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Instrument Landing Minimums are ABSOLUTE!!!!!

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  • #16
    I meant ILS minimums - the topic of the thread...
    Anyway, until they can find a way to get the "lowest common denominator" out of the cockpit, this is what we must require.
    Its not necessarily for the human lowest common denominator.

    I'll expand a little on the Cat I/II/III example.

    For a CAT III approach, the airport requires a certain amount of approach lighting to be operative. If that approach lighting is out, the CAT III approach is not available.

    Now, thats fine, except when you consider that my approved minima at that airport might be say 0' and 100m visibility (for example). At the minima, I may not be required to see anything - or maybe 1 centreline light. In CAT III weather, at those minimas, I will not see anything to do with the approach lighting at all. However, some CAT III operators will have higher minimas. These minimas may put the approach "visual" point at a position that you see approach lights.

    Because of this, the CAT III approach will not be available, and will revert to say CAT I. Is it really a safety issue for me, flying to 0' and 100m, to fly below the minima on the day? Or is it a "one size fits all" approach to make it easier?

    Just one example of why there is no definitive "flying below minimas is unsafe"... because, like always in aviation, there are exceptions...

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    • #17
      Originally posted by MCM View Post
      Just one example of why there is no definitive "flying below minimas is unsafe"... because, like always in aviation, there are exceptions...
      But is it fair to say that flying below YOUR minima is unsafe? I mean, to get to 0 visibility and 100ft, you had to meet a lot of requirements that ensure you can safely fly there, right? So it is safe for you to go there but if another pilot has minima of 100ft and 650ft, they can't safely descend to your minima, i.e. they can't safely descend below THEIR minima. So everybody sticks to the rules, nobody ends up in the trees...

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      • #18
        Originally posted by Evan View Post
        (...) So everybody sticks to the rules, nobody ends up in the trees...
        Ideally, that's the way it goes...

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        • #19
          But on that day, the minima is CAT I minima. No-one can descend below that. I can have CAT III equipment, the critical areas can be protected, all the good stuff in place - but to do the approach would be illegal, but not unsafe.

          So what I'm saying is that while it it would not be unsafe for me to fly to a CAT III minima, it is illegal because the "CAT III" required lighting isn't available (even though, for my approach, I'm not going to see any of it anyway).

          We differentiate between CAT I, II and III, but within those groups the approach is either available, or unavailable. They do not say "CAT IIIb approach approved, CAT IIIa not available". It would get far too complicated.

          Just an example of where we do things, by necessity, that make life "simple" but breaking them wouldn't necessarily be unsafe.

          Obviously you wouldn't break them though!

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          • #20
            Originally posted by Fear_of_Flying View Post
            I guess what 3WE is saying is that even in those situations where clear minimum safety standards apply, they only provide a certain margin of safety. There are many other considerations that may make the relative safety of a given landing more or less safe. And this is when looking at relatively clear-cut guidelines, such as visibility.

            Now to try to apply similar minimum safety standards to something like wind - perhaps the most dynamic condition of all, one that changes from moment to moment, from meter to meter - with an even greater range of variables (specifically different aircraft which react very differently in wind conditions), seems extremely challenging. Not only that, Evan, you've already conceded that there might have to be some sort of cross-referencing system going on, where Aircraft A flying approach B is fine to land, but Aircraft C flying approach D is not. This sounds like mass confusion to me.

            There still has to be a margin of safety, but in the case of wind conditions, unless the airport is closed (and maybe the guidelines for that could be re-evaluated), that margin has to come from the cockpit. If the concern is task-oriented pilots, then the regulators could turn their gaze towards the operators, and make sure there is not a mindset of "land or else", either implicit or otherwise.
            EXACTLY!
            The "keep my tail out of trouble" disclaimer: Though I work in the airline industry, anything I post on here is my own speculation or opinion. Nothing I post is to be construed as "official" information from any air carrier or any other entity.

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            • #21
              OK...real-world example time here. A bunch of years ago I was flying a Jetstream and cleared for the ILS 16R at Seattle. Conditions were such that there was a fog bank right over the approach end of the runway--and the arrival end transmissometer.

              The rules say that to be legal to start the approach we have to have landing minimums at the final approach fix--in this case a runway visual range of 1800 feet. IF the weather goes below minimums AFTER we cross the final approach fix, we can continue to decision height and IF we have the minimum visibility when we get there, we can land.

              So, back to the Jetstream: We were cleared for the approach and halfway down the ILS, the airplane behind us was told the RVR was 1600, thus below landing minimums. The kicker was, the fog bank extended less than 1/4 of the way down the runway and I had the last 3/4 of the runway in sight for the entire approach. So, I landed. Had to go slightly above the glideslope to avoid going into the fog, but I was able to touch down safely. As a CYA move, I told the tower as we were turning off the runway that we had visual on the runway the entire way down the approach.

              So, was this legal? Probably technically not, since the touchdown zone transmissometer was supposedly below minimums when I got there. Was it safe? Yes--the fog bank only extended 1500 or 2000 feet down the runway and I had 8000 or 8500 feet visible; I'd made hundreds of approaches to runways much shorter than that, so I knew I had adequate runway available.

              BTW--in reference to the comment in the first post here about the Jetstream pilots. We hand flew everything. Six or eight approaches to minimums a day hand flown through the turbulence and ice and clouds were just another day at work. Unfortunately I'll never be the instrument pilot I was back then.
              The "keep my tail out of trouble" disclaimer: Though I work in the airline industry, anything I post on here is my own speculation or opinion. Nothing I post is to be construed as "official" information from any air carrier or any other entity.

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              • #22
                So, no one wants to touch the bigger question...

                What good are minimums when the Russians adjust the navigation signals and move trees around?
                Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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                • #23
                  Originally posted by snydersnapshots View Post
                  ...Jetstream...legal?...safe?
                  VOR-DME Approach.

                  You see the airport.

                  But, because you are tired and because of a black-hole effect, you mismanage your descent and do CFITrees?



                  Sounds "moderately legal" and very unsafe (ok, maybe only legal up to the point of impact)...

                  Though the Wiki article suggests that the pilots had not really identified enough stuff to descend below the MDA and had not made some required call outs.
                  Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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