Hi
The example on page 294 is about Oakey, and flying a LOC approach. It says you can descend to 1990 or 1890 as these are the MDA's for the SI-LOC approach.
But then the text says that since no HIAL is installed you should use the visibility of 3.7km.
Now I understand that if you are doing a 2D approach (which a LOC on its own is) you should add 900m to the visibility. But the text specifically says if the HIAL is not available, not that it doesn't exist in the first place.
So are you saying if HIAL is there but off, use 3.7lm plus 900m, but if HIAL isn't installed in the first place you can use the lower published?
According to my copy of the book, the text says that "If you check ERSA you will find that Oakey has no HIAL on Runway 14". That's not the same that it does have HIAL but it is unserviceable. If HIAL has never been installed, the published visibility already accounts for that, so there is no need to add .9 to the visibility.
