JCh-6

JCh-6
The three JCh-6 service variants using the "G turret."
Type	Main battle tank
Place of origin	Menghe
Service history
In service	2004-present
Used by	See "Operators"
Wars	Ummayan Civil War Innominadan Crisis Innominadan Uprising
Production history
Designer	Chikai Tank Design Institute
Designed	1993-2003
Manufacturer	Chikai Heavy Machine Building Plant Insŏng Machine Building Plant Minchŏl Tank Factory
Unit cost	$4.8 million (JCh-6D, 2015)
Produced	2004-2016
No. built	8,450
Specifications (JCh-6G)
Weight	48 tonnes
Length	10.91 m
length	7.74
Width	3.57 m including side armor
Height	2.39 m to turret roof
Crew	3 (driver, gunner, commander)
Armor	welded steel base Composite armor (turret face and hull glacis)
Main armament	125mm L/48 smoothbore gun
Secondary armament	12.7mm GCh-75Ch HMG (commander) 7.5mm GCh-77 MMG (co-axial)
Engine	MTU MB 873 Ka-501 1,500 hp
Power/weight	31.25 hp/tonne
Suspension	torsion-bar
Ground clearance	41 cm
Operational range	925 km
Speed	75 km/h (road)

The JCh-6 (formal designation: 6호 주력 전차 / 六號主力戰車, Ryuk-ho Juryŏk Jŏncha, "No.6 Main Battle Tank;" short designation: 전차-6 Jŏncha-ryuk) is a main battle tank designed and built in Menghe. Mass production began in 2003, with service deliveries early the following year. It is sometimes accompanied by the nickname Sŏnbong (선봉 / 先鋒), meaning "Vanguard," though this is more of a marketing device than an actual designation. The JCh-6 is currently the second most common main battle tank among the Menghean Army's active forces, though the JCh-5 outnumbers it in the reserves and the JCh-8 has begun replacing it in some front-line units.

Compared to the JCh-5 before it, the JCh-6 incorporates a number of new features, most notably a dual autoloader which allows the vehicle to store a large number of one-piece and two-piece 125mm rounds. The narrow bustle autoloader influenced the form of the angular teardrop-shaped turret, one of the JCh-6's most unique identifying features. The JCh-6 also has a very powerful engine for its weight class, resulting in excellent mobility even on later variants with heavy applique armor. This helps formations of JCh-6 tanks rapidly exploit breakthroughs and counterattack against enemy offensives.

Development

Although the JCh-5 MBT had been considered fairly advanced during its early years in service, by the early 1990s concerns about its inadequacy were growing. Menghean policymakers closely followed the 1991 invasion of Kouraki, in which Anglian Challenger 1 and Dayashinese Type 90 tanks easily defeated Kouraki's core force of T-74 tanks. Though Menghe did not operate the T-74, its JCh-5 had the same main gun and fired similar ammunition. Menghean designers were especially concerned by reports that T-74s were unable to defeat the composite turret armor of the Challenger 1 and Type 90, even at the shortest of ranges.

Menghe had developed new ammunition types for the JCh-5 in the 1980s, but such incremental changes had limited potential. The JCh-5's carousel autoloader, which split ammunition into two pieces for storage, imposed a hard upper limit on the length of APFSDS projectiles. This, in turn, limited the main gun's armor penetration capability. The Chikai Heavy Machine Building Plant began work on a revised carousel design with a smaller central hub, allowing slightly longer APFSDS ammunition, but the designers saw this as little more than an interim solution.

The first records of a larger solution date from 1993, when the design bureau of the Chikai Heavy Machine Building Plant drew up blueprints for a prototype vehicle designated S.804. The new tank would be largely identical to the JCh-5, but would feature a modified turret with a box protruding from the rear. This box would house an autoloader with twelve unitary 125mm rounds. The 28-round autoloader within the hull would remain in place as well, albeit with a slightly modified ramming drive to keep the bustle autoloader's reloading path clear. According to design notes, the bustle would be loaded exclusively with a new type of APFSDS ammunition featuring a longer penetrator. The hull autoloader would carry HE, HEAT, and ATGM ammunition, all of which can be broken down into two parts without meaningfully degrading performance.

A working prototype was produced in 1996, built out of a modified JCh-5D hull with the reactive armor removed and an autoloader module welded to the rear of the turret. At this point in time the unitary 125mm round was still in development, so the design team tested the loading process with dummy ammunition. No firing trials were conducted. A Ministry of National Defense procurement team traveled to the Ketchvan SAP to observe a mobility test and demonstration of the new tank, but they were unimpressed with its construction. The thinly armored autoloader box was a particular source of concern; it was built from thin armour steel, meaning that enemy 12.7mm fire from combat ranges would be able to damage or even detonate the stored ammunition. The S.804 prototype was placed in storage in 1998, though it would later see new life as the JCh-5.5.

During the same time frame, the Insŏng Tank Plant developed a competing prototype. This vehicle, designated S.807, was armed with a brand-new 127mm smoothbore gun firing a new type of unitary ammunition. The new calibre was chosen to avoid logistical confusion, as its ammunition was not reverse-compatible with other Menghean 125mm tank ammunition. A total of 22 rounds of main gun ammunition were stored in a bustle autoloader, with 20 more in the hull front alongside the driver. Because of the fighting compartment's small dimensions, the hull ammunition stowage could only be transferred to the autoloader externally, with the commander passing it to the gunner and the gunner loading it through the top of the turret bustle. The S.807 was a surprisingly modern design, resembling the Dayashinese Type 90 in overall layout, but this also made it more complex and expensive. Furthermore, Insŏng was less experienced than Chikai at tank design, having only opened in the 1980s as a secondary production site for the JCh-5. The first fully-functional S.807 prototype was only rolled out in 1999, by which point the S.806 prototype had emerged as a clear front-runner.

The S.806 was Chikai's answer to the MoND's critiques of the S.804 prototype. It used the same basic configuration as the S.804, with a linkless-belt-type autoloader in the turret bustle holding 12 unitary rounds (later increased to 16) and a carousel autoloader in the hull holding the remaining two-piece ammunition. The internal systems, however, were wrapped in an entirely new turret exterior, with autocannon-resistant armor plating entirely surrounding the bustle autoloader and blending smoothly into the rest of the turret. The hull was also slightly enlarged, and the slope of the upper glacis plate was increased. The roadwheels were greatly enlarged and given wear-resistant rubber surfaces to address problems with wheel and track life on the JCh-5. To compensate for the added weight of armor and machinery, a more powerful V-12 diesel engine was installed in the larger rear compartment, generating 1,100 hp.

The initial version of the S.806 prototype featured a "bowl-shaped" carousel autoloader nearly identical to the type used on the JCh-5, with the charges sitting upright in a ring around the fighting compartment. This was more familiar to Chikai's designers, and it allowed for a faster rate of fire than the two-stroke autoloader on the T-74. Analysis of combat losses in the Polvokian Civil War, however, revealed that a number of JCh-5 tanks suffered catastrophic burn-outs due to HEAT charges penetrating the upper hull sides and striking the upright charges. Concerned about survivability, the MoND instructed Chikai to develop an alternative carousel autoloader with a lower height profile and an armored roof. This proved to be a challenge, as Menghe did not have production rights to the Letnian T-74 and a copied version of its electric hoist and ramming system would obstruct the ramming path of unitary shells from the bustle autoloader. A modified prototype was finally rolled out in 2002, this time featuring a carousel autoloader similar in configuration to that of the T-74 but with a hydraulic lifting and ramming system incorporating elements of the JCh-5's autoloader design. This lowered the autoloader's profile within the hull and allowed the installation of an armor plate on top. This modified design received the prototype designation S.806G.

Satisfied with the last round of changes, the MoND approved the S.806G for mass-production in 2002, giving it the designation JCh-6. As the winner of the competition, the Chikai Heavy Machine Building Plant was awarded a contract for mass-production of the JCh-6, with Insŏng handling upgrades and refits of existing JCh-5 hulls.

Description

Layout

The JCh-6 has the same general layout as the JCh-5 before it, with the driver in the front of the hull, the gunner on the left side of the turret, the commander on the right side of the turret, and the engine and transmission in the rear. Its most distinctive visual feature is a long turret bustle which tapers inward at 20 degrees. This distinguishes it from the JCh-5, which has a circular (JCh-5G) or octagonal (JCh-5N/D/R) turret. The front half of the turret also tapers inward at 20 degrees before angling more sharply inward to form the turret face, distinguishing early JCh-6 tanks from later JCh-6 models and the JCh-8 and -10.

In terms of its overall size, the JCh-6 represents an incremental change in Menghean tank design doctrine. It is slightly larger in all dimensions than the JCh-5, measuring 2.38 meters to the turret roof, and consequently heavier, weighing 47 tonnes fully loaded without reactive armor. Yet it is still shorter and ligher than many Western MBTs, including the Ostish Leopard 2 and the Anglian Challenger 2. This puts it in roughly the same league as other foreign 3-crew tanks, such as the Sieuxerrian Leclerc tank and the Dayashinese Type 90. A more powerful engine compensates for the added mass, allowing the JCh-6 to match the JCh-5's speed and mobility, though its increased mass still impacts its airlifting ability and its bridging ability.

Despite the added armor and machinery, the JCh-6 is slightly more spacious than the JCh-5. The turret basket, which measures 1,940mm in diameter internally, is wider than the turret baskets on some 4-crew MBTs. The flat carousel autoloader gives more horizontal space to the commander and driver, as the turret basket is not ringed by ammunition. Moreover, all rotating parts of the carousel autoloader are contained below the turret floor, meaning that there is no risk of injury from body parts or clothing getting snagged during loading. The flat carousel autoloader also allows the crew to move between the driver's compartment and the turret compartment. On the JCh-5, this was only possible if one of the crew members removed three shell and propellant casettes from the autoloader to create an opening. The JCh-6 does offer its turret crew less vertical space than the JCh-5, as the turret floor is higher; but with no human loader competing for horizontal space, the gunner and commander can sit with their legs stretched forward.

Main armament

The main armament of the JCh-6 is the JChP-125 Type 01 125mm smoothbore tank gun. This is an offshoot of the 2A46 tank gun family used by the JCh-5 and other Letnian and Kolodorian tanks before it. Like other 2A46 derivatives, it has a barrel length of 6,000mm, a bore evacuator two thirds of the way along the barrel, and a horizontal sliding block breech. The recoil travel is 260 to 300 mm, with a hard stop at 310 mm. Like newer guns in the 2A46 family, the JChP-125 Type 01 has a thermal sleeve, a chromium-lined barrel, an autofrettaged barrel and chamber assembly, and a disassembly mechanism which allows the crew to replace the barrel at a depot without having to lift off the turret. Compared with earlier versions of the 2A26 and 2A46, these changes give the JCh-6 increased accuracy, a longer barrel life of 1200 rounds, and compatibility with high-energy APFSDS ammunition.

Gun elevation ranges from -7.19 degrees to +14.55 degrees, giving the JCh-6 marginally better hull-down capability than the JCh-5 and T-74 but still less depression than many Western MBTs. With the stabilizer activated, gun elevation is limited to -6.28 to +13.72 degrees. This ensures that the gun does not abruptly ram into its hard upper or lower stops during movement over rough terrain. The JCh-6 has a full degree of additional depression compared to the JCh-5 and T-74, but its depression is still substantially behind that of many Western MBTs, limiting its ability to fight from a hull-down position. The gun's maximum elevation is also relatively poor, because the gun's recoil guard collides with the raised floor of the autoloader. This limits the JCh-6's ability to fight in hilly, mountainous, or urban terrain, but also reduces its overall profile, making it more effective in open terrain.

One of the JCh-6's main improvements over the JCh-5 is its ability to fire unitary APFSDS ammunition. Menghe's first unitary APFSDS projectile, PT-125JNBChT Type 01, uses a monobloc Tungsten penetrator 85 centimeters long excluding the tracer and 28mm in diameter. This projectile has a muzzle velocity of 1,650 meters per second. Official Menghean sources claim that it can defeat 880 mm of rolled homogeneous armor (RHA) equivalent at 60° obliquity from a range of 2,000 meters, nearly double the performance of the best APFSDS rounds used by the JCh-5. The later PT-125JNBChT Type 09 reportedly has a soft steel head and rigid Tungsten body, making it more effective against tanks with reactive armour schemes. An extending-rod penetrator was reportedly in development in 2017, and may now be in limited service. Because they are not reverse-compatible with the JCh-5 and would be useless if delivered to a JCh-5 unit, unitary 125mm APFSDS rounds are designated "long" APFSDS.

The carousel autoloader of the JCh-6 uses the same HE and HEAT ammunition as the JCh-5, allowing for some logistical commonality. These include the PT-125SJ Type 10 round with a three-stage HEAT charge capable of defeating 600mm RHAe of armor behind ERA or 800mm RHAe without ERA. A canister round for the Menghean 125mm tank gun was developed, but never saw widespread service in the Menghean Army.

For engagements at longer ranges, the JCh-6 can fire the YDCh-19 beam-riding ATGM through its gun barrel. Unlike the YDCh-16 before it, this projectile can be loaded directly from the autoloader, without requiring a human loader to insert a third compressed-air stage. Because they are stored in assembled form with a separate booster charge, rather than in separated units, YDCh-19 rounds fired from the JCh-6's autoloader reportedly have a lower failure rate. Increasing accuracy of fire-control systems on the JCh-6N and later models, however, rendered the guided missile redundant, and in practice most tank units do not carry it.

Autoloaders

The most distinctive feature of the JCh-6 is its dual-autoloader arrangement. This was primarily a result of the 1990s MoND requirement that the tank be able to fire unitary 125mm APFSDS ammunition without seriously sacrificing ammunition capacity, and it steadily evolved through Chikai's S.804, S.806, and S.806G prototypes.

The bustle autoloader in the rear of the turret carries 14 unitary rounds in a linkless belt configuration, with the rounds running in a sideways 0 shape around a central belt assembly which cycles them using metal paddles which extend into the spaces between the rounds. This is similar in concept to the bustle autoloaders on the T-10, Type 90, and Leclerc MBTs. The center position in the bottom row has a hydraulically powered semi-rigid chain which rams the selected projectile through a hole in the turret bustle bulkhead and into the breech of the gun. Loading takes place at a fixed elevation of -2.39 degrees, so the gun must depress to this angle as part of the reloading cycle and then return to its previous angle. This is just shy of the maximum allowable depression when the turret is facing to the rear and the gun is over the engine deck. The belt can cycle either clockwise or counterclockwise, and it automatically cycles in the direction with the closest round of the selected type. If the gun is already depressed at close to -2.39 degrees and the desired ammunition type is already indexed, the loading cycle takes slightly over 5 seconds. This equates to a rate of fire of 11 rounds per minute when using the bustle autoloader. At maximum gun elevation, the total loading process increases to just under 8 seconds, and it can increase further if the desired ammunition type is on the far side of the belt and not pre-indexed.

The carousel autoloader is located at the bottom of the turret basket and carries 22 two-piece rounds with the charges stacked horizontally over the projectiles and the front ends of the projectiles facing the hub of the autoloader. The central hub contains the carousel rotation motor as well as the power and communication connections between the turret and the hull. In principle, the JCh-6 carousel is very similar to the T-74 carousel: it rotates independently of the turret to select the desired ammunition type, at which point the desired ammunition is hoisted up behind the gun breech at a fixed elevation of +5.9 degrees and a two-stroke ramming process loads the projectile, then the charge. The actual lifting and ramming mechanism, however, is completely unlike the type used on the T-74, with the ramming chain wrapping horizontally around the turret ring instead of coiling vertically in the rear of the turret. The gun also loads at a higher angle. These changes ensure that the lifting and ramming equipment for the carousel autoloader do not obstruct the path of travel for rounds from the bustle autoloader. If the gun is already close to 5.9 degrees in elevation and the next ammunition type is pre-indexed before firing, the full loading cycle takes 8 seconds, increasing to 10 seconds if the gun is at maximum elevation or depression at the start of the loading process. This equates to 6-8 rounds per minute when using the carousel autoloader.

Both the bustle autoloader and the carousel autoloader are powered by the tank's hydraulic system. The hydraulic motor for the bustle autoloader is located in the turret bustle, and has a small blowoff plate of its own. The hydraulic motor for the carousel autoloader is located on the floor of the hull. Both autoloaders have manual hand crank controls in the event that the hydraulics fail: the carousel autoloader's hand cranks are on the side of the commander's position, and the bustle autoloader's hand cranks stick through the rear wall of the turret behind the commander's head. Manual cycling time depends on the condition of the crew. There is no procedure to manually reload the gun, but this is a negligible drawback, as there is also no loose ammunition stowage outside the autoloader.

Menghean unitary and two-piece 125mm tank round casings are 90% combustible: only the steel base of the propellant section, which seals the breech during firing, remains in the chamber after firing. When the gun recoils, this spent casing stub is ejected into a metal arm behind the breech, which catches it and then ejects it through a spring-loaded hatch in the turret roof. This briefly compromises the tank's airtight seal, but the fighting compartment is pressurized to slightly over atmospheric pressure and the hatch is open for less than a second, so only a small amount of contaminated air can enter. This ejection system also reduces the buildup of fumes in the fighting compartment, as spent 125mm casing stubs often continue to smolder for several seconds after firing.

Replenishing the bustle autoloader from a supply truck is relatively easy: the gunner manually rams new rounds through a hatch in the rear of the turret bustle, as the commander cycles the autoloader from inside the tank and records the round in each position. This is about as fast as replenishing rounds in a tank with a manual loader. Replenishing the carousel autoloader is more time-consuming: the driver and gunner pass ammunition through the commander's hatch to the commander, who loads the projectile and charge into a raised ammunition casette, then lowers the casette and advances the autoloader with a hand crank. Fully replenishing both autoloaders from an external supply vehicle or depot crate takes under 10 minutes in total.

Because the two autoloaders function independently of one another, each one can still function if the other is damaged. Thus, while the probability of at least one autoloader failing is twice as high, the probability that both autoloaders fail independently is much lower. This, however, only applies to mechanical failures and minor battle damage; a catastrophic explosion of ammunition in the turret bustle, even if fully isolated by the protective bulkhead, would shake the tank violently enough to jam the carousel autoloader and damage or misalign the optics. Even so, the decoupling of the two autoloaders compares favorably with some Letnian split autoloader concepts in which the projectiles are stored on the turret floor and the charges are stored in the turret bustle; on these prototypes, a mechanical failure in either autoloader would disarm the tank.

Redundancy is a beneficial side effect of the dual autoloader configuration, but not the main reason for its adoption. The system's main benefits are as follows.

• The carousel autoloaders used on the JCh-5 and JCh-6 (lower hull) break down their rounds into two pieces, usually a charge and a complete projectile, for storage. This is not a problem for other ammunition types, but it imposes a strict upper limit on the length of APFSDS penetrators, which must fit in the projectile section of the carousel. The turret bustle, by contrast, can hold unitary 125mm rounds with very long penetrators.
• Manual internal replenishment of the autoloader is time-consuming for two-piece 125mm ammunition, and impossible for unitary 125mm ammunition, which at over 1100 mm in overall length is far too cumbersome to move around inside the confines of the fighting compartment. On the JCh-6, all 36 rounds of main gun ammunition are in an autoloader of some kind, so there is no need to expand the fighting compartment or replenish unitary rounds externally.
• Loose reserve ammunition stowage was also identified as the leading cause of catastrophic ammunition fires on the JCh-5 and other T-series tanks. With the bustle autoloader separated from the fighting compartment by a steel bulkhead, the carousel autoloader covered by a steel plate, and no loose ammunition anywhere else in the hull, the JCh-6 has a lower risk of ammunition cookoff than most other MBTs.
• A full-width bustle autoloader would only hold 20-24 rounds, insufficient to meet the 36-round stowage requirement.
• A full-width bustle autoloader would also have flat side armor, and would be vulnerable to enemy APFSDS fire if the turret is facing more than a few degrees away from the threat. Fully armoring the turret bustle with composite armor would add excessive weight. The JCh-6's tapering turret bustle is fully masked from view over the turret's 40-degree frontal arc, and too steeply angled for APFSDS projectiles to penetrate over the turret's 50-degree frontal arc. Even at the edges of the turret's 60-degree frontal arc, projectiles striking the front half of the bustle would have to pass through close to a meter of angled composite armor, and projectiles striking the rear half would exit the rear of the bustle without impacting the ammunition.

There are nevertheless some drawbacks of the two-autoloader layout:

• Both the added autoloader machinery and the turret bustle armor add to the tank's weight, bringing the fighting mass close to 50 metric tonnes.
• While the carousel ammunition is relatively well-protected against spall damage, an IED blast or projectile impact on the lower hull can still set off a catastrophic ammunition fire.
• The spent casing ejection hatch briefly compromises the tank's CBRN protection system while open.
• The tank can only carry up to 14 full-length APFSDS rounds, and it can carry no more than 22 HE, HEAT, canister, and beam-riding ATGM rounds in total, limiting a tank unit's ability to customize ammunition loadouts for a particular mission.
• The gun can only depress -0.5° in the 60-degree rear arc over the raised engine deck. To reload from the bustle, the gunner must traverse the turret to the side to extend the gun over the side fenders, then re-acquire the target after returning the gun to its original position. The commander's hunter-killer fire control system speeds this process, but it still adds to the loading cycle.
• While the tapered turret bustle is mostly hidden from view or well-angled over the 60-degree frontal arc, it can easily be penetrated by tank ammunition, ATGMs, and RPG fire from the sides and rear.

Other armament

In addition to the main gun, the JCh-6 is armed with a co-axial GCh-77Ch general-purpose machine gun fixed to the right side of the gun in a sliding mount which allows for a small amount of recoil travel. As on other Menghean tanks, the co-axial machine gun fires through a pill-shaped opening in the turret face rather than a circular opening in the moving mantlet. It is normally fired by an electric solenoid unit on the rear of the receiver, which is linked to trigger buttons on the gunner's powered turret control and manual turret crank. Pressing the fire button also activates an air filter overdrive fan, which helps clear gun fumes out of the turret. If the electric firing line is broken, the commander can fire the machine gun by pressing a mechanical trigger on top of the receiver.

A total of 2,000 rounds of 7.5×54mm ammunition are stored around the tank in 250-round boxes, and the collection box mounted underneath the machine gun can hold 500 spent cartridge casings and 20 25-round belt segments. At 1,200 rounds per minute, the GCh-77Ch rapidly eats through these ammunition belts, and even when firing in bursts it can exhaust a 250-round belt in under a minute. The commander, who sits on the right side of the gun, is responsible for reloading the machine gun, emptying the spent casing collector, and clearing jams, a task which distracts from his regular duties. It is possible to replace the barrel from within the tank, but the heavy barrel of the GCh-77Ch overheats more slowly than the light barrel of the infantryman's GCh-77, especially in short burst fire from a tank.

The commander's cupola on the JCh-6G and JCh-6N is identical to the commander's cupola of the JCh-5R. It is equipped with a 12.7mm GCh-75Ch heavy machine gun on a cantilever mount. This mount has both manual and remote controls, a compromise between the open mount of the JCh-2/4/5 and the closed mount of the T-64. In manual mode, the commander disconnects the cupola drive, opens his hatch, and stands on his seat to operate the weapon. The commander controls the machine gun's elevation with a hand crank on the right side, and traverses it by physically rotating the entire cupola with the help of a handle fixed to the mount. The commander can aim the weapon with either a holographic reflector sight in a protective box or the backup iron sights. Because of the crude traverse controls, manual aiming is not very precise, but it is adequate for slewing the weapon toward a threat and laying down suppressing fire. Manual aiming also leaves the commander exposed to shrapnel and small-arms fire, including sniper fire, and it breaches the tank's CBRN seal. It does, however, give the commander better all-around visibility, and if nothing else it exists as a backup option if the cupola drive or optics are damaged.

In most situations, the commander instead controls the HMG mount from inside the turret. This is done using an electric drive which matches the elevation of the HMG mount to the elevation of the commander's optic. During regular travel this drive is disabled to reduce strain on the commander's optic control motors. The entire cupola has an electrically powered traverse mechanism, which the commander also uses to control the direction of the main cupola optic. The cupola and the commander's sight are fully stabilized in the vertical and horizontal axes, and the horizontal stabilizer can be deactivated to instead stabilize the HMG relative to the turret. Traverse and elevation are controlled by means of thumb joysticks on the sides of the central optics unit. When aimed using the commander's main optical unit, the HMG can only elevate from -15 to +30 degrees, but switching to a separate anti-air sight allows the commander to aim and fire as high as +85 degrees. The main optical unit, described in the next section, has both visual and infrared modes and variable zoom modes, making it much easier for the commander to identify and aim at threats compared to the original T-64 cupola. In the main optic aiming mode, the commander has a precisely aimed and fully stabilized weapon with better visual and infrared visibility than the gunner, and can fire accurately at ranges of up to 2,000 meters.

The 12.7mm HMG fires from 200-round boxes, which are mounted to the cupola rather than the side of the HMG or its carriage. Because the 12.7mm ammunition boxes are too bulky to store inside the tank and move through the commander's hatch, all reserve ammunition boxes are stored on the outside of the turret. Two are stacked on the right side of the turret, close enough for the commander to lean out of his hatch and lift them onto the ammo box mounting frame. The other two are on the left (gunner's) side of the turret, and would be moved to the right side when out of combat.

Optics and fire control

The JCh-6G has the same optics and fire control suite as the JCh-5R, which entered service just a few years earlier and incorporated features from Chikai's S.806 prototype. The gunner has a single large optical unit with a visual camera, an infrared imaging camera, and a laser rangefinder. The infrared imaging camera, based on imported foreign technology, gives the JCh-6 passive night vision capability, eliminating the need for a large infrared spotlight. In addition to extending the infrared detection range, this reduces the vehicle's infrared signature during night fighting. The gunner's infrared sight is able to identify a tank-sized target at a range of 2,500 meters, and can detect an armored vehicle's infrared signature at even greater ranges, albeit with poor resolution. Both the visual and infrared optics have 4× (12-degree) and 12× (4-degree) magnification modes. The laser rangefinder has a maximum range of 5,000 meters, though the effective range of the gun is about half that distance. The gunner's sight is mounted under a rectangular hood made from armor steel, and has hinged lens cover plates which the gunner can open and close from inside the turret, protecting the sensitive optics from shrapnel and environmental damage.

The commander's main optic is fixed to the commander's rotating cupola, which, as per the above section, has powered and stabilized traverse controls. In effect, the powered cupola functions like a Commander's Independent Thermal Viewer. Like the gunner's sight, the main optical unit has an infrared imaging camera with a fixed 5× magnification, a visual-spectrum camera with 1× and 8× magnification modes, and a laser rangefinder with a maximum range of 5,000 meters, as well as stadiametric rangefinding lines for manual ranging based on the height of a typical tank or soldier. The cupola is fully stabilized in the horizontal and vertical axes, and its electric motor can traverse it at up to 40 degrees per second, faster than the turret can traverse. In addition to the main optic, which the commander views through a pseudo-binocular eyepiece, the cupola has six conventional periscopes facing 45°, 90°, 135°, 225°, 270°, and 315°, i.e., in all directions except directly ahead (covered by the main optic) and directly behind (the least-viewed direction). The commander can also cover the blind spot to the rear by rotating the cupola slightly to look through one of the adjacent periscopes. Trials with the S.806 prototype determined that when compared with a separate rotating optic with a fixed display screen, rotation of the entire cupola improves the commander's sense of direction and makes it easier to switch to the secondary periscopes, but also makes it awkward to traverse more than 90 degrees to either side and difficult, though possible, to traverse all the way to the rear, becaus the commander is always seated facing forward and has little room to move his legs.

As on contemporary Western tanks, the commander's optic has complete hunter-killer functionality. With the press of a button, either the commander or the gunner can traverse the turret and elevate the gun to aim in the direction of the commander's sight, with the cupola counter-rotating to maintain its bearing to the target in the process. At this point the gunner takes over, fine-tuning the aim and firing the gun while the commander searches for a new target. The commander can also aim and fire the main gun while the cupola is fixed at 0° forward and its optic is linked to the gun's elevation. The commander's optic has less magnification than the gunner's optic, and its traverse and elevation link to the gun is less precise, so this mode would typically be used only if the gunner is injured or the gunner's sight disabled.

The main gun of the JCh-6 is fully stabilized in the vertical and horizontal axes, and the stabilizer is more precise than the stabilizers on previous Menghean tanks, improving accuracy when on the move. In automatic mode, the maximum turret rotation speed is 30°/s, and the minimum precise turret rotation speed is 0.05°/s. The JCh-6's stabilizer also features a dynamic aim point mode, absent on earlier Menghean tanks. To activate this mode, the gunner aims at a target, takes a range reading, and inputs it into the ballistic computer. Based on the initial range, the direction of the turret relative to the hull, and a precise odometer tracking the hull's movement, the firing computer performs a trigonometric calculation to keep the crosshairs pointed at the initial aim point even as the tank itself moves relative to that point, rather than simply pointing the gun at a constant compass bearing.

Protection

The JCh-6 is relatively well-protected, incorporating a number of lessons learned from the JCh-5 and previous Menghean tanks. It is built from welded steel armor, much like later JCh-5 variants, and incorporates composite armor on the hull upper glacis, the hull lower glacis, the turret front, and the turret sides up to the autoloader bulkhead. It also incorporates a number of internal measures intended to improve survivability.

The armor thickness values below were taken from a JCh-6G tank hull captured by Anglian forces in the Ummayan Civil War, and represent the line-of-sight thicknesses of the plates used in the tank's construction when measured perpendicular to the surface of the plate. Note that these are merely line-of-sight thicknesses and do not account for the effectiveness of the composite armor scheme or the thickness of the ceramic plates.

Location	Armor thickness (perpendicular to plate)	Angle (from vertical)
Hull upper glacis	45mm steel + 110mm composite + 65mm steel	+76°
Hull lower glacis (top half)	45mm steel + 110mm composite + 65mm steel	-60°
Hull lower glacis (bottom half)	20mm dozer blade + 20mm air + 85mm steel	-60°
Hull sides	90mm steel	0°
Hull rear	40mm steel	-27°
Hull bottom	20mm steel	90°
Hull roof	30mm steel (20mm around turret ring)	90°
Turret face (center)	450mm steel	+30°
Turret face (cheeks)	80mm steel + 410mm composite + 90mm steel	+30°
Turret sides	80mm steel + 120mm composite + 90mm steel	+20°
Turret bustle sides	80mm steel (outer only)	+20°
Turret rear	90mm steel	0°
Bustle internal side bulkheads	30mm steel	0°
Bustle internal front bulkheads	90mm steel	0°
Turret roof	70mm steel	+82 to +87°

The upper and lower glacis plates of the captured JCh-6 had a composite armor scheme made from high-hardness steel plates 10 and 20 millimeters thick, stacked with 10mm gaps between them. The upper glacis plate is 220mm thick overall, but angled at 76 degrees from vertical, for a line-of-sight thickness of 910mm. Taking the total steel armor thickness of 45+10+10+20+20+65=170mm, or 703mm by line of sight, and multiplying by the claimed mass efficiency of 1.2, this yields an RHAe value of 843mm against kinetic energy projectiles. The lower glacis plate is thinner and set at a shallower angle, with a line-of-sight thickness of 440mm total (340mm steel only, 408mm RHAe vs KE), but it is often masked by terrain in battle and impacts on the lower glacis plate are statisically uncommon. The hull sides, however, are just 90mm thick and have no composite armor. At 30° off the tank's centerline, this amounts to a line-of-sight thickness of 180mm, and even at just 10° off the centerline it amounts to 518mm. In practice, the side skirts, tracks, return roller and roadwheels provide additional side protection by prematurely detonating a HEAT projectile or destabilizing an APFSDS projectile, but the hull's immunity arc against modern ATGMs and APFSDS ammunition is relatively narrow. The side armor does, however, provide all-around protection against 25mm APFSDS at all ranges and 30mm APFSDS at 500 meters.

The turret used on JCh-6G and JCh-6N tanks has a distinct angular teardrop shape, one of the JCh-6's main identifying characteristics. It has quite good protection against APFSDS fire from directly in front of the turret: the turret cheeks are 580mm thick measured directly through the plate, but this rises to 670mm when accounting for the 30-degree slope of the plate and again to 773mm when accounting for the 30-degree angle of the turret cheeks. Using the same claimed mass efficiency as the hull composite scheme, this is equal to 632mm RHAe vs. KE on the turret face versus a directly incoming threat. Line-of-sight protection falls by 13% when the angled plate is hit from 30 degrees off center. Combat experience in the Ummayan Civil War demonstrated that the new L28A1 APFSDS round fired from the Challenger 2 could usually penetrate the turret face armor of the JCh-6, depending on the range and angle.

The JCh-6 is the first Menghean MBT to also feature composite armor on the turret sides, though the composite scheme only runs up to the point where the composite armor intersects with the autoloader bulkhead. At an angle of 20 degrees off the turret's centerline--the edge of the 40-degree turret frontal arc--the line-of-sight thickness through this armor is nearly the same as the line-of-sight thickness through the turret face when the tank is viewed head-on, and should offer the same protection against APFSDS ammunition. When directly impacted from the side, the turret side armor is easily defeated by modern APFSDS ammunition and newer ATGMs, but it can withstand light anti-tank weapons like the PG-7V/VM/VS and the M72 LAW.

The turret roof armor is 70mm thick over the crew compartment and 20mm thick over the turret bustle. It is also sloped at an aggressive angle, roughly 87 degrees for fire incoming from the front and 82 degrees for fire incoming from the side. This is sufficiently steep that most APFSDS ammunition fired over the turret's 60-degree frontal arc will skim off the surface if it hits the turret roof.

The turret bustle is protected by 80 millimeters of hardened steel angled at 20°, for a line-of-sight thickness of 85mm. Like the hull side armor, this provides all-around protection against 25mm APFSDS at all ranges and all-around protection against 30mm APFSDS at 500 meters. Behind the turret bustle side armor is a 30mm steel bulkhead, which can stop spalling and ammunition fragments which perforated the bustle side armor. Most important, however, is the shape of the turret bustle. Over the turret's 40-degree frontal arc, the bustle is completely hidden from view; at 25 degrees off the centerline, APFSDS penetrators will skim off its surface; and at 30 degrees off the centerline, the edges of the 60-degree frontal arc, APFSDS ammunition will either pass through the side composite armor with a high line-of-sight thickness or pass through the turret bustle armor to the rear and exit the turret rear without hitting the ammunition. Even at 45 degrees off the turret's centerline, there is only a small surface area in which APFSDS ammunition will miss the turret side composite and bulkhead but also hit the stored ammunition.

The JCh-6G/N turret also has a number of weakened zones which are vulnerable at certain angles. In place of an armored gun mantlet, the JCh-6 has a gun port with a small armored shield, and the armor at the center of the turret face is 450mm of steel without composite. The tapered turret cheeks also create weakened zones when the turret is viewed from the side: at 30 degrees off the centerline, line-of-sight armor thicknesses are 510mm through the turret sides, 680mm through the turret face, and 680mm tapering down to 350mm through the outer turret cheeks. The armor around the turret ring is even thinner, especially on the turret sides and rear. The commander's cupola, which is raised above the sloped turret roof and surrounded by periscopes, is vulnerable to APFSDS and autocannon fire, and there is a cutout in the upper glacis composite armor around the driver's position.

Overall, the armor scheme of the JCh-6 is marginally better than that of the JCh-5, and better than that of later T-74 models, but still inferior to that of most Western MBTs. The Menghean Army realized this in 2005, when it lost a number of JCh-6G tanks to enemy fire less than a year after the model's introduction. Subsequent variants of the JCh-6, starting with the JCh-6G1, have supplemented their passive hull armor with reactive armor, particularly on the frontal arc of the turret.

If it is penetrated, the JCh-6's internal layout gives it moderately good survivability. The ammunition in the turret bustle is separated from the crew compartment by a steel bulkhead, and the ammunition ramming hatch is covered by a steel plate inside the autoloader compartment when not in use. The autoloader access hatch on top of the turret bustle doubles as a blowoff panel, relieving pressure in that compartment. A bustle autoloader cookoff will be contained to the turret rear compartment, allowing the crew to survive and drive the tank to safety. The sides of the turret bustle, also behind a bulkhead and under blowoff plates, contain the master hydraulic fluid pump and the turret traverse motor, though a number of other hydraulic components such as the gun elevation drive are located inside the fighting compartment. The JCh-6 uses a new type of non-flammable hydraulic fluid, but this fluid is still hot and highly pressurized, and could pose a threat to the crew if ruptured. The carousel autoloader is located inside the fighting compartment with no blowoff panels, but a circular 35mm steel plate covers most of its surface, except the round and charge in the 6 o'clock ready-to-load position. This plate protects the carousel autoloader and its ammunition against spalling and projectile fragments which hit the turret and upper hull. There are no loose projectiles, missiles, or charges stowed anywhere else in the fighting compartment. This means that a hull ammunition cookoff is only possible if a projectile penetrates through the lower hull. Studies of tanks hit during firing trials and in combat indicate that hits on the lower hull sides are uncommon, and impossible when the tank has entrenched itself or adopted a hull-down position. In this respect, the JCh-6 compares favorably with many foreign MBTs, which store reserve ammunition higher in the hull with no secondary anti-spall plate.

Following Menghe's return to the Septentrion Treaty on Atomic and Nuclear Disarmament in 1988 and the stabilization of the STAND order, Menghe regards the threat of tactical nuclear exchange as negligible, anticipating a focus on strategic strikes even if a major conventional war progresses to the point that the major powers resume nuclear testing. Consequently, the JCh-6 is not fitted with anti-radiation lining. It is, however, fitted with a Kevlar spall liner which reduces the damage to internal systems if the armor is penetrated.

Mobility

The main powerplant of the JCh-6 is a license-produced version of the MTU MB 873 Ka-501 powerpack, originally designed in Eisenmaat. The Menghean version is produced under license by Samsan Heavy Industries and features a revised radiator design to improve engine cooling in hotter climates. The MB 873 is a four-stroke liquid-cooled V12 turbo-diesel engine, and it is installed longitudinally in the hull, with the crankshaft running parallel to the vehicle's path of motion. It generates 1500 metric horsepower at 2,600 RPM and 4,700 newton-meters of torque at 1600 rpm. On the baseline JCh-6G, which carries no reactive armor, this results in a power-to-weight ratio of 30.9 hp/t. During trials, the S.806G was able to reach speeds in excess of 80 km/h on paved roads, but its speed is artificially governed to 75 km/h to reduce the risk of throwing or damaging a track, and in peacetime most road marches are restricted to 50 km/h. The tank also has excellent acceleration, useful when relocating from one position to another, and can maintain high speeds in cross-country travel.

To support these top speeds, the JCh-6 introduced a new model of continuous track with rubber pads on both the inside and the outside of each link. The roadwheels also incorporate thicker rubber coatings than the roadwheels of the JCh-5, reducing friction and increasing the lifespan of the entire suspension.

Fuel tank location	Capacity
Engine compartment left	140 L
Engine compartment right	140 L
Behind turret basket	330 L
Driver's compartment left	180 L
Driver's compartment right	120 L
Right side hull fenders	160 L
Left side hull fenders	580 L
Outer fuel drum 1	200 L
Outer fuel drum 2	200 L
Total fuel capacity	1850 L

Fuel consumption averages 2 L per kilometer on paved roads and 5 L per kilometer offroad, based on data from driving trials with the JCh-6G1. Fuel is stored in four locations throughout the tank: two fuel drums on the rear of the hull, external fuel tanks outside the hull over the treads, two fuel tanks next to the driver, and two fuel tanks in the engine compartment. Typically, fuel is drained from the tanks in this order, so that the drums empty first, followed by the unprotected fender tanks. Tank crews typically jettison the fuel drums before entering battle, using them only to augment range on road marches. The fuel tanks inside the armored hull contain 910 L of fuel, the side fender fuel tanks contain 740 L of fuel, and the rear drums contain 200 L of fuel each, for a total of 1,850 L of fuel. Based on the average fuel consumption levels above, this gives the JCh-6 a travel range of 925 km on roads (825 km without drums) and 370 km in fast offroad maneuvers (330 km without drums). This high autonomy, when combined with the high speeds described above, makes the JCh-6 very effective at exploiting breakthroughs and driving deep behind enemy lines.

The MB 873 Ka-501 is arranged as a unitary powerpack, meaning that the engine, transmission, radiator, and other equipment can be lifted out of the hull as a single unit. With the help of an armored recovery vehicle with a 10-tonne crane, it is possible to remove the JCh-6's powerplant and install a replacement in the field in as little as 30 minutes. In the kind of short but high-intensity war which the Menghean Army intends to fight, this allows a JCh-6 tank battalion to cannibalize severely damaged vehicles with otherwise intact engines to support otherwise intact vehicles with damaged actions.

The JCh-6 can ford water obstacles 1.1 meters deep without preparation. To ford deeper obstacles, the crew must install watertight covers over the radiator grates and use the commander's hatch to draw air into the tank. With these preparations, the tank can cross water obstacles 2.1 meters deep, with only the commander's cupola extending above the surface. For even deeper obstacles, the crew must coat the edges of all hatches in a resinous waterproofing paste and install a snorkel onto a ring on top of the driver's hatch. When not in use, the snorkel is broken down into three telescoping segments and stored on the rear of the turret. The raised snorkel allows the fording of obstacles as deep as 5 meters. During a snorkeling operation, all crew members don rebreather masks and life preservers, so that they can flood the crew compartment and swim to the surface if the tank leaks or becomes stuck. Doctrine also forbids snorkeling for more than 1000 meters, but even in summertime very few sections of river on the Menghe-Maverican frontier area reach this width.

Crew amenities

To protect the crew from chemical, biological, radiological, and nuclear contaminants, the JCh-6 has rubberized seals on all hatches into the crew compartment and rubber-coated canvas sleeves around the main gun and machine gun ports. An onboard filtration system clears contaminants out of incoming air and keeps the crew compartment at a slightly greater pressure than the surrounding atmosphere so that outside air cannot leak through any remaining gaps or openings. The airtight system is briefly compromised during the gun loading cycle when spent cartridges are ejected through the hull roof, and it is entirely compromised if the commander opens his hatch.

The JCh-6 also has an air conditioning system which controls temperature and humidity levels in the crew compartment. Individual vents blow cool air at the faces of all three crew members and into electronics housings. After problems with overheating in the Ummayan Civil War, all JCh-6Ns and subsequent variants were built with a more powerful air conditioning system, which was also retrofitted to JCh-6G hulls as part of the G2 upgrade. This improved air conditioning system can maintain an internal temperature of 20-25°C in exterior temperatures of up to 50°C, allowing the crew to fight effectively in tropical climates.

It is possible for the crew to sleep inside the tank if the outside atmosphere is contaminated or if the risk of an enemy night attack is high. To do this, the driver reclines his seat back, and the commander and gunner fold their seats up and lie on the turret floor, or sleep sitting up. An alarm mode on the radio allows the tank company commander to wake the crew at short notice if the unit comes under attack or has to move quickly.

An interesting feature of the JCh-6 is a water kettle behind the driver's position, which allows the crew to boil water for tea without leaving the crew compartment. Beyond its value for maintaining morale, the kettle also allows the crew to sterilize water by boiling it.

Other features

For protection against guided munitions, the JCh-6 carries smoke grenade projectors capable of quickly laying a multi-spectral smokescreen in front of the tank's turret. This system can be used to disrupt the guidance systems on certain anti-tank guided missiles, or to break the launch platform's lock on the target, during which time the JCh-6 can either prepare to engage the launch platform or retreat to safety. As the smoke grenades are activated manually by the commander upon spotting the incoming missile, it is debatable whether this constitutes a softkill active protection system, though it has some functional similarities. All JCh-6 variants can also inject diesel fuel into the engine exhaust, generating a thick smokescreen behind the tank in order to cover mechanized units advancing behind it or conceal its retreat.

The JCh-6 is fitted with a small dozer blade on the lower glacis plate. When extended, this allows the tank to dig a rudimentary hull-down fighting position in 15-20 minutes by driving back and forth over the soil. During this process, the gunner and commander normally dismount to direct the driver. The dozer blade can also be used to fill in enemy anti-tank trenches or build a rudimentary ramp over obstacles. In either case, a professional engineering unit would be more effective, but the dozer blade can be used if no engineers are nearby.

Mounting points on the lower glacis plate above the dozer blade allow the installation of a variety of mine rollers and mine plows. Because of the different arrangement of mounting points, the JCh-6 cannot use the same mine rollers and mine plows as earlier Menghean tanks.

The "tank log" of the JCh-6 is normally carried on the right side of the hull, above the side skirts. It is a standard wooden log measuring 3,325mm long and 180-220mm in diameter. If the tank becomes stuck in mud or on an obstacle, the crew dismount, unhook the log from the hull, and attach it to the tracks forward of the hull with the help of clips stored on the rear. The commander then provides direction from outside the tank as the driver advances the tracks, pulling the log under the tank and thus advancing it out of the soil or freeing it from an obstacle pressing against the underside of the hull. The crew then detach the log from the rear of the tracks and repeat as necessary until the tank is free. Notably, the tank is slightly too wide to satisfy Menghe's 3800mm oversize railway loading gauge with the log fitted to one side, so for railway transport the crew instead secure the log behind the tank by hanging it from the rear fuel drum supports. The maximum mass of a regulation-size tank log is 450 kg, similar to the mass of two full 200-liter drums, so the supports can easily carry the log if the fuel drums are stored separately during rail transport. This log placement, however, partially obstructs airflow to the radiator intakes, so the log must be moved to the side of the hull after the tank is unloaded from its railcar to attain the desired engine performance on long marches and in combat.

In addition to the three hatches on the roof of the vehicle, the JCh-6 also has an emergency escape hatch under the driver's seat. If the tank is disabled while under enemy small-arms fire, this allows the crew to crawl out safely, though it takes much longer than escaping via the roof hatches. The belly hatch also provides a means of escape if the tank is overturned in an accident.

Normally, each JCh-6 crew is provided with a single JjS-104 carbine and two D-94 pistols so that the crew can defend themselves against enemy infantry while withdrawing to safety. The crew may also fire these weapons through open hatches if the tank is immobilized and under attack from infantry. Though official regulations do not provide for it, during the Innominadan Crisis many JCh-6 crews stowed additional carbines, grenades, and even disposable anti-tank launchers in the crew compartment or in the external stowage bins.

Variants

JCh-6G

This is the designation given to early-production JCh-6 tanks based on the S.806G prototype. The baseline JCh-6G was not fitted with any reactive armour, as the Chikai design team believed that its composite armor was adequate to deal with most enemy anti-armor threats. This assumption turned out to be incorrect, leading to the adoption of reactive armour on later variants.

The JCh-6G was fitted with side skirts over the tracks, but these had only limited anti-armor effectiveness. The first three meters after the mudguards were covered by hardened steel plates 10mm thick, covering the crew compartment up to the engine bulkhead against fire from the forward 60-degree arc. Beyond that point, the side skirts were made from simple rubber and mainly existed to control kicked-up dust and prevent the proper fusing of HEAT rounds incoming at high angles. Over the frontal arc, the side skirts could improve the effectiveness of the hull side armor by detonating HEAT charges early and inducing yaw in kinetic energy penetrators, but they were inconsistent in the latter role and ineffective against enemy fire from directly to either side.

The fire-control suite on the JCh-6G is identical to that of the JCh-5R, incorporating last-generation foreign infrared imaging optics for night vision. It represented a major advance over previous Menghean MBTs, especially with regard to night combat, but lagged slightly behind the newest foreign tanks then entering service in terms of imaging resolution and stabilization.

After combat experience in the Ummayan Civil War revealed that the JCh-6's armor was insufficient to provide consistent protection against 120mm APFSDS rounds from Challenger 2 and Leclerc tanks, the Menghean Army implemented an interim up-armoring scheme for JCh-6G tanks. This involved applying Generation 2 ERA blocks from the JCh-5R to the turret face and hull upper glacis plate, increasing protection sufficiently to defeat enemy 120mm APFSDS ammunition. The added armor also covered the weakened zones at the corners of the turret cheeks. ERA blocks were also fitted to the forward side skirts, though not the rubberized rear ones. Tanks refitted in this way are designated JCh-6G1.

All existing JCh-6G hulls were refitted to JCh-6G1 standard during the late 2000s, and all new-build JCh-6Gs from 2006 onward were built to JCh-6G1 standard. Because these changes did not impact the shape of the hull or its optics cutouts--in effect, these tanks were simply fitted with ERA in the factory instead of in forward depots--they shared the G1 designation despite being new-build variants rather than refits.

Starting in 2012, Menghe began refitting its remaining JCh-6G1 tanks to the same standard as the JCh-6N. Tanks refitted in this way bear the designation JCh-G2. The most visible change is the addition of Generation 3 ERA blocks to the turret face, which along with the mounting of composite armor side skirts, MChGJ-0800 radio, and Ulsae softkill APS makes the JCh-6G2 externally similar to the JCh-6N1. Differences between the two include the JCh-6G2's smaller gunner optics, the different arrangement of its radio antennas, and the slightly lower engine deck masking a smaller radiator.

JCh-6N

The JCh-6N was Menghe's long-term solution to the deficiencies in the JCh-6G. Introduced in 2008, it featured ERA blocks purpose-cut for the JCh-6 hull, including triangular blocks to fit the gaps in the JCh-6G1's scheme. The JCh-6N was also fitted with sturdier mounting points on the side fenders and reinforcing bars to the hull sides, allowing the mounting of thicker and heavier composite armor plates as side skirts. With these plates fitted, the JCh-6N can withstand light man-portable anti-tank weapons like the PG-7 rocket on the hull sides, and can withstand EC 120mm APFSDS over the 60-degree frontal arc.

Additional protection on the JCh-6D comes in the form of an automated softkill active protection system. This consists of passive sensors which can detect enemy missile launches over the 120-degree arc in front of the turret. When alerted to a threat, the commander is given the choice of deploying a smokescreen in the path of the threat or automatically slewing the turret and elevating the gun to face the threat. The softkill smokescreen masks the tank's infrared signature and blocks laser illuminators, interfering in some anti-tank missile guidance schemes. The reactive turret traverse option allows the gunner to destroy the missile launch platform and break the guidance loop of non-fire-and-forget missiles.

The JCh-6N also introduced major upgrades to the optics and fire-control system, using state-of-the-art components imported from Dayashina. Magnification and resolution on the gunner's sight and commander's sight were improved, and a new stabilization system with more precise control was fitted. The optics can reportedly track a moving target even as the tank moves, using IR contrast measurement to keep the target centered in the tank's sights.

Another interesting feature of the JCh-6N was the reworking of the tank's communications suite. It was the first operational Menghean tank to carry the MChGJ-0800 C-band radio communications system. Limited to line-of-sight signals, but by the same virtue difficult to intercept and jam, the C-band antenna allows tanks within the same platoon or company to continue communicating even when lower frequencies are being jammed. For longer-ranged communications, the tank also carries UHF and VHF antennas.

The engine deck of the JCh-6N is slightly reshaped and slightly raised. This allowed the installation of a slightly improved radiator with greater airflow. Field exercises with the JCh-6G revealed that its engine, designed for a cold-temperate North Casaterran climate, underperformed in hot, humid South Hemithean summers and tropical or desert conditions. With the new radiator, the JCh-6N can sustain its maximum rated output of 1,500 hp at temperatures of up to 50°C.

Less visible was the addition of a new type of two-piece 125mm gun round. Designated "dual-purpose," this round's projectile incorporates a tandem HEAT warhead with a prefragmented outer casing around the main charge. It also has an airbursting fuse, which detonates the round near the target based on the distance calculated by the laser rangefinder and the time-of-flight predicted by the firing computer. This increases effectiveness against infantry in trenches or other open-topped covered positions, and allows the tank to more easily engage loitering or slow-moving helicopters. By combining high-explosive and light anti-armor capabilities, this also allows the tank to split its ready ammunition load between only two types of ammunition, APFSDS for heavy armor and dual-purpose for all other targets.

Beginning in 2012, Menghe began refitting its JCh-6N tanks to JCh-N1 standard. This involved installing the Ulsae softkill active protection system, which is comprised of infrared missile-launch warning sensors linked to a traversing jamming unit with a laser and infrared dazzler. The missile-launch warning sensors can also automatically trigger smoke grenade launchers facing the target, and will alert the commander to the bearing of the launch or designator, allowing him or her to turn the cupola or turret to face the threat. As with other early installations of the Jŏgran-un APS family, the sensors only cover the turret's forward 180-degree arc, and do not provide protection against threats to the rear of the turret.

The JCh-6N2, introduced in 2020, applies the full Jŏgran-un active protection system, complete with phased-array radar modules on the forward turret corners and hardkill projectile launchers on the rear turret corners. This required a full replacement of the external stowage bins and a slight forward shift of the external 12.7mm ammunition boxes. As on many other Jŏgran-un installations, the active protection system only covers the 180-degree arc forward of the turret. The reactive armor panels on the hull and the turret were also reverted to 2nd Generation ERA, which, in field testing, turned out to be more mass-efficient than the 3rd Generation type, which did not consistently function as its developers claimed.

JCh-6D

The JCh-6D was introduced in 2013 as an interim upgrade to keep new-production JCh-6 models relevant until the introduction of the JCh-8, which had fallen behind schedule due to increasing design requirements. It retains the basic hull of the JCh-6, but adds a new turret derived from that of the S.810G prototype vehicle, one of Chikai's initial JCh-8 prototypes.

The new turret has an octangular shape with two sloped front plates, in contrast to the more rounded geometry of the JCh-6G/N turret. This eliminates the weakened zones on the outer turret cheeks, which become significant when the early JCh-6's turret is not facing directly toward the threat. The new armor is also thicker, measuring close to one meter in line-of-sight thickness against threats coming from directly in front of the turret. The turret side armor is thicker as well, with a line-of-sight thickness of 350mm. The turret bustle tapers at an angle of 15 degrees on each side, and it is protected by 100mm of hardened steel. This armor deflects APFSDS projectiles at angles of up to 25 degrees off centerline, though it can be penetrated at angles of 25-30 degrees. Official Menghean sources claim that apart from a weakened zone around the gun mantlet, the JCh-6D's turret is protected against 125mm two-piece APFSDS over the 60-degree frontal arc and 125mm unitary APFSDS over the 40-degree frontal arc before the application of ERA.

The construction of the JCh-6D's turret armor scheme is modular, with each "cheek" comprised of angled composite plates inside a steel casing. The armor modules can be lifted off the turret in the field with the help of an armored recovery vehicle's crane, allowing easy repair of the armor plates most likely to be struck by enemy fire. The face plates are made of 90mm hardened steel, which will stop 30mm APFSDS ammunition at combat ranges before it can penetrate into the composite matrix inside the armor modules.

The main armament of the JCh-6D was also upgraded with the help of knowledge spun off from the JCh-8 program. It consists of a 125mm L/57 Type 11 smoothbore tank gun. Compared with the 125mm L/46 used by the JCh-6G/N and JCh-5N/D/R, this weapon has a longer barrel and sturdier barrel walls, giving it a higher muzzle velocity and allowing the use of unitary APFSDS ammunition with a more powerful propellant. The gun is still reverse-compatible with existing Menghean 125mm unitary and two-piece ammunition. Elevation ranges from -6.7° to +15.9°, and the gun reloads at a fixed angle of +5.9 or 0 degrees, depending on the indexed autoloader. In addition to sitting at a different angle, the bustle autoloader was widened to increase its capacity to 18 rounds, bringing total ammunition capacity to 40 rounds, typically including 2-4 YDCh-73 ATGMs, which the gunner controls via a multi-function display. The JCh-6D is reportedly able to accept Chikai's 140mm smoothbore gun with minimal modifications, allowing easy refit of the tank in a field depot, though as of 2021 all JCh-6Ds in service still carry the 125mm L/57 gun.

Co-axial armament consists of a 7.5×54mm GCh-96Ch GPMG. The co-axial weapon was changed from a GCh-77 to a GCh-96 to reduce ammunition consumption and improve reliability. The ammunition feed was changed to a single 4,800-round belt, increasing ammunition capacity and eliminating the need for the commander to change boxes in combat. The tray for catching spent casings and belt segments still has a limited capacity, however, and must be dumped out the commander's hatch as it fills up. The commander's weapon station has a 12.7mm GCh-75Ch on a remote controlled weapon station, with the octagonal cupola fixed in place. This change allows the commander to easily traverse the HMG through 360° without having to twist his or her torso inside the confines of the turret. At low angles the HMG is linked to the commander's high-power IR/TV optic, but a separate optic with fixed-zoom IR/TV optics allows aimed fire over the HMG's full -15° to +80° arc. This separate optic also serves as a backup aiming unit. There are no manual backup controls on the HMG, a compromise which the designers pushed forward over intense opposition from conservative Army officers.

Though still a JCh-6 variant rather than an entirely new tank, and though originating as an offshoot of the JCh-8 development process rather than a precursor, the JCh-6D represented an important transition on the way to the JCh-8, and in many respects it is similar to the JCh-8G.

Service

Ummayan Civil War

In the same year that it entered service, the JCh-6 received its first trial by fire in the Ummayan Civil War. One battalion in the Menghean mechanized infantry division deployed to that conflict was sent a replacement shipment of 31 JCh-6G vehicles for combat evaluation. This battalion initially performed well against militants fighting around Ummayah's cities and towns, but it suffered heavy losses in the Battle of Basra and other engagements against Entente armor. These engagements revealed a number of shortcomings with the JCh-6G, including its inadequate turret and hull armor, which were unable to withstand APFSDS rounds from the EC's 120mm guns. Subsequent variants, namely the JCh-6G1 and JCh-6N, added reactive armor to compensate for this problem, and the JCh-6D entirely redesigned the turret to eliminate weakened zones on the cheeks. Combat experience in Ummayah also confirmed that the JCh-6's unitary APFSDS ammunition was capable of defeating parity Western armor over the frontal arc, whereas JCh-5 tanks were unable to do so outside of flanking engagements.

The Menghean Army lost a total of 10 JCh-6G tanks during the Ummayan Civil War, including vehicles that were disabled by IEDs or abandoned by retreating forces. Among these, the EC captured two examples in relatively good condition, shipping them back to Casaterra to study the JCh-6's armor scheme, optics, and internal layout.

Innominadan Crisis

The JCh-6 saw service again during Menghe's invasion of Innominada, part of the Innominadan Crisis. Unlike the Ummayan Civil War, where JCh-6s accounted for only a small share of Menghean armor, most active-duty units involved in the Menghean intervention were equipped primarily or exclusively with the JCh-6N or JCh-6D.

An unclassified Menghean Army report released in 2017 documents 28 "irrecoverable" JCh-6 losses during that conflict, as well as an unspecified number of tanks which were returned to service after undergoing repairs. Studying losses in further detail, the report concluded that no hull ammunition cookoffs occurred in tanks penetrated by APFSDS projectiles, unguided rockets, and ATGMs, though three tanks were irreparably destroyed after IEDs or land mines detonated the carousel autoloader and several lost their turret ammunition in controlled cookoffs. This confirmed Chikai's assessment that the removal of loose hull ammunition stowage reduces cookoff risk significantly when faced with conventional threats, but not when faced with unconventional ones.

Operators

• Argentstan: 920 JCh-6N delivered secondhand from the Menghean Army in 2018-2021
• Template:Country data Azbekistan
• Dzhungestan: 216 JCh-6N delivered 2013-2015
• Republic of Innominada: 860 JCh-6G1 delivered 2015-2017
• Menghe
• Polvokia: 1380 JCh-6G1 and JCh-6N ordered 2009-2019
• Template:Country data Ummayah