Definition
Designated points along an instrument approach segment that allow a pilot to descend to a lower published altitude only after the aircraft has passed that point. Each step-down fix has its own minimum crossing altitude, creating a stair-shaped descent profile that keeps the aircraft safely above terrain and obstacles between the fixes.
Plain English
Specific points on an approach where you are allowed to drop down to a lower altitude — but only once you have crossed the point. Until you reach it, you must stay at or above the higher altitude shown on the chart.
Context Anchor
Seen on GPS instrument approach charts and in the GPS approach sequence when the descent is broken into more than one altitude step before reaching the runway area.
Derivation
From 'step down,' the same idea as walking down a staircase. The descent is built as a series of altitude steps rather than one continuous slope, with each fix marking the next step.
Why Pilots Care
Ensures obstacle clearance is maintained during each segment of a non-precision approach.
Intuition Check
Do not read “fixes” as repairs. Here, fixes are known positions on the approach path. Do not descend just because the next lower altitude is printed; descend only after crossing the step-down fix that allows it.
Example Sentence 1
After crossing the step-down fix, the pilot descended from 2,400 feet to the next published altitude of 1,800 feet.
Example Sentence 2
The approach plate listed three step-down fixes between the final approach fix and the missed approach point.