Definition
A series of predetermined maneuvers, published by the FAA, that allows a pilot to descend safely from en route altitude down to a point near the runway using only cockpit instruments for guidance. The procedure specifies headings, altitudes, navigation aids, minimum descent altitudes or decision heights, and the missed approach instructions to follow if the runway is not seen at the prescribed point.
Plain English
A step-by-step set of flight instructions, drawn on a chart, that lets a pilot fly down through clouds or low visibility and line up with a runway safely, even when they cannot see outside.
Context Anchor
You see IAPs on instrument approach charts, in instrument flight planning, and in clearances for approaches to an airport.
Derivation
From Latin instrumentum (a tool) and procedere (to go forward, proceed). An 'instrument approach procedure' is literally the step-by-step way of going forward to the runway using your instruments as the tool.
Why Pilots Care
IAPs provide the only legal and safe way to descend and land when clouds or low visibility prevent visual approaches, directly affecting flight completion and safety margins.
Intuition Check
Do not read “approach” here as just flying closer to an airport. An IAP is a specific, published instrument procedure with required paths, altitudes, and missed approach instructions.
Example Sentence 1
The pilot briefed the IAP for runway 27 before beginning the descent, noting the minimum descent altitude and the missed approach point.
Example Sentence 2
After receiving the clearance, the crew flew the published IAP and broke out of the clouds at 800 feet.