What are the three categories of ILS approaches?

The three categories of ILS (Instrument Landing System) approaches are classified primarily based on the precision of the approach and the minimum decision heights or visibility requirements. Category I (Cat I) approaches have less stringent requirements compared to Category II (Cat II) and Category III (Cat III) approaches.

Cat I typically requires a decision height of not lower than 200 feet above ground level and a runway visual range (RVR) of at least 550 meters. Cat II allows for a lower decision height, down to 100 feet, with an RVR of a minimum of 300 meters. Cat III approaches are further divided into Cat IIIA, IIIB, and IIIC, with IIIA allowing for decision heights less than 50 feet and no minimum RVR, while IIIB and IIIC have even lower visibility requirements and no decision height.

This classification is crucial for pilot training and operations, as it determines the necessary equipment, certification, and training for pilots and their aircraft, as well as the conditions under which an approach can be conducted safely. This structured system helps standardize the approach process and increase safety during low-visibility conditions.