Chengdu J-20

The Chengdu J-20 (Jian-20; ) is a fifth-generation, stealth, twin-engine fighter aircraft prototype being developed by the Chengdu Aircraft Industry Group for the Chinese People's Liberation Army Air Force (PLAAF). The J-20 made its first flight on 11 January 2011. General He Weirong, Deputy Commander of the People's Liberation Army Air Force said in November 2009 that he expected the J-20 to be operational in 2017–2019.

The PLAAF designates the J-20 as "Project 718". The general designer of the aircraft is reportedly Yang Wei, who was the general designer of CAC/PAC JF-17 Thunder.

Origin
In 2002, Jane's Defence Weekly reported that Shenyang Aircraft Corporation had been selected to head research and development of the new fighter, a claim repeated in New Scientist the same week. However, a 2006 article in Military Technology referred to three designs; two by Shenyang Aircraft Corporation and one by Chengdu Aircraft Corporation.

According to the report from Jane's, development of the subsystems, including the engine and weapon suite for the next generation fighter, has been under way for some time. A photograph of a wind tunnel model published with the article showed a twin-engine aircraft with twin vertical tail fins. The article text mentioned that the aircraft would carry its weapons internally like the F-22 Raptor. New Scientist called attention to the angular, faceted features of the design, comparing them to the F-117 Nighthawk. Jane's also linked the programme with China's development of an engine with thrust vectoring capability.

The later report in Military Technology featured a picture of a completely different design, speculatively dubbed J-14 and said to be a Shenyang project, with the designations J-12 and J-13 being applied to (possibly competing) designs by Shenyang and Chengdu respectively.

John Pike has written that China probably declined to participate in joint development and production of a new fifth-generation fighter with Russia given the belief that Russia stood to gain more from Chinese participation. Chinese leaders may have determined that their design was superior to the Russian PAK FA.

Since 2009, Chinese internet comments have repeatedly pointed to a merging of the two efforts, to be named J-14. Chengdu is rumored to be responsible for the airframe, while Shenyang focuses on the engines and other components. It was then revealed that Chengdu proposal won PLAAF's endorsement in a 2008 competition against a Shenyang proposal, with the latter reportedly being even larger than J-20. In November 2009 He Weirong (何为荣), deputy commander of the Chinese air force, confirmed that "intense" research and development work on the fifth generation stealth fighter was ongoing. He expected the aircraft to be unveiled soon and gave possible in-service dates of 2017 to 2019.

Flight testing
On 22 December 2010, the J-20 underwent high speed taxiing tests outside the Chengdu Aircraft Design Institute.

The J-20 made its first flight, lasting about 15 minutes, on 11 January 2011. A Chengdu J-10S served as the chase aircraft. China thus became the third nation in the world to "develop and test-fly a full-size stealth combat aircraft demonstrator", after the United States and Russia. After the successful first flight, a ceremony was held. The test pilot of the J-20, Li Gang, Chief designer Yang Wei and General Li Andong (Deputy-Director of General Armaments Department, and Director of Science and Technology Commission of General Armaments Department of the PLA since 2000) attended the ceremony. The jet began making test flights again on 12 November after a month long break from flying.

A second test flight of an hour and twenty minutes took place on 17 April 2011. On 5 May 2011, a 55-minute test flight included retraction of the landing gear. In March 2012 a video was taken of the J-20 showing various maneuvers done in flight. On 10 May 2012, a second prototype was reported to have undergone low speed taxiing tests at an unspecified airport in Chengdu. The second aircraft began flight tests in May 2012.

In late October 2012, photographs of what believed to be a new prototype emerged. This aircraft features a different radome, speculated to house an AESA radar.

Pictures of J-20 testing its side weapon bays began to surface in late March 2013. Early pictures first revealed a missile launch rail being extended out of the right-side of the aircraft. A few days later, new photographs showed a mock-up of an unidentified missile installed on the launcher.

Technology transfer allegations
While no specific analysts have claimed the J-20 used stealth coatings from the 1999 F-117 downed over Serbia, analysts have noted that if Chinese designers used stealth coatings based on the F-117, the result would be decades behind current American state-of-the-art. However, Chinese test pilot Xu Yongling said that the J-20 was a masterpiece of home-grown innovation, and also noted the F-117 technology was already outdated even at the time it was shot down, and could not be applied to a next-generation stealth jet. Janes editor James Hardy agrees that it was unlikely China would have learned much from the wreckage.

Information used by subcontractors of Lockheed Martin for the F-35 project has been significantly compromised during development of the J-20. As a result, there are accusations that the J-20 design may have been based on cyber-espionage of the Lockheed Martin FB-22 and F-35 projects.

A United States federal prosecutor has suggested that China may have used technology supplied by Noshir Gowadia from the Northrop Grumman B-2 Spirit program for their stealth aircraft.

Douglas Barrie has noted that the canard-delta configuration with canted vertical fins appears to resemble the MiG 1.42. Yet, Barrie notes that key differences include greater forward fuselage shaping as the basis for low observable characteristics, along with the different engine intake configuration. Despite the similar basic configurations between the aircraft noted by Russian sources, MiG spokeswoman Yelena Fyodorova has denied that any of the MiG Project 1.44 materials had been provided to China. The basic configuration of the J-20 also resembles a wind tunnel model of the Chengdu J-9, showing Chengdu has been working on the design for over 40 years.

Characteristics


The J-20 has a long and wide fuselage, with the chiseled nose section and a frameless canopy resembling the F-22 Raptor. Immediately behind the cockpit are low observable intakes mounted with a pair of upturned canards. They are followed by leading edge extension and a diamond wing. The aft section of J-20 features canted all-moving fins resembling those on F-35 and conventional round engine exhausts. An estimation using ground support vehicle as a reference shown the aircraft's length to be around 19 to 20 meters, slightly shorter than the length of a Flanker. In January 2013, a satellite picture taken over an airport at Xi'an showed J-20 to have similar length as a J-15/Su-33.

Song Wencong, the chief engineer of Chengdu Aircraft Industry, published a paper describing flight dynamics of the J-20. The paper cites high instability as an important design criteria in a fifth generation fighter. This necessitates good pitch-authority at high angle-of-attack, which cannot be provided by a tailplane due to its ineffectiveness at such flight profile. Hence, a decision was taken to employ a canard layout. An all-moving canard like the one on J-20 is capable of deflecting at the same magnitude but opposite sign to the angle-of-attack, thereby maintaining stability and control.

A canard delta offers greater efficiency in both subsonic and supersonic flight. Song Wencong's paper further explains the combination of canard, leading-edge extension, and body lift for enhancing performance in a canard layout. According to a diagram attached to the paper, the J-20's configuration is able to generate 1.2 times the lift than an ordinary canard delta, and 1.8 times more lift than an aircraft that purely relies on wing for lift. This permits the use of small aspect-ratio wing, reducing supersonic drag without compromising transonic lift-to-drag characteristics that are crucial to the aircraft's turn performance.

The J-20 may become the first operational combat aircraft that carries sufficient fuel to supercruise throughout its missions, doubling its sortie rate.

Engines
The prototype's engine is unknown, but is speculated to be either a AL-31 derivative or a version of the domestic WS-10. Western analysts believe that China is still working on a domestic turbofan engine to power the J-20 and will continue to use Russian engines for the aircraft for the time being. There have also been claims that China is seeking the AL-31 117S engine through Su-35 purchase. In response to such claims, China denied any deal of the Su-35. At the 2012 Zhuhai air show, Russia approached China with its 117S engine in an unsolicited yet unsuccessful attempt to sell Su-35.

The J-20's intended engine is speculated to be the WS-15, a turbofan engine producing 18 tons of thrust in development since the early 1990s. According to Global Security, the engine core, composed of high pressure compressors, the combustion chamber, and high pressure turbines were successfully tested in 2005. An image of the core appeared in the 2006 Zhuhai Airshow.

In late 2012, China announced a $24 billion investment program to catch up in the field of military turbofans. At the end of 2012, the Aviation Industry Corporation of China (AVIC) announced several breakthroughs in producing alloys for engine turbines, reaching standards used by leading global engine manufacturers.

Avionics
Official information on J-20's avionics is not publicly available. Examination of J-20 pictures revealed two small dark diamond shaped windows on both sides of the nose, which could house certain electro-optical sensors, such as a Missile Approach Warning System (MAWS) or an Infra-Red Search and Track (IRST) system. Windows similar to those in the Electro-Optical Distributed Aperture System (EODAS) onboard American F-35 can be found underneath the aft fuselage and on the fuselage above the canard. The J-20 is speculated to feature an advanced fly-by-wire (FBW) system that is integrated with the fire-control and the engine systems. China is known to have developed and deployed AESA radars on board its KJ-200 and KJ-2000 aircraft. In December 2012, new photographs emerged showing a J-20 prototype with a revised radome speculated to carry an AESA radar. As of January 2013, analysts expect the fire-control radar to be the Type 1475 or KLJ5 Active Electronically Scanned Array (AESA), roughly comparable in performance to the APG-77.

Cockpit
The aircraft features a pure glass cockpit, with two large color liquid crystal displays (LCD) situated side-by-side and three smaller ones in the surrounding. A wide-angle holographic head-up display (HUD) can be seen from close-up photos of J-20's cockpit. Many of these subsystems have been tested onboard J-10Bs to speed up the development.

Armament
The J-20 has a large belly weapon bay for short/long-range air-to-air missiles (AAM) (PL-10, PL-12C/D & PL-21) and two smaller lateral weapon bays behind the air inlets for short-range AAMs (PL-10).

One photo depicts the same air-to-air loadout as the F-22, that is six medium range and two short range air-to-air missiles.

In March 2013. A J-20 prototype is shown in a video armed with air to air missile similar to the F-22A. And in July 2013 a photo was released showing the hinged doors of the main bay open in flight.

Stealth
Analysts noted that J-20 uses similar stealth shaping design as the F-22 and F-35, providing good stealth capability at the front. However, these analysts also claimed the aircraft's side and axi-symmetric nozzles may expose the aircraft to radar detection. However, one of the prototypes uses WS-10G engines with stealthy jagged-edge nozzles and tiles.

Richard Aboulafia raised general doubts about the use of canards on a low-observable design, saying "there’s no better way of guaranteeing a radar reflection and compromise of stealth". However, canards and low-observability are not mutually exclusive design features. Northrop's proposal for the Naval Advanced Tactical Fighter (ATF), termed NATF-23, incorporated canard on a stealthy airframe. Lockheed Martin employed canards on a stealth airframe in the Joint Advanced Strike Technology (JAST) program, ending development only due to unexpected operational issues surrounding the flight control of Eurofighter and Saab Gripen. McDonnell Douglas and NASA's X-36 featured the use of canards and was shown to be extremely stealthy. The Eurofighter managed to reduce its Radar Cross Section (RCS) by controlling the deflection of its canards through the flight control software.

The diverterless supersonic inlet (DSI) improves stealth performance by eliminating unwanted radar reflections between the traditional diverter and the aircraft's skin. As of January 2013, analysts have also noted that the J-20 DSI reduces the need for application of radar absorbent materials. Additionally, the "bump" surface reduces the engine fan's exposure to radar, significantly reducing the strongest radar reflection from a combat jet. While the diverterless supersonic inlet (DSI) intakes are easier to maintain than more complex stealth-compatible intakes, such as on the F-22, their fixed form limits the aircraft to around Mach 2.0.

The J-20 also features the use of a missile deployment device in its side-bays whereby the missile is extracted from the bay before the door is closed behind it. This essentially reduces the need for the doors to open mid-flight which would have exposed the fighter to an opposition radar temporarily, making this feature especially useful in a WVR environment where even the slightest increase in RCS may prove deadly.

Political
The first test flight coincided with a visit of United States Secretary of Defense Robert Gates to China, and was initially interpreted by Pentagon officials and the media as a possible signal to the visiting delegation from the U.S. However, after meeting with senior Chinese officials including Chinese President, CMC Chairman Hu Jintao, Secretary Gates remarked, "The civilian leadership seemed surprised by the test and assured me it had nothing to do with my visit." Jin Canrong, a professor at Renmin University in Beijing who specializes in China-U.S. relations, suggested that President Hu's ignorance of the test raises questions about the nature of civilian control of the Chinese military. However, as Michael Swaine, an expert on the PLA and United States – China military relations, explained, although it's possible and even likely that "senior officials in the [Chinese] leadership did not know that this flight test would occur on this precise day," this is not necessarily evidence of a military-backed effort to insult Secretary Gates' delegation or embarrass President Hu. Rather, decisions regarding the production, development and testing of such military aircraft are routinely managed by engineers and low-level officials more than by senior civilian or military leadership. Coupled with the fact that there was relatively limited coverage of the event in Chinese media initially, it is likely that the test may not have been considered a significant enough event to warrant notification to President Hu.

Military
The U.S. Director of National Intelligence James R. Clapper has testified that the United States has known about the program for a "long time" and that the test flight was not a surprise. On the other hand, a 2012 report by the U.S.‐China Economic and Security Review Commission suggests that the United States may have underestimated the speed of development of the J-20 and several other Chinese military development projects.

Robert Gates has questioned how stealthy the J-20 might be although he did say the development of the J-20 had the potential to "put some of our capabilities at risk, and we have to pay attention to them, we have to respond appropriately with our own programs." Pentagon spokesman Geoff Morrell has said that it was premature to call the J-20 a stealth fighter or to judge if it had any other fifth-generation characteristics.

As early photographs of the prototype surfaced, Bill Sweetman commented that the design may suggest a large, long range ground attack aircraft, not unlike a "stealth version" of the General Dynamics F-111 Aardvark. However, that assessment is in conflict with the "J" designation which PLAAF has traditionally reserved for its fighters with air superiority mission. Bill Sweetman argues that the J-20 will be more similar to a MiG-25 with stealth capability. He says this is the most likely role for such a large aircraft with low thrust to weight ratio and limited agility that is optimized for range and speed. Loren B. Thompson has said that this combination of forward sector only stealth and long range will allow the J-20 to make attacks on surface targets while the United States lacks sufficient bases for F-22s in the area to counter these attacks and American allies have no comparable aircraft. Thompson has also said that a long-range maritime strike aircraft may cause the United States more trouble than a shorter range air-superiority fighter like the F-22. The Pentagon's 2011 report on the Chinese military agrees that the J-20 is "a platform capable of long range, penetrating strikes into complex air defense environments." Because the aircraft's center of gravity must be within the triangle defined by the landing gear, the J-20 depends on lift from its canards, which limits its maneuverability to the lifting power of its canards. Hence the J-20 is not a fighter, but rather a light supersonic bomber. The J-20 may have lower supercruise speed (yet greater range) and less agility than a Lockheed Martin F-22 Raptor or PAK FA, but might also have larger weapons bays and carry more fuel.

Roger Cliff, senior political scientist at the RAND Corporation, states that "What we need is to be able to put 25 jets in the air and take down 75 of theirs, without many losses. But it’s just not going to be that one-sided anymore" and "We have become accustomed to a world where our air power is dominant, but that dominance is now in question."

Specifications
Because the aircraft is in development, these specifications are preliminary and are taken as estimates from the available images.