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Aichi Experimental Three-seat Reconnaissance Seaplane (HD-28)
The Aichi Experimental Three-seat Reconnaissance Seaplane (HD-28) was the third of three Heinkel designs imported into Japan in 1926, and was tested for use as a long range reconnaissance aircraft.
Like many Japanese companies when Aichi decided to produce aircraft it began by creating a link with a European company, in this case Heinkel. The HD-25 and HD-26 were both designed as ship-borne reconnaissance aircraft. The HD-25 was produced in small numbers, but the HD-26 never progressed beyond testing.
The HD-28 was intended to serve as a long range reconnaissance aircraft. It was a single-span biplane, with a mixed wood and metal structure and a fabric covering. The fuselage was constructed around a frame of welded steel tubes, while the wings were wire-braced. The wings could be folded back for storage. The crew of three sat in tandem open cockpits.
The imported HD-28 was something of a disappointment. The Lorraine-Dietrich engine caused problems, and visibility was poor (a major failing in a reconnaissance aircraft). The Japanese Navy withdrew its interest in the design in 1928, but Aichi continued to modify the aircraft. First they installed a 450hp Nakajima Jupiter engine, compensating for the loss of power by making the aircraft smaller. The fuel tank was moved from the fuselage to the upper wing and the three seats were moved forward. These modifications didn't have the required effect, and a second set of changes were made. This time the wings were staggered and the lower wing was reduced in span, but again the changes were ineffective. Work on the HD-28 ended in 1929.
Although the HD-28 wasn't a success, Aichi learnt valuable lessons from its design, and the basic construction method was used on the AB-5 and AB-6.
Engine: Lorraine-Dietrich 18-III eighteen cylinder W-type water-cooled engine
Span: 49ft 2.5in
Length: 35ft 11in
Height: 13ft 8.25in
Empty weight: 5,214lb
Loaded weight: 8,488lb
Max speed: 125mph at sea level
Cruising speed: 93mph
Climb Rate: 19min 24sec to 9,843ft
Service ceiling: 14,763ft
Armament: Two forward firing 7.7mm machine guns, one flexibly mounted rear firing 7.7mm machine gun
Bomb load: Two 242lb bombs if same weight of fuel was removed
Operational history [ edit | edit source ]
The prototype was completed in February 1933 and made its maiden flight from Nagoya harbour. While it had good handling in the air, its speed and its take-off and landing performance was disappointing, and the aircraft was modified to try to improve matters, being fitted with revised wings, of different aerofoil section and with full-span leading edge slats, while the original Hamilton-Standard two-bladed metal variable pitch propeller was first replaced by a two-bladed wooden propeller and then a four-bladed wooden unit. Despite these changes, Kawanishi's design remained superior, and in 1934 was ordered into production as the Navy Type 94 Reconnaissance Seaplane, or Kawanishi E7K. ΐ] Α]
Initial deliveries of the He 60 were to Kriegsmarine training units in June 1933.  From 1934, the major production version, the He 60C began to be delivered to the shipboard floatplane units of the Kriegsmarine, operating from the catapults of all German cruisers.  It also saw action with Spanish Nationalist forces during the Civil War. 
In 1939 it was replaced as a shipboard aircraft first by the He 114 in service, then soon after by the Arado Ar 196, but it remained in service with several coast reconnaissance Staffeln (squadrons) when World War II began.  It had been withdrawn from front-line service by 1940, but returned to use following Germany's invasion of the Soviet Union in 1941, being used for coastal patrol work in the Baltic and Mediterranean Seas. All He 60s were removed from service by October 1943. 
Heinkel HD 28
From Wikipedia the free encyclopedia
The Heinkel HD 28 was a reconnaissance seaplane developed in Germany in the 1920s for export to Japan. It was a conventional single-bay biplane with equal-span, unstaggered wings and three cockpits in tandem. The fuselage was braced to both the upper and lower wings with a number of struts on its sides, in addition to the normal cabane struts. The rudder extended below the line of the lower fuselage, and there was a large ventral fin fitted. The rearmost cockpit incorporated a ring mount for a gunner.
A single example built by Heinkel and supplied to Aichi as a pattern aircraft, given the designation Aichi Experimental Three-seat Reconnaissance Seaplane, for possible production in Japan, but was rejected due to problems with the engine and also failure to meet performance and weight reduction targets.
Aichi Experimental Three-seat Reconnaissance Seaplane (HD-28) - History
Aichi E13A floatplane after surrender at Jacquinot Bay, New Britain 1945 (RNZAF Museum)
Country of origin:
Single-engine, twin-float, reconnaissance seaplane
One 791 kw (1,060 hp) Mitsubishi Kinsei 43 fourteen-cylinder two-row radial air-cooled engine
One flexible rear firing 7.7 mm (0.303 in) Type 92 machine gun provision to carry one 250 kg (551 lb) bomb or four 60 kg (132 lb) bombs or depth charges
In 1937 the Japanese Navy sought the design of a three-seat reconnaissance floatplane, and a specification was issued to a number of aircraft manufacturing companies. One of the designs entered in the competition was the E13A by Aichi, the designer being Kishiro Matsuo, the design having a Mitsubishi Kinsei 43 engine. The prototype was completed in late 1938 and during trials against the E12A1 produced by Nakajima, the E13A was found to be the best of the designs despite being larger in size and heavier, and was more stable and manoeuvrable.
Testing of the designs indicated the Aichi design provided the best performance, and the type was placed in production in December 1940 as the Navy Type O Reconnaissance Seaplane Model 1, later Model 11. Aircraft were produced by Aichi Tokei Denki KK (133), which was then directed to concentrate on production of the D3A and D4Y carrier bombers, and the remainder of production was by Dai-Juichi Kaigun Kokusho (48), and Kyushu Hikoki KK (1,237). The E13A received the Allied name ‘Jake” for record purposes.
The type was used extensively throughout the Pacific campaign and, in addition to reconnaissance operations, was used for air-sea-rescue, staff transport, shipping attack, and eventually kamikaze missions. It was regularly operated from Japanese Navy battleships, cruisers and seaplane tenders, as well as coastal bases. Occasionally it was used for bombing missions and a couple performed reconnaissance missions during operations against the Hawaiian Islands on 7 December 1941.
Its combat debut was in late 1941 when, operating from cruisers and seaplane tenders, examples made attacks on the Canton to Hankow railway in China and on anti-shipping patrols. Like many Japanese aircraft, it suffered from a lack of crew protection and had a limited defensive armament, but it was very successful on long patrol reconnaissance missions, having a maximum endurance of up to 15 hours. When Allied air opposition was limited, it was used in the bombing role, and on occasions was used for air-sea-rescue, staff transport, shipping attacks and, later in the war, Kamikaze attacks.
Two further models were produced, the E13A1a Model 11A, with improved radio equipment, and the E13A1b Model 11B, which was fitted with air-to-surface radar. An in-field modification was the installation of a flexibly mounted 20 mm Type 99 Model 1 cannon in a ventral position for use against shipping.
The type was operated from coastal bases in New Guinea and a couple of wrecks were left behind by retreating Japanese forces. Examples of wrecks have been located at Kavieng, Sohanbo Chand and Jacquinot Bay, and one which was surrendered at Kokopo at the Japanese floatplane base at Rabaul was later flown to Jacquinot Bay by a Royal New Zealand Air Force pilot. Plans at the time were to ship it to New Zealand as a museum piece but it was abandoned and not recovered to New Zealand due to lack of shipping space. It has been recorded that an example from the 954th Kokutai was shot down near Wesselklap on 10 May 1943.
One unusual event related to an E13A involved the 36.8 metre (301 ton) converted wooden fishing vessel which had been requisitioned by the Royal Australian Navy as HMAS Patricia Cam. This vessel had been obtained for minesweeping and had been fitted with one Oerlikon gun, two Vickers machine guns and a Browning gun. However, it was used to convey stores and passengers to small communities, military outposts, outlying missions and coastwatchers along the top end of Australia. It had a complement of two officers and 17 men.
On 22 January 1943 the vessel was heading from Millingimby Mission for Elcho Island. At 1.30 pm that day an Aichi E13A of the 734th Kokutai attacked the ship, dropping a bomb which hit the ship amidships, sinking the vessel within a minute. Most of the crew escaped into the water where the aircraft dropped another bomb on them, and then machine-gunned the survivors. The aircraft then landed and captured the Reverend Leonard Kentish of the Methodist Northern Australian Mission District and flew back to its base at Dobo on the Aru Islands 500 km (310 miles) north of Arnhem Land. The Reverend Kentish was interrogated by the Japanese, later executed and buried on 5 February 1943. In 1946 the perpetrators of this crime were tried, one being executed and the other two receiving life sentences. This is thought to be the only prisoner taken by Japanese forces in mainland waters during World War II.
Aichi Experimental Three-seat Reconnaissance Seaplane (HD-28) - History
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The significance of these dates may relate to the activities of the aircrew or the unit, rather than the aircraft, as may be seen below: On 29/9/39 a Do.18, K6+RK, of 2./Ku.Fl.Gr.506 was engaged in a fight with a Hudson, N7250 of 224 Squadron, over the North Sea. The Hudson crew believed that they had killed the front gunner of the Dornier during the fight, but in fact no-one was injured and the flying boat made good its escape with only minor damage from five bullets.
29/11/39 was a bad day for Ku.Fl.Gr.406 (the new designation of the amalgamated Ku.Fl.Gr.506), when five of the unit's Do.18s were lost on mining sorties. There was also an inconclusive engagement between a Saro London of 240 Squadron with a Do.18, possibly 6K+FH of 1./Ku.Fl.Gr.406, where both aircraft returned safely to base.
On 11/4/40, two days after the invasion of Norway, two Blenheim fighters of 254 Squadron on a strafing attack over the Hardangerfjord, met a Do.18, K6+AH, of 1./406 in the air at 17.40. The Dornier managed to inflict damage on both Blenheims, forcing them to break off the attack - the flying boat receiving just 6% damage.
اچایی ۵۱ای به عنوان مدلی از هاینکل اچایی ۴۹ که توسط برادران گونتر طراحی شده بود، با سفارش نیروی هوایی آلمان (فعالیت مخفی با توجه به محدودیتهای قرارداد ورسای) در ماه مه سال ۱۹۳۳ با عنوان هواپیمای آموزشی برای مخفی نگاه داشتن برنامه آلمان در توسعه نیروی هوایی خود  نخستین پروازش را انجام داد و سال بعد وارد خط تولید شد. اچایی ۵۱ای در بخش دم، بالها، ارابه فرود و رادیاتور با سلف خود مقداری تفاوت داشت.  این امر اچایی ۵۱ را پس از تشکیل رسمی نیروی هوایی آلمان در آوریل ۱۹۳۵ به نخستین جنگنده این نیرو تبدیل کرد. 
این هواگرد با طراحی سنتی به صورت دم چرخ، تمام فلزی با پوشش پارچه ای از موتور بامو ۶ خنک شونده با مایعات و دو مسلسل هماهنگ سازی شده با کالیبر ۷٫۹۲ میلیمتر بر روی موتور استفاده میکرد. ارابههای فرود این هواگرد ثابت و اتاقک خلبان زیر بال بالایی  و سر باز بود. اندازه بالهای آن متفاوت و بال بالایی اندکی جلوتر از بال پایینی بود. 
این هواپیما جهت جایگزینی آرادو آر ۶۵ طراحی شده بود اما به صورت همزمان با آرادو آر ۶۸ مورد استفاده قرار گرفت. نسخه اولیه اچایی ۵۱ بلافاصله پس از ورود به خدمت و با توجه به ضعف عیان عملکرد در مقابل آر ۶۸  منسوخ شده به حاسب میآمد، از همین رو تنها ۱۵۰ فروند از آن تولید شد. در ادامه اچایی ۵۱بی به عنوان نمونه بهبود یافته که شامل مدل آبنشین (اچایی ۵۱بی-۲) با ابزار شناوری آلومینیومی برای استفاده نیروی دریایی نیز میشد،  معرفی گردید. در این مدل جهت استحکام بیشتر از دو سیم برای تقویت ارابه فرود استفاده گردید و یک محفظه سوخت ۵۰ لیتری جداشونده نیز در زیر هواپیما تعبیه شد.  ۴۵۰ فروند از این نمونه تولید گردید. در نهایت ۱۰۰ فروند اچایی ۵۱سی که در طول جنگ داخلی اسپانیا با اتصال حداکثر ۶ بمب ۱۰ کیلوگرمی به زیر هواپیما به عنوان هواگرد تهاجمی طراحی گردید، نیز تولید شد.
در ماه اوت ۱۹۳۶ شش فروند اچایی ۵۱ با درخواست ژنرال فرانکو از آدولف هیتلر،  برای حضور در جنگ داخلی اسپانیا در جانب سلطنت طلبان به همراه شش خلبان آلمانی جهت آموزش  به این کشور ارسال گردید. در ابتدا این جنگنده در مقابل هواپیمای دوباله قدیمی تر جمهوری خواهان به موفقیتهایی دست یافت و تنها در روز اول شروع به کار خود در این کشور، چهار هواپیمای دشمن را ساقط کرد. با ادامه جنگ تعداد بیشتری از این هواپیما به اسپانیا اعزام شد و ۱۲ فروند از مورد استفاده نیرویهای «داوطلب» آلمانی موسوم به لژیون کرکس نیز قرار گرفت.
این دوره برتری کوتاه مدت با ورود هواپیمای مدرن تر شوروی از جمله پولیکارپوف آی-۱۵ و آی-۱۶ به خلبانی «داوطلبان»  به میدانها جنگ به پایان رسید. به توجه به ظرفیت آتش بیشتر  و سرعت بسیار بالاتر هواپیمایهای جدید دشمن اچایی ۵۱ دیگر نمیتوانست از نیروهای خودی محافظت کند. به همین جهت کاربرد این هواپیما به عملیاتهای شبانه تغییر کرد. با توجه به ناتوانی در مقابله با بمب افکنهای سریع تر دشمن، اچایی ۵۱ از خدمت به عنوان جنگنده کنار نهاده شده و تنها به صورت هواگرد تهاجمی مورد استفاده قرار گرفت.
با وجود شکست در وظایف خود به عنوان جنگنده، اچایی ۵۱ به صورت هواگرد تهاجمی موفق ظاهر شد و متخصصان نیروی هوایی آلمان را در طراحی عملیاتهای پشتیبانی هوایی نزدیک که در جنگ جهانی دوم به کار گرفته شد، یاری فراوان کرد. دست ۷۹ فروند از این مدل در اسپانیا در درگیریها حاضر شد.  با این حال بیشتر هواپیماهای اچایی ۵۱ ارسال شده به اسپانیا در طول جنگ از بین رفتند.
۴۶ فروند اچایی ۵۱ توانستند تا پایان جنگ داخلی اسپانیا سالم بمانند و با الحاق ۱۵ فروند دیگر تا سال ۱۹۵۲ در نیروی هوایی اسپانیا خدمت کنند.
اچایی ۵۱ فقط تا سال ۱۹۳۸ در خط مقدم نیروی هوایی آلمان نازی خدمت کرد و پس از آن تنها به عنوان هواپیمای آموزشی پیشرفته مورد استفاده قرار گرفت. با عدم موفقیت نسبی این هواگرد، آلمان نازی مجبور شد پیش از آنکه باید جنگنده مسرشمیت باف ۱۰۹ را وارد خدمت کند.
Specifications (K4Y1 seaplane)
Data fromJapanese Aircraft, 1910-1941 
- Crew: 2
- Length: 9.05 m (29 ft 8 in)
- Wingspan: 10.90 m (35 ft 9 in)
- Height: 3.51 m (11 ft 6 in)
- Wing area: 29.5 m 2 (318 sq ft)
- Empty weight: 740 kg (1,631 lb)
- Gross weight: 990 kg (2,183 lb)
- Powerplant: 1 × Gasuden Jimpu 2 seven-cylinder air-cooled radial engine, 97 kW (130 hp)
- Maximum speed: 163 km/h (101 mph, 88 kn) at sea level
- Cruise speed: 93 km/h (58 mph, 50 kn)
- Range: 310 km (200 mi, 170 nmi)
- Endurance: 3 hours 30 min
- Service ceiling: 3,460 m (11,350 ft)
- Time to altitude: 29 min 20 sec to 3,000 m (9,800 ft)
The Last IJN Carrier Aircraft
IJN Taihō was designed to carry 53 aircraft (24 A7M, 18 D4Y, 6 C6N plus 5 spares). Only D4Y were ready when she fought in Philippine Sea. Since her overall dimensions were approximately the same as the Shokakus but her hangar smaller she carried a small contingent on her flight deck so the distribution among the three ships was essentially equal.
The IJN Shinano’s organic air group was intended to consist of 18 Mitsubishi A7M Reppū (Allied reporting name “Sam”) fighters (plus two in storage), 18 Aichi B7A Ryusei (“Grace”) torpedo-dive bombers (plus two in storage), and 6 Nakajima C6N Saiun (“Myrt”) reconnaissance aircraft (plus one in storage). The remainder of the hangar space would have held up to 120 replacement aircraft for other carriers and land bases
Mitsubishi A7M Reppu
The Mitsubishi A7M Reppu was supposed to be the replacement for the struggling A6M, but never got past a prototype/test programme. It showed promise but also had many faults and could in no way be considered an active type. Large production orders were supposedly placed off the drawing board, but by this stage the Japanese had no operational carriers, so even if the war had dragged on for another couple of years, none would have ever put to sea. The Reppu never entered service mainly because of the constant change in specifications it was submitted to by the IJNAF Headquarters.
On May 6, 1945 The Mitsubishi A7M1, Navy Experimental 17-Shi Ko (A) Type Carrier Fighter Reppu (Hurricane) makes its first flight. The aircraft had been under development since 1942 as a replacement for the Mitsubishi A6M, Navy Type 0 Carrier Fighter, Allied Code Name “Zeke.” The A7M1 was as maneuverable as the “Zeke” but was underpowered and lacked performance. Only ten of these aircraft, given the Allied Code Name “Sam,” were built by Mitsubishi at Nagoya.
A7M3-J and A7M3 Model 23: The former was to have a turbocharged MK9A engine with a estimated speed of 403mph at 32,810ft., this height being reached in 15min. drawings completed in Nov. of 1944 and in Feb. of 1945, the mock-up was inspected by the Navy prototype was to be complete by October of 1945 but the close of the war prevented this. The latter was based on the A7M2 fuselage and had a MK9C powerplant had no folding wings and the pilot was provided with armored windscreens and aft fuel tankage armed with six Type 99 20mm cannon max speed of 399mph at 28,454mph prototype scheduled for completion in December of 1945 and thus was still under construction by war’s end.
Navy Carrier Attack Bomber Tenzan “Heavenly Mountain” Model 11 – Nakajima B6N2
In 1939 the Imperial Japanese Navy drew up its specification for a carrier-based torpedo-bomber to supersede the Nakajima B5N. The specifications issued by the navy called for very modern characteristics. A maximum speed of 288 mph (463 km/h), a cruising speed of 230 mph (370 km/h) and a range of 1,000 nautical miles (3335 km) without a bombload. To meet the requirement, Nakajima decided to use an airframe very similar to that of the earlier aircraft, differing primarily in its vertical tail surfaces. The navy had specified use of the Mitsubishi Kasei radial engine, but Nakajima decided to use instead its own 1,870 hp (1395 kW) Nakajima NK7A Mamoru 11 radial engine of similar output driving a four bladed Hamilton type propeller. The first of two prototypes was flown in spring 1941, but initial flight testing revealed a number of problems, including engine vibration and overheating, but the most serious was that of directional stability, requiring revised vertical tail surfaces. Final flight testing carried out aboard the aircraft carriers Ryuho and Zuikaku in the end of 1942, revealed further problems with the tuning of the engine and the need to reinforce the arrester hook and landing gear. It was not until February 1943 that the type entered production as the Navy Carrier Attack Bomber Tenzan Model 11, company designation Nakajima B6N1, incorporating a number of refinements as a result of extended flight testing. However, after only 135 production Tenzan (heavenly mountain) aircraft had been delivered a new crisis arose when Nakajima was ordered to terminate manufacture of the Mamoru engine, and use the more reliable 1,850 hp (1380 kW) Mitsubishi MK4T Kasei 25 engine, a step also taken to allow greater emphasis to be placed on production of the widely-used Nakajima Homare and Sakae engines.
The company was now compelled to use the engine which the navy had specified originally, the Mitsubishi Kasei, but fortunately the adaptation of the B6N airframe to accept this powerplant presented no major difficulties. The resulting aircraft, which was also the major production version, had the designation B6N2 and differed only from the B6N1 by the installation of the Mitsubishi Kasei 25 engine. The B6N2a variant had the rear-firing 7.7 mm (0.303 in) machine-gun replaced by one of 13 mm (0.51 in) calibre. When production ended, Nakajima had built a total of 1,268 B6Ns of all versions, this number including two modified B6N2 airframes which had served as prototypes for a proposed land-based B6N3 Model 13. The powerplant had been the improved 1,850 hp (1380 kW) Mitsubishi MK4T-C 25C version of the Kasei engine and the strengthened landing gear had larger wheels for operation from unprepared runways, but production did not start before the war ended. Allocated the Allied codename ‘Jill’, the B6Ns saw intensive use during the last two years of the war for conventional carrier operations and, in the latter stages, in kamikaze roles.
Nakajima B6N2 – Nakajima was ordered to cease using the Mamoru engine and use instead the Mitsubishi Kasei 25 engine, thus resulting in the redesignated B6N2. Although the Kasei 25 was slightly less powerful, this was offset by introducing a less drag version of the exhaust ports which also gave a slight jet-thrust like boost effect.
Nakajima B6N2a – This type differed from the B6N2 only by having a rear firing machine gun of 13 mm (0.51 in) calibre, instead of the 7.7 mm (0.303 in) type used on the B6N2.
Nakajima B6N3 – Two conversions of the B6N2a resulted in the B6N3 prototypes equipped with 1,850 hp (1380 kW) Mitsubishi MK4T-C Kasei 25C engines for evaluation as land-based bombers.
Nakajima C6N Saiun reconnaissance aircraft
The three-seat Nakajima C6N Saiun, of which 463 were produced, was one of the few World War II reconnaissance aircraft specifically designed for operating from carriers. With a maximum speed of 379 mph, a maximum range of 3,300 miles, and service ceiling of 34,236 ft, the C6N proved virtually immune from Allied interception. Unfortunately for Japan, it did not become available for service until the Mariana Islands Campaign in the summer of 1944.
Identifying the need for a long-range carrier-based reconnaissance aircraft, as a result of early experience in the Pacific war, the Imperial Japanese Navy drew up a specification which it issued to Nakajima in early 1942 for an aircraft to meet this requirement. The combination of high-speed, long-range and carrier compatibility presented considerable problems which Nakajima resolved by adopting its own efficient 1,820-hp (1358-kW) NK9B Homare 11 engine and incorporating in the wing design leading-edge slats and a combination of Fowler-type and split trailing-edge flaps. Appearing similar in external configuration to the company’s B6N, the Nakajima C6N had a fuselage also accommodating a crew of three, but the lower surfaces and sides of the structure incorporated camera ports and observation windows.
The first C6N1 prototype made its maiden flight on 15 May 1943, but disappointing performance of the Homare 11 engine led to 18 more prototypes/preproduction aircraft, some tested with the more powerful Homare 21, before the type was ordered into production in early 1944 as the Navy Carrier Reconnaissance Plane Saiun (painted cloud) which had the company designation Nakajima C6N1. Entering service in the summer of 1944, these aircraft soon demonstrated their long-range capability in keeping a watchful eye on the US fleet, and their speed was good enough to give them almost complete immunity from interception by Allied fighters. The type played a significant role in the closing stages of the war and a total of 463 had been built by Nakajima when production ended in August 1945. Originally designed for high-speed reconnaissance, Nakajima’s C6N, known to the Allies as “Myrt,” proved especially capable despite the absence of onboard radar. A small number of C6N1-S two-seat night fighter conversions from C6N1s, armed with two 20- mm cannon mounted to fire obliquely forward and upward. At least six C6N1s were converted with obliquely angled 20mm or 30mm cannons as the C6N1-S. One C6N2 which was flown with a prototype installation of a 1,980-hp (1476-kW) Homare 24 turbocharged engine. Projected, but not built, were the C6N1-B carrier-based attack bomber and the C6 3 night-fighter powered by the Homare 24 engine.
This outstandingly clean aircraft was an example of Japanese specialization defeated by circumstances. No other nation built a purpose-designed carrier-based reconnaissance aircraft in World War II. and the 17-Shi (spring 1942) specification was very challenging. The C6N was faintly like a Fw 190 stretched to seat a pilot, navigator/observer and radio operator/gunner in tandem As evidence of advanced design, the flaps were tabbed Fowlers, and the laminar-section wing (only slightly larger than a Zero’s) also had drooping ailerons and slats, and was almost entirely given over to six integral tanks. The troublesome Homare was beautifully cowled and had thrust-giving ejector exhausts. Another feature that was new to Japan was thick-skinned structure, reducing the numbers of parts and cutting the number of rivets from 220.000 for a Zero to under 100.000. Altogether 463 of these speedy machines were built, but need for the C6N1-B was swept away by loss of the carrier force.
Yokosuka D4Y Suisei dive-bomber
The Yokosuka D4Y (“Judy”) reconnaissance/dive-bomber entered service on Japanese carriers early in 1943 and was very fast for a bomber. Initially assigned to reconnaissance units, it was intended to replace the D3A, but it was insufficiently armed and protected and suffered from structural weakness in dives. In common with most other Japanese aircraft, it was used for kamikaze attacks, and a D4Y carried out the last kamikaze attack of the war on 15 August 1945. A total of 2,819 D4Ys were built.
Well-proportioned and purposeful in appearance, the Yokosuka D4Y possessed an excellent performance and owed much of its concept to the German He 118, for whose manufacturing rights Japan negotiated in 1938. Designed as a fast carrier-based attack bomber and powered by an imported Daimler-Benz DB 600G engine, the D4Y1 was first flown in December 1941 D4Y1-C reconnaissance aircraft were ordered into production at Aichi’s Nagoya plant, the first of 660 aircraft being completed in the late spring of 1942. The first service aircraft were lost when the Soryu was sunk at Midway. Named Suisei (comet) in service and codenamed ‘Judy’ by the Allies, many D4Yls were completed as dive-bombers, and 174 Suiseis of the 1st, 2nd and 3rd Koku Sentais were embarked in nine carriers before the Battle of the Philippine Sea. However, they were intercepted by American carriers, and suffered heavy casualties without achieving any success. A new version with 1044-kW (1,400-hp) Aichi Atsuta 32 engine appeared in 1944 as the D4Y2 but, in the interests of preserving high performance, nothing was done to introduce armour protection for crew or fuel tanks, and the sole improvement in gun armament was the inclusion of a 13.2-mm (0.52-in) trainable gun (replacing the previous 7.92-mm/0.31-m gun) in the rear cockpit. This version suffered heavily in the battle for the Philippines. Problems of reliability with the Atsuta (DB 601) engine led to adoption of a Kinsei 62 radial in the D4Y3, and this engine was retained in the D4Y4 which was developed in 1945 as a single-seat suicide dive-bomber. A total of 2,038 production D4Ys was completed.
These early versions of the D4Y were difficult to keep in service because the Atsuta engines were unreliable and difficult to maintain in front line service. From the beginning some had argued that the D4Y should be powered by an air-cooled radial engine, a type Japanese engineers had experience with and trusted. The aircraft was therefore fitted with the reliable Mitsubishi MK8P Kinsei 62, a fourteen-cylinder two-row radial engine. This version was the Yokosuka D4Y3 Model 33.
Flight trials showed that performance was roughly the same as the D4Y2, the gain being easier maintenance and greater reliability. Although the new engine improved ceiling and rate of climb (over 10,000 m, and climb to 3,000 m in 4.5 minutes, instead of 9,400 m and 5 minutes), the higher fuel consumption resulted in shorter range and a slower cruise speed, while the bulky engine obstructed the forward and downward view of the pilot, hampering carrier operations. These problems were tolerated because of the increased availability of the new variant. Late production aircraft also received provisions for RATO units (Rocket Assisted Take Off) to improve take-off from smaller aircraft carriers.
B7A2 Unit: Kougeki (Attack) 5th Hikotai, 752nd Kokutai Serial: 752-03 Katori Naval Air Base, Chiba prefecture, end of April 1945.
Aichi’s B7A Ryusei torpedo bomber
Aichi’s B7A Ryusei torpedo bomber (‘Grace’) was part of the 16-Shi (1942) programme. It was intended to extend the reach of Japanese carriers and thus to minimise the problem of carrier air defence: if the Japanese fleet could outreach the US fleet, and if its aircraft could penetrate US defences, then it could strike without being struck. The Japanese consistently managed to outrange the US fleet, but the combination of effective fighter control and effective anti-aircraft fire made that outreach useless. The Ryusei was intended to replace both the standard attack aircraft: the B6N torpedo bomber and the D4Y dive bomber. Given enough engine power, an airframe stressed to dive-bomb could lift a torpedo. That was the case with both the US SB2C Helldiver (although it was not used as a torpedo bomber) and the British Barracuda (a torpedo bomber used exclusively as a dive bomber). Maneuverability was to be equal to that of a Zero (A6M) fighter, to give the Ryusei reasonable immunity from interception. Normal range was to be 1000nm (maximum 1800nm). The prototype was completed in May 1942. Note that the operational concept considerably predated Midway. Production seems to have been hampered by slow engine development, as it did not begin until April 1944.
In June 1944, IJN Taihō, the only Imperial Japanese Navy aircraft carrier then large enough to operate the B7A Ryusei in its intended role, was sunk during the Battle of the Philippine Sea before enough B7As were even available to embark. Thereafter, the B7A was relegated to operating from land bases, primarily with the Yokosuka and 752nd Air Groups. The Japanese completed only one other carrier capable of operating the B7A, IJN Shinano, but she was sunk by an American submarine. Around 110 Ryusei aircraft were completed.
US Hellcats from VF-15 flying off USS Essex attack a formation of ‘Jills’ and ‘Zeros’, 19 June 1944. (Jim Laurier © Osprey Publishing)
Philippine Sea – The End of IJN Carrier Power
The encounter in the Philippine Sea was almost exclusively a carrier battle, the fifth of the Pacific War and by far the largest ever fought. Fifteen fleet and light carriers took part on the American side and nine on the Japanese. For sheer size alone, the Battle of the Philippine Sea was the second largest naval engagement of the Pacific War, surpassed only by the Battle of Leyte Gulf fought a few months later.
In line with the planning for the seizure of the Marianas, the US Navy expected a major reaction from the Imperial Japanese Navy. As a result, the destruction of the Japanese carrier fleet was one of the operation’s primary objectives. The Japanese Navy had been hoarding its carriers for almost 20 months, and its commitment to defend the Marianas was planned to be a decisive encounter with the US Navy.
Admiral Raymond A. Spruance, commander of the US Fifth Fleet, had the primary mission of conducting the Marianas invasion (Operation Forager) and defeating any Japanese naval reaction. Spruance issued his plan on 12 May 1944: the Fifth Fleet’s mission was to capture Saipan, Tinian and Guam while being ready to ‘drive off or destroy enemy forces attempting to interfere with the movement to or the landing operations at each objective.’ To achieve this, Task Force 58 would take up position to the west of the Marianas, ready to respond to any Japanese counter-attack.
On 15 June 1944, in response to the preliminary air and naval attacks on Saipan, Tinian and Guam, the Japanese activated Operation A-Go to defend the Marianas. The Japanese First Mobile Fleet, under Vice Admiral Ozawa Jisaburo, departed the Guimaras and entered the Philippine Sea later that day, where it was spotted by an American submarine. Two days later, the fleet was again spotted, this time by the submarine Cavalla, 700 nautical miles west of Guam, and by 18 June it was within 400 nautical miles of US Task Force 58. By now, Spruance had decided to await the Japanese fleet and fight a defensive battle.
A first wave of Japanese search aircraft was launched at 4.45am on 19 June, and gained contact with Task Force 58. The first Japanese strike raid against Task Force 58 comprising 69 aircraft was launched at 8.30am US radar picked up the raid while still 125 nautical miles distant, and just after 10.20am, Task Force 58 launched all available fighters. The first Japanese attack aircraft were intercepted just over ten minutes later. Only 17 aircraft would eventually return to the Japanese carriers.
The second Japanese strike force, featuring the best-trained aviators in the First Mobile Fleet and consisting of 128 aircraft (48 ‘Zero’ fighters, 53 ‘Judy’ dive-bombers and 27 ‘Jills’ with torpedoes), left the Japanese carriers at 8.56am, and comprised the largest Japanese attack of the day. The flight was detected by US radar at 11.07am. It suffered even greater losses than the first attack wave: a mere 31 planes made it back out of the original 128.
The third attack launched at 10.00am, comprising 15 fighters, 25 ‘Zeros’ with bombs, and seven ‘Jills’ with torpedoes. From this wave, 40 out of 47 aircraft returned to the ships, chiefly because the contact location given to the aircrews turned out to be erroneous with no US ships present seven of the returning aircraft were intercepted by US fighters, however, and shot down.
A fourth Japanese attack was launched at 11.00am, comprising 30 ‘Zero’ fighters, ten ‘Zeros’ with bombs, 36 dive-bombers (27 ‘Vals’ and nine ‘Judys’) and six ‘Jills’. These 82 aircraft were directed at another non-existent contact and, after finding nothing, split into three smaller groups. The final tally was dismal: only nine returned to their carriers, with 30 of them having been shot down over Guam. Despite these heavy losses, no American ships were hit.
Some of the Japanese attack aircraft did make it through to the US ships. In Task Group 58.7, one hit was scored on the battleship USS South Dakota and near misses were recorded on two of its cruisers just before 10.50am, from Japanese aircraft in the first attack wave. Around 12.00pm, remnants of the second Japanese attack inflicted minor damage on the carriers USS Wasp and Bunker Hill.
US submarines also inflicted damage on the First Mobile Fleet. At 9.09am, the Japanese carrier Taiho was hit by a torpedo from the submarine Albacore, and at 12.22pm the submarine Cavalla torpedoed the carrier Shokaku. The latter sank just after 3.00pm with heavy loss of life. A massive explosion ripped apart the Taiho at 3.32pm, and she followed Shokaku to the bottom.
By the end of 19 June, Task Force 58 was heading west to engage the Japanese First Mobile Fleet. Morning searches the following day failed to locate the carrier force, but at 3.40pm it was finally spotted and Spruance decided to launch an all-out attack with 216 US aircraft. Once detected, the First Mobile Fleet took evasive action to the north-west in an attempt to avoid the attack. Between 6.40 and 7.10pm, the US aircraft made a series of hasty attacks on the First Mobile Fleet, striking the carrier Hiyo with a torpedo, and damaging two other carriers, two escorts and two oilers. The Hiyo sank just after 8.30pm. Shortly after, Vice Admiral Ozawa was ordered to break off action and head for Okinawa, and the following day, Spruance ordered Task Force 58 to abandon its pursuit of the First Mobile Fleet.
The Battle of the Philippine Sea was certainly a decisive encounter. In only ten days in mid-June, the Americans realized all their major objectives and the Japanese Navy suffered a major defeat. Most of its carriers escaped, but their aircraft and trained aircrews did not. This effectively meant the end of the Japanese Navy as a major threat to future American moves in the Pacific, and led directly to the desperate and ill-conceived Japanese plan to defend Leyte in October that resulted in the final destruction of the Japanese Navy.
The Battle of the Philippine Sea clearly demonstrated to key leaders in the Imperial Japanese Navy that there was no future in conventional air attacks against the US Navy. The solution was the adoption of suicide missions that would increase in ferocity until the end of the war.