Hmmm
Pretty poor post,
Tee Emm!
Not necessarily so - especially at night where ground features may not be discernible and it is impossible to see if you are maintaining safe terrain clearance of 400 ft (Cat C).
The 400' terrain clearance for visual manoeuvring in Australia is for daytime only, as I recall.
Once you deliberately elect to descend below the published circling MDA on downwind or base, you are entirely responsible for your own terrain clearance. Only a courageous pilot would risk descending on base until you are established within the approach splay.
Not so, the whole point of visual circling, is that you are maintaining visual terrain clearance. With that terrain clearance (i.e. seeing the ground - you may descend safely. Every flight has to get pretty close to the ground to land!
In some countries a PAPI or VASIS may be seen on base leg but obstacle clearance not guaranteed until within plus or minus 15 degrees either side of extended runway centre-line. Short answer: Don't descend until on final.
See above. That statement is simply not correct.
With regard to timing of the downwind leg. The timing policy was an old one from countless years back when bad weather low level circuits sometime encountered IMC during parts of the downwind leg.
Timing a circuit is not usually policy - it is a technique. "Countless years back" must mean 1920 or so!! ANY aircraft circling who encounters IMC (even in 1920) is no longer visual circling!
In those cases timing was the method used depending on height and it was acceptable to go IMC but for short periods only.
See above - silly comment.
Hence timing. In those days a circling MDA hadn't been invented and it was a case of preflight study of relevant aerodrome charts and familiarity with the terrain.
Yes - in 1920, or before - is this a history lesson?
With the advent of DME or availibility of a reliable distance aid, there is nothing to stop you from extending downwind to keep within the limits of 4.2 nm circling MDA (ICAO).
Whilst a quick look at some guidance is OK, you appear to be assuming every DME is located at the landing runway threshold here!
With a relatively high circling MDA there is a myth that at night you can descend below the circling MDA (potentially dangerous unless you know exactly the position of the critical obstacle that dictates the MDA) at any time downwind or base in order to suit the profile of your aircraft type.
It is not "a myth" - it is approved procedure! You descend according to your descent profile. As you have the runway, or lights associated with the runway in sight, you have a straight line of sight, which = no terrain in between for a standard descent.
The designers of the published circling MDA couldn't care less about your profile descent problem.
No, they don't. That's because the circling MDA is for circling - the descent to the runway is not circling.