Definition
A decision altitude expressed as 200 feet measured vertically above the elevation of the touchdown zone of the runway being approached. On a precision or approach-with-vertical-guidance procedure, reaching 200 feet HAT is the point at which the pilot must have the required visual references in sight to continue the approach to landing, or else execute a missed approach.
Plain English
It is the point on the approach where the aircraft is 200 feet above the start of the landing runway. At that height the pilot must either see the runway environment well enough to land, or go around.
Context Anchor
Seen in instrument approach minimums, especially when comparing how low an RNAV (GPS) approach can take you before you must see the runway area to continue landing.
Derivation
HAT stands for Height Above Touchdown. The reference is the touchdown zone elevation — the highest elevation in the first 3,000 feet of the landing runway — rather than the airport elevation or sea level. This matters because what the pilot needs to know at that moment is how high they are above the runway they are about to land on, not above some other reference.
Why Pilots Care
Reaching this altitude without visual contact with the runway requires an immediate missed approach.
Grounding Statement
Picture the aircraft on final approach, 200 feet directly above the start of the landing runway — about the height of a 20-story building above the pavement.
Intuition Check
Do not read 200 feet HAT as 200 feet above sea level. It means 200 feet above the runway touchdown zone elevation.
Example Sentence 1
The LPV approach minimums showed a decision altitude of 200 feet HAT, so the pilot briefed a go-around if the runway environment was not in sight at that point.
Example Sentence 2
If the runway lights are not in sight at 200 feet HAT the pilot executes the missed approach procedure.