Definition
The height of the Decision Altitude (DA) or Minimum Descent Altitude (MDA) above the highest runway elevation in the touchdown zone (the first 3,000 feet of the runway). HAT is published on instrument approach charts for straight-in approaches and is expressed in feet.
Plain English
On an instrument approach, HAT tells you how high you'll be above the runway when you reach your lowest legal altitude on the approach. If HAT is 250, you'll be 250 feet above the runway when you decide whether to land or go around.
Context Anchor
Seen on instrument approach charts, usually near straight-in landing minimums.
Derivation
“Height” means vertical distance, and “touchdown” means the point or area where an aircraft first contacts the runway during landing. In HAT, the word “touchdown” points to the runway touchdown zone, not to the moment your wheels actually touch.
Why Pilots Care
Tells the pilot the exact height at which to decide whether to continue to land or go around.
Intuition Check
HAT is not your aircraft’s current height above the runway. It is a published chart value showing how high the approach minimum is above the runway touchdown zone.
Example Sentence 1
The approach plate showed a DA of 1,450 feet with a HAT of 250, so I knew I'd break out — if at all — about 250 feet above the runway.
Example Sentence 2
The pilot confirmed the HAT met the published minimum before continuing the descent.