Can someone explain Foall/Piclo?

The ILS RWY 4 approach at San Antonio International Airport (KSAT) incorporates named intermediate fixes — FOALL and PICLO — that define discrete segments of the procedure prior to glideslope intercept. The 267-degree course notation visible on the approach chart represents the published magnetic course of that segment, flown for 2.2 nautical miles between the two fixes. The reference to the Stinson VOR (SSF), located at Stinson Municipal Airport just south of San Antonio, is used in the conventional (non-GPS) sense to define fix position through radial and/or DME intersection — a standard method for establishing named fixes on instrument procedures developed before widespread GPS availability.

On a GPS-equipped aircraft, which represents the overwhelming majority of IFR-certified aircraft currently flying, the pilot simply sequences through the waypoints as loaded from the avionics database. The GPS computes the direct course between FOALL and PICLO automatically, and the course of 267 degrees shown on the chart should closely match what the moving map and CDI display during that segment. The pilot does not manually tune or interpret the Stinson VOR for navigation purposes unless flying the procedure with raw VOR data only — an increasingly rare scenario in line operations but still a testable skill for IFR certification and recurrency. The chart annotation exists primarily to define the geometry of the procedure and provide situational awareness verification.

Understanding how fixes like FOALL and PICLO are constructed matters beyond the initial IFR certificate. Fixes on instrument approaches are established using one of several methods: GPS-defined coordinates, VOR radial intersections, VOR/DME fixes, or NDB references. Conventionally-defined fixes that predate GPS are increasingly being replaced or supplemented with RNAV equivalents under the FAA's Optimization of Airspace and Procedures in the Metroplex (OAPM) program and NextGen infrastructure efforts. At busy Class B airports like KSAT, many legacy VOR-based procedures have received RNAV overlays or have been redesigned entirely, meaning pilots transitioning from training to line operations may encounter both chart formats and must be comfortable reading either.

The broader instructional point embedded in this approach segment is that IFR chart literacy requires pilots to distinguish between what defines a fix and what describes the segment flown between fixes. The 267-degree course is a segment descriptor — it tells the pilot the direction of travel — while the Stinson VOR reference is the underlying fix-definition mechanism. GPS collapses this distinction in practice, but examiners and check airmen consistently probe whether instrument pilots understand the underlying navaid architecture of a procedure, particularly during partial-panel or GPS-inoperative scenarios. The FAA's Instrument Flying Handbook and instrument rating ACS both expect applicants to demonstrate this conceptual understanding, not merely the ability to follow magenta lines.

For professional and corporate operators, clarity on this topic has direct operational relevance during NOTAM-driven GPS outages, avionics failures, or operations into international airports where RNAV capability cannot be assumed for all procedures. Flight departments operating under Part 91K or Part 135 that file IFR regularly into metro airports like KSAT benefit from crews who can revert to conventional navaid interpretation without confusion — precisely the kind of foundational knowledge this approach chart segment tests.