward of the impending laniding of the American forces on the Marianas. These failed to sink a single American carrier, the main targets.
The Suisei was in the front line up until the day Japan surrendered. On August 15 Admiral Ugaki led eleven aircraft in the last Kamikaze attack near Okinawa. They failed to meet their objectives.

Strengths:

Weaknesses:

 

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© by Frans Bonné, 2000
Last revision: 5/27/02