May give my view.... I think pinoy is too excited to showcase its "modern" ship capability. But... how on earth a corvette, with only a "hull mounted sonar" (HMS) can detect & classify a submarine?? Even an advanced warship with HMS has also difficulties to detect sub. I have experienced following our frigate during sub tracking exercise. Even if it is a planned exercise, meaning u know already a submarine is there... just to localise it, the HMS always give false echoes, and it will be more difficult if tracking sub at tropical weather sea during monsoon.