Any radar in this world be it the BARS N011M PESA on the Sukhoi Su-30MKI or the Phazotron Zaslon PESA on the MIG-31 can detect and track a stealth fighter such as the J-20. Stealth doesn't mean "invisibility to radar detection" and neither is stealth claimed to make any aircraft (employing stealth-technology) invisible to radars.
I have already written a detailed post on the topic of "
Stealth technology". Please read this.
Post in thread 'AMCA - Advanced Medium Combat Aircraft'
https://defenceforumbharat.com/threads/amca-advanced-medium-combat-aircraft.110/post-1622
Now coming to the topic of IAF's Sukhoi Su-30MKI detecting & tracking a stealth aircraft. If the IAF said that they detected and tracked a J-20, then they most certainly did, the word of the IAF is enough for me. Add to that, IAF's Su-30MKI has detected the J-20, not just once but on multiple occasions. But we need to discuss the various factors & scenarios that may have played out during the J-20's detection.
The most commonly/widely accepted theory is that the J-20 that was detected by the Sukhoi was carrying a Luneberg lense/ radar reflector. This is the most likely possibility and makes the most sense to me. The J-20 will carry luneberg lenses for the same reason the F-22 and F-35 would carry them, that is conceal their true RCS. Though I doubt that it's RCS is something that China can hide forever, I am certain that we have radars that can penetrate deep inside the Chinese mainland.
Now let's keep aside the the theory of "
Luneberg lenses". In which other scenario could we have detected the J-20?
- 1. The J-20 exposed a bad angle to the BARS PESA radar. The RCS of any aircraft differs from different angles and profiles. At some angles, even a stealth aircraft such as the J-20 can give a huge RCS return, comparable to those of fourth generation aircraft such as Su-30, Rafale, F-16, F-18 etc to name a few. For e.g, the frontal RCS of an F-22, F-35 or even an F-117 would not be the same as that of its rear profile, look up RCS spiking diagrams online.
- The canards on the J-20 are definitely one source of higher RCS returns, especially those when they are moving during flight.
- 2. The J-20 is just a big-fat-lie. It's just a big plane painted with black to give an illusion of stealth, it's RCS, and onboard sensors are equal to or worse than current fourth generation aircraft.
- 3. The IAF was lying. Do you think that a renowned and well respected AF such as the IAF would lie? I think not.
Now how did the IAF conclude that the radar signature that was displayed on one of their radar was a J-20? It could have been anything, it could have been a J-10, J-11, J-16 or even Jadoo's spaceship, so it literally could have been anything. Now I will address this in point form.
- You see, the IAF has a whole series of radars that track the movements of any aircraft that files in the region.
- Any time a J-16, J-15, J-11, J-10, F-16 or any other jet flown by our enemies flies especially close to the border, the IAF radars track their each and every move and all that RCS data is stored in their RCS library, so the next time an F-16 or JF-17 comes towards us, we will know whether it was a JF-17 or F-16.
- That day when the J-20 was detected, the IAF radar picked up something that didn't match anything recorded in the RCS library of that time, so it wasn't a J-16, J-10, F-16 or anything that we already have the RCS signatures of, so that is how the IAF concluded that it was a J-20.
As for China's J-20 stealth fighter and it's combat capabilities, all I will say is this.
- It's a machine at the end of the day, and I will criticize any design where I should criticize it and appreciate it where I should appreciate it.
- The topic of the J-20's capabilities is an ambiguous one, one side says the J-20 is not as capable as Chinese propaganda tout it to be, the other side says it's a very capable aircraft that can go toe to toe with the best Stealth Fighters (such as the F-22, F-35, Su-57 etc). It's upto you on which side's words you want to believe.
- I do not think that the J-20 is as capable as the Chinese project it to be, but neither do I believe that it's some 3rd-rate junk, that shouldn't be taken seriously/should be taken lightly.
To know and assess the actual capabilities of any fighter, we all have to keep aside our biases and analyse it with an objective approach, the truth is somewhere in the middle. We may not reach the absolute truth but we should come closer to it rather than further away and closer to a lie.
Regards. Hope sense prevails.