Height above touchdown elevation (HAT) is the height of the DA/DH or MDA above the highest runway elevation in the touchdown zone (first 3,000 feet of the runway).

• A. The highest runway elevation in the touchdown zone
• B. The airport's elevation
• C. The touchdown zone length
• D. Runway surface height

Answer: (A)

Height above touchdown elevation is the vertical difference between the published decision altitude/height or minimum descent altitude and the highest point of the runway within the touchdown zone. The touchdown zone is the first 3,000 feet of the runway, so you look at the highest elevation in that segment and subtract it from the DA/DH or MDA. That difference is how high you are above the point on the runway you must clear to complete the landing. This reference matters because it accounts for any ups or downs in the TDZ, ensuring you have adequate clearance at the moment you must decide to continue the approach or execute a go-around. The airport’s overall elevation, the TDZ length, or the runway surface height aren’t used as the reference for HAT, which is why the highest TDZ runway elevation is the correct basis. For example, if the highest point in the TDZ is 60 feet and the DA is 350 feet, the HAT would be 290 feet.