Which category of ILS approach has a decision height of less than 50 feet?

Which category of ILS approach has a decision height of less than 50 feet?

• A. CAT IIIa
• B. CAT IIIb
• C. CAT IIIc
• D. CAT II

Answer: (B)

The correct choice identifies CAT IIIb as the category of ILS approach that has a decision height of less than 50 feet. Specifically, CAT IIIb approaches can operate with a decision height as low as 20 feet or even no decision height at all, allowing operations in extremely low visibility conditions. This flexibility is essential for airports that experience frequent low-visibility weather, enabling aircraft to land safely even when visual references are minimal or absent. In contrast, CAT II approaches have a decision height that is usually allowed down to 100 feet, while CAT IIIa approaches can go down to a decision height of less than 200 feet but are still above 50 feet. CAT IIIc approaches, while also generally categorized with very low decision heights, are primarily concerned with operations that may not require a decision height, but the specificity of the question regarding less than 50 feet directly aligns with CAT IIIb. Thus, recognizing the functionality and operational protocols associated with each category is crucial for understanding their respective applications in ILS operations.

The correct choice identifies CAT IIIb as the category of ILS approach that has a decision height of less than 50 feet. Specifically, CAT IIIb approaches can operate with a decision height as low as 20 feet or even no decision height at all, allowing operations in extremely low visibility conditions. This flexibility is essential for airports that experience frequent low-visibility weather, enabling aircraft to land safely even when visual references are minimal or absent.

In contrast, CAT II approaches have a decision height that is usually allowed down to 100 feet, while CAT IIIa approaches can go down to a decision height of less than 200 feet but are still above 50 feet. CAT IIIc approaches, while also generally categorized with very low decision heights, are primarily concerned with operations that may not require a decision height, but the specificity of the question regarding less than 50 feet directly aligns with CAT IIIb. Thus, recognizing the functionality and operational protocols associated with each category is crucial for understanding their respective applications in ILS operations.