Chinese stealth Chengdu J-20

The Chengdu J-20 is a Stealth, twin-engine fifth-generation fighter aircraft prototype being developed by Chengdu Aircraft Industry Group for the Chinese People’s Liberation Army Air Force(PLAAF). Chengdu_J_20The J-20 made its first flight on 11 January 2011, and is expected to be operational in 2017–2019. China’s J-20 platform has the potential to be a capable, long-range strike system in the Asia-Pacific region, but a number of technical challenges will need to be overcome before production can begin.

Origins of the J-20 came from the J-XX program which was started in the late 1990s. A proposal from Chengdu Aircraft Industry Group, designated “Project 718”, had won the PLAAF endorsement following a 2008 competition against a Shenyang proposal that was reportedly even larger than the J-20. On 22 December 2010, the first J-20 prototype underwent high speed taxiing tests outside the Chengdu Aircraft Design Institute.

On 11 January 2011, the J-20 made its first flight, lasting about 15 minutes, with a Chengdu J-10S serving as the chase aircraft. After the successful flight, a ceremony was held, attended by the pilot, Li Gang, Chief Designer Yang Wei and General Li Andong (Deputy-Director of General Armaments).

On 17 April 2011, a second test flight of an hour and 20 minutes took place.On 5 May 2011, a 55-minute test flight was held that included retraction of the landing gear.

On 26 February 2012, a J-20 performed various low-altitude maneuvers. On 10 May 2012, a second prototype underwent high speed taxiing tests, and flight testing that began later that month. On 20 October 2012, photographs of a new prototype emerged, featuring a different radome, which was speculated to house an AESA radar.

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On March 2013, images of the side weapon bays appeared, including a missile launch rail.

On 16 January 2014, a J-20 prototype was revealed, showing a new intake and stealth coating, as well as redesigned vertical stabilizers, and a system that appeared to be an Electro-Optical Targeting System. This particular aircraft numbered ‘2011’ performed its maiden flight on 1 March 2014 and is said to represent the initial pre-serial standard. Overall the year 2014 was quite a successful one and until the end of 2014 three more pre-serial prototypes were flown: number ‘2012’ on 26 July 2014, number ‘2013’ on 29 November 2014 and finally number ‘2015’ on 19 December 2014.

The J-20 has a long and wide fuselage, with the chiseled nose section and a frame-less canopy resembling that of the F-22 Raptor. Immediately behind the cockpit are low observable intakes. All-moving canard surfaces with pronounced Dihedral (aeronautics) are placed behind the intake ramps, followed by leading edge extensions merging into delta wing with forward-swept trailing edges. The aft section features twin, outward canted all-moving fins, short but deep ventral strakes, and conventional round engine nozzles. In one paper published on a Chinese aerodynamic journal, a designer of J-20 described high instability as an important design criterion for J-20. A canard is used to achieve sustained pitch authority at high angle of attack, as traditional tail-plane would start to lose effectiveness. This is because tail-plane would go into even higher angle-of-attack and stall, whereas canard can avoid this effect by deflecting to the same magnitude but opposite to the angle-of-attack.A canard configuration can also provide good supersonic performance, excellent supersonic and transonic turn performance, and improved short-field landing performance compared to the conventional design.

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The same journal paper also explained how leading edge extensions and body lift are incorporated to enhance performance in a canard layout through interactions amongvortices. One graph shows the configuration to generate 1.2 times the lift of an ordinary canard delta, and 1.8 times more lift than a pure delta configuration of similar size. This allows the use of a smaller wing, reducing supersonic aerodynamic drag without compromising transonic lift-to-drag ratio characteristics that are crucial to the aircraft’s turn performance.

Engines

The production version of the J-20’s is speculated to be WS-15 a turbofan engine currently under development in the same class as American F-119. 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 Air Show. Since 2012, China has reported numerous breakthroughs in development military turbofans and invested up to 20 billion US dollars in turbofan engine research and development. The J-20 has the potential to rival the F-22A Raptor in performance once appropriate engines become available.

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Western analyst believe that the current prototypes are powered by WS-10 or the AL-31F engine. China is a large importer of Russian-made jet engines, prompting rumors that China seeks to obtain AL-41 117S engines for the initial production of J-20 through Su-35 purchases. However, these rumors have since been denied by China, and were proven as false. It was also reported that Russia approached China in an unsuccessful bid to sell 117S engines during the 2012 Zhuhai Air Show.

Avionics

The aircraft features a glass cockpit, with two main large color liquid crystal displays (LCD) situated side-by-side, three smaller auxiliary displays, and a wide-angle holographic head-up display (HUD).

A PLAAF Tupolev Tu-204 test bed aircraft was seen featuring a J-20 nose cone. It is believed to house the Type 1475 (KLJ-5) active electronically scanned array (AESA) radar with 1856 transmit/receive modules.

Prototype “2011” featured a revised nose section with elements resembling a IRST/EOTS system used to hunt low observable aircraft, and a metal finish that loosely reminds the radar absorbing Haze Paint first used on F-16s, and reportedly included sensor fusion technology.

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Armament

The main weapon bay is capable of housing both short and long-range air-to-air missiles (AAM) (PL-9, PL-12C/D & PL-21).

Two smaller lateral weapon bays behind the air inlets are intended for short-range AAMs (PL-9). These bays allow closure of the bay doors prior to firing the missile, thus enhancing stealth.

No gun has yet been seen on any J-20 model and there have not been signs of provisions for one.

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Stealth

Analysts noted that J-20’s nose and canopy use similar stealth shaping design as the F-22, yielding similar signature performance in a mature design at the front, while the aircraft’s side and axi-symmetric engine nozzles may expose the aircraft to radar. One prototype has been powered by WS-10G engines equipped with a different jagged-edge nozzles and tiles for greater stealth.

Others have raised doubts about the use of canards on a low-observable design, stating that canards would guarantee radar detection and a compromise of stealth.However, canards and low-observability are not mutually exclusive designs. Northrop Grumman’s proposal for the U.S Navy’s Advanced Tactical Fighter (ATF) incorporated canards on a stealthy air frame. Lockheed Martin employed canards on a stealth airframe for the Joint Advanced Strike Technology (JAST) program during early development before dropping them due to complications with aircraft carrier recovery. McDonnell Douglas and NASA’s X-36 featured canards and was considered to be extremely stealthy. Radar cross-section can be further reduced by controlling canard deflection through flight control software, as is done on the Eurofighter.

The diverterless supersonic inlet (DSI) enables an aircraft to reach Mach 2.0 with a simpler intake than traditionally required, and improves stealth performance by eliminating radar reflections between the diverter and the aircraft’s skin. Analysts have noted that the J-20 DSI reduces the need for application of radar absorbent materials.Additionally, the “bump” surface reduces the engine’s exposure to radar, significantly reducing a strong source of radar reflection.

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Specifications

Data from Aviation Week & Space Technology

General characteristics

  • Crew: one (pilot)
  • Length: 20 m (66.8 ft)
  • Wingspan: 13 m (44.2 ft)
  • Height: 4.45 m (14 ft 7 in)
  • Wing area: 78 m2 (840 sq ft)
  • Empty weight: 19,391 kg (42,750 lb)
  • Gross weight: 32,092 kg (70,750 lb)
  • Max takeoff weight: 36,288 kg (80,001 lb) upper estimate
  • Fuel capacity: 25000 lb
  • Powerplant: 2 × Saturn AL-31F (prototype) or Xian WS-15 (production) afterburning turbofans, 76.18 kN (17,125 lbf) thrust each dry, 122.3 or 179.9 kN (27,500 or 40,450 lbf) with afterburner
  • Wing loading: 340 kg/m2 (69 lb/sq ft)
  • Thrust/weight: 0.94 (prototype with interim engines)

Armament

  • PL-10 SRAAM
  • PL-12 Medium Range AAM

source: wikipedia

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