Can somebody explain when a pilot needs a VMC Descent (Doc 4444, 12.3.3.2, t)? A few examples will greatly clarify it.
Never experienced it in 12 years in ATC.
My guess would be, when aircraft are procedurally separated and want to change levels, instead of waiting for certain conditions to be met procedurally (i.e. deemers, distance on a radial, established on a procedure etc) they do a VMC climb/descent and expedite things that way.
Think of an aircraft holding overhead an airfield at 4000 feet and for some reason they can't make an approach.
There's another one at 5000 feet and they want to descend through and make an approach.
Something like that. But I've never done procedural approach so I'm only guessing...