Advanced radars, missiles, an ability to network with other platforms, and low-observable technology count for little if a pilot cannot fly an aircraft safely, complete a mission and come back to base, owing to a lack of a capable engine, bring these capabilities to bear in combat. Engine capability and reliability are – and always have been – perhaps the single most important technical requirement in the success or failure of a combat aircraft. The engine will take you to the sky and return you back home safely.
Problems encountered in development of new WS-15 engine mean PLA Air Force’s first J-20s are not so stealthy at supersonic speeds. Under current state, J-20 cannot sustain supersonic flight without using inefficient afterburner hence fuel thirsty J-20 was once visible by fourth generation Su-30MKI.
China rushed its first advanced stealth fighter jet into service ahead of schedule last year, using stopgap engines, in the face of rising security challenges in the region, the South China Morning Post has stated.
But that means its capabilities will be severely limited, affecting its maneuverability and fuel efficiency as well as its stealthiness at supersonic speeds.
Without saying how many were in operation, the People’s Liberation Army Air Force confirmed that the J-20, the country’s fifth-generation fighter, had entered combat service, meaning it was combat-ready.
However, the aircraft was equipped with inferior engines designed for earlier warplanes when it first joined the air force in March last 2018 because “critical problems” with its tailor-made WS-15 engine, exposed by an accident in 2015, had not been fixed, two independent military sources told the South China Morning Post.
The most WS-XX series started with WS-10. At the core of all Chinese engines now a days relay on the development of WS-10. The WS-10B is a modified version of the WS-10 Taihang engine, which was designed for the country’s fourth-generation J-10 and J-11. The future powerplant of Beijing’s flagship fighter, the WS-15 is the centrepiece of a family of engines, developed by a universe of companies grouped under the Aero Engine Corporation of China (AECC). The Aero Engine Corporation of China (AECC) received the highest development fund from Chinese government, building a working jet engine is like a manned moon landing project of Chinese defense industey. family includes the Shenyang WS-10 Taihang that powers Beijing’s fleet of J-11Bs (early versions of the J-11, a local copy of the Su-27, are powered by a version of the AL-31). The WS-10 will also eventually power the J-15 naval fighter, some examples of the J-20 and future J-10Cs.
“Using the WS-10B engines is just a temporary, expedient stage of the J-20’s engine development … in the future, the aircraft may use another new engine, the improved performance engine (IPE) version of the WS-10, the WS-10 IPE, until the development of the WS-15 is successful,” Andrei Chang, editor-in-chief of Canadian-based Kanwa Asian Defence said citing two sources of PLAAF.
“It’s so embarrassing to change engines for such an important aircraft project several times … just because of the unreliability of the current WS-15 engines. It is the long-standing core problem among home-grown aircraft.”
It is at least the third time the J-20 has changed engines. The aircraft’s maiden flight was powered by two Russian AL-31 engines, which are less capable than China’s WS-10B.
In addition, there is the WS-13 that will, hopefully, one day power locally produced UCAVs such as the AVIC Dark Sword, and the WS-19 that could one day power the FC-31. The WS-13 is also seen as potential interim powerplant for the developmental AVIC FC-31 Gyrfalcon, now powered by a pair of Klimov RD-93s. From a testing perspective, the engine has also been found on several J-10Bs and J-20As. The powerplant as emblematic of China’s aerospace sector. The WS-13 will eventually power the PAC-CAC joint venture JF-17 Thunder.
“The WS-15 engine designed for the J-20 exploded during a ground running test in 2015,” one source said, adding that no one was injured in the accident.
“The explosion indicated the WS-15 is not reliable, and so far there is no fundamental solution to overcome such a problem … that’s why the J-20 is using WS-10B engines now. The status of the type’s ultimate engine, the developmental Xian Aero Engine WS-15 Emei, is far from clear. Estimates suggest that the WS-15’s maximum thrust will be 18.4t (180kN), potentially giving the J-20 genuine “fifth generation” performance, including supercruise – the ability to travel at supersonic speeds without engaging the afterburner. The lack of positive news – or any news whatsoever – could be interpreted as an admission by Beijing.
China is moving closer to mass-producing an improved engine with a longer lifespan and more power for its first aircraft carrier-based fighter jet, the J-15, according to military analysts.
They said technical problems had been overcome and the WS-10H turbofan engine now had the thrust and lifespan to put it on par with the AL-31F Russian-made engine that was initially used in the fighter jet.
The WS-10H engine had been criticised as not powerful enough for the J-15 fighter jet, China’s heaviest and only active carrier-based warplane, which has a maximum take-off weight of 33 tonnes. Instead, the Russian engine was earlier used in the fighter jets for the navy’s first and only aircraft carrier in service, the Liaoning.
Li Jie, a naval expert in Beijing, said the WS-10H now had the thrust and lifespan of Russia’s AL-31F, but it still lagged behind America’s F414 afterburning turbofan engine, as used in the F-18 warplane. China needs a better engine that can cope with sea environments of high humidity, temperature and salinity. Although WS-10H powers J-15, WS-10H limits payload capacity of J-15 hence the WS-10H limits operational capability of PLAN.
According to Zhou Chenming, another military analyst in Beijing, the J-15 no longer uses the Russian engine, so there was a need to get the WS-10H to mass production stage.
China Is Not Alone
China is not alone when comes to indigenous fighters with foreign engines. The Hindustan Aeronautics Tejas, Saab Gripen, and KAI FA-50 are all powered by a General Electric engine. KAI’s planned KFX will also be powered by the F414, as will New Delhi’s Advanced Medium Combat Aircraft (AMCA). The trend is most common in commercial aircraft but for a fighter aircraft, it is not uncommon that an indigenous fighter would carry an foreign engine but for those who can’t they either licensed produced an engine. The Russian Yak-130 is powered by Ukrainian Engines.
In the case of China, China imports engines from Russia and integrate into indigenous fighter aircraft.
Only America, the Great Britain and France were able to perfect the science of manufacturing jet engines.
The Russian has some working engines but Russian engines have short lifespan and maintenance problems in home country Russia and countries where those engines were exported. Russian engines are prune to failure resulting large numbers of aircraft crashes in India, China, Russia, Uganda,Venezuela, Vietnam, Bangladesh and Myanmar.
Buy, Build or Steal
Pouring great resources into its own development work, but is not above stealing technology. It is understood that the core of the WS-10 is based on CFM International CFM56 technology that China obtained in the 1980s. In October 2018, an alleged Chinese intelligence officer was extradited to the USA to face criminal charges related to a scheme to steal trade secrets from leading US aviation companies, including GE Aviation. Court documents suggested the alleged theft targeted technology related to engine fan blades and “containment structures”. Pratt-Whitney received hefty fines to sale software codes which control, measure and monitor powerplant of helicopters. China bought the software to use in commercial helicopter but later on sources confirmed State Department that China used the software in Z-10 attack helicopter. China faces tremendous trade barrier to acquire such sophisticated technology from western countries.
The requirement for Beijing to steal technology was highlighted as early as 2011 in a report from the Washington DC-based Institute for National Strategic Studies entitled Buy, Build, or Steal: China’s Quest for Advanced Military Aviation Technologies. The report concluded that China would find it increasingly difficult to develop highly advanced aerospace technologies, and its traditional partner Russia is ever more wary of sharing technology owing to fear of intellectual property theft. This will force China to rely increasingly on espionage to obtain advanced capabilities.
The WS-15 explosion was confirmed by another source close to the military, who said the reasons it happened were complicated, with one being the quality control of its single-crystal turbine blades, the key component for such a powerful turbofan engine.
The new-generation, single-crystal turbine blades designed for the WS-15 were supposed to be able to cope with the increased mechanical loads caused by significantly higher rotational speeds and extremely high temperatures.
Learning Curve For Temperature Control of Engine
Former Aviation Industry Corporation of China (AVIC) chairman Lin Zuoming told state media last year that China’s third-generation single-crystal turbine blades could withstand temperatures of up to 3,632 degrees Fahrenheit (2,000 degrees Celsius) in WS-10 engines, extending the engine’s lifespan from 800 hours to 1,500 hours when compared with those using the previous generation of turbine blade.
However, the thrust-to-weight ratio of the original WS-10 engine was only 7.5, while that of the WS-10B tops out at about nine. The thrust-to-weight ratio of the all-direction, vector turbofan WS-15 Emei engine is more than 10 – one of the basic requirements for giving the J-20 “supercruise” ability.
Supercruise allows stealth fighters like the US’ F-22 Raptor to fly at supersonic speeds without using afterburners, making them harder to detect. The F-22 is powered by the world’s most advanced jet engine, the Pratt & Whitney F119.
Development of Crystal Blade
But achieving supercruise would require the single-crystal turbine blades of the WS-15 engine to cope with temperatures even more extreme than those handled by the WS-10.
“Chinese technicians are able to produce cutting-edge-quality single-crystal turbine blades when concentrating on a specific single item,” the second military source said. “But they’ve still failed to turn the advanced technology into a standard product for mass production. It’s a bottleneck problem that needs more time to overcome after countless experiments and tests, based on Western experiences.”
Observers will also be watching Chinese firm Skyrizon’s effort to buy a majority stake in Ukrainian engine manufacturer Motor Sich, which produces turbofans and turboshafts. The potential deal is reportedly under review by the Ukrainian government, and is opposed by Washington DC. In May, the Washington Post reported that the company, which formerly relied on Russian aerospace work, sees few opportunities for its future outside of China.
Rupprecht adds that Beijing’s ultimate goal is to be completely “self-reliant in every aspect” of engine development and manufacturing.
“A good number of J-10s and J-11As, as well as their Xian Y-20s and H-6Ks, depend on Russian engines,” WS-20 eventually will power Y-20 transport aircraft. “This is unacceptable for the longer term, especially if the political climate with Moscow were to change. Therefore they are placing great effort to develop new engines in different classes and establish a broad industrial base.”
Russia has refused to export its most advanced engines to China because they are the core technology of its aviation industry. That prompted China to develop an indigenous alternative, the WS-15, as part of its drive towards producing one of the world’s most advanced combat aircraft.
Beijing has stepped up the development of sophisticated jet engines since the turn of the century, with at least 150 billion yuan (US$23.7 billion) invested between 2010 and 2015, military insiders told the Post in 2016.
State-owned Aero Engine, a company formed in August 2016 through the merger of 24 AVIC subsidiaries with about 10,000 employees, has led China’s development and production of aircraft engines and gas turbines in recent years. One of the former AVIC subsidiaries, Shenyang Aeroengine Research Institute, developed the WS-10 and WS-15.
China Central Television boasted last year that the performance of the WS-15 had matched that of the F119, with a documentary aired in May claiming the WS-15 engines would be widely used in the J-20 by 2020.
That would make China the third country to have a fifth-generation fighter – after the US and Russia. Justin Bronk, a research fellow specialising in combat air power at the Royal United Services Institute, told Business Insider the design of the J-20 gave it “longer range, more internal fuel capacity, and larger internal weapons capability” than its US counterparts, the F-22 and F-35, and that meant it presented a real threat to US forces in the Pacific.
However, military analysts said it was too early for such prognostications because the underdeveloped WS-15 engine was not yet as sophisticated as the F119, which had a lifespan of more than 4,000 hours.
The prototype of Russia’s first fifth-generation fighter jet, the Su-57, took to the air for the first time in January 2010 but its maiden flight powered by the new Izdelie 30 engine, which was specially designed for it, only took place last month. The new engine will enable the Su-57 to achieve supercruise speed and fly consistently at 1,242mph (2,000km/h), but it still faces many tests, with the Russia Beyond website saying it would not be mounted on the Su-57 before 2019 or 2020.
Long Painful Development Process
China’s WS-15 project started in the 1990s, with the first prototype delivered in 2004 and the first successful ground-running test staged in 2015, Antony Wong Dong, a Macau-based military observer, said.
“China took 11 years to test the WS-15 after its prototype was created,” Wong said. “It’s very normal to take three to eight years for further development.
“And it’s still a significant achievement for China to develop the WS-10B as a stopgap for the J-20. China’s advanced aircraft engine technology foundation is very weak because its research and development started several decades later than its Western counterparts.”
America’s Pratt & Whitney and General Electric spent more than 12 years developing prototypes of the F119 engine in the 1980s, followed by another 14 years of testing after the engine’s maiden flight, fitted to an F-22, in September 1997.
The US also began developing the F-35, a single-seat, single-engine, all-weather stealth multirole fighter in the 1990s, with the first squadron – using Pratt & Whitney F135 engines, a derivative of the F119, joining its air force in 2016.
The US has started deploying F-35s at its military bases in the Asia-Pacific region, with 12 arriving at the Kadena Air Base in Japan in November. South Korea has said it plans to take delivery of 40 F-35s this year.
Earlier reports said Japan’s Maritime Self-Defence Force was also considering buying the F-35B “jump jet” version for its two new 25,000 tonne, flat-topped Izumo-class helicopter carriers. That pushed Beijing to put the J-20 into service as early as possible, military sources said.
Andrei Chang, editor-in-chief of Canadian-based Kanwa Asian Defence, said the J-20 might need at least eight years to improve its engine performance, but it was still the PLA Air Force’s most capable combat aircraft when it came to countering America’s F-22.
“The J-20 is more advanced than China’s fourth-generation fighters because of its stealthiness,” he wrote in the latest edition of the magazine, adding that it could also carry a greater quantity of more advanced air-to-air missiles.
Future Is WS-15
Chang said he did not expect China to put the J-20 into mass production until the WS-15 project was wrapped up, but that training of J-20 pilots had been going on for a while. He said the PLA Air Force had deployed J-20s to the Dingxin Test and Training Base in Gansu province, where they and other warplanes had been used to study counter measures against the F-22 and F-35.
Hong Kong-based military commentator Liang Guoliang said there was a “very urgent” need for China to develop a carrier-based stealth fighter based on the J-20 because of the regional security environment was becoming more challenging.
“The US F-35B is much more powerful than China’s current carrier-based fighter, the J-15,” Liang said. “In case there is a war, the fighting capability of a Japanese Izumo helicopter carrier could come up to that of a Chinese aircraft carrier if each ship is equipped with five to six F-35Bs, with each one the equal of 10 J-15s.”
But, he cautioned, it would take at least a decade to turn a land-based fighter jet like the J-20 into a carrier-based aircraft because of the extensive modifications required, adding that the US had been developing carrier-based aircraft since the 1930s, while China had just started doing so this century.
China’s carrier-based J-15 is based on the Russian Su-33, a variant of the fourth-generation Su-27 fighter.
“China should hurry up; the central leadership should make a decision as soon as possible,” Liang said.
Beijing has been pushing the development of more sophisticated jet engines in the past decade, investing at least 150 billion yuan (US$21.94 billion) in that goal between 2010 and 2015.
China is so close to developing a good domestic engine for indigenous fighter jet but so far from the reliability and performance of domestic engine compared to that of the American and European jet engines.
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