J-11B a generation behind J-10B in IRST.....
J-15, J-16 and the J-10B / C infrared search tracker (IRST) contrast. It can be seen that although they are nuances, but generally belong to the second generation of domestic IRST. The search distance sensitivity of the anti-jamming ability of Su-27 OLS-27 has greatly improved. The J-11B on the IRST has no protective cover for the first generation of domestic IRST, equivalent to OLS-27's older version...
The new generation of domestic IRST comes with a protective cover. The IRST optical head is actually a sphere, can be rotated...
When not in use the electro-optical head rotates 180 degrees to hide inside. When needed it goes out in a 90-degree range for scanning and tracking....
So the so-called protective cover is actually the photoelectric head back, and the Eurofighter Typhoon IRST installed on the Rafale and Gripen fighter aircraft have a similar design...
The J-15 newer aircraft are equipped with forward looking infrared search and track system (IRST), located in the cockpit in front by infrared imaging detection system, laser rangefinder and other components....