With a given minimum MDH for instance of MDH 600' .. our operator authorizes to begin the approach if at the " door" ( would it be the FAF for the an initial straight in vor approach )we have minimum ceiling of 2/3 * MDH = 400' during daytime and 3/3*MDh= 600' during nighttime..
Hope it's clear enough now...and would like to know how it is by ur place.??
As I said earlier, we do not start a Circling Approach unless the weather is 1000-3, or higher if the approach has higher ceiling or visibility minimums. Period.
It doesn't matter at all what the minimums are for the straight-in approach, if you are cleared for the circling approach. Period.
While the approach weather minimums MAY be defined by visibility only, the MDH is a very good indicator of the required minimum ceiling as well. On a straight-in approach, you may well break out in a "hole" at or above the MDA, and be able to continue a normal approach to a landing. However, that is generally NOT the case for a circling approach.
If the circling approach has a 600' AGL MDH, why attempt an approach when the ceiling is 400'? Even if you see the airport at 600' before the MAP, what makes you think you will KEEP sight of the airport at 600' throughout your maneuvering to final? Why would you risk it?
How many approaches will you attempt before you go to your alternate?