TDZE – THRE – Touchdown Zone – Threshold

19/01/2023 M.Durgut 2632 Views Elevation, TDZE, THRE, Touchdown zone

In the aviation world, pilots, dispatchers, and aviation enthusiasts often encounter highly technical terminology that can easily become confusing—especially when several concepts sound similar but serve different operational purposes. Two of these frequently misunderstood terms are Threshold Elevation (THRE) and Touchdown Zone Elevation (TDZE). Although both relate to runway elevation data and play a vital role in approach procedures, instrument landings, and overall flight safety, they refer to distinct points on the runway. Understanding the difference between THRE and TDZE is essential for interpreting approach charts accurately, maintaining situational awareness, and ensuring safe aircraft operations in all phases of landing. Below, we break down what each term means, why it matters, and how they influence modern aviation practices.

What is Touchdown zone?

The portion of a runway, beyond the threshold, where it is intended landing aeroplanes first contact the runway. – Source: ICAO Annex 14

Airport Layout - Touchdown zone — Airport Layout

What is Threshold?

The Runway Threshold is the position across the runway that denote the beginning and end of the designated space for landing and takeoff under non-emergency conditions.

What is Displaced Threshold?

A Threshold not located at the extremity of a runway. – ICAO Annex 14

What is Runway?

Defined rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft. – ICAO doc4444

TDZE?

The TDZE is defined as the highest elevation in the first 3000 feet of the runway starting at the threshold.

So, if Threshold consists the highest point in Touchdown zone area, TDZE = THRE.

Understanding these aviation terms is like deciphering the secret language of pilots. So, the next time you hear “Touchdown Zone” and “Threshold,” remember this: they’re partners in precision, ensuring every landing is a graceful touchdown, not a bumpy touchdown. Now go forth and conquer the skies (metaphorically, of course)!