Fifth generation fighter aircraft feature many enhanced capabilities compared to older fourth generation fighters, including highly capable and integrated sensor suites and mission avionics.
As a fifth generation fighter, the J-20 will likely be equipped with certain key sensors and mission avionics to be competitive with other fighter aircraft of its generation. Verified details of J-20’s sensor suite and mission avionics do not exist due to the high operational security of the Chinese military, however it is possible to reach certain likely conclusions, through the combination of credible open source rumours, analysis of J-20 pictures, and the application of common sense and critical thinking.
However, first it is important to determine the sensors and avionics typical of a fifth generation fighter. These may usually an advanced active electronically scanned array radar, an advanced electronic support measures suite, an advanced datalink or datalinks, as well as possible electro-optic/infra-red sensors and even secondary radars. Of course, the integration of the sensors via data fusion and the actual capability of the sensors compared to each other are not known and may never be known, therefore the table below should not be viewed as an exhaustive qualitative comparison.
Confirmed and/or Highly Suspected:
These following sensors and avionics are either confirmed to be present on the J-20, or highly suspected to be present, due to a variety of reasons that may range from suggestion by credible rumours, identification by assessing pictures of J-20, or simply common sense
The primary radar of J-20 will virtually be guaranteed to be a X band AESA radar. The X band features characteristics perfectly suited for a fighter aircraft, and the Chinese radar industry has produced many domestic AESAs in recent years. Rumours have suggested the J-20’s radar may be designated Type 1475. It may possibly include transmit/receive modules numbering near 2,000, which would be greater than the ~1,500 T/R module count for the F-22’s APG-77 and the T-50’s N036-1-01, as well as the 1,200 T/R module count for the F-35’s APG-81 – and given the large radome and bulkhead of the J-20 compared to its peers, such a high T/R module count may be quite within reach.
However, it is important to emphasize that it is impossible to know how each radar of each fighter may ultimately compare with each other in all sorts of domains from probability of interception, to differing modes available, to maximum power.
Beginning from J-20 prototype 2011, all J-20 airframes since then have featured a chin mounted, faceted window for what is virtually guaranteed to be an electro-optical/infra-red sensor capable of search and track functions. Prototypes tend to have fielded a mock up of the sensor window during their first flights, before being replaced with what appears to be an actual sensor. The configuration of this sensor is not dissimilar to the Electro Optic Targeting System fairing on the F-35’s chin, however J-20’s appears to be less “deep” and “longer” than the EOTS. The configuration of the faceted windows on J-20’s sensor also appears different to F-35’s EOTS.
However, the superficial similarity between J-20’s EOIRST and F-35’s EOTS has led some individuals to also call J-20’s sensor as “EOTS”. This is somewhat misleading, as the EOTS is very much a product name with capabilities specific to the F-35, which J-20’s EOIRST may not have. For instance, the F-35 EOTS is capable of air to air tracking and targeting as well as air to ground tracking and targeting, with the air to ground function being a key part of F-35’s overall strike fighter capability. The air to ground tracking and targeting function includes laser spot tracking and laser designation to assist in the guidance of precision guided munitions.
The J-20 on the other hand, likely was not designed with air to ground strike capabilities as a role given the configuration of the aircraft and its limited weapons bay size and depth, therefore it is doubtful if J-20’s EOIRST is capable of the same air to ground tracking and targeting as F-35’s EOTS. It has been suggested that the chin mounted “downwards facing” orientation of J-20’s EOIRST may optimize it for air to ground roles. However such claims are doubtful, because the size and configuration of J-20’s nose and radome makes a dorsal nose mounted position for the EOIRST difficult to implement especially when considering the vast array of other machinery and sensors on the dorsal side of the nose (including a retractable in-flight refuelling probe and a fixed centreline EO sensor aperture). More so, other past and current aircraft have also featured chin mounted EO/IR sensors for the air to air role, such as F-14’s AN/AAS-42, or the Legion pod and Tiger Eyes pod intended for retrofit for US Air Force F-15s and F-16s as air to air tracking and targeting sensors. The air superiority oriented YF-23 and F-22 were both designed with an EOIRST system in mind, with both aircraft featuring chin mounted, downwards facing sensors. Together, this suggests that a chin mounted EOIRST system does not necessarily mean it or the aircraft it is mounted on, is oriented for air to ground missions.
Note, a private Chinese aerospace company called Beijing A-Star has offered a range of “EOTS” products, with specifications and performance details, as well as illustrations depicting their products equipped aboard both J-20s and FC-31s, however at present there is no evidence to suggest that the the company is a contractor for any Air Force project, let alone the secretive and high priority J-20. Indeed, it would be a major change in Chinese military operational security if such a major subcontractor for a vital system on J-20 were allowed to openly display the specifications of its sensor on the open market.
360 degree EO PDS:
The J-20 is equipped with six discrete, low profile window apertures around the aircraft, suspected to house electro optic sensors. The apertures are arranged in the aircraft in such a way where they appear to provide three hundred and sixty degree spherical coverage around the aircraft, and the placement and configuration of the apertures are similar to the placement of the six apertures for the F-35’s AN/AAQ-37 Distributed Apertures System.
Therefore, some Chinese military watchers have described J-20’s Electro Optic Passive Detection System as a “DAS”. However, much like the EOTS name, the AN/AAQ-37 DAS is a very specific product with specific capabilities for the F-35, and it is unknown if the J-20’s EO PDS will feature similar capabilities, therefore it is likely prudent to separate the designations of the two to avoid confusion.
For instance, the F-35’s DAS is capable of providing traditional missile approach and warning functions, but is also capable of providing specific launch point detection, automatically tracking contacts and cueing sensors or weapons, and also assist day and night navigation, all within the spherical field of view around the aircraft. Most impressively, when integrated with the F-35’s helmet mounted display system, the DAS allows the pilot to essentially “see” through the DAS apertures seamlessly, such that they can even “look through” the floor of the aircraft to what is occurring immediately below the aircraft.
It is unknown how many of the capabilities of DAS will also be present aboard J-20’s EO PDS, but what can be suggested is that J-20’s EO PDS is meant to provide three hundred and sixty degree spherical coverage. It is possible that various detection, tracking, situational awareness, and navigational potentials of the apertures could be exploited through increasingly capable software enhancements through the aircraft’s incremental development.
An advanced Electronic Support Measures suite is an essential part of a modern fighter aircraft’s mission avionics. An ESM suite helps to detect, identify, locate, record, analyze and even geolocate sources of electromagnetic energy, which for a fighter aircraft typically means an opposing force’s radar system. Modern ESM suites have grown in capability and complexity from mere warning systems to alert a pilot when their pilot was possibly being targeted by radar, to being capable of simultaneously geolocating multiple sources of radar emissions in real time and automatically activating counter measures, targeting solutions and cueing weapons.
Such suites are immensely difficult to identify, and may only sometimes be visible as small, low profile conformal antennae around an aircraft. Multiple sites that could hold small conformal antennae have been identified on J-20 through picture analysis, and there are likely multiple other sites with antennae which are not outwardly visible. Either way, it is certain that J-20 will be equipped with an ESM suite of some kind, and if trends for other fifth generation ESM suites are anything to go by, it is likely the Chinese Air Force would have similarly high requirements for J-20’s ESM suite.
High bandwidth datalinks to provide communication and coordination and transference of information between friendly aircraft, ships and other combat forces are also a vital fixture for fifth generation fighter aircraft, as well as past generations of fighter aircraft as well.
The J-20 will likely be equipped with a datalink that could at least receive the Chinese military’s Joint Service Integrated Datalink System (JSILDS), a system which is said to be similar to the Link 16. It is possible that J-20 may also feature advanced iterations of other datalinks, such as an equivalent to the Multifunction Advanced Datalink of the F-35, or the F-22’s Intra Flight Datalink, to provide effective stealthy and secure communications between aircraft which JSILDS may be incapable of.
Possible and/or Speculated:
The following sensors and avionics are those which have thus far not received any credible rumours for and whose presence cannot be strongly suggested to exist through picture analysis and can only be suggested as a possible explanation for particular characteristics visible on the aircraft. The relative rarity of these sensor types among other fighter aircraft of the world is also a reason for classifying these potential sensors as possible and speculated, rather than “likely”.
Side looking radar:
Some fighter aircraft feature side looking radars, usually mounted on the sides of an aircraft’s nose. Such a configuration is present aboard the PAK FA/T-50 with two X band AESAs, was suggested as an upgrade for the F-22 (now cancelled). Side looking radars can allow an aircraft to track targets in a much greater field of view on the sides of an aircraft compared to merely the forward sector provided by nose mounted radar, and can potentially allow an aircraft to maintain a weapons quality track and datalink whilst turning away from the target.
Photos of J-20 appear to show a long, diamond shaped grey dielectric fairing expected for an antenna of some kind. Whether this specific fairing is for side looking AESAs or merely other functions such as ESM or IFF or even ECM, is another matter.
Wing mounted radar:
Wing mounted radar, such as in the leading edge slats of an aircraft like in the PAK FA/T-50, provide additional forward sector situational awareness. The physical characteristics of the leading edge slat allows radars of greater size and different frequency bands to be mounted to provide complementary surveillance capabilities to the main X band radar of an aircraft. In the case of the PAK FA, L band AESAs are mounted, which provide superior anti stealth characteristics compared to the X band.
The leading edge slats of J-20’s main wings appear to also be wholly grey, suggesting a dielectric covering consistent with an antenna, therefore one possible explanation for the grey covering over the leading edge slats could be the presence of a wing mounted radar. However, as with the case for the side looking radar, the grey dielectric paint could be indicative of any sort of antenna.
Tail mounted radar:
Much like side looking and wing mounted radar, a tail mounted radar helps to provide rear sector coverage for an aircraft. Few fighter aircraft are equipped with tail mounted radar just as few fighter aircraft are equipped with side looking and wing mounted radar, and the few aircraft which are equipped with such radars typically mount them within an aircraft’s tail sting.
In the case of J-20, two tail stings are present, and have been steadily modified in geometry throughout the prototype stage. Again, the distinctive grey dielectric cover of the tail stings suggest the presence of an antenna within each tail sting, and the location of an antenna in such a location would be sensible for any sort of transmitting or receiving array or an array capable of both. Whether the suspected antenna is actually a radar or if it is ESM, IFF, ECM or any other type of antenna is something which cannot be ascertained.
This entry has described certain sensors nd avionics that J-20 is confirmed or at least highly expected to be equipped with, including a primary AESA radar, a chin mounted EO IRST system, a three hundred and sixty degree EO PDS, one or more advanced datalinks of some kind, and an ESM suite.
Other possible sensors include side looking, wing mounted and tail mounted radar systems, but these cannot be substantively ascertained nor have they been strongly suggested by rumours as of yet. If higher quality pictures of upcoming Low Rate Initial Production J-20s in yellow primer emerge, it may help to further identify and confirm grey dielectric fairings which contain antennae, as such fairings would be very visible against the yellow primer of the rest of the aircraft’s surface structure.