Missed Approach Point at the threshold?

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Missed Approach Point at the threshold?

Postby snippyfsxer » Sun Jun 27, 2010 4:21 pm

I was flying an NDB approach the other day (sorry don't have the chart handy, so I'll just ask the question in general) in which the MAP was right over the threshold, but the minimums were 300 or so feet agl.  This strikes me as kind of stupid, since if you did see the runway right at the moment that your timer runs out, you would already be over the darned runway!  Unless you did a helldive for the pavement, you would already burn up a mile of runway before you can get down.  Isn't that kind of dangerous???  I was flying category C (flying the Duke) but the minimums for category E were the same...so if you were flying a jet, it would be REALLY bad. How common is this?
(Since I haven't uploaded the chart, which was out of date by several years, don't bother looking it up, but it was NDB 35L, kcos)
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Re: Missed Approach Point at the threshold?

Postby Brett_Henderson » Sun Jun 27, 2010 7:09 pm

NDB approaches are ambiguous by design. Especially those where the NDB is not at the field. With some(very few), you have the luxury of something like a VOR radial for reference between the FAF and MAP... or in this case (even though it's not referenced on the descent profile),you've also got a middle-marker.

Assuming (as we should), there is no middle-marker; you've got 6nm to lose a mere 1300 feet.. a normal NDB technique would be to loose that 1300 as soon as possible, level off, and look for the runway.. going around as time expires, OR, if you DO see the runway as you near it, still at 400agl, but too near to land, then go around. It's not so much that the runway is the MAP, it's more like, which ever comes first; timer or catching sight too near to land.

The theory is (obviously).. if you're at 400agl, in 3/4 mile visibility, and on approach course, you'll see the runway in plenty of time to go visual. Also.. for D/E catagory, the visibility minimum is nearly double ( 1-1/4).

Personally, unless it was an airport I'm intimately familiar with; I'll only fly an NDB as 'Circling'.. higher ceiling and visibility minimums.
Last edited by Brett_Henderson on Sun Jun 27, 2010 7:10 pm, edited 1 time in total.
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