PPRuNe Forums - View Single Post - So WestJet almost puts one of their 737 in the water while landing at St-Maarten...
Old 15th Mar 2017, 18:01
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Aluminium shuffler
 
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Rat, the "M" is the missed app point. It's not a great name for it. It's not the point at which you should commence a missed app; that should happen at the minima on the glide path. It is the earliest point that lateral navigation should switch from the approach path to the missed app path, preventing early turns on intercept headings and not relevant (and hence rarely shown) where the missed app tracks a radial or is flown straight ahead.

The minimums callout, automatic or from PNF, would, on a non-precision app or Cat 1 ILS be baro alt related, so again, incorrectly high subscale settings would create an excessively low callout. More evidence that this could be the cause, but, again, far from conclusive.

The 737NG does not have GPS related altimetry, though the side profile view on the NAV display on aircraft with this customer option will show a GPS derived profile to a database display of terrain and airfield elevation. While there is no warning generated, a close look at that profile wile show a mismatch between baro and GPS profile by having the runway floating above or buried under the terrain, depending on which direction the altimeter setting error occurs. The rad alt displays from 2500' on the PFD. Custome spec may have a number of automatic callouts. Any crosscheck against the baro alt while over the sea should have revealed misset altimeters if that was the case.
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