Sibiwŏl Hyŏgmyŏng class aircraft carrier

File:Sibiwol Hyogmyong.png 4-view of Sibiwŏl Hyŏgmyŏng without aircraft
Class overview
Name:	Sibiwŏl Hyŏgmyŏng class
Builders:	Kimhae Naval Yard, Donggyŏng, Menghe
Operators:	Menghe
Preceded by:	Menghean aircraft carrier Haebang
Succeeded by:	Choe Sŭng-min-class aircraft carrier
Built:	2004-2016
In service:	2012-present
Planned:	2
Completed:	2
Active:	2
General characteristics
Type:	fleet carrier
Displacement:	57,000 tonnes fully loaded
Armament:	4 × 1 Subisu CIWS 2 × 1 RBDJ-34/8 ASW rocket projector 6 × 1 12.7mm HMG
Aircraft carried:	48 aircraft
Aviation facilities:	CATOBAR flight deck 2 catapults 3 arrestor wires

This article is about an aircraft carrier class in the Menghean Navy. For the 1987 coup serving as its namesake, see Decembrist Revolution

The Sibiwŏl Hyŏgmyŏng-class (Menghean: 십이월 혁명급 항공모함, Sibiwŏl Hyŏgmyŏng-gŭb Hanggongmoham) is a class of two conventionally powered fleet aircraft carriers built in the Socialist Republic of Menghe in the early 21st century. The first ship, Sibiwŏl Hyŏgmyŏng (Decembrist Revolution), was laid down in 2004 and commissioned in 2012. The second ship, Gukga Gyŏngje Gijŏk (National Economic Miracle), was laid down in 2009 and commissioned in 2015.

Compared to the preceding Menghean aircraft carrier Haebang, the Sibiwŏl Hyŏngmyŏng class feature a 50% larger air wing, with a normal air wing of 36 fighters instead of 24. They also have CATOBAR launch equipment, and the ability to operate fixed-wing AEW and ASW aircraft. Nuclear propulsion was considered during the design process, but both ships were ultimately built with high-pressure oil-fired boilers. As such, they represent an intermediate evolutionary stage between the Haebang and the larger Choe Sŭng-min-class aircraft carriers.

Development

Preceding carrier class

Menghe commissioned its first postwar aircraft carrier, MH-10 Haebang, in 1990. Though Haebang was the largest postwar Menghean warship, she suffered from a number of drawbacks and limitations, the result of Menghe's limited experience with aircraft carrier design. These faults included a narrow flight deck, a cramped forward elevator, and a relatively small hangar, which constrained the air wing to 24 fixed-wing aircraft (or 28 for surge operations). The Haebang also used a STOBAR configuration with a low-angle ramp, which prevented her from launching airborne early warning and maritime patrol aircraft, and restricted the maximum payload of her fighters.

During the 1990s, the Menghean Navy proceeded with regular testing and evaluation of the Haebang, in the hopes of improving upon her design in future classes. Due to budget constraints, however, the Ministry of National Defense refused to finance the construction of a second aircraft carrier.

Design work resumes

The Polvokian Civil War served as a wake-up call for the Menghean aircraft carrier program. During this conflict, Menghe dispatched the Haebang and her battlegroup to a patrol area off of Polvokia's southern coast to protect the capital city of Ryŏngdo from rebel bombing attacks. Without shipboard airborne early warning aircraft, the Haebang's air group struggled to detect incoming aircraft in time, and because of the low-angle ski jump they had to operate without drop tanks. The Haebang also suffered from disappointing range and poor reliability, and had to cycle in and out of port during the conflict to undergo maintenance and refuel in safety.

As economic windfalls allowed an increase in military spending after 2000, the Navy began to solicit plans for a new aircraft carrier class. The competing proposals were very diverse, and included a number of STOBAR designs which were intended to support the GIA Goshawk. The proposals also differed greatly in size, ranging from small sea control ship concepts to 100,000-ton supercarriers, and in power, with both conventional and nuclear concepts.

The contemporary competition to select a naval fighter prolonged this flurry of designs: at various points, the Goshawk, F-16N, Iolar, MiG-29, and Or-27 were all considered as the basis for a new naval fighter. With their different folded dimensions and capabilities, these fed debate over the necessary characteristics of the new carrier class.

In the end, after all the competing options fell short of various requirements, the Menghean Navy selected the Daesŭngri DS-9 as the basis for a naval fighter. Though less capable than some of the alternatives the Navy had hoped for, the DS-9 could fit the DS-5's deck park footprint with wing folds installed, and its short-takeoff performance allowed it to operate from the Haebang's ski jump without major problems.

The winning design, selected in 2003, was a mid-size carrier moderately larger than the Haebang. In place of a ski jump, it had two steam-driven aircraft catapults, allowing larger payloads on takeoff and the launching of larger utility aircraft. Despite initially favoring nuclear-powered concepts, the Navy reversed course and selected a conventional version of the 36-fighter CATOBAR design. This decision may have been influenced by the 2003 Chimgu nuclear accident, which raised concerns about the maturity of Menghe's domestic nuclear power sector. Apart from questions of safety, the conventionally driven design was projected to be less expensive, faster to build, and cheaper to operate, and it would ultimately serve as a stepping stone on the road to a nuclear aircraft carrier class.

Construction

The first ship in the class was laid down on in April of 2004. Because the Gyŏngsan Songsu-do Shipyard's "battleship drydocks" were too small, she was instead built at a specially excavated drydock in the Kimhae Naval Yard, on the outskirts of the capital city of Donggyŏng. The hull was launched on February 29, 2009, to be fitted out at the same facility, and three years later she was commissioned as MH-12 Sibiwŏl Hyŏgmyŏng.

The second ship, provisionally designated MH-13, was laid down in the same drydock several months later. She was commissioned as Gukga Gyŏngje Gijŏk on October 24th, 2015.

Design

Layout

In terms of overall layout, the Sibiwŏl Hyŏgmyong design makes a number of improvements over the older Haebang. In place of a ski jump, the forward section of the flight deck is level, which allows for a steam catapult position and creates more space for parked aircraft. Moving further aft, the narrow inboard elevator of the preceding design is replaced by a second outboard elevator, immediately forward of the island. The flight deck also extends further outward on the port side, creating space for four fighters and two helicopters. These changes allow the Sibiwŏl Hyŏgmyŏng to carry substantially more aircraft than the Haebang, despite a proportionally smaller increase in displacement.

The landing strip on the Sibiwŏl Hyŏgmyŏng class is set at an angle of 11.3 degrees, and is 24 meters wide. The angle and position were chosen so as to optimize clearances around the takeoff positions and deck park areas. There are two medium helicopter landing circles on the aft end of the flight deck, sized for GH-28 helicopters, and there is a single 10.5-meter-radius helicopter landing circle further forward on the landing strip, this time sized for a larger utility helicopter like the Mil Mi-8. Though not part of the carrier's air wing, large helicopters of this kind are regularly used for carrier onboard delivery duties.

Four small munitions elevators link the flight deck to the magazines below. As on the Haebang, each elevator uses a two-stage design: munitions are first brought up to an intermediate-stage point at the level of the hangar deck, where they are either wheeled directly into the hangar, or moved onto a second elevator which leads to the flight deck. This transition between elevators can be performed while the fireproof doors to the hangar deck are closed, and munitions can also be moved from the first elevator to the hangar deck while the flight deck elevator is closed. At no point in either process is there a direct open shaft from the flight deck to the magazine spaces. Furthermore, all munitions elevators are set a safe distance away from the jet blast deflectors, correcting a safety hazard present on the preceding class.

Catapults

The two forward-facing catapults were the main improvement of the Sibiwŏl Hyŏgmyŏng class. They are driven by compressed steam from the ship's oil-fired boilers, and allow her to launch heavily laden fighter aircraft and low-speed utility aircraft, namely the Demirkan-Yŏng'an DY-11.

One catapult runs down the forward section of the flight deck, and is offset to port. With a normal complement of aircraft at normal parking locations, this catapult is always available to both small-wingspan (DS-9) and wide-wingspan (DY-11) aircraft, with deck park aircraft offset to starboard to keep the launch area clear. The other catapult is located on the port side of the flight deck, 5.18 meters from the edge at its closest point. Both catapults are paired with 4.8 by 9.4 meter jet blast deflectors, and both launch directly forward along the ship's bearing.

Among the Haebang's main drawbacks was the fact that both takeoff routes ran along essentially the same axis, such that a fighter on the rear position could not take off as long as another fighter was conducting checks in the forward position. The rear position was also situated directly on top of the landing strip, and aircraft could not prepare for takeoff there during recovery operations. These drawbacks severely hampered the ship's sortie generation rate. On the Sibiwŏl Hyŏgmyŏng, by contrast, aircraft can launch from one catapult regardless of the status of the other. Moreover, the forward catapult is accessible at all times, and while the aft catapult cannot conduct take-offs during landing operations, there is enough space for a DS-9 fighter to undergo pre-launch checks while recovery operations are underway.

Defensive armament

Defensive anti-aircraft armament consists of four Subisu CIWS installations, each with two 24mm rotary cannons, eight YDG-61 missiles in ready boxes, and an additional 24 YDG-21 missiles in a magazine within the protruding ledge under the mount. This arrangement ensures that at least one mount can intercept threats from any given direction, with wide areas of overlap to port and starboard and narrow areas of overlap forward and aft.

The distinct Haebang-style weapons platforms at the forward and aft ends of the island are retained, but they carry HBDJ-21/12 launchers rather than missile launchers. These HBDJ-21/12 mounts can be loaded with conventional anti-submarine projectiles, but they are typically loaded with hardkill or softkill torpedo defense projectiles (H-21ŎDN and H-21ŎDG respectively). Reload projectiles are stored in ready magazines two decks under each mount, at the level immediately above the flight deck.

For defense against light boats, the ships are fitted with six 12.7mm machine guns, three on each side of the causeways around the flight deck. The Subisu CIWS system can also engage surface targets by means of an electro-optical fire-control system, using a reduced rate of fire to conserve ammunition.

Propulsion

The two carriers of the Sibiwŏl Hyŏgmyŏng class use conventional propulsion, which was deemed less technologically risky than nuclear power. Each ship contains eight high-pressure oil-fired boilers, which drive four steam turbines, each coupled to a single propeller shaft. The maximum speed is reportedly 28 knots, but this cannot be sustained for very long due to the corresponding reduction in range.

Hangar

The hangar on the Sibiwŏl Hyŏgmyŏng class is 150 meters long, 24 meters wide, and 6.4 meters high. In a typical deck park arrangement, it can carry 12 fighter aircraft, five utility aircraft, and four helicopters. Two outboard elevators, both on the starboard side, link the elevator to the flight deck, and each one can carry two DS-9 fighters with folded wings, one DS-9 fighter with extended wings, one DY-11 utility aircraft, or two helicopters.

A unique feature of the Sibiwŏl Hyŏgmyŏng class is the presence of two turntables, each one 17 meters in diameter and situated just in front of the elevator door. These turntables make it easier to rotate aircraft while moving them from their parking spot to the elevator, or vice versa. They are usually kept empty during regular operations, to make them available to different aircraft types inside the hangar.

A fireproof barrier wall can divide the hangar into two halves in the event of a missile impact or accident, limiting damage to one side. Because each side has access to a hangar, a turntable, and two munitions elevators to the magazine spaces, this does not interfere in regular flight operations in the other side of the hangar.

Electronics

Like many aircraft carriers of its time period, the Sibiwŏl Hyŏgmyŏng employs an optical landing system to help guide pilots down onto the landing section. The light array is located to the port side of the landing runway, and is paired with a radome which can track the aircraft’s approach more precisely if needed. Fresnel lenses and fiber-optic source lights to produce a sharper display that is visible from further away, allowing landing aircraft to adjust their approach from a greater distance. The optical landing system allows the carrier to guide aircraft to a landing even under conditions of total radar and radio silence, which would be normal during wartime carrier operations.

Underway replenishment

There are four sets of receptacles for taking on fuel, all of them at hangar deck level on the starboard side of the hull. Each of the four consists of an overhead receiving point for boiler fuel and an underside receiving point for jet and helicopter fuel. Boiler water and drinking water can be delivered through a separate hose adapter.

Solid goods are delivered to mechanical kingposts situated just within the hangar doors. These normally sit suspended on the hangar ceiling, but pivot downward and lock onto the hangar deck when needed. This requires that the turntable be set to a precise zero-degree bearing and locked in place.

During the design process, the Menghean Navy considered ordering a cargo variant of the DY-11, but cut the program on the reasoning that the Sibiwŏl Hyŏgmyŏngs would not operate far enough from Menghe to justify such a capability. Instead, carrier onboard delivery is conducted by heavy utility helicopters, usually Mi-8 derivatives. These helicopters are administratively part of the Navy's land-based aviation, rather than part of the carrier's air wing, and are dispatched from the nearest base as needed. They are also incapable of fitting within the carrier's hangar, due to a lack of folding rotors and tail booms. Instead, during a typical vertical delivery operation, the helicopter lands on the large landing point, is towed to the forward catapult area, refuels there while offloading supplies, and takes off again once finished. Helicopters can also deliver underslung pallets of supplies onto the flight deck.

Aircraft

Strike Airgroup

During the carriers’ construction, Navy high command intended for the Sibiwŏl Hyŏgmyŏng to serve as an expeditionary force which could deploy overseas with the support of other regional powers to intervene in local conflicts. As such, its initial carrier air wing reflected a sea-to-land strike role. Its combat aircraft were a mix of single-seat fighters and twin-seat tactical bombers, both based on the Sŏngrim SL-8 heavy multirole. These were joined by a number of DeSilvo D-4 support aircraft, for radio and radar jamming, AEW, large-area anti-submarine warfare, and carrier onboard delivery.

Unfortunately, the first ship in the class was commissioned just as the Menghean Navy was pivoting away from expeditionary warfare, meaning that much of the initial work configuring the ships’ air group had to be revised. For some time, the Navy retained the original layout in a revised form, with additional AEW aircraft in place of the jamming D-4s and the tactical bombers repurposed to deliver anti-ship missiles rather than bombs.

Support Airgroup

Efforts to repurpose the old air wing for parity warfare were only a temporary measure, however. In 2013, the Sibiwŏl Hyŏgmyŏng went to sea with a revised carrier air wing. The new carrier air wing renders permanent the temporary practice of replacing jamming aircraft with AEW platforms, bringing the total for the latter up to four. It also replaces most of the D-4 ASW and COD aircraft with D-8 tiltrotors, which are more compact in stored form and can take off vertically but retain adequate range and loiter time. The reduction in deck area devoted to support aircraft, and the use of elevators as parking space, allowed for an additional eight SL-8 multirole aircraft. The air wing totals were thus revised to:

• 32x SL-8MK or SL-8MK2 multirole aircraft
• 4x D-4Ch AEW&C aircraft
• 6x D-8A ASW tiltrotor
• 4x GHZ-28B ASW helicopter
• 2x GHZ-28D rescue helicopter

In the last few years, there have been some reports of Sibiwŏl-class carriers taking on supplies, mail, or personnel via one or more D-10 tiltrotors flying in from shore or from another ship. This initially led to speculation that the air wing had been modified, with two D-10s and four D-8As rather than six D-8As. A 2015 documentary sponsored by the ISN, however, stated that these D-10s were actually not part of the ship’s air wing, and had flown in from shore bases or other ships as an improvised means of extending endurance or delivering urgently needed small parts. In regular operation, the Sibiwŏl-class carriers still rely on port facilities and support ships for most of their supply needs.

New subclass

The third ship of the class, launched in 2014 but still in fitting-out, was built on the same hull as the previous two ships but appears to incorporate a number of modifications and improvements. The most noticeable change concerns the location of the island, which was moved further back to leave more room for aircraft leaving the rear elevator. In addition, all three steam catapults were replaced with electromagnetic catapults that allow a smoother acceleration to reduce strain on pilots and aircraft. Other changes included the revision of the defensive armament, with space for a 10-cell shallow-depth VLS array off the port side for longer-range missile defense. The composition of the air wing is not believed to have undergone any major changes.

Role

Though originally intended as an expeditionary warfare platform, the Sibiwŏl Hyŏgmyŏng and her sister ships now play a more cautious fleet support role. In the event of a local counter-offensive war, their air groups would be responsible for extending fighter cover further outward from the mainland, thus shielding surface fleets and submarines from enemy strike aircraft and ASW patrols. Although the SL-8MK2 is capable of carrying anti-ship missiles, most serious anti-shipping missions would come from land-based airfields. The air group is also relatively light on ASW aircraft, and these are mainly geared toward self-defense of the battlegroup. Area ASW missions would be left primarily to coastal maritime patrol aircraft and lighter vessels such as the Changzha-class aircraft carriers.

Ships in the Class

• Sibiwŏl Hyŏgmyŏng (Decembrist Revolution): laid down 1992, launched 1999, commissioned 2006
• Joguk-ŭl Gaebalhae ("Build up the Nation"): laid down 2000, launched 2006, commissioned 2013
• Unnamed hull: laid down 2007, launched 2014, undergoing fitting-out

After the launching of the ISS Um-eul Baucheone's hull in 2010, the upper leadership of the Menghean Navy has maintained that it was only interested in building three aircraft carriers - seen as the minimum needed to ensure that one is on patrol at any given time. In August 2016, however, it was reported that a fourth carrier, as yet unnamed, was laid down in the large drydock which had been used to build ISS Um-eul Baucheone. Satellite imagery of the port at Masad has confirmed that a large keel and bracing supports similar to those in the early construction of the other three carriers are in place. Classified documents leaked the following October suggest that the ISN plans to expand the carrier fleet to five or six ships within the next fifteen years. The ISN has thus far denied these allegations, though the large drydock at the Masad-Meng Special Naval Shipyard remains off-limits to non-military personnel.

See also

• Sinbukgang-class aircraft carrier
• Dolsando-class helicopter carrier
• Haeju-class destroyer
• Jŏngdŏk-class frigate