![]() That’s two miles a minute, or a tenth of a mile every three seconds. ![]() How fast will you descend and how quickly will you initiate that descent? Consider: You’re going 120 knots. The practical answer actually lies mostly in aircraft speed. Neither is ATC radar or your 100-foot-resolution Mode C transponder. By the book, you cannot cross AMASE at anything less than 4700 feet and that means that 4699 feet is a bust. Your call just don’t bust the crossing altitudes.īut when are you established on the next leg from whence you can start down? Good question, and the answer applies equally to feeder routes, transitions and even MEA changes at an en-route waypoint. ![]() So you can ride the glideslope and monitor your compliance with the crossing restrictions, or you can dive-n-drive after each step until intercepting the glide slope at the FAF. ![]() Jeppesen more clearly depicts the stepdowns as restrictions. Atmospheric conditions can conspire to make the crossings at FISTA and AMASE higher than the glideslope by a hundred feet or more, and ATC might get testy about it. The glideslope doesn’t guarantee you’ll meet the minimum crossing altitudes at FISTA and AMASE. The FAA charts depict a continuous slope through the step-down fixes, which might mislead you into flying the glideslope from 7000 feet down. Rather than bother with those step-downs, perhaps you should just ride the glideslope down. Outside FISTA at 7000 feet, the glideslope centers. So, you’d be quite safe using “course alive” as your definition of “established” if you needed a little extra time or distance-so long as you’re not on a checkride or anything. Yet, the laterally protected airspace at five miles on an ILS is 5000 feet each side. Extrapolating from the old “one degree equals one mile at 60 miles,” that 1.25 degrees for half-scale at five miles is just over a tenth of a mile. A localizer increases sensitivity four times, so full-scale here is now only 2.5 degrees. A five-dot instrument represents 10 degrees full-scale. Recall that your CDI shows two degrees per dot. Now what? Before we answer, let’s look at the “What if?” case of needing to descend more quickly. You turn and smoothly intercept final and note that you’re outside FISTA -textbook perfect for ICAO. Then wait until you’re “established.”Įventually the localizer needle approaches half-scale. Cleared ILS Runway 14 approach.” If terrain permits, you might get, “Cross FISTA at or above 5900.” Just begin the turn and descent then level off on heading and altitude. Maintain at or above 7000 until established on the localizer. Say you’re on a heading from the north into Medford, Ore., and you hear those empowering words, “Fly heading 180. Useful, but there must be more.įor “more,” let’s work our way through the various cases, starting with the simplest. Only in the Instrument Procedures Handbook (FAA-H-8261-1A) does a definition pop up, and it just says that ICAO defines “established” as within half-scale indication on a localizer or VOR course. Surprisingly, the FAA is not the place to look for a definition of “established.” The AIM and the Instrument Flying Handbook say nothing on the topic. We’ve all heard “Maintain … until established.” We fly the route and make our descents without ATC yelling (usually).
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