Sorry
Tartan, I can't help with your specific question, but can give everyone else a bit of perspective on the situation in this pocket of the planet. First off, no operator I know of requires an additional 50FT for "sink thru" on any NPA around here.
Unless your aircraft's PEC is "zero" you need to adjust your MDA accordingly. In our official publications we're told that, if we don't know the extent of PEC, we need to add an arbitrary 50FT to the MDA.
Next point is that many pilots, myself included, prefer the 3-degree approach due to the simplicity of it and the options and flexibility it provides. It facilitates a stabilised approach, is more fuel efficient, kinder on the engines and puts you in a good position to go around and/or handle an engine failure.
It isn't especially difficult to figure how far from the THR that the MDA intersects the real 3-degree approach path to the THR. Having established that position, check for any limiting descent steps on final approach and make any allowance necessary. Then just work backwards to find out what altitude you need when joining the final segment. This is sometimes awkward, depending on proximity to terrain, but can usually be compensated quite readily with temporary use of a 2x profile.
While this can all be worked out quite readily when there's a DME available, or if you have the properly certified GPS gear, or INS etc., it ain't much more complex when you have to DR the distance aspect.
This is because the chart shows you the outbound timing, which you can adjust to take account of headwind or tailwind. Whatever effect the wind has on the outbound leg, it'll have the opposite effect on the inbound - unless it's a straight crosswind, of course. Anyway, the point is that you'll have a pretty good idea how much time will be available for the inbound leg. This, in turn, helps you to identify the time available to descend, so as to reach MDA near enough to the point of interception of the 3-degree approach path to the THR.
Once you have that point worked out, in terms of actual distance, or just time, you can fly the NPA at your 3-degree profile to MDA. If you get visual, you'll be near as dammit to being on the VASI or PAPI GP and that's how it's mostly worked out for me.
The larger operators hereabouts have already worked all of this out for their crews and the info is in their SOPs.
Now, if you don't get visual at MDA ... well, in the B200 I fly, it never gets the chance to sink thru. It's a very responsive aeroplane.
The other good thing about the stabilised approach is that it's better for the comfort of your pax. THEY know when you're on descent so they start to get nervous if the plane levels off and engine noise increases, sometimes massively, just to keep the plane in level flight. Then they all but lose their meal as the plane noses over as soon as the pilot spots a hole!
The pax are the thing that keep us in our jobs, by using our company's services. If they have a good flight, you'll see them again. If they have a bad one, the company loses them - and all their friends and rellies ... except, perhaps, the mother-in-law!
There's only other reason I can think of for adding some kind of fudge factor to the MDA. It's sometimes applied as something akin to an F/O MDA. This sort of thing is used in some parts of the world, I understand,
though I have no idea what sort of MDA buffering is used, or even how it's calculated. Maybe someone out there can enlighten me on this?
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