by78
General
Removal of gun. Would be a good place to put one.
Patches both left and right under the second seat, visible when painted, dark colored when unpainted --- same color as the bandpass composite on the radome. Also visible on the J-15D/J-17 prototype. When you have a flank radar, you can still track an aircraft even if performs a beam maneuver meant to drop its doppler signature. Greys are good indications for radar receiver locations also.
Also check previous J-16 photos.
View attachment 47012
That photo's quality is too poor to judge whether the 'same color' under the second seat indicates the same material as the radome, or whether the radome and the patches in question even share the same color at all. It could just be unpainted metal not reflecting light. Besides, it's too large for a side radome; in other words, I can't imagine a side radome would require that large of a patch of RF-transparent cover. Note that J-20's side radomes are tiny by comparison.