Japanese light bombers and reconnaissance aircrafts

[gekho]

When the Pacific War exploded in all its fury on December 7, 1941, the Nakajima B5N2 carrier torpedo bomber was the best in service with any of the world's navies. One hundred and forty-four aircraft of this type participated in the Pearl Harbor attack as torpedo and level bombers, and they crippled the American Pacific Fleet's battleship force. During the following twelve months, carrier-based B5N2s were to participate in sinking three American aircraft carriers, while land- and carrier-based B5N2s supported Japanese amphibious landings on all fronts. But by 1944, the Kate, as it was code-named by the Allies, was plainly obsolete, and so it finished out the war in second-line units, mainly as an anti-submarine patrol plane. The Japanese Navy never regarded its B4Y1 biplane torpedo bomber (a contemporary of the essentially similar Fairey Swordfish) as anything other than a stop-gap type, because they wanted a monoplane torpedo bomber with performance more compatible with that of the Mitsubishi A5M carrier fighter (which see). They issued, in 1935, a specification calling for a single-engined monoplane "carrier attack bomber" (as the Japanese termed torpedo bombers). The requirements called for: (1) a wingspan of less than 52 ½ ft. with provision for hydraulic wing folding to reduce the plane's span to no more than 24 ft. 7 9/32 in.; (2) an armament of one 1,764-lb. torpedo and a single rearward-firing 7.7mm machine gun for protection; (3) a maximum speed of 207 mph at 6,560 ft.; (4) a normal endurance of 4 hours or a maximum of 7 hours at 155 mph; (5) a normal crew of three; and (6) either a Nakajima Hikari or Mitsubishi Kinsei radial engine.

Katsuji Nakamura's design team at Nakajima created a beautifully clean low-wing monoplane with a hydraulically-operated retracting undercarriage. The large wing folded upwards, and the hinging points were so arranged that the wingtips overlapped one another when folded above the cockpit. When compared to the large wing, the fuselage seemed oddly small, but it was kept relatively short at 33 ft. 9 ½ in. to fit on the Navy's standard carrier elevators. Other innovations on the Type K, as the company named its creation, were Fowler flaps and a variable-pitch propeller. Powered by the Nakajima Hikari 2 nine-cylinder radial engine, the prototype, given the official designation B5N1, first flew in January 1937. Hydraulic-system difficulties marred the initial flight tests, but the troubles were soon fixed, and the JNAF was particularly pleased with the B5N1's speed, which at 230 mph exceeded the requirement by a comfortable margin.But they were worried that the many technical innovations being introduced by the new aircraft would make it excessively hard to maintain under operational conditions. Nakajima accordingly simplified the second prototype, changing the Fowler flaps to more conventional types and replacing the hydraulic wing-folding mechanism with a manual one. It also had a newer Hikari 3 engine with a constant-speed propeller-the first ever fitted to a production Japanese naval plane of any type-and integral wing fuel tanks with increased capacity. In this form the B5N1 easily won the competition with Mitsubishi's B5M1, and it went into production in November of 1937 as the Navy Type 97 Carrier Attack Bomber Model 11 (B5N1 Model 11).

Carrier qualification trials were carried out at the same time the new bomber was flying its first combat missions in China in the spring of 1938. Armed with bombs, the B5N1 was used as a single-engined level bomber, in a fashion similar to a twin-engined machine. The observer, who was seated between the pilot and the rear gunner/radio operator, was also the bombardier during these missions; he would aim the bombs using a pair of small folding doors in the floor of the fuselage to see his target. Covered by A5M fighters, the B5N1 was a success despite its lack of protection for the crew and fuel and its modest defensive armament of a single 7.7mm machine gun. No major modifications were necessary for China operations, and the only minor change made was to add a mast antenna to replace the trailing antenna. But the JNAF was aware that there would be other opponents than the Chinese, and so in 1939 they instructed Nakajima to develop a better-performing variant of the B5N1. The B5N2 Model 12, or Type 97 Carrier Attack Bomber Model 12, first flew in December 1939; it was externally similar to the older variant aside from its engine, a Nakajima Sakae 11 fourteen-cylinder radial. A tighter-fitting cowling was used, to improve pilot view and reduce drag, and a small hub was fitted to the propeller to further reduce drag and improve the engine cooling. Oddly the B5N2 was not much faster than the B5N1 in spite of the 36% increase in power, but the Navy was pleased, as the Sakae was more reliable than the Hikari, and the B5N2 would fly most of its missions over long stretches of water.

 

[gekho]

By the time of the Pearl Harbor attack, the B5N2 had totally replaced the B5N1 in all front-line units, both land- and carrier-based. Commander Mitsuo Fuchida was the aerial commander for the Hawaiian Operation; he flew in a B5N2 as observer/bombardier, and was also lead bombardier of the 49 Kates used as level bombers in the first wave. All of the B5N2 level bombers carried a single 1,653-lb. bomb made from a remanufactured armour-piercing shell. The 40 planes earmarked for the actual torpedo attack were led by Lt. Cdr. Shigeharu Mutara, considered the finest torpedo bomber pilot in the Imperial Navy if not the world. His planes were carrying a specially modified torpedo for use in shallow harbours like Pearl; the idea had been gleaned from study of the British attack on Taranto, Italy, in December 1940, where Swordfish torpedo bombers had sunk or crippled a number of Italian battleships. Stupidly, the United States had ignored the lessons of Taranto, and had disdained using torpedo nets at Pearl; they paid heavily for their neglect. Between the high-level bombers and the torpedo planes, the US Navy lost two battleships sunk outright, three more sunk but recoverable with difficulty, and three damaged heavily (the Pennsylvania, in dry dock, was damaged by dive bombers and strafing fighters). But that did not end the B5N2's career. In the furious carrier battles of 1942, the Nakajima torpedo bomber played a prominent role in sinking the American carriers Lexington, Yorktown, and Hornet. But in all those battles losses were very heavy; Lt. Cdr. Murata, for example, was killed in the Battle of Santa Cruz, shot down by US Navy fighter ace Lt. (j.g.) Stanley "Swede" Vejtasa. Murata was just one of seven kills Vejtasa scored that day, October 26, 1942 (in 1969, Vejtasa, as a captain, was commander of Miramar NAS, and was one of the founders of the "Top Gun" training program).

The Kate did most of its later combat flying from land installations, figuring prominently in the Solomons, Marianas, and Philippines campaigns. Its last carrier-based engagement was the Battle of the Philippine Sea in June 1944. Insufficient performance, and poor crew and fuel-tank protection, contributed to staggering losses in all these campaigns, and so the Kate was relegated to second line and training units by the end of 1944. But the B5N2 found a new lease on life because it still had excellent long range endurance; it was used for maritime reconnaissance and anti-submarine patrol, in areas where Allied fighters were unlikely to be encountered. The B5N2 gave Japanese convoys desperately needed escort against the depredations of Allied submarines. Some B5N2s were fitted with a primitive form of ASV (Air-to-Surface-Vessel) radar, with antennas fitted along the rear fuselage sides and the wing leading edges, and others were given Jikitanchiki magnetic airborne submarine detection gear. The most war-weary B5N2s joined B5N1s in service as trainers, target-tugs, and even tow planes for gliders. One thousand, one hundred and forty-nine B5Ns were built, 669 by the parent company Nakajima between 1936 and 1941, 200 by Aichi in 1942-43, and 280 by the Naval Air Arsenal at Hiro in 1942-43. The B5N Kate enjoyed a brief status as the finest torpedo bomber in the world, and helped bring Japan to its pinnacle as an Empire; but eventually, its increasingly poor performance and protection left it outclassed, and it finished its operational life as a supernumerary, a spear-holder, as it were.

 

[vikingBerserker]

Excellent!

 

[gekho]

At a time when the triumphs of the B5N were still almost three years in the future, the Japanese navy issued a specification for a replacement, recognizing that only limited overall design improvement of the B5N could be achieved in the B5N2. Accordingly design went ahead in 1939 of the Nakajima B6N and, despite the navy's preference for the Mitsubishsi Kasei radial, a Nakajima Mamoru was selected for the prototype which flew early in 1941. Superficially the B6N Tenzan (heavenly mountain) resembled the earlier aircraft, but the much increased power and torque of the big engine and four-blade propeller was found to impose considerable directional stability problems, demanding that the vertical tail surfaces be offset to one side. Flight trials dragged on, and were further delayed by troubles during carrier acceptance tests; then Nakajima was ordered to stop production of the Mamoru engine, so modifications had to be introduced to suit installation of the Kasei. In due course B6N1 aircraft (of which only 133 were built) were embarked in the carriers Shokaku, Taiho, Hiyo, Junyo and Zuikaku, and took part in the great Battle of the Philippine Sea of June 1943, many being lost when the three first-named carriers were sunk. In that month production started of the slightly improved B6N2 (of which 1,133 were produced before the end of the war), but the heavy losses among Japanese carriers resulted in the 'Jill' being largely deployed ashore, particularly after the Battle of Leyte Gulf. Thereafter many BSNs were consigned to the kamikaze role.

 

[gekho]

Early experience in the Pacific war showing the need for a long-range carrier-based reconnaissance aircraft, Nakajima was instructed in early 1942 to develop an aircraft to meet this Imperial Japanese Navy requirement. It resulted in an airframe similar to that of the company's B6N, the fuselage incorporating camera ports and observation windows, with power provided by a 1358kW Nakajima Homare 11 radial engine. The first prototype flew on 15 May 1943, its performance being disappointing with the Homare 11 engine, and 18 more prototype/pre-series aircraft followed, some with the more powerful Homare 21 engine, before the type was ordered into production in early 1944 as the Navy Carrier Reconnaissance Plane Saiun (Nakajima C6N1). Allocated the Allied codename 'Myrt' when it entered service in the summer of 1944, the Saiun (painted cloud) was fast enough to enjoy almost complete immunity from interception by Allied fighters. A total of 463 had been built' when production ended in August 1945, the total including a small number of C6N1-S two-seat night-fighter conversions from C6N1 aircraft, and one C6N2 prototype with a 1476kW Homare turbocharged engine.

 

[vikingBerserker]

Great info!

 

[Gnomey]

Good stuff!

 

[Wayne Little]

Excellent!

 

[gekho]

In 1933, the Imperial Japanese Navy (IJN) issued a requirement for an experimental large flying boat. Kawanishi submitted two designs for monoplane flying boats, including the "Type Q" with four engines and the "Type R" with three. The IJN puzzled over these submissions for a time, then issued a revised specification in early 1934. Kawanishi replied with a new design, the "Type S", evolved from the two earlier submissions. The Type S was accepted, and the first of four prototypes of the "H6K1", as the IJN designated it, performed its initial flight on 14 July 1936, with Katsuji Kondo at the controls. Service trials began at the end of the month. The second and third prototypes followed in 1937 and the fourth in 1938. The H6K1 was designed by a team under Yoshio Hashiguchi and Shizuo Kikuhara, leveraging off data provided by a Kawanishi group that had visited Short Brothers in the UK. It was a neat prewar flying boat design of metal construction, with some similarities to the US Consolidated PBY Catalina, but arguably more attractive and certainly bigger. The initial prototype had a streamlined hull, a strut-mounted wing with four Nakajima Hikari 2 nine-cylinder air-cooled radial engines with 625 kW (840 HP) each, and a twin-fin tail. It carried a crew of nine. The H6K1 had light defensive armament of three guns, consisting of a single 7.7 millimeter (0.303 caliber) Type 92 machine gun in a power-driven dorsal turret, and the same weapon on flexible mounts in nose and tail. Offensive armament consisted of two 800 kilogram (1,764 pound) torpedoes mounted on the wing bracing struts, or up to a total of 1,000 kilograms (2,200 pounds) of bombs using a similar carriage scheme.

Some changes in the design were made during prototype evaluation. The first, third, and fourth prototypes were brought up to full operational fit, re-engined with Mitsubishi Kinsei 43 radials with 745 kW (1,000 HP) each, and delivered to the IJN in January 1938. They were given the designation "H6K1 Type 97 Flying Boat Model 1". These three aircraft were followed by ten basically identical full production aircraft, which were designated "H6K2", and then two machines built as VIP transports and designated "H6K3". The H6Ks performed operational missions in the Japanese war in China. The main production version was the "H6K4", which went into service in 1941. A total of 127 was built. The major changes in this variant were increased fuel capacity and improved armament. The hand-held 7.7 millimeter Type 92 gun in the nose was retained, but the dorsal turret was replaced by another hand-held 7.7 millimeter gun and the tail position was "up-gunned" to a Type 99 Model 1 20 millimeter cannon. A glass blister was fitted on each side of the rear fuselage, with each blister featuring a Type 92 machine gun on a flexible mount. Offensive weapon load remained as before.

There were actually two subvariants or "blocks" of the H6K4. Initial production was the "H6K4 Model 2-2", which retained the Kinsei 43 engines of its predecessors. From August 1941, production moved to the "H6K4 Model 2-3", fitted with uprated Kinsei 46 radials with 798 kW (1,070 HP) each. Later on, they would both be referred to as "Model 22", with no distinction for the powerplants. 64 H6K4s were in service with the IJN when the Pacific War broke out in December 1941. The type saw considerable action, particularly in the South Pacific, even conducting bombing raids on Rabaul and the Dutch East Indies. The H6K4 had extreme range and endurance, able to undertake 24-hour patrols. The Allies gave the machine the codename "Mavis", in accordance with the doctrine that gave Japanese fighters male names and other Japanese aircraft types female names.

 

[gekho]

At the same time the type's predecessor, the Kawanishi H6K, was going into service in 1938 the Navy ordered the development of a larger, longer-ranged patrol aircraft under the designation Navy Experimental 13-Shi Large-size Flying Boat. The result was a large, shoulder-winged design that is widely regarded as the best flying boat of the war. Despite this, initial development was troublesome, with the prototype displaying terrible handling on the water. Deepening of the hull, redesigning of the planing bottom and the addition of spray strips under the nose rectified this. Two further prototypes -actually pre-production aircraft- joined the development program in December 1941. The IJNAF accepted the first production version as the H8K1, Navy Type 2 Flying Boat, Model 11, of which 14 would be built. The improved H8K2 variant soon appeared, and its extremely heavy defensive armament earned it deep respect among Allied aircrews. The H8K2 was an upgrade over the H8K1, having more powerful engines, slightly revised armament, and an increase in fuel capacity. This was to be the definitive variant, with 112 produced. 36 examples of a dedicated transport version, the H8K2-L, were also built, capable of carrying 62 troops. This aircraft was also known as Seiku (晴空, "Clear Sky"). The side defensive blisters, ventral defensive hatch, and dorsal turret were discarded. To increase the available space within the aircraft, its hull tanks were removed, thus reducing its range.

The H8K entered production in 1941 and first saw operational use on the night of 4 March 1942 in a second raid on Pearl Harbor. Since the target lay out of range for the flying boats, this audacious plan involved a refuelling by submarine at French Frigate Shoals, some 550 miles north-west of Hawaii, en route. Two planes from the Yokohama Kokutai (Naval Air Corps)[8] attempted to bomb Pearl Harbor, but, due to poor visibility, did not accomplish any significant damage. H8K2s were used on a wide range of patrol, reconnaissance, bombing, and transport missions throughout the Pacific war. The H8K2 was given the Allied code name "Emily"

 

[gekho]

The requirement for a large torpedo/ dive-bomber for operation from a new, larger class of aircraft carrier caused the Imperial Japanese navy to draw up in 1941 the specification of an aircraft to replace the Nakajima B6N and Yokosuka D4Y. As this specification called for an internal bombload of up to 500kg, or the carriage of a 800kg torpedo externally, coupled with high maximum speed and long range, a powerful engine was essential. The navy selected what was virtually an experimental powerplant for this task: the Nakajima Homare 11 twin-row radial developing around 1342kW. Aichi began work on this requirement, and its AM-23 prototype flew in mid-1942. This large aircraft, then designated Navy Experimental 16-Shi Carrier Attack Bomber (Aichi B7A1), was a mid-wing monoplane of inverted gull-wing configuration, a layout selected so that the main units of the retractable tail-wheel landing gear, mounted at the 'elbows' of each wing, would be as short as possible. A section of each outer wing panel folded for carrier stowage. The fuselage and tail unit were conventional, the former providing enclosed accommodation for a crew of two.

As might have been anticipated, the combination of problems from the air-frame, coupled with the teething troubles of the new engine, meant that it was almost two years before the type was ordered into production as the Navy Carrier Attack Bomber Ryusei (Shooting Star), or Aichi B7A2. Apart from nine prototype B7A1s, only 80 examples were completed by Aichi before its factory was destroyed in the serious earthquake of May 1945; an additional 25 were built by the Navai Air Arsenal at Omura. By the time these aircraft entered service, when they were allocated the Allied codename 'Grace', the Japanese navy no longer had any carriers from which they could operate, with the result that they saw only limited use from land bases.

 

[gekho]

During 1942 Watanabe designed an ASW aircraft to meet an Imperial Japanese Navy requirement for a specialized aircraft in this category. Designated Kyushu Q1W, this was a cantilever mid/low-wing monoplane with retractable tailwheel landing gear, and powered by two Hitachi GK2C Amakaze 31 radial engines. Operated by a crew of three, the Q1W was planned to use an advanced search radar, but this failed to materialize and instead the Q1W had to make do with an earlier and somewhat ineffective radar complemented by MAD (magnetic anomaly detection) equipment. First flown in September 1943, the Q1W1 was ordered into production in early 1944 as the Navy Patrol Plane Tokai (eastern sea), later allocated the Allied codename 'Lorna'. It proved to be unsuccessful in operational service, too slow and too vulnerable to attack by Allied fighters, and only about 150 had been built by the time the Pacific war ended.

 

[gekho]

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 1044kW 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 13.2mm tramable gun (replacing the previous 7.92mm 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 2,033 production D4Ys was completed.

 

[gekho]

The P1Y was designed by the Yokosuka Naval Air Technical Arsenal to Navy specification 15-Shi, calling for a fast bomber with speed matching the Zero, range matching the G4M, a 907 kg (2,000 lb) bombload, and the ability to dive-bomb as well as carry torpedoes. As the result, the construction suffered from excess complexity, difficulty of manufacture, and poor serviceability. Problems with the availability of enough reliable Nakajima Homare engines led to their replacement by the Mitsubishi Kasei in the P1Y2-S night-fighter version. The streamlined design of the Ginga is attributed to Miki Tadanao, an engineer who, after World War II, went on to create a similar aerodynamic design for Japan's earliest `bullet trains` (Shinkansen), while working with the Japan National Railways(JNR).

The first flight was in August 1943. Nakajima manufactured 1,002 examples, which were operated by five Kokutais (Air Groups), and acted as land-based medium and torpedo bombers from airfields in China, Taiwan, Marianas, Philippines, Ryukyu, Shikoku, and Kyūshū. During the last stages of the war the P1Y was utilized as a kamikaze aircraft against the United States Navy during the Okinawa Campaign in Operation Tan No. 2. A night fighter version, the P1Y2-S Kyokko (極光, "Aurora"), with Mitsubishi Kasei engines, was equipped with radar and Schräge Musik-style upward-firing -- as well as forward-firing -- 20 mm cannon. A total of 96 were produced by Kawanishi, but due to inadequate high-altitude performance against B-29s, many were converted back to Ginga bombers.

 

[Wayne Little]

Excellent pics!

 

[vikingBerserker]

I agree, and another excellent thread!

 

[Gnomey]

Good stuff!

 

[Wayne Little]

Bring on some more...!

 

[TimEwers]

Great thread But what I want to know is what color were the early kates like up to battle of midway time frame? were they green or the same as the Val's and Zero's?.

 

[tony french]

Extensively test-flown in 1934, the Nakajima Ki-4 sesquiplane had divided landing gear with streamlined wheel spats, and accommodated pilot and observer in tandem open cockpits, the pilot just below a cut-out in the trailing edge of the upper wing. The Ki-4 went into production and service in 1935 as the Army Type 94 Reconnaissance Aircraft Model 2 which dispensed with the wheel fairings and had a redesigned tail unit. Production continued for several years, some aircraft being licence-built by Tachikawa among the total of 516.

The Type 94 was used widely in China by the Japanese army on direct co-operation duties, in close support of the ground forces. It was armed with up to four 7.7mm machine-guns and could carry 50kg of light bombs. A number were still in service in the supply and liaison role in 1941. The Japanese army tested two Ki-4s as seaplanes, one with twin floats and the other with one main and two stabilising floats. A landplane was used for flotation bag tests to check buoyancy in the event of an emergency put-down on water. Powered by a 477kW Ha-8 radial engine, the Type 94 could attain a speed of 300km/h. Wing span was 12.00m and maximum take-off weight 2500kg.

Dear Gekho, Beautiful photos of a beautiful plane and its pilots. The beauty of the wings, their generous area, the dihedral and general proportions make the Ki-4 an excellent flying peanut scale subject. I have searched the net but cannot find a drawing or 3 view. Would you be so kind to help me if you can. Tony French