Hi Rich / Bob,
I am not sure, but the question / answer from the on-line exam below seems incorrect to me (Having said that, I do appreciate that the questions are probably "worded" to mimic the CASA-type format, and therefore may purposely be presented as such).
"You have been cleared to fly the RWY 14 LOC approach into Oakey. If you do not become visual the altitude you must commenced a missed approach -
Choose one answer.
a) at .4 nm not below 1990 feet Incorrect (I Believe to be "More" correct)
b) when you reach 1890 feet Correct
c) when you reach 1540 feet Incorrect
d) at .5 nm not below 1990 feet Incorrect
The question says that you have been cleared for the approach so you must have been given the actual QNH. The LOC MDA is 1990 feet and you can take 100ft off that since you have the actual QNH and the box is shaded. [AIP ENR 1.5 para 5.3.2]. You can descend to 1890 feet.
The missed approach point for the LOC approach is .4nm DME at the middle marker. A LOC approach is a non precision approach, so if you arrive at the MDA of 1990ft before the missed approach point, you can fly level to the missed approach point before commencing the missed approach if it is necessary.
"
The reason I believe option (a) to be more correct is that this is a non-precision approach, and the MAPt is final "indicator" of where the missed approach must be executed (irrespective of alt 1890 or 1990). Whilst I understand that one
may go down to 1890 feet (due actual QNH), it should have no bearing on the decision to go around - after all, one could reach 1890 well before the MAPt (Somewhere between the OM and the MAPt), and continue flight to the MAPt?
In other words, my altitude would be 1990 (though 1890 is available), but I would HAVE to do a missed Appr @ .4 nm, but my alt could be 1890 (before 0.4 nm) and I would not be necessitated to do a missed appr.
Sorry gents for all the questions, I'm on short finals hopefully with the exams though