Definition
A precision instrument approach and landing classification with a decision height not lower than 200 feet above the touchdown zone elevation and a runway visual range not less than 1,800 feet (or visibility not less than 1/2 statute mile). Category I is the least demanding of the ILS precision approach categories and is the standard ILS minimum flown by most general aviation and commercial operations.
Plain English
The standard ILS approach minimums. The pilot must be able to see the runway by 200 feet above the ground, and the runway visibility must be at least about half a mile. If those conditions aren't met at decision height, the pilot has to go around.
Context Anchor
Seen on ILS approach charts, approach briefings, and FAA discussions of instrument landing system minimums.
Derivation
The word 'category' comes from the Greek 'kategoria,' meaning a class or division. The Roman numeral 'I' simply marks this as the first (and least restrictive) tier in a graded series. Categories II and III have progressively lower minimums and require more capable equipment, training, and ground facilities.
Why Pilots Care
It sets the weather minimums that determine whether a pilot can legally continue an ILS approach to landing.
Grounding Statement
For Category I, picture following electronic guidance down to about 200 feet above the runway, then continuing only if you can see enough to land safely.
Intuition Check
Category I does not mean the aircraft category, pilot certificate category, or a general difficulty level. In the ILS context, it means a specific class of ILS approach minimums based on decision height and visibility.
Example Sentence 1
The forecast called for a 300-foot ceiling and one mile visibility, which was well above Category I minimums for the ILS approach.
Example Sentence 2
Aircraft and crew must meet specific equipment and training standards before they can fly Category I ILS approaches in actual instrument conditions.