Definition
The highest elevation, measured in feet above mean sea level, within the first 3,000 feet of the landing surface beginning at the runway threshold. TDZE is published on instrument approach charts and is used as the reference elevation for certain straight-in approach minimums.
Plain English
The height above sea level of the highest point in the first 3,000 feet of the runway after the threshold. It tells pilots how high the touchdown area sits.
Context Anchor
Seen on instrument approach charts and in runway information where approach heights and landing references are given.
Derivation
Built from three plain words: 'touchdown' (where the wheels meet the runway), 'zone' (a defined area), and 'elevation' (height above sea level). Together they describe the height of the area where the airplane is expected to land.
Why Pilots Care
Pilots use TDZE to calculate decision altitudes, minimum descent heights, and visual descent points on instrument approaches.
Intuition Check
TDZE is not the average height of the runway, and it is not always the height right at the runway beginning. It is the highest point in the touchdown zone.
Example Sentence 1
The approach chart listed a TDZE of 412 feet, so the pilot used that value to confirm the published minimums for the ILS.
Example Sentence 2
We noted the TDZE on the airport diagram before planning the visual approach to runway 27.