If you're referring to an FAR Part 121 operation, you have to adhere to the Ops Specs issued to that carrier by the FAA. A Part 135 carrier is also limited by the specifications issued to that carrier. I only mention it because the answer to your question may vary from airline to airline and operation to operation.

For a "plain vanilla" approach minimums (for whatever that's worth) try the Instrument Procedures Handbook (FAA-H-8261-1A)

G'Luck Mate

 

It is very important that a pilot fully understand the minimum requirements in order to be "legal" to land from an instrument approach. What has not been said here is:

Visibility is CONTROLLING and must be equal to or above the authorized landing minimum (governed by Ops Specs etc). IF RVR is reported, it has a higher priority than prevailing visibility and is controlling. (Reported RVR trumps visibility every time)

A reported ceiling (i.e. 200, 250 etc) IS NOT CONTROLLING. If Tower advises ceiling 100 and visibility 1/2 mile, if you are shooting a "normal" CAT I ILS (200 & 1/2) then you are legal to shoot the approach.

In Summary, Ceiling is advisory and VISIBILITY is controlling.

Hope this helps!

 

Perfinit is absolutely correct and I'll add one comment. You are "legal" to shoot the approach in the example cited above. I would hope that everyone knows, despite the reported ceiling, one cannot descend below the published minimums without either the runway or the applicable "runway environment", as defined by FAR, in sight.

I thought that would be obvious; however, I've seen a couple of posts that make me think the obvious should be stated. Also, remember, your OpsSpecs are your "bible" when deciding what you can and cannot do.

Fly Safely Mates

 

What if we are 7nm final on a Cat 1 ILS Part 121, prior to crossing FAF (I know this is not a VOR), and tower reports viz less than published mins. Would we be legal if we did not acknowledge report, continued and landed safely having RWY insight?

 

Not completely correct. You can continue and land if: you are in a position to land, you have the required flight visibility, and one of the elements of the runway environment are in sight.

The only time that continuing an "additional 100 feet" comes into play is when using the approach lighting system as the only reference for the runway environment. If this is the case, then you are allowed to make a descent to 100 feet above TDZE. If you are shooting a standard Cat I ILS with mins of 200-1/2, then continuing an additional 100 feet below DA puts you at the same altitude as 100 feet above TDZE; but we can also use this part of the regulation for approaches other than an ILS.

My real life example goes like this: Rwy TDZE is 100 feet MSL, Wx is 200 OVC/1SM in FG, in the dark of night, lowest approach mins are 400-1 for a straight-in LOC. We configure for landing, and slow to Vref+5 as the aircraft descends down to the LOC MDA of 500 MSL (400 AGL). We level off at 500 feet, and drive towards the runway on the LOC at Vref+5. About 30 seconds later the FO reports the moving glow of the SFL in the clouds below and ahead of us. Now, using only the approach lights as a reference I can descend 300 more feet (not 100 feet) down to 200 MSL which is also equivalent to 100 feet above the TDZE. At 200 MSL, we're now below the cloud deck, the threshold lights are identified (not the runway itself), and I can legally land as long as we're still in a position to land and we have the required flight visibility.

 

When ever you consider pursuing such course of action, and it's not an emergency, ask yourself these three questions;

1) What if something goes wrong after I've made my decision?

2) What am I going to tell them in the hearing?

3) Will they believe what I tell them in the hearing?

NO, you DON'T have to answer here, just sayin'