Watch your step (downs)

These restrictions are included to ensure that you clear obstacles and when they can allow an MDA that is at least 60 feet lower or reduce the visibility minimums.

Aeronautical Information Manual 5−4−5 explains that “Altitude restrictions depicted at stepdown fixes within the final approach segment are applicable only when flying a Non−Precision Approach to a straight-in or circling line of minima identified as an MDA. These altitude restrictions may be annotated with a note ‘LOC only’ or ‘LNAV only.’ Stepdown fix altitude restrictions within the final approach segment do not apply to pilots
using Precision Approach (ILS) or Approach with Vertical
Guidance (LPV, LNAV/VNAV) lines of minima identified
as a DA(H).”

Note the phrase “may be annotated.” Stepdown fixes inside the final approach fix have long been marked with asterisks tied to notes in the profile view to confirm that they apply only when you are flying to an MDA. But at an Aeronautical Charting Meeting in 2022, representatives from the FAA reported that Order 8260.19 has been updated, and as procedures are amended, the “LOC only” or “LNAV only” notes are being removed. That slow process means that for a long time we’ll see charts both with and without the notes. For now, consult the legends in the Terminal Procedures Publication (TPP) and the Aeronautical Chart Users’ Guide to confirm when the stepdown altitudes apply.

This inconsistency is one reason why I annotate my charts, using blue boxes to mark altitudes associated with LNAV-only minimums, such as stepdown fixes and visual descent points (VDP). That markup helps me notice such details during preflight planning and when I brief an approach in the air.

If you have a WAAS-capable GPS that provides advisory vertical guidance (+V), you should clear stepdown altitudes between the FAF and the MAP if you’re on that glidepath. But your altimeter is still the primary reference, and you must verify your altitude at each stepdown fix. You also may see stepdown restrictions along the intermediate legs of an approach, outside the final approach segment. As AIM 5−4−5 also admonishes, “Pilots are responsible for adherence to stepdown fix altitude restrictions when outside the final approach segment (i.e., initial or intermediate segment), regardless of which type of procedure the pilot is flying.”

Elsewhere in the AIM, paragraph 1−1−17 cautions that unnamed stepdown fixes in the final approach segment may not appear in the navigation database, so you may have to use along-track distance to confirm passing those waypoints—another reason to review approaches carefully during preflight planning.

In fact, you must take particular care when flying the localizer-only version of an ILS approach. Consider the ILS or LOC RWY 06 at Coeur d’Alene, Idaho (COE). As the chart title implies, both the full ILS with a glideslope to a decision altitude and its localizer-only sibling appear on the same plate. But if you load the ILS in your GPS, the localizer-only stepdown fix at ONUCU, with a 3,480-foot crossing altitude, doesn’t appear in the waypoint list. Neither does TIYOS, which marks the missed approach point. You must instead load the LOC RWY 6 procedure to see and confirm crossing those fixes, unless you have distance measuring equipment. FT

Bruce Williams is a CFI. Find him at youtube.com/@BruceAirFlying and bruceair.wordpress.com