The J-20 (K/JJ20?) #2001 technology demonstrator made its maiden flight on January 11, 2011 over the city of Chengdu, wearing a distinctive dark green color scheme and powered by two AL-31F turbofan engines.
The prototype features a pair of all-moving tailfins and Russian 1.44 style twin ventral stabilizing fins and tail booms, which shield the engine nozzles and its heat exhausts but might increase RCS.
Also there are four large underwing actuator fairings but their size was reduced on later prototypes.
It also features an F-22 style forward fuselage, including adjustable Caret inlets but with DSI bumps installed at the upper inner corners, as well as a one-piece frameless canopy.
Small LERX are installed between the canards and main wings in order to generate vortex together with the canards at high AoA.
Two small dark diamond shaped windows can be seen on both sides of the nose, which could house a certain kind of EO sensors.
Two more diamond shaped windows are seen underneath the rear fuselage, plus two more located forward and aft the cockpit, suggesting a distributed situational awareness system similar to the EODAS onboard American F-35 could have been installed to provide a full 360° coverage.
Besides a large belly weapon bay for medium/long-range AAMs (up to 4 PL-12, PL-15, or 4 PL-21?), two smaller lateral weapon bays have been identified behind the air inlets for short-range AAMs (one PL-10 inside each).
The 2001 prototype appeared to fly without an internal gun, it also might be flying without the RAM coating applied but this may change later.
First disclosed by US Office of Naval Intelligence (ONI) in 1997 as XXJ, J-20 (Project 718) is a 4th generation heavy air superiority fighter to enter the service with PLAAF between 2016 and 2018, a time frame much faster than the one (>2020) anticipated by the western military analysts.
Since early 90s both CAC/611 Institute and SAC/601 Institute had been working their own designs to bid for a twin-engine heavy fighter with stealth capability and maneuverability comparable to American F-22.
All designs would feature a belly internal weapon bay to reduce RCS, which has been speculated to be <0.05m2 (head-on). J-20 also incorporates an advanced optic HSDB system fully integrating the fire-control and the engine systems.
The aircraft has a smooth surface without any protruding tubes or inlets, suggesting an FADS has been installed in order to reduce RCS. Its fire-control radar is believed to be AESA (Type 1475/KLJ5?) based on the less powerful model onboard J-10B, both are developed by the 14th Institute.
The radar is thought to be comparable to American APG-77. Both the radar and the CNI system were tested onboard a modified Tu-204C testbed, similar to American Boeing 757 testbed for F-22. The next generation advanced datalink (MADL) is believed to be installed as well which provides secure networking with other J-20s and KJ-200/2000 AWACS.
The aircraft also features a "pure" glass cockpit and possibly HMDS.
J-20 has a retractable IFR probe hidden beneath a cover on the starboard side of the cockpit similar to the one onboard American F-35.
Many of these subsystems have been tested onboard J-10B to speed up the development.
The exact types of engine powering the prototypes are unclear, even though a Russian or Chinese turbofan engine including AL-31F/F-M2 (12.5t/14.7t class) and enhanced WS-10 (WS-10G? 13t class) was speculated. In the end the Russian engine is believed to be the likely candidate (AL-31F onboard initial #200x prototypes then AL-31F-M2 onboard #201x prototypes/A Configuration?).
The engine features a silver color (ceramic coating?) "stealth" nozzle with saw tooth edges to reduce RCS and IR emission.
However the nozzle has yet to demonstrate an axisymmetric TVC capability. It was reported in November 2006 that a 16-17t class T/W=9 turbofan (WS-15/"Large Thrust"/Emei?) with a TVC nozzle is being developed and will eventually power J-20s of later production batches (B Configuration?).
J-20 appears slightly longer and slimmer than both F-22 and T-50, suggesting a compromise between achieving high speed/maneuverability and the less powerful engines available.
Therefore currently the J-20 prototype still lacks the supercurise capability until the planned WS-15 turbofan becomes available. Russian assistance was also speculated in terms of software support for calculating the RCS and aerodynamics of various designs.
The overall performance of J-20 is thought to be superior to that of Russian T-50 but still inferior to that of American F-22.
Once entering the service, J-20 could pose a significant impact/challenge to the air power balance in eastern Asian and western Pacific region.
It has prompted the neighboring countries including Japan and South Korea to pursue other 5th-generation stealth fighters such as F-35.
In August 2008 it was reported that 611 Institute was selected to be the main contractor for the development of J-20 and 601 Institute as the sub-contractor. Subsequently a full-scale metal mockup was built at CAC.
One rumor in May 2010 claimed that 611 Institute started to construct the first prototype, which was expected to fly by the end of 2010.
Two prototypes were constructed and the first low-speed taxi trial by 2001 took place on November 4, 2010.
The #2002 technology demonstrator made its maiden flight on May 16, 2012.
Both #2001 and 2002 were sent to CFTE in Yanliang in 2012, where #2002 prototype was renumbered as 2004 and #2001 flew with a new gray RAM paint. The #2002 technology demonstrator was seen conducting weapon integration tests with a dummy PL-10 IIR guided short-range AAM on its retractable side missile launch rail in March 2013.
Unlike that of F-22, the weapon bay door is closed while the missile is fully exposed to maintain low RCS and reduce drag during dogfight.
In July 2013 it conducted similar tests carrying dummy PL-12 AAMs (modified with cropped fins) inside the belly weapon bay.
The completion of building the third prototype was delayed until late 2013 due to the fact that the #2011 prototype would feature certain "major improvements" and is no longer considered as a "technology demonstrator".
The first low-speed taxi test of #2011 prototype took place on January 16, 2014, high-speed taxi test on February 18, 2014.
The aircraft was seen to have a nosed mounted IRST and frame-strengthened one-piece canopy plus a new holographic HUD with a slimmer frame.
Its cockpit might have also been upgraded with a large touchscreen panoramic cockpit display (PCD) similar to that of American F-35 plus a smaller LCD between the legs.
As the result a side-stick and the throttle are expected to be used to control the aircraft.
The emergence of IRST suggests that J-20 might possess a limited AG capability using laser or TV guided PGMs.
In addition it has numerous aerodynamic refinements including reshaped tailfins, extended tail booms, nose landing gear door, LERX and engine intakes with two hexagonal inlet/outlet of the fuel-air heat exchanger (?) as well as smaller underwing actuators to further reduce RCS.
Two side-looking radar antennas could have been installed underneath the elongated hexagonal dielectric fairings (in X & Y directions) on each side of the nose, which provide a better situation awareness and extended missile guidance during the dogfight.
Two large tail booms appear to house additional ECM or rear-view radar antennas to protect the rear hemisphere of the aircraft.
A new ECM antenna can be seen aft the air intake as well.
The prototype also started to wear a new light blue/gray RAM coating.
A more powerful engine (AL-31F-M2) was believed to have been installed.
The #2011 prototype first took off into the sky on March 1, 2014.
Different types of"stealth" nozzle were tested on one of the engines onboard #2011 in April 2014.
The first flight of #2012 took place on July 26, 2014.
The #2013 prototype took off for the first time on November 29, 2014, and the #2015 prototype on December 19, 2014. Both 2013 and 2015 have the pitot tube removed from the nose and both feature a further refined nose radome and tail booms, suggesting the AESA radar has been installed.
They have been speculated to represent a nearly "frozen" technical configuration before the initial production.
The relatively fast pace of two aircraft being rolled out within one month suggested that the J-20 program is moving towards the low-rate initial production which could start as early as 2016.
The initial batches are still powered by the AL-31F-M2 engine.
It was rumored in April 2015 that both 2013 and 2015 prototypes were to be transferred to CFTE for further testing, after that various weapon tests were expected to start at the PLAAF Test and Training Base.
The #2016 prototype made its first flight on September 18, 2015.
The aircraft appears to feature slightly reshaped DSI bumps, engine nozzles as well as a new ejection seat.
The aircraft was transferred to CFTE for further testing on December 2, 2015.
The last prototype (#2017) had its maiden flight on November 24, 2015 before the initial production started in late 2015.
The aircraft appears to feature a slightly reshaped canopy.
Chaff and flare launchers were installed in the tail booms between the vertical tailfin and the engine nozzle.
There has been speculations that a compartment was reserved for an internal gun underneath a top panel on the port side of the fuselage next to the canard wing but this has not been confirmed.
It is likely that the LRIP model is produced without a gun.
A new J-20 in yellow primer first appeared in December 2015 which is likely to be the first LRIP model (2101, 00 batch). First flight took place on January 18, 2016. More 00 batch J-20s are being built in 2016, at least 4 (2101-2104?) by mid-2016, wearing a gray color scheme and low-visibility PLAAF insignias.
The aircraft appears to have 4 hardpoints underneath the wings for external payloads such as PL-10/PL-12 AAMs and fuel tanks.
They can be carried during routine air patrols in peacetime.
The pylons can be jettisoned in case of an emergency situation and the aircraft will turn into the stealthy combat mode. In the meantime J-20 prototypes have been undergoing weapon launch tests including lunching PL-15 AAMs.
The latest images (September 2016) indicated that new LRIP J-20s were built without any visible serial numbers.
The first batch is expected to enter the service with PLAAF by the end of 2016 (S/N 78xxx & 4xx4x).
Recent images (October 2016) indicated that two LRIP aircraft is wearing a new splinter camouflage similar to that of Russian T-50.
In addition test flights were flown by a prototype at CFTE carrying 4 external fuel tanks. J-20 was officially unveiled to the public at the 2016 Zhuhai Airshow.