Instrument Approach Procedures
Chart anatomy
Know the segments - initial, intermediate, final, missed - plus the MSA, procedure turn or hold-in-lieu-of-procedure-turn, FAF, MAP, and the missed approach holding fix. Understand DA (precision, LPV) versus MDA (non-precision, LNAV, circling), and that a DA is a decision altitude while an MDA is a minimum descent altitude with a level-off. Approach categories are set by Vref at maximum certificated landing weight: A below 91 knots, B 91–120, C 121–140, D 141–165. Circling minimums expand with category.
Descending below minimums
91.175(c) governs: you need the aircraft continuously in a position to land using normal maneuvers and a normal rate of descent, flight visibility not less than that prescribed, and one of the specified visual references distinctly visible and identifiable. With only the approach light system visible, descent below DA is limited to 100 feet above the touchdown zone elevation (Category I).
Missed approach and traps
Fly the published missed immediately at the MAP unless the airport is in sight. Report a course reversal to ATC. Know the inoperative-components tables and the VDP.
Worked example
Vref at maximum landing weight is 130 knots, so the aircraft is Category C and uses Category C minimums, even if you plan to fly the approach slower. Using your actual approach speed instead of Vref is a classic error.
Trap: substituting reported ground visibility for required flight visibility, and assuming a tower clearance to land authorizes descent below minimums before the visual references exist.