Changes to Instrument Jargon

In 2007, the U.S. approach charting vocabulary became “more in tune” with the rest of the world. The term Height Above Touchdown (HAT) will slowly be replaced with Height Above Threshold (HATh). Touchdown Zone Elevation (TDZE) will be replaced with Threshold Elevation (THRE).

THRE is measured at the runway threshold and TDZE is measured at the touchdown area, 1,000 feet beyond the threshold. The change from HAT to HATh and TDZE to THRE will occur when the charts are updated, or when a new chart is published. So, when Phoenix Sky Harbor amended its ILS  7R in 2012, THRE was inserted where TDZE once was.



THRE replaces TDZE. It’s “1111”







If you see THRE instead of TDZE, that’s your clue that the small number next to the Straight-in minimums and visibility required, (1364-3/4) – the “253” – is the HATh, and no longer the HAT.

NOTE: the minimums of 1364 have NOT changed.

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