Definition
Category I is a precision instrument approach classification that permits a pilot to descend to a decision height (DH) no lower than 200 feet above the touchdown zone elevation, with a runway visual range (RVR) no less than 1,800 feet (or visibility no less than 1/2 statute mile). It is the least demanding of the precision approach categories and is the standard ILS approach minima used at most airports. For helicopter Copter ILS approaches, Category I criteria apply with helicopter-specific minima sometimes published.
Plain English
Category I is the most common type of precision instrument approach. It lets the pilot fly down to 200 feet above the runway in fairly low visibility, and if the runway is in sight by then, they can land. If not, they must go around.
Context Anchor
Seen in instrument approach procedure discussions and minima for copter-only precision approaches to an airport or heliport.
Derivation
‘Category’ comes from the Greek katēgoria, meaning ‘a class or grouping.’ The Roman numeral I marks this as the first (and least demanding) tier of precision approaches. Categories II and III allow lower minima but require additional aircraft equipment, crew training, and ground facilities.
Why Pilots Care
It defines the lowest weather conditions under which a pilot may legally continue the approach and land.
Grounding Statement
On a CAT I approach, the pilot follows the instruments down to the published decision point, then continues only if the required outside visual cues are in sight.
Intuition Check
CAT I does not mean aircraft approach Category A, B, C, or D based on speed. Here, Category I means a class of precision instrument approach minimums.
Example Sentence 1
The crew briefed the CAT I ILS approach with a 200-foot decision height and 1,800 RVR.
Example Sentence 2
CAT I minimums allow a decision height of 200 feet with visibility of one-half mile.