ILS categories

Classification system for Instrument Landing Systems based on decision height, runway visual range, and required equipment. Category I allows approaches to 200 feet decision height; Category II to 100 feet; and Category III subdivides into IIIA (no decision height, 700 feet RVR), IIIB (no decision height, 150 feet RVR), and IIIC (no decision height or RVR minimum).