Definition
The highest elevation in the first 3,000 feet of the landing surface, measured in feet above mean sea level (MSL). TDZE is published on instrument approach charts when a straight-in landing is authorized and is used as the reference elevation for certain approach minimums.
Plain English
The height above sea level of the highest point in the first 3,000 feet of runway where you'll touch down. It's printed on approach charts so you know what altitude corresponds to the runway surface at the landing end.
Context Anchor
You will see TDZE on instrument approach information, runway data, and discussions of how high an aircraft is above the runway touchdown area.
Derivation
‘Touchdown zone’ is the portion of the runway where aircraft normally touch down — the first 3,000 feet beyond the threshold. ‘Elevation’ comes from Latin elevare, ‘to lift up,’ and refers to height above sea level. So TDZE is the height of that touchdown area above sea level.
Why Pilots Care
Used to calculate height above touchdown for determining landing minimums on instrument approaches.
Intuition Check
TDZE is not the elevation of the whole airport, and it is not necessarily the runway threshold elevation. It is the highest point in the runway’s touchdown zone.
Example Sentence 1
The approach chart showed a TDZE of 1,247 feet, so the pilot knew the runway surface at the landing end sat about 1,247 feet above sea level.
Example Sentence 2
Subtract the TDZE from your current altitude to find your height above the landing area.