Chengdu J-20, THE dark horse in the race for 5th generation combat aircraft
1/13/2017 0 COMMENTS
A comprehensive study into the J-20 as it develops as an operational 5th Generation fighter.
a competitive and ambitious program
ile it has often been dismissed as an inferior platform to any other 5th Generation program in existence, the shroud of secrecy and the heavy criticism which quickly stereotype the aircraft as "impotent" in the evolving battle space give the J-20 its biggest advantage in the development process as it manages to keep a lower profile in the general public eye.
There are a set of preconceptions about the aircraft and its performance, but here's what we know now:
1. The J-20 is slightly shorter than a Flanker unlike what was speculated about the size when the aircraft first flew in 2011.
2. The weapons bay of the J-20 is quite shallow; it can probably carry small diameter bombs but definitely not any standoff munitions. This puts to the rest that the J-20 is an overhyped ground attack platform.
3. The current engines are variants of the AL-31F. These engines give the Flanker, a larger aircraft, sufficient thrust but the J-20 might be heavier than the Flanker (speculation) so it can be expected to have lower thrust-to-weight ratio.
4. An F-119-class engine called WS-15 is confirmed to be in development. This new engine is almost definitely going to be mounted on the J-20 when its development concludes.
5.The J-20 has entered service with the PLAAF with the first examples sporting grey low-visibility roundels as well as the RAM treated splinter camouflage .
6.The J-20 is integrated with next-gen A2A ordnance like the PL-10 SRAAM and PL-15 MRAAM.
Size analysis of the J-20 in comparison with the J-15
engines- the heart of the aircraft
.The "go to" statement to discredit the aircraft is often its powerplant, and while the initial shortcoming has been addressed by using Russian engines for the Flankers, the AL-31FN series engines, the WS-15 engines being developed are expected to give it a favorable operating thrust envelope.
There are 4 major stages in China with respect to developing and certifying a new engine.
The first phase is the test/experimental stage prior to the initial flight. This involves all of the ground based testing on the parts of engine and as a whole. It goes through a series of test on the test vehicle and its parts to make sure that it's ready to go through flight testing.
The second phase is the research test flight stage. Before going into the process of certification test flights, the test vehicle is flown under realistic flight scenarios and flight envelope. The main tasks include preliminary assessment of engine flight performance, features, reliability, maintainability, testability and supportability. Flight tests could be carried out in a flight engine test bed or on an intended aircraft. At the conclusion of test flights, the technological maturity level should reach level 7. In WS-15 testing, it had to complete 60 hours of endurance testing on flight testbed before completing this phase. So at this point, the engine is demonstrated to have at least 60 hours of service life prior to overhauling.
The third phase is the design certification stage. Before low rate initial production, it must go through a series of ground testing of the engine, its systems and the individual parts. It must also go through with high altitude testing and flight certification. Most importantly, it has to go through the initial overhaul long endurance testing on testbed. For WS-10 and WS-10B, they had to complete a 300 hour endurance testing to complete this stage. Under testing of full flight envelope, these tests will determine the reliability, maintainability, testability, safety and service life. At its conclusion, the technological maturity level should reach level 8.
The fourth phase is the production certification stage. Before mass production of an engine, it must be deployed in smaller number of aircraft (with active service aircraft) for test usage in order to become mature. It must go through with full service life endurance testing on test bed. It must complete comprehensive verification of engine performance and reliability under mass production quality. Mass produced version of WS-10 must complete 1000 hour of endurance before completing this stage, the initial overhaul time is at least 1000 hours. At its conclusion, the technological maturity level should reach level 9.
This gives a decent idea about the quality measures of taken for the developing the powerplant and the WS-15 engines are quickly approaching maturity as the engineers take design inputs from existing engines and the AL-41 engines from the Su-35S aircraft delivered last year.
Even if there are stop gap variants of the AL-41 produced and utilized on the J-20 aircraft, it can be comparable to the newer J-11B and follow on variants of the Chinese produced Flankers.
Primary sensor suite
Type 1475 Active Electronically Scanned Array (AESA) radar
Chinese AESA radars. The top one is for the J-10B fighter and has about 1200 transmit/receiver (T/R) modules, the middle one is for the J-16 strike fighter and has 1760 T/R Modules. The bottom one destined for the J-20 5th generation stealth fighter, and has 1856 T/R modules (generally, the more T/R modules on an AESA radar, the more powerful and flexible it is).
The radar is said to have LPI and with 1856 T/R modules, the radar can have an estimated power output of 18 Kilowatts with low power modules which would be slightly less than the Irbis-E. As per recent developments mentioned, the AESA module is expected to have 2000 T/R modules which is not far fetched as the estimated plate diameter and radar aperture size is similar to that of the F-22 Raptor which houses the AN/APG-77(v1) AESA.
We are yet to judge the efficiency of the radar as details about the modules, cooling channel and side lobe cancellation aren't publicized or have a convincing comparison against existing modules being used by other AESA radars.
EOTS-89 electro-optical targeting system (EOTS)and EODAS
Wang Yanyong, technical director for Beijing A-Star Science and Technology, confirms that two systems – the EOTS-89 electro-optical targeting system (EOTS) and the EORD-31 infrared search and track (IRST) – are in development for China’s J-20 and J-31 fighters.
Marketing brochures on A-Star’s booth suggest that the J-20 could use the passive sensors to detect and aim missiles against other VLO aircraft without using its Radar to actively detect and targets. A long range concentrated monopulse can be used to cue the EOTS and DAS which if comparable to the F-35 Lightning II's EOTS and EODAS will be used for 360-degree, spherical situational awareness system. The DAS sends high resolution real-time imagery to the pilot’s helmet from six infrared cameras mounted around the aircraft, allowing pilots to see the environment around them – day or night – without loss of quality or clarity. With the ability to detect and track approaching aircraft from any angle, the DAS also greatly reduces the potential for mid-air collisions and virtually eliminates surprises.
However, there is no photographic evidence of the EOTS and EODAS installed as the space reservations can be noticed on the aircraft without the sensors on the operational aircraft with the PLAAF.
EODAS Space Reservations
Low obsevrability
The S-duct intakes and DSI reduce frontal RCS of the aircraft. The engine cowling is shielded all the way to the nozzle with saw tooth panels which again reduce RCS. The "close coupled" canards deflections can be mitigated by the FBW and FCS to have signature reduction. the control surfaces and vortex stabilizers are planform and at high deflection angles.
Front hemisphere designs appear to be in accordance with standard radar laws, with parallel lines, and minimum rough or flat edges. The J-20 uses angled chines along the sides of the aircraft (like the F-22), and a hidden engine intake design both to help lower side-section and front aspect RCS (Radar Cross Section).
Aside from the canards however, the J-20 design retains a stealthy frontal rcs. The design of the engine inlets, chined nose, flat lower fuselage, sawtooth design incorporation on internal bays, and extensive use of planform alignment should reduce the airframe's frontal radar signature considerably.
There is however some discrepancy as to whether the aircraft's RCS estimates can classify as a VLO platform ( -30 dBSM or lower) or LO platform ( -20 dBSM or .01m^2)
The use of RAM further reduces the RCS however its limited by the reflective non-planform surfaces and edges.
not a Strike Aircraft
Everything from the delta-canard planform arrangement, LERX, WS-15 development, and shallow weapons bay strongly indicate that the J-20 was designed to be an aerodynamically unstable, and manoeuvrable air superiority fighter with limited consideration for its strike capabilities.
The aerodynamic instability was highlighted when the J-20 carried four external fuel tanks on pylons from which the position of Center of Lift and Center of Weight could be related to each other and equated against aerodynamic models.
Had the J-20 been designed primarily for strike missions, it would have dispensed with the canards and gone for a configuration similar to the FB-22, featuring low drag and low pitch-authority. In addition, its weapons bays would have been much deeper to host dedicated strike munitions like the LS-500J. The WS-15 project would also have been unnecessary if the J-20 were a strike aircraft as the thrust-to-weight ratio of the J-20 in its current configuration is already much higher than what is needed for strike aircraft.
All in all, the J-20 can be expected to be a competitive and effective platform as time reveals the aircraft's capabilities and characteristic flight enveloped are opened.
It will take minimum 10 years now ,if all goes well
Rafale frontal RCS is close to 01-1m2 depending on the weapons load
Spectra is ECM kit , it does not change the RCS
The DEDIRA program will further improve the active stealth aspect of SPECTRA to bring down the frontal RCS of Rafale close to 0.0006m2. For reference, the unofficial frontal RCS of Raptor is 0.0001m2 without active cancellation, which is a Very Low observable (VLO) aircraft. DEDIRA is already integrated on a test Rafale numbered B301.
