Definition
Terrain characterized by an elevation change of 2,000 feet or more within a 6 nautical mile radius of the obstacle evaluation area used to design an instrument procedure. The presence of precipitous terrain may require the FAA to add an additional buffer to obstacle clearance values, because steep, abrupt terrain creates unpredictable wind effects, altimetry errors, and reduced margins for error.
Plain English
Ground that rises or falls very steeply near the area where an instrument procedure is flown. Because the land changes height so quickly, procedure designers add extra altitude cushion to keep aircraft safely clear of it.
Context Anchor
Seen in instrument procedure and en route holding discussions when a route or holding area is near steep mountains, cliffs, or sharply rising ground.
Derivation
From the Latin praeceps, meaning 'headlong' or 'steep.' The same root gives us 'precipice' -- a cliff or sheer drop. In aviation it carries that same sense: terrain that drops or rises sharply rather than gradually.
Why Pilots Care
Requires higher minimum holding altitudes and careful consideration of climb gradients to maintain safe obstacle clearance.
Intuition Check
Precipitous does not mean rainy or related to precipitation here. It means very steep, abrupt terrain.
Example Sentence 1
Because the holding pattern was charted over precipitous terrain, the controlling agency had added an extra buffer to the minimum holding altitude.
Example Sentence 2
The procedure requires an increased climb gradient when departing over precipitous terrain.