China's J-20 stealth fighter on afterburners. Photo: China military

China has started J-20 stealth fighter patrols over the South China Sea, the latest sign of Beijing’s rising assertiveness in the increasingly militarized and hotly contested strategic waterway. News of the patrols was confirmed on Wednesday (April 13) by state-owned Aviation Industry Corporation of China (AVIC), which is the manufacturer of the J-20.

News of the patrols comes hot on the heels of reports last month of a close encounter between US F-35s and J-20s over the East China Sea. According to US Pacific Air Forces Commander Kenneth Wilsbach, US pilots were “relatively impressed” with the command and control associated with the J-20. 

However, Wilsbach also remarked that it is still too early to know how China will deploy the J-20, as it is not yet known whether the type is “going to be more like an F-35, that is primarily an air superiority fighter that has an air-to-ground capability.”

In a conference on April 12, Ren Yukun, head of the discipline inspection and supervision team at AVIC, said the J-20’s capability to conduct patrols over the South China Sea was enabled by its use of domestically-made engines, which is most likely the WS-15.  

This engine type significantly increases the J-20’s maneuverability and combat performance. According to Chinese military expert Wang Mingliang, the upgrades give the J-20 supercruise and super maneuverability, adding to its already formidable stealth capability and situational awareness to match US fighters such as the F-22 and F-35.

If China has indeed commenced J-20 patrols in the South China Sea, with its stealth fighters sporting engines of acceptable performance, these jets can seriously affect the air power balance in the disputed body of water and enable long-range strikes on US and allied bases in the Pacific.

No other claimant state in the South China Sea operates 5th generation fighter jets. As such, the J-20 presents a significant challenge to more advanced Southeast Asian air forces such as that of Singapore, which arguably operates the most advanced fighter fleet in the region.

The J-20 will utterly overmatch weaker air forces such as that of the Philippines, which has no multi-role fighters. However, it is possible that China will deploy its J-20 only in the most high-risk scenarios, as they are expensive to operate and too valuable to lose.

A 428th Fighter Squadron F-15SG multirole fighter flown by Republic of Singapore air force pilots approaches a 151st Air Refueling Wing KC-135 Stratotanker to receive fuel midair over Idaho, Aug. 25, 2020. Photo: US Air Force / Master Sergeant Natasha Stannard

Against these relatively weaker air forces, China may choose to employ aerial attrition warfare rather than risk its most advanced assets. Even without the J-20, China still enjoys a numbers advantage versus rival claimants’ air forces.

China could choose to conduct intensive and persistent patrols over contested areas in the South China Sea, forcing claimant states’ air forces to respond beyond their capability, inducing fatigue, increasing chances of miscalculation and force equipment losses through wear and tear.

These newer engines may also enable the J-20 to perform its possible intended mission to conduct long-range strikes into complex air defense environments far from Chinese mainland airbases, before retreating into the safety of China’s air defense network.

Initial J-20 prototypes used less powerful Russian Saturn 117S and Chinese WS-10C engines. However, these engines did not have enough power to reach desired speeds, with the lack of thrust potentially making the J-20 vulnerable in dogfights with US fighters.

Moreover, these less powerful engines preclude the use of directed energy weapons such as lasers and microwaves aboard the J-20 and may hinder further development of the type as an optionally-manned fighter.

For some time, the J-20 used Russian-made AL-31F engines, used by Russia’s Su-35 heavyweight fighter which China also operates. However, a Chinese defense industry insider remarked that it is not feasible to depend so much on Russian engines, as Russia insists that China purchase more Su-35s to obtain more engine units.

The same insider, who requested anonymity, mentioned that longer range is the sole advantage the Su-35 has over comparable Chinese fighters such as the J-16, with the former’s radar, navigation system and other electronic components all being inferior.

Russia is looking for customers for its Sukhoi Su-35 fighter jet. Photo: Wikimedia

China has long struggled to produce quality jet engines for its air force, a key bottleneck in its air force modernization program. In the 1990s and 2000s, China attempted to copy certain Russian engines but produced inferior underpowered copies with very low lifespans.

Russia is also aware that China has poached its Su-27 design and made its own unlicensed copy. Moscow does not sell standalone engine units, which makes reverse engineering on the part of China extremely difficult.

China still faces technical hurdles in manufacturing jet engines, as it has not yet perfected its jet engine metallurgy and precision machining processes. Moreover, China’s state-run defense companies have long struggled with innovation and research, and are better attuned to reverse-engineering and manufacturing simpler components.