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Well-known member
May 2, 2002
Part 121, what wx min(s) are controlling in determining if you are legal to fly an approach? (Please site the reg also) i.e. you are being vectored to the standard ILS Cat 1, 1 mile from the FAF what do you need?
Outside the FAF,

You cannot continue the approach past the final approach fix unless the wx is reported at or above the minimums for the procedure you are flying, in your case CAT I.

Inside the FAF is another story, if you are inside and wx falls below minimums you can continue the approach to its lowest prescribed minimums and if you see the runway AND have met all other criteria you can land, if not go around.

I think the reg you want is 121.651 or close to it.

Req mins

I depends on each individuals (company) Operating Specifications or Standard Procedures (SP's). Depending on the training and equipement provided, the FAA will certify a carrier for certain mins. Some could be Cat III mins and others can only do Cat I mins. Hope that helps. P.S. That is what the reg states too!:cool:
The inevitable question that will come up is what determines or what is the definition of "landing minimums". Is it ceiling and visibility or just visibilty that determines whether you can continue an approach. For example: you are authorized for your standard Cat I ILS. (200/ 1/2 ). You are outside of the FAF and weather reported as 100 X and 3/4 mile. Do you continue?
Yes, continue. Visibility is controlling, not ceiling. The minimums assigned in an approach have nothing to do with ceiling. A ceiling isn't necessarily a hard layer, and despite being below minimum descent altitude or DA/DH, may still allow visual reference to the runway on arrival at published minimums.

One needs to temper this decision with fuel status, traffic, etc. Does one wish to waste time on a questionable approach at all, when it may be better spent diverting, holding, etc? Is the obscuring phenomenon lifting, or changing, or in a state of change? How far is the alternate, or what are the alternatives? These things must be considered, along with company policy, when determining weather to execute the approach, hold, or go elsewhere.

Approach minimums and ceiling are not the same, nor are they coincidental.
Be careful on this one....

Below is a copy of a letter regarding the legal opinion of the FAA on this subject. Although I have always been taught as well in Indoc and otherwise that VIS is the controlling factor, there are those at the FAA that believe otherwise.

I would assume that this could apply to 121 as well.

FAA Legal Interpretation:
March 21, 1991
Mr. Glenn Rizner
Technical Specialist, Membership Services Department
Aircraft Owners and Pilots Association
Frederick, MD 21701-4798

Dear Mr. Rizner:

We recently received a letter from the Assistant Chief Counsel for the Eastern Region of the Federal Aviation Administration asking us to give a legal interpretation of a question you posed to them concerning Part 135 of the Federal Aviation Regulations (FAR). We apologize for the delay in answering your query.

The question was: Are both ceiling and visibility required in order for an FAR Part 135 air carrier pilot to initiate an instrument approach?

FAR 135.225(a) and 135.225(a)(2) forbid a Part 135 pilot from beginning an instrument approach unless reported weather conditions at the destination airport are at or above the authorized IFR landing minimums for that airport. So, even though ceiling is not a criterion on the approach plates, it must be considered by the pilot in his decision to initiate the approach, and in deciding whether the reported ceiling is above or below the decision height or minimum descent altitude for the approach. Similarly, FAR 135.225(b) forbids initiation of a final approach segment unless reported conditions are at or above minimums. Again, the pilot must know the reported ceiling and visibility before deciding whether that approach segment can legally be initiated.

This interpretation has been coordinated with the Air Transportation Division of the Flight Standards Service. We hope that this satisfactorily answers your question.



Donald P. Byrne
Assistant Chief Counsel
Regulations and Enforcement Division

cc: AGC-220/AGC-200/AFS-230/AEA-7
mc: 200 91 0021
why is this confusing

I am interesteded how this is something that everyone has a different opinion on... but I know why.. When I went through my 121 ground school I was tought that minimums for planning purposes is one thing the mins are for, but once you are inbound and about to fly the approach (still outside the FAF) visibility is controlling. Even the Jepps state that certain approaches will have "ceiling required" in bold type when the ceiling is controlling as well as the visibility to fly an approach.

So what do you say in interviews? Until I was at the 121 carrier I always said I was not legal to fly the approach, but my groundscool taught me that visiblity was controlling.. What should I say when the question is: you are 1 mile from (outside) the FAF and wx reports vis 2miles, OVC100feet.. Are you legal to fly this CAT1 ILS approach? I think yes, vis is controlling.. however be prepared for the missed and look for the visual cues when you get near mins so you can proceed the extra 100 feet below DH. Is that the correct answer?
So is this interview question to find what side of the grey area you will side with? I would think there would be a hard fast reg stating when it is legal to start the approach, especially in the 121 environment.

Personally I agree with Avbug "Visibility is controlling, not ceiling. The minimums assigned in an approach have nothing to do with ceiling. A ceiling isn't necessarily a hard layer, and despite being below minimum descent altitude or DA/DH, may still allow visual reference to the runway on arrival at published minimums. " That is exactly what I was taught in my 121 training. Was it airline specific? We only had CAT 1 capability, and as far as I know, an ILS receiver is an ILS receiver so why would one airline have vis as controlling and the other would have ceiling and vis controlling doesn't make sense.

I don't understand how we fly approaches every day as a large part of this profession yet we don't have a common denominator about what is controlling in determining if it is legal to "shoot" the approach. What about an ILS when you are planning to circle? i.e. You have the visibility but are 400 feet away from the circling altitude with the reported ceiling.... any thoughts? Personally I wouldn't fly the approach until reported ceilings are higher, but I think it would be legal to go test the waters and find out where you break out if you have the fuel, etc... because you have the min visibility. (I am begging to get some black and white answer.. lol!)
I was always under the understanding that VIS is the only criteria. I think we all are and avbug stated it the best. But in true FAA fashion, their OPINION may always suggest different. I have never found anything in the FARs that is concrete either way. As one FAA guy put it to me, "do you see it in writing where the ceiling ISN'T a consideration?". Whatever.....
We do have clear criteria. Visibility is controlling. What would you do with an indefinite ceiling, sky obscured, but with visibility above minimums? Continue, in most cases.

The legal interpretation above is carefully worded to say nothing; it is tantamount to a warning, but lacks the substance of a warning. In essence it's intent is to state what has been stated in a number of previous legal interpretations on this subject. Visibility is controlling, but the pilot may be called into question on how he obtained the necessary visual references if the ceiling was below DH/DA/MDA.

In such a case, the pilot may find himself or herself presented with the burden of proof in explaining how the required references were noted under the circumstances. If the pilot has justification, and can explain himself, it's for the best.

I don't have the time now, or the energy, to look up other interpretations, but visibility is controlling.

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