Локалайзер ниже ILS

Why does the ILS approach to Runway 23 at Frederick require *1 mile of visibility**, while the localizer-only approach requires just **¾ mile* for Category A aircraft? Aren't precision approaches supposed to have better minimums? In this video, we investigate a surprising feature of the ILS or LOC Runway 23 approach at Frederick Municipal Airport in Maryland, and explain how obstacles near the runway can affect instrument approach minimums in ways you might not expect. We'll use a visual illustration to compare how precision and nonprecision approaches provide obstacle clearance, why an ILS decision altitude works differently from a localizer minimum descent altitude, and how an obstruction near the runway can produce a seemingly backward result. We'll cover: Why ILS approaches normally provide lower minimums How required obstacle clearance affects instrument approach design The difference between a decision altitude (DA) and minimum descent altitude (MDA) Why raising an ILS decision altitude can also affect required visibility How obstacles in the visual segment can change approach minimums Why the localizer-only approach at Frederick can have a lower visibility requirement than the ILS It's a great reminder that the numbers on an instrument approach plate aren't arbitrary. They're the result of carefully designed obstacle-clearance and visibility requirements—and sometimes those requirements produce surprising results. *Go deeper into instrument approaches, IFR procedures, and approach minimums with FlightInsight IFR Ground School:* https://www.flight-insight.com/ifr