Well Snigs, a lot of the uncertainty comes from the terminology.
VMC means "visual meteorological conditions".
VM(C) means "visual manoeuvring (circling)".
A circling manoeuvre at the end of an instrument approach need not be carried out in VMC. For example, in 3000 m visibility in a class D CTR, the conditions would most definitely still be IMC, and a flight would remain operating under IFR. But a circling approach within the VM(C) area is still permitted.
The VFR minima, which define VMC, are irrelevant to a circling approach. Of course you *can* cancel IFR and proceed VFR if you are in VMC and can maintain it, and, provided you can satisfy the judge that the VFR circling manoeuvre was part of "taking off or landing in accordance with normal aviation practice", you may not even have to satisfy Rule 5 in choosing the level at which you do so. But generally speaking, ATC is expecting the manoeuvring to be carried out under IFR, and must provide appropriate separation.
I have to take issue with martinidoc's example:
Consider my base airfield EGNT The AIP gives for a Cat A non-precsion approach NDB/DME 25 an OCH of 371 ft labelled for the procedure. However it also gives a VMC OCH for the total area of 534 ft.
Consider carrying out the procedure as an instrument-rated pilot. The MDH for the straight-in approach is 371 ft. The MDH for the circling manoeuvre is 534 ft. In descening on the IAP intending to circle to land on 07, you would not descend below the 534 ft MDH for circling, despite the lower straight in MDH. There's no question of
climbing back up to 534 ft. If you need to descend below 534 ft, you should either be making a straight-in approach, or you should be going around.
The same principle should apply to an IMC-rated pilot. Because the increments are recommendations, I can't use the word
must, but if you feel you need a 200 ft buffer for the straight in part of an instrument approach where you can focus entirely on the instruments, it would be very brave to abandon that buffer for the circling manoeuvre where your attention is split between the external environment and the instruments. Most commercial operators would regard this as the most dangerous stage of flight.
For what it's worth, the minimum obstacle clearance afforded by:
a non-precision approach with FAF is 246 ft
a non-precision approach without FAF is 295 ft
a visual manoeuvring (circling) area is 295 ft
You have a similar buffer between you and the obstacles in each case. If you're unsure of your ability to hold altitude, add something in each case.