Dual seat variant of the J-20 via Twitter
The J-20 is a large and heavy all aspect stealth fighter, sometimes referred to as a light bomber. Based on the geometry of its shape, it likely has a very low front aspect RCS and reasonably low side aspect RCS. However, rear aspect RCS reduction is minimal.
The J-20 was developed to penetrate undetected airspace in the vicinity of a US Navy Carrier Battle Group to a depth required to track the warships for guiding ballistic missiles such as the DF-26 or to directly attack the ships using anti-shipping cruise missiles in its internal bomb bay.
Suppression of Enemy Air Defense Systems
The size of the J-20 and the lack of rear aspect stealth compromise its overall RCS to a value that is likely significantly more than 0.0015 dBsm RCS of the F-35. However, there can be little doubt that the J-20 would be able to penetrate Indian airspace completely undetected for suppressing our air defense systems including command and control centres, radars and missile sites.
A statement by the former IAF CAS Air Chief Marshal BS Dhanoa (Retd.) that IAF Su-30MKI have been able to detect the J-20 must be taken in the right context. The J-20's lower side aspect stealth would allow such detection at ranges or around 40-50 kms using the Su-30MKI's powerful BARS radar, but the radar would not be able to obtain a weapon grade track. Also, it is likely that PLAAF J-20 fighters flying in close proximity to the LAC would use RF reflectors or lenses to spoof RCS assessment.
Operating undetected in Indian airspace, the J-20 would be able to strike radar and missile sites with its internally carried precision guided LACMs to degrade IAF air defenses. The stealth fighter would also be able to act as a forward penetrating sensor of massive cruise missile attacks launched by PLAAF H-6 bombers. (The PLAAF's cruise missile threat would be covered in a subsequent post.)
The stealth advantage of the J-20 would give it a first see, first shoot advantage in BVR combat over all IAF fighters except the Rafale and the Su-30MKI. The Rafale would stand a fighting chance against the J-20 with its low RCS, Spectra self protection suite with RF cloaking and Meteor 150-km BVR missile, My earlier Thumkar post J-20 vs Rafale delves into the relative strengths of the two fighters in greater detail.
The Su-30MKI would stand a survival chance against the J-20 with its powerful BARS that could alert it's pilot to the presence of a J-20, if not provide a weapon grade track. Also, the Su-30MKI with its super maneuverability could outmaneuver a J-20 launched JL-15 air-to-air missile during its end game maneuvering.
Exploiting the J-20's Sensor Fusion Weakness
Recent reports of a dual seat J-20 variant sighting, in the context of China's earlier claim that a dual seat variant is under development, confirms that the J-20's sensor fusion is subpar - otherwise there's no operational reason to put a second seat on a stealth fighter! (Ironically, the dual-seat variant of the J-20 corroborates the assessment that the J-20 stealth shaping is good. Adding a second seat will increase the RCS and the fact that China is doing so suggests that the RCS is low enough to absorb a compromise.)
Without excellent sensor fusion and cockpit displays interpreting readouts from multiple sensors can easily overwhelm the sharpest of pilots leading to paralysis by analysis of incorrect decisions. The IAF could exploit this weakness of the J-20 to its advantage. For example, by putting multiple threats in the J-20 's vicinity to bait it into WVR combat.
The PLAAF has a limited number of operationally deployed J-20 stealth fighters. They are based in Wuhu, Anhui Province, near the eastern coast. The J-20 is a highly specialized aircraft which likely depends on a lot of support facilities at its home base. It's RAM coating for example would need to be frequently tended.
It's unlikely that the J-20 can be deployed for extended periods at bases in Tibet.
Also, operating from high altitude air bases on the Tibetan plateau, J-20 fighters would not be able to carry their full weapon / fuel payload. As a result, their combat range or potential would be constrained. Also,The physical displacement of PLAAF air bases from the LAC would result in longer time to target, and restricted fuel load would mean shorter time on target.
It's unlikely that the J-20 could operate from Hotan (4,672 ft) or Kashghar (4, 529 ft) for operationally significant time. (Ngari (14,022 ft) is likely unsuitable for J-20 operations. Of course, the J-20 could operate from Wuhu and tank up in the air en-route to Ladakh. But then its role would hardly be operationally significant.
For the IAF, one way of mitigating the J-20 threat would be to acquire a reliable detection capability. We have the time and we have the sources to acquire radars that can obtain non weapon grade tracks on the J-20.
Deployment of such radars would allow the IAF to detect the presence of J-20s in proximity to the LAC and send a package to exploit the sensor fusion weakness of the aircraft. If not that, detection would allow IAF fighters operating in the vicinity to evade the J-20s
Also, the IAF would be able to use gaps between J-20 patrols for its interdiction and close support missions along the LAC.
In the context of an IAF vs PLAAF faceoff in Ladakh, the J-20s could play a limited but operationally significant role.
Because of their limited number and operational deployment challenges, it's unlikely that the PLAAF would use the aircraft extensively. However, sensational deep penetration of Indian airspace followed by painful strikes would be good publicity for Chinese technology. It's likely that the PLAAF would carry out such strikes with their best trained pilots using the best of their weapons.
The J-20 threat is real and cannot be wished away by loud shouting on television debates. The IAF must move quickly to augment its stealth fighter detection capability to mitigate the threat.