Plain English Meaning

A type of low-visibility approach where the pilot can land with almost no forward visibility, using the aircraft's automatic landing system. The runway visual range can be as low as 150 feet, and there may be no decision height at all.

Full Definition

A precision instrument approach and landing classification with a decision height lower than 50 feet (or no decision height at all) and a runway visual range less than 600 feet but not less than 150 feet. CAT IIIb approaches require specially certified aircraft, qualified flight crews, an approved airborne system (typically autoland), and a with the necessary lighting, , and protected /sensitive .