My Boeing 737 manual (not a company designed one, but the manufacturer's FTM), states flap 15 and gear down for the circling approach but as the aircraft turns on to base leg take landing flap and reduce to speed to Vref plus additives. Different config if one engine inop.
The real discussion should centre on circling approaches at night and at the circling visibility limit, which could be as low as 2.4 kms.
Obviously the circling MDA is there to protect you from terrain/obstacles. On a black night you will not see the controlling obstacle, but never fear, it has been worked out for you. It could even be near base leg.
Therefore on an inky night, you are committed for safety reasons to sticking to the circling MDA until on final with runway and or VASIS in view.
If a relatively high circling MDA means that on base you would have to descend in order to ensure a stabilized approach - then stiff cheddar, you should not be carrying out a circling approach in the first place. Same thing with downwind descent.
The designers of the chart MDA couldn't care less about your problems with a stable three degree descent from the circling MDA. That is your problem, not the chart designer.
Daytime circling is another story because one assumes you can see where you are going and descend as required providing you maintain legal safe visibility (runway in sight)and minimum legal obstacle clearance.
But night is the real killer on circling approaches. You can see the runway (I hope) but it is too black around you to see that unlit deadly hilltop, with its 100ft high trees, situated somewhere in your circling area - You know it is there somewhere, but its real black outside your windscreen so you cannot see a thing except the lit runway. Certainly the chart will not necessarily display the position of the controlling obstacle. Hence the danger.
Therefore you are only safe to descend below the chart MDA when you are established on final, within the circling distance limit for your category, and runway in sight. If that puts you too high to complete a stable approach, then that is your problem.
Regardless of all the FAA/JAA/ Afghanistan CAA rules in the world, the plain fact is that at night you have no choice (if you want to live) except to stay at the charted MDA until on final.
[This message has been edited by Centaurus (edited 28 June 2001).]