JCh-7

JCh-7
The two service variants of the JCh-7, and a three-view diagram.
Type	main battle tank
Place of origin	Menghe
Service history
In service	2014-present
Used by	Menghe Polvokia
Wars	Innominadan Crisis
Production history
Designed	1999-2011
Produced	2012-present
No. built	~600 (all variants)
Variants	JCh-7G, JCh-7N, M110 (Polvokia)
Specifications (JCh-7G)
Weight	16.7 metric tonnes
Length	9.77 m
Width	3.03 m
Height	2.31 m (turret roof, excluding elevated section)
Crew	3 (driver, gunner, commander)
Armor	welded steel plate aluminum turret and applique plate
Main armament	107mm L/56 smoothbore gun
Secondary armament	12.7mm HMG (commander) 7.62mm GPMG (co-axial)
Engine	WK-500/G turbine 365 kW (490 hp)
Power/weight	29.3 hp/tonne
Suspension	torsion-bar
Ground clearance	35 cm
Operational range	500 km (internal fuel)
Speed	75 km/h (road)

The JCh-7 (Formal designation: 7호 경형 전차 / 七號輕型戰車, Chil-ho gyŏnghyŏng jŏncha, "No.7 Light Tank;" short designation 전차-7 Jŏncha-chil) is a type of amphibious light tank designed and built in Menghe. It is based on the chassis of the BSCh-6 APC, but fitted with an autoloading 107mm gun turret. It also incorporates a more powerful gas turbine engine and applique steel armor on the hull front. It is mainly used by the Menghean Marine Infantry and some reconnaissance units in the Army.

Development

The JCh-7 had a long and convoluted design history. The Menghean Army's overall procurement program for a "new-generation amphibious light tank" began in the early 1980s, and the BSCh-6 APC still in pre-production trials immediately stood out as a usable chassis.

Prototypes of the JCh-7 tank, including early development vehicles.

This gave rise to Sije-Chalyang 717, a prototype armed with a 57mm anti-aircraft cannon in a truncated-conical turret. The chamber section of the gun was rotated 90 degrees, allowing the loader to insert five-round from the side. The 717 had a crew of three, with the gunner doubling as commander; this saved space in the turret, but the commander's poor situational awareness would have constrained its usefulness as a reconnaissance vehicle.

After the Decembrist Revolution, plans for an amphibious light tank were temporarily frozen. The single prototype Sije-Chalyang 717 was shipped to the Northeastern Tank Museum in Bansŏk-ri, Songrimsong Province, where it can still be seen today.

Development resumed at some time in the mid-1990s, and in 1996 the Menghean Ministry of Defense released an informational video that included a light tank of unknown designation undergoing trials at the Tusan-ri proving ground. This model, variously described as Sije-Chalyang 602 or Sije-Chalyang 604, used the BSCh-5 IFV chassis and was armed with a 125mm smoothbore gun of the same type used by the JCh-5 main battle tank. Sources differ on whether the gun used an autoloader. Very little is known about this vehicle, including the name of the design institute involved and its eventual fate; some analysts have concluded that it was intended as a testbed to see whether the BSCh-5 hull could withstand the weight and recoil of a 125mm high-velocity gun. The project was cancelled in 1998, apparently due to the prototype's poor mobility.

The third series of prototypes, Sije-Chalyang 614 and 615, were produced in 2004. They were also based on the BSCh-5 hull, but incorporated an all-new 85mm rifled gun, which was loaded from a carousel of single-piece shells stored vertically. This allowed for a dedicated commander, rather than a commander/gunner. The unique turret design also kept a low profile over the crew positions, while also allowing an impressive 9-degree gun depression - though the crew could only take advantage of this when firing to the side of the hull. The two prototypes differed mainly in the presence of waterjets, improved optics, and a wind sensor on the 615; this was apparently intended as the finalized, pre-production version. The type received extensive coverage in state media, and was expected to enter service in 2007; according to some, it had already been given the official designation JCh-7.

In 2006, however, the project abruptly fell out of public view. There was widespread speculation that one of the prototypes had suffered an accident on trials, although the Ministry of Defense never released an official report. The following year, a new prototype, Sije-Chalyang 679, was seen carrying the same 85mm turret on a BSCh-6 hull. While less well-armored, it did sport a lower profile and better amphibious performance. This type proved equally short-lived, but for different reasons: the Ministry of Defense had updated its design requirements, and no longer considered the 85mm weapon adequate for the light tank project.

Only in 2011, a quarter-century after the original light tank prototype was produced, did Menghe unveil the Sije-Chalyang 957, which was accepted as the official winner of the JCh-7 development competition. The actual production-model JCh-7G featured some additional improvements, including a gas-turbine powerpack and applique hull armor, but in all other respects it was identical.

Design

Armament

The main armament of the JCh-7 consists of a 107mm smoothbore high-velocity gun, the same type introduced on the JCh-4 tank. Though unable to defeat contemporary main battle tanks over the frontal arc, it can defeat their side armor at a wide enough angle, and is able to easily engage IFVs, APCs, and fortified firing positions. An elevated, angled centerline section in the turret roof allows the gun to depress to -8 degrees, enabling the tank to fire from a hull-down position.

The 107mm gun is fed from a belt-style autoloader in the turret bustle, which contains 26 rounds and is reloaded through a hatch in the turret roof. An additional 12 rounds are stored within the tank interior, on either side of the driver and behind the turret, but must be manually fed into the autoloader through the loading port behind the gun's recoil path. The autoloader can complete a full loading cycle in six seconds; spent casing rear stubs are ejected through a small hatch in the hull roof.

While the bustle is mounted externally, with the external reloading hatch doubling as a blowoff panel, extensive weight-saving measures around the vehicle suggest that the bulkhead between the crew compartment and the ammunition storage space is not thick enough to fully contain an ammunition cookoff. Even so, it provides a slightly higher degree of protection than internal ammunition stowage.

Other armament consists of a co-axial 7.62mm GCh-77 machine-gun on the gunner's side of the turret, and a 12.7mm GCh-75Ch HMG on the commander's cupola. This uses the same mount on the JCh-6, enabling the commander to fire either manually or from within the tank. Some 2000 rounds of 7.62mm ammunition and 500 rounds of 12.7mm ammunition are carried.

Protection

The BSCh-6 hull, which forms the chassis of the JCh-7, is only protected against 7.62mm armor-piercing ammunition over the frontal arc. To offset this protection, the JCh-7 adds applique plates to the upper and lower glacis, and a heavily sloped welded turret. Both the applique plates and the turret are made from aluminum, while the basic hull is made from steel. To save weight, the design employs neither composite nor reactive armor.

State sources report that the JCh-7 is protected against 12.7mm ammunition at regular combat ranges. As no applique plates are visible on the sides, it is unclear how far across the frontal arc this protection extends, or what distance "regular combat ranges" implies. The armor is easily defeated by armor-piercing autocannon projectiles of 20mm caliber or above, and by handheld anti-tank weapons.

The prototype Sije-Chalyang 957 was designed from the ground up with provisions for eventual addition of an active protection system, but this was not actually mounted until 2018, when the Jŏgran-un system entered operational service. Variants equipped with the system are designated JCh-7N.

Mobility

As a result of the added turret and applique forward plates, the JCh-7 has a combat weight of 16.7 metric tonnes, some 4,500 kilograms more than the BSCh-6 off which it is based. This required the use of a slightly stronger torsion bar suspension, as well as a new powerplant. Production versions of the JCh-7 carry a 490-horsepower powerpack consisting of a gas turbine engine and a revised transmission. This is nearly twice the horsepower of the original 1983-vintage diesel engine in the BSCh-6.

With its more powerful engine, the JCh-7 has a highly favorable power-to-weight ratio of 29.3 hp/tonnne, giving it excellent acceleration and mobility. It can also achieve a top speed of 75 kilometers per hour on a level paved surface; higher speeds were achieved in early testing, but speed is governed to this level to prevent damage to the tracks, which return on top of the road wheels.

Despite its heavier weight, the JCh-7 is still capable of amphibious operations, though it does sit significantly lower in the water. The revised powerplant does include a more powerful waterjet assembly, increasing swimming speed to 14 kilometers per hour. It can cross water obstacles without preparation, but for greater safety in heavy seas - for example, when conducting an amphibious landing, or crossing a river with a strong current - the crew can erect a trim vane at the hull front and short snorkels over the engine intake and exhaust. The trim vane can be raised and lowered remotely, but the snorkels must be mounted or de-mounted from outside the tank.

Service

Prototype Sije-Chalyang 759 was accepted into service as the JCh-7 in mid-2011, with the first deliveries to combat units taking place in 2014. It is mainly used in the Menghean Marine Infantry, and also sees service in a few river-crossing brigades of the Menghean Army, though overall it is a rare vehicle in comparison with the JCh-5 and JCh-6.

In 2009, Polvokia negotiated a contract for 98 units of the Sije-Chalyang 679, which was the most highly-evaluated prototype at the time. These were given the Polvokian designation M110. They use a Polvokian-built diesel engine - final assembly is conducted domestically - and include some changes to the fire-control system. After Dayashina blocked a deal to export YDCh-72 missiles to Polvokia in 2013, the Polvokian Army refitted its M110s with YDCh-70 ATGMs, which lacked proprietary foreign electronics.

The JCh-7 saw limited service during the Innominadan Crisis, in support of Menghe's armed intervention in southeastern Innominada. Their performance has been subject to some debate; the type suffered relatively heavy losses to RPG fire, especially in the later stages of the campaign, but High Command of the Menghean Marine Infantry considered them a valuable asset in surprise landings along the coast. Nevertheless, high vulnerability to man-portable AT weapons may have influenced the development of the N variant, which adds an active protection system.

See also

• BSCh-6
• JCh-5
• JCh-6