SongMan

91.175(c)(2)
"The flight visibility is not less than the visibility prescribed in the standard instrument approach being used."

Where can i find this "visibility prescribed" ?

I understanding that it's asking for in flight visibility and not RVR. Just don't see anywhere in my chart where it specifies how much "in flight visibility" I need for the approach. Again, I only see RVR.

Is it just saying that I need my flight visibility to be what's prescribed for RVR or better? So if my RVR is 2400', I need flight visibility of 2400", right? If not, where do I find what's flight visibility is prescribed for the approach in general???

Thank you!

cfii2007

You are required to have the visibility stated on the approach plate which can be SM or RVR.

Twin Wasp

What plate you looking at? Most say something like "RVR 1800 or 1/2".

SongMan

My chart does say RVR 1800 or 1/2. But 91.175(c)(2) does not say anything about RVR.
Hence I'm trying to figure our what figures to reference for "visibility prescribed".

I'm not asking how I determine flight visibility as ALS and Runway marking reference gives me just that.

Thanks

Fly Boy Knight

I think you are thinking into this a little too much.

The "Prescribed Visibility" is the visibility on the approach chart. The FAA determines the minimum safe visibility they believe you need to have to NOT be in danger and they write it on the approach chart. The SM visibility and the RVR are telling you what FLIGHT VISIBILITY is required for that approach.

If the chart says a certain RVR and the RVR sensor is inoperative...

91.175(h) - Comparable values of RVR and ground visibility. (1) Except for Category II or Category III minimums, if RVR minimums for takeoff or landing are prescribed in an instrument approach procedure, but RVR is not reported for the runway of intended operation, the RVR minimum shall be converted to ground visibility in accordance with the table in paragraph (h)(2) of this section and shall be the visibility minimum for takeoff or landing on that runway.

RVR (feet) Visibility (SM)
1,600 1/4
2,400 1/2
3,200 5/8
4,000 3/4
4,500 7/8
5,000 1
6,000 11/4

In order to descend from an MDA / DA, the flight visibility you see out of the airplane window must be at or above the visibility or visual range (RVR) shown ("prescribed") on the approach chart for your category.

Believe it or not, it really is that easy!

Now, arguing "flight" visibility vs what the ground sensors are reporting is a whole other topic and is significantly different for GA / Part 135 / Part 121 airplanes.

TheFly

The prescribed visibility is referring to the minimum visibility required to continue beyond the FAF, which is listed on the approach plate. 1/2 sm, 3/4 sm, 1 sm, etc.

Yoda2

What!? Could you possibly rephrase this?