visibility and RA

[pacinolove]

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。

[MarkerInbound]

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.

[MrHorgy]

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.

[VH-ABC]

1000km vis... Hope you mean 1000m!

I'll get my coat.

[Slasher]

I picked up the same as ABC - 1000km. If vis is that good you don't need any
ILS!

I use the 3x tool too but only to baro alt. RA can vary.