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Nakajima B6N Tenzan (Heavenly Mountain) 'Jill'

Nakajima B6N Tenzan (Heavenly Mountain) 'Jill'


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Nakajima B6N Tenzan (Heavenly Mountain) 'Jill'

Introduction and Development
Variants
Combat Record
Specifications

Introduction and Development

The Nakajima B6N Tenzan (Heavenly Mountain) Jill was designed to replace the Nakajima B5N 'Kate', but delays meant that it didn't enter service until 1943, two years after originally planned, and too late for it to have any real impact on the fighting in the Pacific.

The B6N was designed in response to a 14-Shi (14th year of the Emperor Hirohito's reign) specification for a new carrier attack aircraft, which was to replace the Nakajima B5N. The new specification called for a three-seat low-wing all-metal monoplane, small enough to fit o the deck elevators of current Japanese carriers. The new aircraft was to have a top speed of 288mph, a cruising speed of 230mph, a range of 1,151 miles with a 1,764lb bomb load or one torpedo and a range of 2,072 miles with no bomb load. It was to be lightly armed, with a single rear firing flexibly mounted 7.7mm machine gun. It was hoped that the new aircraft would be ready in two years.

The B6N was designed by the same design team as the B5N, and had a very similar air frame to the earlier aircraft. It was to be powered by a radial engine, had a circular fuselage, and a long glazed cockpit with a greenhouse canopy. The main external differences were on the wing - the wing on the B5N had a flat central section with dihedral beyond the folding point, while the B6N wing had dihedral along its entire length; and on the vertical tail surface, which appeared to leaning slightly forward (although its leading edge did actually lean back slightly).

The increase in performance came entirely from an increase in available engine power. The B5N2 used a 1,000hp Sakae 11 radial engine, but the B6N was to get an engine producing at least 1,800hp. Here Nakajima disagreed with the Japanese Navy, which had suggested that the new aircraft use the Mitsubishi 'Kasei' 14-cylinder radial engine. Understandably Nakajima wanted to use one of their own engines, the new Nakajima Mamori Model 11 radial engine. Nakajima cited the new engine's lower fuel consumption and better growth potential, but the financial implications of using one of their competitors engines must also have played a part. This would prove to be a poor decision - problems with the new engine fatally delayed the B6N, which was unavailable for the battles of 1942, and Nakajima were eventually forced to use the Mitsubishi engine anyway.

The first prototype, a B6N1, was completed in March 1941, and was soon followed by the second prototype. Both were powered by the Nakajima engine. The first aircraft made its maiden flight on 14 March 1941, and was then used for flight tests with the Navy. These revealed a number of problems with the new aircraft. The most significant problem with the B6N itself was that the torque from the four-blade propeller made it roll in flight. This flaw was solved by moving the vertical tail 2 degrees 10 minutes to the left. The Mamori engine caused longer delayed, and proved to be very unreliable. It wasn't accepted for use until the end of 1942, delaying the B6N's carrier trials. The aircraft's higher performance also came at a cost - its higher landing speed meant that it could only be used from the larger carriers.

The first carrier trials took place on Ryuho and Zuikaku at the end of 1942. This time the arrester hook mounting caused problems, and had to be strengthened. Finally, early in 1943 the B6N was finally accepted for production, as the Navy Carrier Attack Aircraft Tenzan (Heavenly Mountain) Model 11 (B6N1).

Variants

B6N1 Model 11

The B6N1 Model 11 production aircraft differed from the prototype in a number of ways. The single large exhaust of the prototype was replaced with multiple smaller exhausts, reducing the glare at night. The torpedo rack was angled down by 2 degrees. A second 7.7mm machine gun was added, in a rear firing ventral position, while earlier aircraft had a single fixed forward firing 7.7mm gun in the port wing. The main landing gear and tail plane were both strengthened.

One chance that was considered but not made was to replace the unprotected semi-integral fuel tanks with self sealing tanks, but this would have reduced the range by around 30%, and the change was rejected by the navy.

A total of 133 production B6N1 Model 11s were built by Nakajima before they were ordered to cancel production of the Mamori engine. Their own 'Sakea' engine was still in wide-spread use, and their new 'Homare' engine was considered to be more useful and easier to produce than the 'Mamori'. The Navy ordered Nakajima to modify the B6N to use the Homare, but supplies of that engine were limited.

B6N2 Model 12

Instead Nakajima were forced to use the 1,850 Mitsubishi 'Kasei' Model 25. This was similar in size to the Mamori, and the switch was fairly easy. The nose had to be lengthened to compensate for the lighter weight of the new engine, and a new propeller used. The retractable rear wheel was also removed, and was replaced with a fixed wing. The B6N2 was lighter and faster than the earlier B6N1. Production began in June 1943 and continued through 1944.

B6N2a Model 12A

The B6N2a saw a slight increase in the defensive armament. The two 7.7mm machine guns were replaced, the dorsal gun with a 13mm machine gun and the ventral gun with a 7.92mm machine gun. This aircraft was produced from late in 1944 until the end of the war. A total of 1,133 B6N2s and B6N2as were built, at Okawa and at Handa.

B6N3 Model 13

The B6N3 was an unofficial designation given to two prototypes for a land based version of the B6N, designed in response to the loss of most Japanese aircraft carriers. They were produced by modifying the 751st and 752nd production aircraft. They were given a 1,850hp Mitsubishi MK4T-C Kasei 25c engine, had the arrestor hook removed and a retractable tail wheel installed. The engine cowling and cockpit canopy were also modified. The B6N3 never entered production.

Combat Record

The B6N1 made its combat debut during the fighting at Bougainville on 5 November 1943. The aircraft involved had originally been intended to reinforce the air fleet at Rabaul, but the American invasion of Bougainville forced the Japanese to change this plan. On 5 November fourteen B6N1s with an escort of only four Zeros attacked the American fleet south of Bougainville. As was so common in the later part of the war, Japanese claims were wildly exaggerated. On this occasion they claimed to have sunk one large aircraft carrier, two small aircraft carriers, two large cruisers and two smaller cruisers or large destroyers. Four B6N1s were lost.

This would have been a major victory for the Japanese if it has actually happened, but in fact the Japanese had attacked a force of two large landing ships (presumably the 'carriers') escorted by one gun ship, and all three American ships survived the attack. By the time the Japanese carrier force returned to Rabaul all but six of its B6Ns had been lost. Again as was often the case later in the war, the Japanese high command believed the exaggerated claims, and considered the B6Ns combat debut to have been very successful.

The B6N's first major test came during the fighting around the Mariana Islands, in June 1944. On 15 June the Americans landed on Saipan, and over the next few days were involved in battles with land-based and carrier based aircraft. The first B6N attack came on 15 June, when eleven aircraft from Truk claimed to have hit one carrier and sunk one transport ship, but at a cost of six aircraft lost. The remaining five reached relative safely on Truk.

The first truly large scale use of the B6N was during the Battle of the Philippine Sea. On 19 June 44 B6Ns took part in the large scale carrier attack on the US fleet (37 in the first wave of attacks and 7 in the second). Both attacks were disastrous failures - 27 of the 37 B6Ns in the first wave were lost and 4 of the 7 in the second wave. Only 14 aircraft survived the attack, and none of their torpedoes struck home. By the end of the second day of the battle the Japanese carrier force had been destroyed - three carriers were lost, and others damaged. Only 35 carrier borne aircraft survived, including two B6Ns. The heavy losses of the more experienced Japanese aircrews were even more important, and they proved to be almost irreplaceable.

Significant numbers of aircraft still existed elsewhere. In October aircraft in Taiwan came under attack during preparations for the invasion of the Philippines. In mid-October large numbers of aircraft were sent against the American fleets, but with little or no success. One formation of seventeen B6Ns that did make contact with an American force on 14 October was nearly wiped out, with only one survivor.

The last major naval battle in the Pacific came in late October, after the American invasion of Leyte, in the Philippines. The Battle of Leyte Gulf saw the once-mighty Japanese carrier force reduced to a decoy, carrying just over one hundred aircraft. Even with the help of B6Ns based on the Philippines, the Japanese torpedo bombers were unable to achieve anything in the face of overwhelming American fighter defences.

The B6N had one minor success early in 1945. On 21 February 1945 three B6Ns managed to score a hit on the USS Saratoga. The carrier was never fully operational again, but by this stage the US had so many aircraft carriers in the Pacific that this didn't matter.

The B6N was also used during the battle of Okinawa, where is served as both a conventional bomber and a kamikaze aircraft. The suicide attacks were the most successful, sinking three destroyers and damaging the carrier USS Intrepid, but once again they were unable to affect the course of the battle.

Specifications

B6N1
Engine: Nakajima NK7A Mamoru 11 fourteen-cylinder air-cooled radial
Power: 1,800hp at take off, 1,750hp at 4,595ft, 1,600hp at 16,075ft
Crew: 3 - pilot, observer/ navigator/ bomb-aimer, radio-operator/ gunner
Wing span: 48ft 10 3/8in
Length: 34ft 0 1/16in
Height: 12ft 1 21/32in
Empty Weight: 7,105lb
Loaded Weight: 11,464lb
Max Speed: 289mph at 15,750ft
Cruising Speed: 207mph at 13,125ft
Service Ceiling: 28,380ft
Climb to 16,405ft: 11min 1sec
Range: 909 miles normal, 2,142 miles maximum
Armament: Two flexibly mounted rear-firing 7.7mm machine guns, one in dorsal and one in ventral position
Bomb-load: 1,764lb of bombs or one torpedo

B6N2
Engine: Mitsubishi MK4T Kasei 25 fourteen-cylinder air-cooled radial
Power: 1,850hp at take-off, 1,680hp at 6,880ft, 1,540hp at 18,040ft
Crew: 3 - pilot, observer/ navigator/ bomb-aimer, radio-operator/ gunner
Wing span: 48ft 10 3/8in
Length: 35ft 7 3/4in
Height: 12ft 5 19.32in
Empty Weight: 6,636lb
Loaded Weight: 11,464lb
Max Speed: 299mph at 16,075ft
Cruising Speed: 207mph at 13,125ft
Service Ceiling: 29,660ft
Climb to 16,405ft: 10 min 24 sec
Range: 1,085 miles normal, 1,892 miles maximum
Armament: Two flexibly mounted rear-firing machine guns, one 7.7mm ventral gun and one 13mm dorsal gun
Bomb-load: 1,764lb of bombs or one torpedo


Nakajima B6N Tenzan (Heavenly Mountain) 'Jill' - History

Poster Art: Japanese Aircraft of WW2

Nakajima B6N

The Nakajima B6N Tenzan (Japanese: 中島 B6N 天山—"Heavenly Mountain", Allied reporting name: "Jill") was the Imperial Japanese Navy's standard carrier-borne torpedo bomber during the final years of World War II and the successor to the B5N "Kate". Due to its protracted development and most of the Navy's experienced combat pilots being killed, as well as the United States Navy's achievement of air superiority by the time of its introduction, the B6N potential was never realised.

The B5N carrier torpedo-bomber's weaknesses had shown themselves early in the Second Sino-Japanese War and, as well as updating that aircraft, the Imperial Japanese Navy began seeking a faster longer-ranged replacement. In December 1939 it issued a specification to Nakajima for a Navy Experimental 14-Shi Carrier Attack Aircraft capable of carrying the same external weapons load as the B5N. The new plane was to carry a crew of three (pilot, navigator/bombardier and radio operator/gunner) and be of low wing, cantilevered, all-metal construction (though control surfaces were fabric-covered). Further requirements included a top speed of 250 knots (460 km/h 290 mph), a cruising speed of 200 knots (370 km/h 230 mph) and a range of 1,000 nmi (1,900 km 1,200 mi) with an 800 kg (1,800 lb) bomb load or 2,072 nmi (3,837 km 2,384 mi) without external armament. The prototype B6N1 made its maiden flight on 14 March 1941. Following continued testing, however, several problems became evident. In particular, the aircraft exhibited an alarming tendency to roll while in flight, the cause of which was traced to the extreme torque developed by the four-bladed propeller. To compensate, the aircraft's tail fin was thinned down and moved 2 degrees ten minutes to port. This modification greatly improved the plane's handling characteristics. After only 133 B6N1s had been produced by July 1943, the Japanese Ministry of Munitions ordered Nakajima to halt manufacture of the Mamori 11 engine in order that the Navy reduce the number of different engines then in use. Pending availability of the 18-cylinder Nakajima Homare engine, Nakajima was asked to substitute the 1,850 hp (1,380 kW) Mitsubishi MK4T Kasei 25 engine on the B6N1 airframe, the very engine the Navy had originally requested them to use. As the Mamori 11 and Kasei 25 were similar in size, installation was relatively straightforward, requiring only that the nose be extended to maintain the aircraft's center of gravity and minor alterations to the oil cooler and air intakes on the engine cowling. A smaller 3.4 m (11 ft) diameter four-bladed propeller and shorter spinner were also installed at this time, resulting in a small weight-savings, and the retractable tailwheel was fixed permanently in the down position. Finally, the single exhaust stacks on either side of the engine cowling were replaced with multiple smaller stubs to reduce glare at night and to supply a minor amount of forward thrust. The resulting modification was designated Navy Carrier Attack Aircraft Tenzan Model 12 or B6N2. Starting in the autumn of 1943, one of every three B6N2s manufactured was equipped with 3-Shiki Type 3 air-to-surface radar for detecting enemy ships. Yagi antennas were installed along the wing leading edges and also protruded from the sides of the rear fuselage.

The B6N Tenzan began reaching front-line units in August 1943 but only in small numbers. The intent was to gradually replace all of the older B5N Kate torpedo planes then operating aboard the carriers of the Third Fleet at Truk Atoll in the Caroline Islands. With a forthcoming invasion by the Allies, a likely invasion at Bougainville, the IJN initiated Operation Ro. This involved reinforcing land-based air units at Rabaul with 173 carrier aircraft from First Carrier Division (Zuikaku, Shokaku and Zuiho), including forty B6Ns. These aircraft were flown from Truk to Rabaul between 28 October and 1 November. On 5 November fourteen B6N1s, escorted by four Zero fighters, were sent to attack American shipping anchored off Bougainville and with wild claims by inexperienced Japanese pilots of many warships sunk including 2 carriers, no hits of any ships were recorded. 4 B6N's failed to return. Additional attacks mounted on 8 November and 11 November and suffered heavy losses in return. Only 52 of the original 173 planes from First Carrier Division made it back to Truk on 13 November, among them just six B6N1 Tenzan's out of the forty initially committed.
On 19 June 1944, the B6N made its carrier-borne combat debut at The Battle of the Philippine Sea, which was the final collapse of the Japanese Naval Air Arm. By this time of the war it was no match for the hordes of F6F 'Hellcat's, along with radar directed AA. With such destruction of these newly reformed IJN Air groups, the battle was refered to as 'The Great Marianas Turkey Shoot'. Some 400 IJN aircraft were lost in the battle with the last of the experienced and newly trained pilots of the Japanese Naval Air Arm.
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Due to the loss of carrier pilots, along with the loss of the large carriers, the vast majority of B6N2 operations therefore took place from land bases and failed to achieve any major successes. The planes were extensively used in the Battle of Okinawa where they were also used for kamikaze missions for the first time. By war's end in August 1945, Nakajima had completed a total of 1,268 B6Ns (almost all of them B6N2s) at its plants in Okawa in the Gumma district and at Aichi in the Handa district. Production never exceeded more than 90 planes per month.
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Japanese Aircraft of WWII

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.

(Navy Carrier Attack Bomber Tenzan "Heavenly Mountain" Model 11 - Nakajima B6N2)

Type: Three Seat Carried based Torpedo Bomber

Design: Nakajima Hikoki KK with Kenichi Matsamura as led Technical Director

Manufacturer: Nakajima Hikoki KK

Powerplant: (B6N1) One 1,870 hp (1395 kW) Nakajima NK7A Mamoru 11 14-cylinder radial engine. (B6N2) One 1,850 hp (1380 kW) Mitsubishi MK4T Kasei 25 14-cylinder radial engine. (B6N3) One 1,850 hp (1380 kW) Mitsubishi MK4T-C Kasei 25C 14-cylinder radial engine.

Performance: Maximum speed 298 mph (480 km/h) service ceiling 29,660 ft (9040 m) initial climb rate 1,885 ft (575 m) per minute.

Range: Normal 1,084 miles (1745 km) Maximum (overload) 1,892 miles (3045 km) on internal fuel.

Weight: Empty 6,635 lbs (3010 kg) with a maximum take-off weight of 12,456 lbs (5650 kg).

Dimensions: Span 48 ft 10 1/2 in (14.90 m) length 35 ft 8 in (10.87 m) height 12 ft 5 1/2 in (3.80 m) wing area 400.42 sq ft (37.20 sq m).

Armament: One 7.7 mm (0.303 in) Type 98 machine gun manually aimed from rear cockpit and one manually aimed by middle crew member from rear ventral position and one fixed 7.7 mm (0.303 in) Type 98 machine gun in left wing (often absent from the B6N1). A 1,764 lbs (800 kg) 18 inch torpedo carried offset to the right of centreline, or six 220 lbs (100 kg) bombs carried under the fuselage.

Variants: B6N1 (Mamoru engined), B6N2 (Kasei engined), B6N2a, B6N3 (prototypes for land based version).

Avionics: Some later models were equipped with ASV radar for night operations.

History: First flight March 1941 service delivery (B6N1) early 1943 service delivery (B6N2) December 1943.


Nakajima B6N

The Nakajima B6N Tenzan (Heavenly Mountain), Allied reporting name: 'Jill', was the Imperial Japanese Navy's standard carrier-borne torpedo bomber during the final years of World War II and the successor to the B5N 'Kate'. Due to its protracted development, a shortage of experienced pilots and the United States Navy's achievement of air superiority by the time of its introduction, the B6N was never able to fully demonstrate its combat potential.

The B6N Tenzan began reaching front-line units in August 1943 but only in small numbers. The intent was to gradually replace all of the older B5N Kate torpedo planes then operating aboard the carriers of the Third Fleet at Truk Atoll in the Caroline Islands. However, the B6Ns were prematurely committed to battle when increased Allied naval activity in the Solomon Islands indicated a likely invasion at Bougainville. In response to this threat, the IJN initiated Operation Ro. During this operation the IJN lost 40 Tenzans.

On 19 June 1944, the B6N made its carrier-borne combat debut at The Battle of the Philippine Sea, operating in an environment where the U.S. Navy had virtually complete air superiority. Subsequently, it failed to inflict any significant damage whatsoever whilst taking heavy losses from the U.S. Navy's F6F Hellcat fighter.

The planes were extensively used in the Battle of Okinawa where they were also used for kamikaze missions for the first time.


Nakajima B6N Tenzan

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.

(Navy Carrier Attack Bomber Tenzan “Heavenly Mountain” Model 11 – Nakajima B6N2)

Type: Three Seat Carried based Torpedo Bomber

Design: Nakajima Hikoki KK with Kenichi Matsamura as led Technical Director

Manufacturer: Nakajima Hikoki KK

Powerplant: (B6N1) One 1,870 hp (1395 kW) Nakajima NK7A Mamoru 11 14-cylinder radial engine. (B6N2) One 1,850 hp (1380 kW) Mitsubishi MK4T Kasei 25 14-cylinder radial engine. (B6N3) One 1,850 hp (1380 kW) Mitsubishi MK4T-C Kasei 25C 14-cylinder radial engine.

Performance: Maximum speed 298 mph (480 km/h) service ceiling 29,660 ft (9040 m) initial climb rate 1,885 ft (575 m) per minute.

Range: Normal 1,084 miles (1745 km) Maximum (overload) 1,892 miles (3045 km) on internal fuel.

Weight: Empty 6,635 lbs (3010 kg) with a maximum take-off weight of 12,456 lbs (5650 kg).

Dimensions: Span 48 ft 10 1/2 in (14.90 m) length 35 ft 8 in (10.87 m) height 12 ft 5 1/2 in (3.80 m) wing area 400.42 sq ft (37.20 sq m).

Armament: One 7.7 mm (0.303 in) Type 98 machine gun manually aimed from rear cockpit and one manually aimed by middle crew member from rear ventral position and one fixed 7.7 mm (0.303 in) Type 98 machine gun in left wing (often absent from the B6N1). A 1,764 lbs (800 kg) 18 inch torpedo carried offset to the right of centreline, or six 220 lbs (100 kg) bombs carried under the fuselage.

Variants: B6N1 (Mamoru engined), B6N2 (Kasei engined), B6N2a, B6N3 (prototypes for land based version).

Avionics: Some later models were equipped with ASV radar for night operations.

History: First flight March 1941 service delivery (B6N1) early 1943 service delivery (B6N2) December 1943.


IPMS/USA Reviews

The Imperial Japanese Navy entered the Pacific War with the most advanced ship-based attack bomber in the world, flown by the most experienced aircrews of any service. First flown in 1937, and introduced into squadron service during the Sino-Japanese conflict in 1938, the Nakajima B5N was faster, flew farther and carried a heavier payload than either of its British or American contemporaries (principally, the Fairey Swordfish and Douglas TBD Devastator, respectively). When used as either a level bomber against stationary targets, or as a torpedo bomber against ships, the "Kate" (as it came to be known to the Allies) would wreak havoc against Japan's enemies for the first year of the war.

Design specifications for the B5N's replacement were issued even before the advent of hostilities against the western allies. Finally reaching frontline service in mid-1943, the Nakajima B6N Tenzan (Heavenly Mountain to its Japanese crews, and "Jill" to the Allies) was a considerable improvement in speed and range over the B5N, while being of similar size (due to carrier elevator size restrictions) and carrying the same 800 Kg bomb load or torpedo. Unfortunately for the Japanese, by that time the U.S. Navy had obtained nearly complete air superiority anywhere its carriers sailed, and both the Jills and remaining Kates suffered accordingly. Both ended up being expended in futile Kamikaze attacks in the final months of the war.

Authors Mark Chambers and Tony Holmes have extensively researched Japanese files to present a concise history of the IJN's carrier attack operations. Much of the information on early wartime operations - Pearl Harbor, Indian Ocean, Coral Sea and Midway - are drawn directly from the memoirs of Commander Mitsuo Fuchida, who planned and led many of them. Both his observations and critiques add color and depth to the descriptions of actions involving the Kate squadrons up through the reduction of Rabaul. The desperate air battles in and around the Solomons, including Eastern Solomons and Santa Cruz, are described in detail, as are the actions of B6N Tenzans in the Central Pacific and from Formosa, as well as from carriers during the Philippine Sea and Leyte Gulf battles. An added bonus, to the best extent possible where records are available, is the systematic breakdown throughout the text of the numbers of B5N and B6N aircraft assigned to individual carriers or air groups for each of the Pacific War's principal carrier clashes.

Although some of the photos in this volume have been previously published, the majority are from Japanese sources, and are new or have rarely been seen by western readers. Jim Laurier's 30 profiles, as always, are superb.

This is an edition of Osprey's well regarded Combat Aircraft Series that enthusiasts of Japanese naval aviation have long awaited. They won't be disappointed. Thanks to IPMS and Osprey Publishing for the opportunity to review this outstanding publication.


Nakajima B6N "Tenzan"

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.


Variants [ edit | edit source ]

Nakajima B6N2 "Tenzan" as 752nd Kōkūtai flying in formation (note aircraft numbers on hinomaru).

Nakajima B6N2 "Tenzan" unit before take-off.

  • B6N1 : Prototypes - Engine Nakajima NK7A Mamori 11 of 1,394 kW (1,870 hp), four-blade propeller. Two examples built.
  • B6N1 Tenzan Navy Carrier Based-Attack Bomber, Model 11: First series model. 133 built (work number 1�).
  • B6N2 Model 12: Main production model, featured Mitsubishi MK4T Kasei 25 of 1,380 kW (1,850 hp). 1,131 built as B6N2/B6N2a (work number 134�, 753𔂿,266).
  • B6N2a Model 12A: Revised tail armament. 7.7 mm (.303 in) Type 97 machine gun, replaced with one 13.2 mm Type 2 machine gun.
  • B6N3 Model 13 Prototypes: Engine Mitsubishi MK4T-C Kasei 25c of 1,380 kW (1,850 hp). Modified landing gear for operating from land bases two built (work number 751�).
  • Total Production (all versions): 1,268 examples.

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Special controls:
Vtol: flaps

History of the aircraft:
The Nakajima B6N Tenzan (Japanese: ?? B6N ??—"Heavenly Mountain", Allied reporting name: "Jill") was the Imperial Japanese Navy's standard carrier-borne torpedo bomber during the final years of World War IIand the successor to the B5N "Kate". Due to its protracted development, a shortage of experienced pilots and the United States Navy's achievement of air superiority by the time of its introduction, the B6N was never able to fully demonstrate its combat potential.


Nakajima B6N Tenzan (Heavenly Mountain) 'Jill' - History


Nakajima B6N "Tenzan" is available online fromSquadron.com

FirstRead


Nakajima B6N 'Tenzan' (Heavenly Mountain) is the third book in the Famous Airplanes series of from Kagero, a Poland based publishing company.

The Nakajima B6N 'Tenzan', (codenamed "Jill" by the allies) was a single engined three place carrier based torpedo bomber that was designed as a replacement for the Nakajima B5N "Kate".

The book is in both Polish and English languages. Each page is split into two columns. The left hand column is printed in the Polish language and the right hand one in English. The captions to the photographs as well as the colour artwork receive a similar approach with the polish language first followed by the English translation. Other books in the Kagero range follow a similar format. Some of these suffer from quirky translations from the Polish to English but I'm happy to say that this is not one of them.

It is logically laid out with sections on the design development and production, operational usage, painting and markings, and a technical description of the aircraft.

Each section is very informative but I have to say that the operational usage and painting ones stand out. Information on how Japanese naval aircraft, let alone the Jill, were painted is not all that easy to come by, happily though the section guides you through the interior colours as well as the propeller, spinner and upper and lower surfaces. Markings worn by the Jill are also fully explained.

The book is illustrated with black and wartime photographs as well as a couple of post war ones of the machines that were tested in the United States following the war's end. Each of the photographs is captioned and identifies which unit the machine belonged to. The hard-bitten fan of Japanese Naval aviation will be familiar with some of the photographs but there are quite a few new ones amongst them.

Colour is in the form of profiles of eleven different machines (painted by Zygmunt Szesementa).

A decal sheet is included with the book.

The decals are in both 1/72 (for the Fujimi kits) and 1/48 scale (for the Hasegawa kits) and are printed by Techmod. Techmod decals are very nice but require care when applying. Use plenty of water to float the decal to where you want it and you won't have a problem. Markings are offered eleven different machines (the same ones as the colour profiles). No hinomarus are provided but these are not too hard to find elsewhere. Thankfully, Kagero has chosen not to replicate the markings found in the 1/48 scale Hasegawa kit as they are quite useable.

The final offering in this package is a set of 1/48 scale vinyl canopy masks designed to fit the Hasegawa kit. Nice touch this as it saves an evening's worth of struggling with masking tape to mask the Jill's huge greenhouse.

The decal sheet and masking set is packed into a sealed plastic bag that is placed into a plastic mount on the inside of the front cover.

The book is B5 in size (a little smaller than the Osprey Aircraft of the Aces series). It consists of 36 pages printed on glossy paper between cardboard covers.

Good stuff from Kagero and definitely worth the asking price as you get clear well written text as well as a decal sheet and a masking set.


Watch the video: Nakajima B5N 中島 B5N Kate upgrade (June 2022).


Comments:

  1. Nagar

    I have thought and have removed the message

  2. Kirk

    On the Shoulders Down! Street tablecloths! So much the better!

  3. Hod

    There are still more many variants

  4. Steathford

    Certainly. All above told the truth. Let's discuss this question. Here or in PM.

  5. Gami

    But is there a similar analogue?

  6. Stock

    It's out of the question.



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