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-   Tech Log (https://www.pprune.org/tech-log-15/)
-   -   RVR and Visibility in ILS charts (https://www.pprune.org/tech-log/610170-rvr-visibility-ils-charts.html)

Escape Path 20th June 2018 02:46
Never seen vis and RVR on the same report. At least not one where vis is lower than RVR. AFAIK, (in my country at least), below 800m, which is standard vis for takeoff, you need RVR. So in any case vis<800m, we need RVR before we can do anything, hence RVR is controlling. Vis is pretty much useless (legally) by that point

flyburg 20th June 2018 06:52
Originally Posted by wiggy (Post 10175554)


Ah, having read the above is the “grey area”/the confusion down to the way the Ops manual is written/semantics? For some approaches the “controlling” minima will be a vis....for others it will be an controlling RVR...however the way the manual has been written has conflated :} the two.



Also, some airports, generally smaller ones don’t have RVR equipment or the RVR equipment may be out of service! Above mentioned rule in the manual covers that situation. EASA covers that by allowing conversion, I’m not sure FAA regulations have the same rule.

sonicbum 20th June 2018 08:51
Originally Posted by extricate (Post 10175095)
Hi there,

Let’s say an airport reported METAR visibility 0200, RVR 750. The requirements to shoot the ILS approach requires CAT 1 of Visibility 800m / RVR550m, The airport only has CAT 1 landing. I’m able to meet the RVR criteria but not the Visibility criteria, am I able to shoot the approach?


Yes, the RVR is controlling.

Originally Posted by extricate (Post 10175095)
How about dispatch stage? Do we need both the vis and RVR?
At dispatch You will only have the forecasted visibility issued by the TAF. In Your example a RVR reading is available at destination so You are not allowed to use the conversion of reported meteorological visibility to RVR, hence if forecast vis +/- 1 hour is less than the required one for the approach You are considered below minima and need 2 suitable alternates to dispatch (EASA land).

extricate 20th June 2018 12:40
Originally Posted by sonicbum (Post 10177215)
Yes, the RVR is controlling.



At dispatch You will only have the forecasted visibility issued by the TAF. In Your example a RVR reading is available at destination so You are not allowed to use the conversion of reported meteorological visibility to RVR, hence if forecast vis +/- 1 hour is less than the required one for the approach You are considered below minima and need 2 suitable alternates to dispatch (EASA land).
thanks for this. I've noticed during dispatch that both taf and metar were given. Metar has both rvr and viz. Understand we should look at taf to decide whether the aerodrome is below landing minima since metar' validity is shorter. Taf only has viz.

sonicbum 21st June 2018 09:44
Originally Posted by extricate (Post 10177409)


thanks for this. I've noticed during dispatch that both taf and metar were given. Metar has both rvr and viz. Understand we should look at taf to decide whether the aerodrome is below landing minima since metar' validity is shorter. Taf only has viz.
Yes that's it.


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