Instrument Approach Procedure

An Instrument Approach Procedure (IAP) is a published series of maneuvers that guides an aircraft from the en-route environment to a point from which a landing can be made visually, or if landing is not possible, to a position where a missed approach procedure begins.

Types of approaches:

• Precision (PA): ILS, GLS — provides both lateral and vertical guidance with decision altitude
• Approach with Vertical Guidance (APV): LPV, LNAV/VNAV, Baro-VNAV — lateral and advisory vertical guidance
• Non-Precision (NPA): VOR, NDB, LNAV — lateral guidance only with minimum descent altitude

Each approach has defined segments: initial, intermediate, final, and missed approach. Minima (DA/DH or MDA) depend on approach type, aircraft category, and available lighting.