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HIAL vis requirements
Hari
Topic Author
Hari created the topic: HIAL vis requirements
G'day Bob,
Just went through one of your IREX prep exams. I came across a question (below), which got me a bit confused regarding the HIAL Vis Minima's.
Q) You have been cleared to fly the Canberra 35 ILS-Y approach in VH-OZY on a day when a notam advises that the HIAL is not available due maintenance. Your maximum asymmetric missed approach gradient will be 2.5% under the ambient conditions.
The visibility required to permit you to continue the approach beyond the published decision altitude is -
I chose 1.5, but was wrong.
So, my understanding is when HIAL is not available, and you intend to do a precision app, the vis you must use is 1.5km.
The app minima states the vis is 2km (using actual QNH).
Your explanation states that - " AIP ENR 1.5.para 4.7.3a says that a visibility of 1.5km should be used if HIAL is not available. However, in this case, the published visibility is higher than that. You would have to use 1.7km visibility for the minimum on this approach." (Im assuming the 1.7km is the old minima)
And must we always use the higher vis requirement when comparing HIAL req, and app plate requirements?
Yes, you would always have to use the higher visibility. Obviously, you are never going to have the advantage of a LOWER visibility if HIAL is not available. Thanks for the feed-back on that question. The visibility has been changed to 2.0 km.
