An instrument approach procedure is often described as a series of windows, or gates, extending from the final approach fix (FAF) to the missed approach point (MAP). Stay within the ever-narrowing vertical and lateral limits and you’ll arrive at the MAP on glide path and centered on the inbound course. It’s far less common to extend this concept backward from the FAF through the terminal area to the en route environment, and forward from the MAP through the missed approach to the holding fix.
I find it at least as helpful to think in terms of a succession of gates from the beginning of descent to entering the missed approach hold. Approaching each gate prompts you to complete a checklist or flow, and gives you specific criteria to gauge your progress and decide if and how you can continue. To illustrate what I mean, let’s take a hypothetical flight from cruise through an approach and to the missed approach hold, or perhaps breaking out and being able to land.
