Did PLAN retrofit the VDS to the first block? That sounds like a perfectly reasonable thing to do for me.They all use towed array sonar. Later after the first block, the second block and subsequent ones added a variable depth sonar. So from one to two towed arrays.
p.s. Can you explain why the Sino-SURTASS towed sonar isn't being used on the frontline vessels? I'm pretty curious about that one.