Songrim SR-12

Songrim SR-12
	3-view of No.304 "Night Dragon" as it appeared at the Songrimsŏng Airshow in 2020.
Role	Multirole stealth aircraft
National origin	Menghe
Manufacturer	Songrim Aircraft Corporation
First flight	2015
Introduction	2024 (planned IOC)
Primary user	Menghe
Produced	2019-present
Number built	6 prototypes; 12 production models (est)

The Songrim SR-12 (Formal designation: 송림 12호 전투기 / 松林十二號戰鬪機, Songrim Sibi-ho Jŏntugi, "Songrim No.12 Fighter;" Short designation 송림-12 Songrim-Sibi "Songrim-12") is an all-weather twinjet fifth-generation jet fighter developed in Menghe by the Songrim Aircraft Corporation. It is designed as a multirole combat aircraft capable of taking on both air superiority and precision ground attack roles.

After a long development project spanning the 2000s, the SR-12 made its first flight in May 2015, and was first publicly unveiled at the 2019 Victory Day celebration. As of March 2021, roughly a dozen production-model SR-12 airframes are in service with a training and evaluation squadron, but no deliveries to combat-ready units have been made, and initial operating capability is scheduled for 2024. This development and evaluation timeline, unusually slow by Menghean standards, may be part of an effort to iron out safety issues and stealth compromises before deploying the plane to front-line bases.

Development

Preliminary work

The Songrim Aircraft Corporation began preliminary work on a stealth fighter some time around 1999 or 2000, producing a series of conceptual sketches under the designation "JG-S." Most of this work was done under the leadership of Han Mun-su, a talented designer and advocate of stealth aircraft. The Ministry of National Defense expressed interest in the aircraft, as nearby Dayashina was the only country in Septentrion to operate 5th-gen fighters, but after the resolution of the Renkaku Islands dispute in 2001 the urgency of this requirement disappeared. Nevertheless, Han argued successfully for a small stream of funding to support conceptual studies of stealth aircraft.

State interest in a fifth-generation fighter increased after 2005, when relations with Anglia and Lechernt, Innominada, and Maverica soured over the Ummayan Civil War. The MoND's initial emergency plan focused on accelerating procurement of existing designs and pushing in-progress weapons into service, but by 2010 Han Mun-su and his work team were given the green light to expand the JG-S project, with new funding tied to the completion of a flyable prototype by May 2013.

Challenges

Even with consistent state support, Songrim's JG-S project met repeated delays due to the plane's technological complexity. The engineers struggled with radar-absorbent materials and configurations, which were at the cutting edge of even the leading military powers' research. As the JG-S project was a state secret, Songrim was also unable to seek input from engineers in Dayashina and Tír Glas, which closely guarded their own stealth aircraft projects.

These problems were compounded by gradual mission creep. As the years passed, the "fifth-generation" requirement was expanded to include a new sensor suite and electronic warfare system, demanding requirements that called for new electronics and lengthy computer code. While the initial design was purely conceived of as an air superiority fighter, the MoND later insisted on organic ground-attack capability, including the ability to carry 1000-kilogram guided bombs.

Other delays stemmed from the engines: initially Songrim opted to use an up-rated version of the Donghae Type 74 turbojet, itself a licensed TF-530, but the increasingly heavy airframe cancelled out the gains from higher wet thrust, and left the plane slower at dry military power. Development of a supercruise-capable engine encountered repeated delays, as the high temperatures and pressures required very durable turbine blades.

As a result of all these delays, by the May 2013 deadline Songrim had failed to produce a full-scale prototype, let alone conduct flight tests. A year later, Songrim delayed its proposed timetable yet again, citing problems with the airframe materials and the engine improvement program. Subsequently released documents suggest that Choe Sŭng-min repeatedly expressed deep dissatisfaction with the prototype's delays and cost overruns, suggesting that the MoND cancel the JG-S and redirect funds toward procurement of more SR-8s and DS-9s. For a time, the stealth skeptics seemed poised to crush the program, but the outbreak of the Innominadan Crisis in September 2014 heightened the sense of urgency around military development. As the Glasic-Hallian Huntress and Letnian MiG-55 fifth-gen fighters entered production overseas, and as tensions with Maverica escalated, Songrim secured new funding for the JG-S, but was also given stern deadlines to put it into service.

Testing

The first test flight with a JG-S prototype took place on May 4th, 2015, and lasted for a total of 25 minutes. No announcements about the test were made, and no photographs were released. After several months of work on avionics, a second, 90-minute flight took place on August 12th. This time, photographs specially approved by the Ministry of National Defense were released to the press, though the images were of poor quality and the announcements that accompanied them said little about the plane's characteristics.

A thin stream of vague but confident reports on JG-S progress continued until early 2016, when the MoND abruptly stopped releasing any information about the new stealth fighter program. Around the same time, online censors began targeting any online or press discussion of the plane's status. Analysts abroad speculated that the program had been cancelled, or that the design team had been purged; only in late 2019 was it confirmed via a leaked document that the second prototype had crashed after one of its experimental Donghae Type 110 engines exploded mid-flight, killing the pilot and destroying the plane.

After the crash, development proceeded more slowly, at the cost of additional delays. The third prototype carried Glasic engines of the same type used on recent Iolar models, imported and later licensed for the SR-8, with more thrust than the first prototype's Type 74 but less than the experimental Type 110. There were also rumors, still unconfirmed, of problems with the fly-by-wire system, the radar, and the lengthy programming tying together the sensor suite.

New images of the fighter were released in early December 2017, ending a year and a half of closely enforced silence, though detailed information remained scarce. A few months later in May, a scale model of the aircraft appeared at a tech expo celebrating the 30th anniversary of Menghe's opening-up and reform, giving visitors the first all-round view of the new aircraft. The model also bore the designation SR-12, a sign that it had been accepted for service, and included a brief description of its capabilities.

The SR-12 made its first public appearance on July 27th, 2019, with three aircraft flying over Donggwangsan during a military parade celebrating the 55th anniversary of Menghe's victory in the War of Liberation. During this overflight display, the parade announcer stated that the SR-12 had been accepted for service and was ready for low rate initial production, with deliveries of production airframes expected to take place the following year. In the months that followed the parade reveal, the Ministry of Defense also began publishing more detailed information on the SR-12's features and capabilities, painting a more thorough, if possibly optimistic, picture of Menghe's first fifth-generation fighter.

Introduction and evaluation

Rear and underside views of No.304 "Night Dragon" as it appeared at the 2020 Songrimsŏng Airshow.

Despite these optimistic announcements, the SR-12 has not yet been delivered to combat units. A separate press release issued in January 2020 stated that the fighter would reach initial operating capability in 2023.

The first production-model SR-12 made its first flight on March 3rd, 2020. While the previous two aircraft were workshop-built units, these units were internally and structurally identical to later production units. After the Menghean Ministry of National Defense released photos of the taxi runs and test flights, observers noticed a number of differences between the production models and the prototypes unveiled in December 2017 and July 2019:

The side missile bays had single rather than double doors.
The doors of the landing gear compartments were enlarged.
The leading-edge wing flaps were made of a different material.
The underside of the nose was more squared-off and less rounded.
Attachment points for under-wing pylons were added.
Forward radar warning receivers were moved from the sides of the nose to the sides of the intakes.

Production-model aircraft made another appearance at the Songrimsŏng airshow and defense exposition in February 2021. This airshow included the first clear images of the SR-12's open weapons bays, previously distinguishable only from panel lines. The centerline weapons bay was shown with six YGG-7 Hwasal missiles, with the center missile on each side offset forward to clear the space around the fins. This in-flight missile display also revealed the reasoning behind the shift from two-panel to single-panel side bays: the SR-12 can extend an arm carrying an air-to-air missile on a launch rail outside the weapons bay, then close the door behind it, blocking radar reflections from the inside of the weapons bay while allowing the exposed missile to acquire a target's infrared signature. Small notches in the weapons bay door, normally covered by small panels, leave space for the struts connecting the launch rail to the airframe inside.

Better-quality photographs from the 2021 airshow also confirmed that the production-model SR-12 eliminated some panel lines and structural rivets that independent analysts had previously identified as flaws in the prototype's stealthiness.

Currently (as of March 2021), it is believed that roughly a dozen production-model SR-12s are undergoing initial operational testing and evaluation (IOT&E) at a remote site in northern Menghe. The base's distance from the front line, along with the duration of testing, suggests that the Menghean Armed Forces are adopting an unusually cautious approach to the SR-12's late development process, possibly a response to the loss of a prototype in early 2016. Photos and press releases, while drumming up attention about the SR-12, have been deliberately vague about its performance characteristics, and observers from Menghe's closest allies have been denied access to the test site. A press release in January 2021 stated that the projected deadline for IOC had been moved back from 2023 to 2024, which would put the total length of the development program at close to 25 years.

Foreign assistance

The relatively early appearance of the first JG-S prototype - just a year after Septentrion's first fifth-generation fighters entered operational service - fed extensive speculation about whether Menghe had imported most of the jet's technology from abroad. Tír Glas, Dayashina, and Hallia, all participants in the Huntress fighter jet project, had licensed military electronics to Menghe in the past.

A spokesperson for Glasic International Aircraft confirmed in 2017 that GIA had shared certain dual-use technologies, including carbon fiber aircraft skin and titanium alloys, with Menghean companies, but also stated that this was part of a previously negotiated technology transfer deal negotiated before the existence of JG-S was known. GIA denied sharing any information on radiation-absorbent material, or on the principles of stealthy airframe design. Representatives of Dayashinese and Hallian aerospace contractors have also denied turning over sensitive or classified information, including radar and passive sensor designs. Some less sensitive components, including the autocannon and the production-model engines, are known to be built under license, but were approved for export in relation to earlier Menghean combat aircraft.

For its part, the Menghean Ministry of National Defense insists that the aircraft is "fundamentally domestic in design," though it acknowledges building on undisclosed "state-of-the-art materials and principles." The radar-absorbent material is purportedly entirely indigenous, and may be related to radar-absorbent composites used on the SR-8R and the DS-9D/R, which are also purportedly indigenous.

Design

Layout

Compared to most of Septentrion's other fifth-generation fighter programs, which incorporated lambda wings, diamond wings, and canards, the SR-12 follows a rather conservative tailed delta layout, reminiscent of Songrim's SR-8. Letnia's MiG-55 follows a similar configuration. Some defense analysts have speculated that the SR-12's conventional design may compromise its radar cross-section, with one calling it a "display-only stealth fighter." Others have presented more cautious assessments, noting that it displays good planform alignment and has other RCS-reducing features.

The SR-12 is also the largest and heaviest of Septentrion's three service-ready fifth-generation fighters, a characteristic which became apparent as soon as the first taxiing photographs were released. In conjunction with a proportionally larger wing area, this gives it a longer range, a heavier payload, a larger bomb bay, and more space for supplemental radar antennas. Like the SR-8, it may be intended as a "high-cost, high-capability" fighter, which will pair with a mass-produced "low-cost, low-capability" design; but Daesŭngri's DS-13 fifth-generation program has yet to produce a flying prototype, so the SR-12 may instead be complemented by reduced-RCS variants of the SR-8 and DS-9.

Performance

Photograph of a taxiing SR-12 with refueling probe extended.

The production-ready model of the SR-12 appears to use the Donghae Type 89/160 turbofan, which Menghe licensed from Tír Glas for the "R" variant of the Songrim SR-8 in 2017. The engine nozzles, also adapted from the SR-8R, incorporate two-dimensional thrust vectoring for increased maneuverability and thrust reversal for shorter landing distances.

While the SR-8R is supercruise-capable and has an excellent thrust-to-weight ratio, the SR-12 is larger and heavier despite having the same power. State sources have not released any information on its top speed using maximum military power, but independent estimates suggest that it should be incapable of supercruise. This means that in order to cruise at supersonic speeds, the SR-12 must rely on reheating, which greatly increases fuel consumption and leaves a larger infrared signature.

Diverterless supersonic intakes on either side of the fuselage eliminate the need for heavy variable-geometry intakes, which could compromise frontal stealth. The airflow from the intakes is also piped up through the back of the fuselage through S-shaped conduits, such that the radar-reflective turbine blades are not visible from in front of the aircraft. Jagged panels on top of the fuselage allow the aircraft to bleed out excess intake airflow; some defense analysts have speculated that these panels could be reversed to serve as auxiliary intakes during rough-field landings, but their position would supply very little positive air pressure.

Background footage from a factory inspection in 2020 shows that a panel on the right side of the cockpit conceals a retractable refueling probe, which would allow the SR-12 to further extend its range on long-distance ferry flights or over-sea strike missions. Footage of a pre-production model taxxing at an airbase, released later that year, confirmed the probe's presence.

Sensors and electronics

A mockup SR-12 cockpit revealed at a defense expo. Note the large displays and side-stick controls.

The SR-12 has six infrared-spectrum cameras distributed around the fuselage to provide 360-degree detection and imaging. Conceptually, the array is reminiscent of the Dayashinese AN/AAQ-37, though Menghean sources claim that the cameras and their network are of domestic design. If functionality is similar between the two systems, these cameras will allow the SR-12 to detect aerial targets, ground vehicles, and missile launches in all directions, improving the pilot's situational awareness.

These are supplemented by passive radar antennas in the wings and vertical stabilizers, which can pick up on emissions from aircraft, missiles, and ground installations, cross-referencing these with infrared signals to eliminate false positives.

The nose contains an advanced AESA radar of domestic design and construction. In addition to reducing radar reflections, the scanned-array layout allows the radar to simultaneously form multiple target-tracking beams over a wide area while also scanning the full sky or regions of interest. Beams can also be pointed at returns from passive detection, allowing target tracking with minimal emissions or focused tracking of low-RCS targets. State sources report that the radar is immune to jamming and passive detection, which likely indicates the use of high-rate, pseudo-random frequency hopping, and it is possible that it incorporates a built-in high-powered jamming capability.

An angular glass aperture underneath the nose reportedly contains an electro-optical targeting system with a high-resolution infrared camera and a laser designator. This eliminates the need for an external targeting pod like Maenun, which would increase drag and radar returns. A large infrared aperture above the nose likely contains an IRST system for passively identifying airborne targets.

Cockpit and avionics

Cockpit camera footage released during the 2019 parade reveal, showing the pilot's Keikō helmet good visibility to the rear.

A mock-up training cockpit revealed to expo visitors in 2020 shows a large multi-function LCD screen in the center and a narrower display centered beneath it. The absence of screen-side buttons has led some observers to speculate that the displays may be touchscreens, or more reliant on HOTAS controls. The glass cockpit layout is even more thorough than that on the SR-8 and DS-9, which still retained some analog or steam dials, though the training cockpit also appears to omit some functions and may not fully represent the production fighter's avionics. Some non-combat functions can be activated by voice command, a feature also present on late-model DS-9s.

Interestingly, the control column appears to be located on the right side of the cockpit, even though all previous Menghean fighter aircraft used a centre stick layout. The reason for this change is unclear; it may be intended to free up more space ahead for display screens. So far there have been no reports that the Menghean Army will order DS-10 trainers with the side-stick layout.

The SR-12 is fully integrated with the joint-developed Keikō helmet-mounted display, which projects sensor information into the pilot's field of view and allows off-boresight targeting of certain missiles. Unlike the Huntress, it retains a full-function reflective head-up display centered in front of the pilot, indicating that Menghean designers did not opt for increased reliance on the helmet-mounted display.

The aircraft's canopy is reportedly made of an advanced composite material which reduces high-temperature strain and absorbs radar emissions which could otherwise reflect off of the pilot or cockpit instruments. The first prototype had a clear canopy, but on the production-ready parade variants it appeared slightly purple or gray.

Armament

Front view of an SR-12G showing payload options that were approved for flight testing.

Photos of the first prototype surprised many observers due to the apparent absence of a gun port. Nor was any mention of gun armament made in official press releases. The mockup displayed in May 2018 also contained no visible gun port. The parade reveal the following year mentioned a single 6-barrel 24mm cannon, which careful observers eventually traced to a small panel under the right wing root; when retracted, this allows the gun to fire, but the rest of the time it remains flush with the plane's skin to reduce drag and radar returns.

Other armament is carried in three internal weapons bays. One, centered under the fuselage, has space for six YGG-7 Hwasal missiles, in a clipped-fin variant. The missiles are slightly staggered to fit closer together, and they are mounted on special ejector arms that propel them free of the bay before the rocket motor fires. State sources also claim that some of the launch arms can be replaced with hardpoints for bombs of up to 1,000 kilograms, though there is still speculation about how this is accomplished spatially. Two more weapons bays, one on each side of the fuselage behind the intakes, carry short-range infrared-guided missiles. There are two attachments for pylons under each wing, allowing mounting of even more missiles or bombs, but because these positions compromise the plane's stealth they are mainly used to carry fuel tanks on ferry missions.

A placard displayed at the February 2021 Songrimsŏng airshow unveiled additional information about the SR-12's payload management system, and provided a list of weapons that were being tested on the aircraft. In addition to air-to-air missiles, the SR-12 will be able to carry medium-range cruise missiles, guided bombs, and anti-radiation missiles. These options will make it effective in the air-to-ground role. Also on display was a scale model of a stealthy weapons pod, capable of carrying two long missiles, two 250kg guided glide bombs, or four 125kg WYGP-100 Saehorigi light bombs.

Stealth

No official figures on the SR-12's radar cross section have been published, and no signatures from foreign defense radars are available. Pre-production models, such as those filmed during the July 2019 parade, all carry radar reflector pods under the fuselage to increase their returns for safety in air traffic control and navigation, and possibly to hide their true radar signature from independent measurement. The exact composition or distribution of its radiation-absorbent materials is also not publicly known, though the production-ready units appeared to have a different coating on the wing edges and over some panel seals.

Nevertheless, independent assessments of the SR-12's shape and composite 3D models pieced together from camera and movie footage have turned up few prominent flaws in the RCS-reduction scheme. The design displays very consistent planform alignment and has few clear bumps, curves, or other irregularities which could present radar reflections from the side or beneath.

No independent estimates are available on infrared signature, as the composites used in the wing leading edges and other high-strain areas are not known. If the leading-edge extensions use active cooling, as some speculate, this could dramatically reduce head-on IR signature; on the other hand, if the engines must enter reheat for dogfighting or supersonic flight, this would greatly increase the plane's infrared signature from the rear and heat up the rear fuselage.

Operational service

As of July 2019, low-rate initial production of early-model SR-12s is believed to be in its early stages, though the first production airframes probably will not be completed until some time in 2020. It is estimated that there are five flyable prototypes currently in existence, three of them in a production-ready configuration.

The Ministry of National Defense announced in 2019 that the SR-12 is on track to reach initial operating capability by 2024; until then, LRIP models will be used in training, endurance testing, and weapon qualification. Given the pace of the program until now, it is likely that further delays will push back IOC even further.

So far, there has been no discussion of exporting the SR-12, even to close allies like Argentstan. The Ministry of National Defense considers the plane's technology and capabilities sensitive, and has also denied observers from Tír Glas and Dayashina access to test airframes. Additionally, given its size and technical complexity, the SR-12 probably comes with a high price tag; the MoND shows no sign of ending production of the cheaper DS-9 and SR-8.

Specifications

General characteristics

Crew: 1
Length: 20.2 m (66 ft 3 in)
Wingspan: 13.8 m (45 ft 3 in)
Height: 5.2 m (17 ft 1 in)
Wing area: 73.5 m² (791 ft²)
Empty weight: 20,000 kg (44,000 lb)
Loaded weight: 32,000 kg (70,000 lb)
Max. takeoff weight: 38,000 kg (84,000 lb)
Powerplant: 2 × Donghae 89/160 afterburning turbojet
- Dry thrust: 89 kN (20,000 lbf) each
- Thrust with afterburner: 160 kN (36,000 lbf) each

Performance

Maximum speed: Mach 2+ (est.)
Cruise speed: Mach 0.9 (est.)
Combat radius: 1,200 km (745 miles) on internal fuel, 8 missiles
Ferry range: 4,000 km (2,500 miles) with three external tanks
Service ceiling: 20,000 m (66,000 ft)
Wing loading: 435 kg/m² (88.5 lb/ft²)
Thrust/weight: 1.02 (full internal fuel)

Armament

Guns: 1× GP-24/6 revolver cannon, 220 rounds
Hardpoints: 8 internal (6 central, 1 per side) and 6 external (3 per wing) with a capacity of 6,000 kg and provisions to carry combinations of:
- Missiles:

Air-to-air:

Air-to-ground: