visibility and RA
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Join Date: Feb 2011
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visibility and RA
I have a question is that when I make an ILS approach,the TOWER report that the visibility is 1000km, at which RA height I can see the runway?and how can i calculate this。
There's not a direct connection beween visibility and when you'll see the runway on approach. Visibility is measured horizontally, you could have unlimited visibility with a 100 foot overcast. And I've seen time reports of clear and 1/4 mile visibility. Very dense ground fog but you could look up and see stars all around.
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MI is correct, just because you have a certain viz doesn't mean you will see the runway at a certain point. I once landed with RVRs of 300m and NSC!
However... You could apply the 3 x rule, and therefore 1000km viz would be around 0.6 miles, and maybe you'd get the runway at 1.5 - 2 miles. But that's a very general estimate. Also, depending on where your flying, you should appreciate the difference between RA and BARO alt, RA does not always represent height above airfield datum.
However... You could apply the 3 x rule, and therefore 1000km viz would be around 0.6 miles, and maybe you'd get the runway at 1.5 - 2 miles. But that's a very general estimate. Also, depending on where your flying, you should appreciate the difference between RA and BARO alt, RA does not always represent height above airfield datum.
