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Ornis · 6th May 2012, 07:13

The NZ CAR do not use the term VMC, as far as I can see(!) The terms are VFR meteorological or weather minima.

Therefore it seems to me that it is the definition of VMC that changes for SVFR, not that one is given a clearance to fly visually in IMC, Tarq57.

A descent from an altitude above 3000ft amsl or 1000ft agl does not require sight of the surface until that level is reached. There could be cloud above fog.

Visibility of 5km means ahead of the aircraft. If there is a corner 2km ahead, the pilot assumes it is 5km around the corner until proved otherwise. Which could happen. I have flown through Haast Pass with the cloud base lowering, landed at Haast to watch that cloud become fog.

Oktas8, I don't think you could legally orbit through a deep hole 4km across above 3000ft. If obeying the law (to remain 2km clear of cloud) outweighed all else, one could try a stall...

The descent in a break in the cloud cover from ~FL160 to <2000ft, ie an open shaft 4km deep, was performed by Captain Collins in the Antarctic. You're onto it, prospector.

I cannot get a mental picture of what this descent would have been like, or how one would judge the visibility within this space, or how it related to the visibility outside it. Collins certainly seems to have come within cooee of Mt Bird without realising it; SOP required 20km visibility.

Seems under close examination, there is a problem with definitions. Take a chair. If I say a chair is a piece of furniture with four legs people sit on, what would an alien make of a chair that had one leg broken off?

Yes, remoak, there is limit to what you can do to save pilots with rules. In another thread, ampan argues Collins was not VMC under SOP, I am trying to analyse the initial descent.

6th May 2012, 07:13	#16 (permalink)
Ornis Join Date: Jun 2009 Location: Auckland Age: 70 Posts: 68	The NZ CAR do not use the term VMC, as far as I can see(!) The terms are VFR meteorological or weather minima. Therefore it seems to me that it is the definition of VMC that changes for SVFR, not that one is given a clearance to fly visually in IMC, Tarq57. A descent from an altitude above 3000ft amsl or 1000ft agl does not require sight of the surface until that level is reached. There could be cloud above fog. Visibility of 5km means ahead of the aircraft. If there is a corner 2km ahead, the pilot assumes it is 5km around the corner until proved otherwise. Which could happen. I have flown through Haast Pass with the cloud base lowering, landed at Haast to watch that cloud become fog. Oktas8, I don't think you could legally orbit through a deep hole 4km across above 3000ft. If obeying the law (to remain 2km clear of cloud) outweighed all else, one could try a stall... The descent in a break in the cloud cover from ~FL160 to <2000ft, ie an open shaft 4km deep, was performed by Captain Collins in the Antarctic. You're onto it, prospector. I cannot get a mental picture of what this descent would have been like, or how one would judge the visibility within this space, or how it related to the visibility outside it. Collins certainly seems to have come within cooee of Mt Bird without realising it; SOP required 20km visibility. Seems under close examination, there is a problem with definitions. Take a chair. If I say a chair is a piece of furniture with four legs people sit on, what would an alien make of a chair that had one leg broken off? Yes, remoak, there is limit to what you can do to save pilots with rules. In another thread, ampan argues Collins was not VMC under SOP, I am trying to analyse the initial descent.