South Korea's first prototype of its 4.5-generation fighter, officially dubbed KF-21 Boramae, revealed at the Korea Aerospace Industries Co. facility in Sacheon, South Korea. Image: Screengrab / CNN

Nations must possess the knowledge, technology and resources to indigenously build fighter jets, which count among the most complex weapons ever made.

Asia’s accelerating race to develop the next generation of warplanes is increasingly pitting China against South Korea, military tech competitors on opposite sides of an emerging new Cold War.   

South Korea and China have designed their respective indigenous stealth fighters, the KF-21 Boramae and Chengdu J-20, in rival bids to fill their existing air warfare capability gaps, achieve strategic independence and flex techno-scientific prowess on regional and international stages.

Last month, South Korea joined the elite fighter developer club when it completed its KF-21 Boramae fighter’s first test flight, Defense News reported.

The article said that the KF-21 took off from a South Korean air force base at Sacheon, South Gyeongsang province loaded with four Meteor beyond-visual-range (BVR) missiles and flew at 400 kilometers per hour for 30 minutes to check the airframe’s essential functions.

The KF-21 is a 4.5-generation aircraft with advanced capabilities, such as active electronically scanned array (AESA) radar, high-capacity data links, enhanced avionics, and the ability to deploy current and reasonably foreseeable advanced armaments.

However, unlike 5th-generation fighters, the KF-21 lacks an internal weapons bay, forcing it to carry munitions on external hardpoints, which can compromise its stealth characteristics and handling capabilities.

While billed as an entirely indigenous design using a high proportion of South Korean-made components, the KF-21 may have taken design cues from America’s F-35, as shown by the striking visual similarity between the two aircraft.

In addition, it is powered by two US-made General Electric F414 engines, which offer less operational cost yet less power than other engines on comparable 4.5 or 5th generation fighters.

Thomas Newdick in The Warzone notes that the KF-21 may eventually be partnered with an indigenously-designed loyal wingman drone. While the KF-21 was designed with North Korea as its primary adversary, Newdick mentions that the KF-21 could be deployed at Liancourt Rocks, which are thought to hold substantial undersea oil and gas reserves and are contested between South Korea and Japan. 

South Korea has completed the KF-21 Boramae’s first successful test flight. Image: KAI

Moreover, South Korea may offer the KF-21 for sale to foreign customers, as Indonesia has already expressed interest in acquiring the type and had pledged to shoulder 20% of its development costs. South Korea hopes its KF-21 will be a less-costly substitute for Western-made 4.5 and 5th generation fighters.

China is on a similar fighter flight path. In 2010, the J-20 became China’s first stealth aircraft to be revealed to the public, notes Carlo Kopp in Air Power Australia.

He mentions that it is designed to compete against the US F-22, with its stealth shaping based on the latter aircraft. He claims that China may have obtained F-22 design information by hacking into US defense contractor networks involved in the project.

The J-20 can be expected to deploy current and future Chinese or Russian armaments; it is equipped with an internal weapons bay – a key characteristic of 5th generation fighters which allows them to preserve stealth, unlike 4.5 generation designs such as the KF-21.

Kopp notes that while the J-20 has very sound stealth shaping, it is unknown whether the aircraft’s other components, such as engines, avionics, and composite materials, will allow it to be competitive against the F-22.

At present, the J-20 is limited by China’s inability to produce high-quality jet engines, which Asia Times has previously reported. J-20 units with Russian or current Chinese jet engines do not have enough power, making the aircraft vulnerable in dogfights against US fighters and incapable of generating enough power for future upgrades such as directed-energy weapons or optionally-manned capability.

However, the J-20 could become a powerful competitor against the F-22 should China’s technology in those areas mature. In its current form, Kopp mentions the J-20 outclasses the F-35 and F/A-18 E/F, as these latter aircraft do not match the performance of the F-22 and are designed for non-stealth air operations.

But suppose China’s jet engine technology matures enough to produce jet engines with sustained supercruise capability. In that case, Kopp mentions that the J-20 will be able to evade most surface-to-air missile (SAM) systems in the Pacific and will be out of range of most fighters in the region except the F-22.

Accordingly, China has focused much of its efforts on improving its jet engine technology, with later units of the J-20 equipped with the WS-15, an engine that is supposedly comparable to Russia’s Saturn 30 used on the Su-57 and US Pratt and Whitney F119 on the F-22, Military Watch reported.

China’s J-20 stealth fighter is developed to operate across vast maritime areas. Credit: Handout.

In comparing South Korea’s KF-21 and China’s J-20, the former appears to have taken a more general purpose approach to its design, akin to the F-35. However, the relatively small size of the Korean Peninsula may offset the need for the KF-21 to have an extended range in favor of standoff strike capabilities and to maintain overmatch against North Korea’s outdated air force.

In contrast, the J-20 may be designed to operate across the vast expanses of the South China Sea and Pacific. It may thus have been designed with an extended range for long-range strike missions.

However, the J-20, equipped with its internal weapons bay, may be more effective in penetrating defended airspace than the KF-21. The J-20’s more powerful engines and superior stealth characteristics may also give it certain advantages in air-to-air combat – although much depends on the performance of both aircraft’s avionics, sensors, munitions, pilot training and air doctrine.

While it may be tempting to compare the KF-21 and J-20’s technical aspects using limited publicly available information, these aircraft may be hindered by more fundamental issues and questions on the concept of air power itself.

These limitations include air power’s lack of staying ability, overreliance on unproven technology and the trend toward robot-driven air forces.

First, air power alone does not win wars, as it lacks the staying power of land power. Jahara Matisek and Jon McPhilamy, in an article for the Modern War Institute at West Point, note that while air power can bring massive firepower, land power combined with a coherent strategy is still needed to take, hold and secure territory.

Matisek and McPhilarmy note that underdogs can still find effective fighting methods despite facing superior enemy air power. The wars in Korea, Vietnam, Iraq and Afghanistan have shown the limits of what US airpower can do against technologically inferior but determined and well-supported adversaries.

Although they point out that Operation Deliberate Force in 1999 achieved victory solely through air power, NATO victory took so long due to its self-imposed limitations, resilient Serb economy, rough terrain, and foliage which limited the effectiveness of air power.

Second, air power’s technological superiority is not the sole guarantor of success. It must be viewed as a component of a more extensive system that combines material, technical and human factors. Overreliance on technology while overlooking non-material factors may blunt any technological advantage.  

Third, air denial might be the future of air warfare, as noted by Maximilian Bremer and Kelly Grieco in a War on the Rocks article. They note that in a future regional or great power conflict, opposing sides will increasingly deny airspace to each other instead of trying to establish air superiority.

Bremer and Grieco apply the concept of sea denial as espoused by naval theorist Julian Corbett into the context of air power. Suppose an air force is not strong enough to secure air dominance. In that case, it could attempt to deny airspace to an enemy by keeping ground-based air defenses dispersed and mobile to act as a “threat in being” to enemy combat aircraft.

A Ukrainian army service member with a US-made Javelin anti-tank missile during a military parade in 2018. Image: Screengrab / Sky News

Such has been the case of Ukrainian air defenses in the face of superior Russian air power. Ukraine has deterred Russian aircraft from staying long in its airspace by keeping air defense systems intact via mobility, radar silence and concealment.

Moreover, Ukrainian air defenses have forced Russian aircraft to fly lower to avoid radar detection, bringing them within range of anti-aircraft guns and man-portable air defense systems (MANPADS), adapting Corbett’s naval doctrine of setting up traps and limited strikes to aerial warfare.

They also note that the immense costs of modern combat aircraft such as the KF-21 and J-20 limit their use and development by major military powers. As a result, too few of these aircraft may be available for missions.

Moreover, the democratization of air power enabled by the Internet and dual-use technologies drives air power to favor cheap, robotized air forces built around drones, loitering munitions and ballistic missiles over multi-million fighters.

Israel, Turkey, Azerbaijan and Iran have all used drones and ballistic missiles as a substitute for power projection and precision strike missions traditionally performed by manned aircraft. These are all lessons Asia’s new generation warplane developers must take on board.