How far South Korea's "4.75th generation fighter" can go

The KF-21 prototype flew in test flights. Image source Screenshot of YouTube video

Comprehensive compilation of Zhang Haotian

On July 19, the KF-21 fighter jet, which is known as South Korea's independent research and development, took off into the sky for the first time. The twin-engine medium fighter is not yet fully mature, but it marks that South Korea has put one foot in the "Stealth Fighter Club."

According to Yonhap News Agency, the first KF-21 prototype was code-named Eagle and the test flight site was selected in Sacheon, southeast of South Korea. Sacheon Airport is adjacent to the Korea Aviation Industry (KAI) Company's factory and is also home to the Third Flight Training Team of the Korean Air Force. Due to the weather, the prototype number 001 flew for only 33 minutes in total that afternoon. Photos from the scene show that the head of the prototype is spray-painted with the flag of South Korea and the project partner Indonesia, and the belly of the aircraft carries four "Meteor" long-range air-to-air missiles produced by the European MBDA company in a semi-buried manner, which is speculated to be just equal scale models.

The KF-21's test flight date was 3 days earlier than predicted, which seems to indicate that the project is progressing smoothly. South Korea has previously successfully developed a domestic fighter, that is, the T-50 trainer/attack aircraft, but this time it has developed a stealth fighter, and it is no wonder that the Korean media have sent praise. Yonhap News Agency mentioned that despite multiple obstacles such as technology and cost, KF-21 was successfully launched six and a half years after the official launch of research and development.

South Korea's Defense Procurement Administration (DAPA), which manages armaments research and development, issued a statement saying: "We have taken a step towards the successful development of domestic fighters, symbolizing the leap in Korean aviation technology and the rise of a high-tech military." ”

Phased R&D reduces risk

As the most complex aviation project ever built in South Korea, the KF-21 fighter began to brew more than 20 years ago. According to the situation released by the South Korean media, in 2000, then-South Korean President Kim Dae-jung first announced the "Future Advanced Fighter Plan", and the military and military industry carried out a comprehensive assessment in the following 9 years, aiming to develop a better model than the US-made F-16. In 2013, the first draft of the project proposal code-named KF-X was completed. In 2015, DAPA officially signed a contract with KAI.

DAPA has long described the KF-21 as a "4.5th generation fighter," and most of these models were born in the 1990s, including the American F/A-18E/F, European Typhoon, and French Rafale fighters. Compared to typical fifth-generation fighters, they lack at least one key attribute, such as radar stealth capabilities, advanced information perception capabilities, supersonic cruise capabilities, or supermanual capabilities that are hallmarks of fifth-generation fighters.

Even compared to its "predecessors" who have been in service for many years, the KF-21 is still a long way off. In order to reduce risks, the machine adopts a "spiral" phased research and development route. In the initial technical state, the so-called Block 1 batch, the only equipment worthy of the "4.5 generation" name is active phased array radar and infrared search and tracking equipment. The aircraft will gradually improve its combat capabilities through version iterations, with a focus on improving low detectability. Due to the immature technology of the fuselage magazine, KF-21's current weapons and equipment can only be mounted, which makes it basically incapable of radar stealth.

KAI plans to build the first mass-production KF-21 between 2026 and 2028, replacing the RoKAF's heavily aging F-4 and F-5 fighter jets. By 2032, when 120 Block 1 models are deployed, the more advanced Block 2 batch is expected to make a breakthrough. At that point, the KF-21 will be able to perform air-to-ground missions, combining stealth capabilities with long-range air-to-ground ammunition to penetrate enemy air defenses and destroy high-value targets. Dapa's earlier disclosure of promotional videos shows that the KF-21 can also collaborate with South Korea's homegrown stealth drones.

However, even the Block 2 version of KF-21 still doesn't have full stealth capabilities. The South Korean Air Force, which has long been prepared for this, has purchased F-35 fighter jets from the United States, including the F-35B, which can take off short distances and land vertically.

The total investment in the KF-21 project is approximately USD 6.67 billion. According to the US "Global Flight" website, South Korea seems to have found a shortcut to avoid the huge costs and long construction periods of developing advanced fighters from scratch. The KF-21 program promises to deliver the same performance as rival 4.5th-generation fighters and has the added advantage of local production. Given these benefits, some have informally referred to the KF-21 as a "4.75th generation fighter."

Success or failure remains constrained by foreign factors

South Korea's decision to "rely on itself" to develop the next generation of fighters is largely forced to be helpless. According to Yonhap News Agency, at the beginning of the KF-X project, South Korea expected the United States to provide it with key subsystems such as radar, infrared sensors, aiming pods and electronic countermeasures equipment. But around 2015, the U.S. government refused to share technology, and South Korea had to start a different story. This has instead promoted the enhancement of the strength of the South Korean defense industry and is conducive to the export of South Korean military products.

However, the KF-21 can still fly smoothly without the help of foreign suppliers. The prototype was powered by two General Electric F414-GE-400K engines, which were fully validated by the American F/A-18 series fighters and the Swedish Gripen fighter, demonstrating excellent reliability around the world.

The same is true with regard to airborne weapons. According to the British "Jane's Defense" website, in addition to the above-mentioned "Meteor" long-range air-to-air missile, KF-21 also plans to be equipped with Germany's IRIS-T short-range air-to-air missile. For such a project from scratch, the direct use of shelf products for supporting weapons can significantly reduce the risk, not to mention that some of the performance indicators of these two European missiles are more prominent than similar products in the United States.

The KF-21 prototype, which has just completed test flights, took two years to build, and five more are still on the production line. Of course, this ambitious project also faces many challenges, with uncertainties at both the technical level and international cooperation. As the first overseas user of the KF-21, Indonesia, which owns a 20 percent stake in the first phase of the program, has said it wants to buy 50. Indonesia is also seeking to position similar products internationally and has not chosen KF-21 as its only option, suggesting that there may be a potential funding gap for the project and that South Korea will have to pay for it itself or find another foreign financier.

The KF-21's biggest competitive advantage is that it is quoted below the F-35, which is attractive to some countries that cannot afford or cannot buy American-made fighters. It can be said that how far KF-21 can go in the international market largely determines the success or failure of the entire project.

Source: China Youth Daily client