There is information in the Chinese newspaper Global Times on how China has improved the J-15 fighter. It is the only fighter of this type in the Chinese navy that can take off from an aircraft carrier. However, as Warrior Maven points out, at best this modernized Chinese Shenyang J-15 could compete with the American F / A-18 Super Hornet, an example of the 4th generation work.
How did China improve the J-15 on-board fighter?
The modernization of the J-15, based on the Sukhoi Su-33 itself, is necessary and far-reaching, but compared to even older US or Japanese fighters, the on-board combat fighter is not particularly impressive. This fighter has new rocket pylons on the wing tips, a new wing configuration, radar, and even an infrared targeting (finding and tracking) system.
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While it is known that, thanks to these first two upgrades, the J-15 is now capable of flying short-range PL-10 missiles rather than the less destructive PL-8 missiles, the radar and tracking system is somewhat cryptic. We do not know the advancement of the latter, and we do not really know anything about the former, although according to the newspaper the modernized J-15 radar may be an Active Electronically Scanned Array (AESA) system.