What constitutes a Category I ILS approach?

A Category I Instrument Landing System (ILS) approach is defined by specific parameters that include a decision height (DH) and visibility requirements. In this context, a decision height of 200 feet and a visibility requirement of 1/2 mile characterize a Category I ILS approach. At this threshold, pilots must make a decision to continue to the runway or execute a missed approach based on their ability to see the required visual references.

This standard ensures safety during landing operations, requiring pilots to maintain a certain level of situational awareness and instrument precision, especially in poor visibility conditions. The 200 feet decision height allows pilots to transition from instrument flying to visual references in a controlled manner, reflecting the capabilities of the aircraft and the crew to execute a safe landing.

In contrast, an approach that has no decision height and no visibility requirements does not meet established safety standards for instrument approaches. Similarly, an approach allowing visual flight at all times or with a decision height of 500 feet does not adhere to Category I specifications, which clearly delineates the lower thresholds necessary for instrument-based landings under controlled conditions.