6/17/2023 0 Comments When to intercept localizerThe GPS receiver uses CNFs in conjunction with waypoints to navigate from point to point. If the pilot chooses to track the glide slope prior to the glide slope interception altitude, they remain responsible for complying with published altitudes for any preceding stepdown fixes encountered during the subsequent descent.Ī Computer Navigation Fix (CNF) is also a point defined by a latitude/longitude coordinateand is required to support Performance−Based Navigation (PBN) operations. Interception and tracking of the glide slope prior to the published glide slope interception altitude does not necessarily ensure that minimum, maximum, and/or mandatory altitudes published for any preceding fixes will be complied with during the descent. If you’re flying an ILS, make sure you observe any altitude restrictions outside the published GS intercept altitude. Pilots should not use CNFs for point-to-point navigation (e.g., proceed direct), filing a flight plan, or in aircraft/ATC communications… (REFER to AIM 1-1-17b5(i)(2), Global Positioning System (GPS). CNFs are not recognized by ATC, are not contained in ATC fix or automation databases, and are not used for ATC purposes. Eventually, all CNFs will be labeled and begin with the letters “CF” followed by three consonants (e.g., ‘CFWBG’). A five-letter identifier denoting a CNF can be found next to an “x” on en route charts and on some approach charts. The Pilot/Controller Glossary explains CNF thus:ĬOMPUTER NAVIGATION FIX (CNF)- A Computer Navigation Fix is a point defined by a latitude/longitude coordinate and is required to support Performance-Based Navigation (PBN) operations. The plan and profile views for the KLWS approach may further confuse matters because they include a computer navigation fix (CNF) in this case (CFLSK). Precision approach profiles also depict the GS angle of descent, threshold crossing height (TCH) and GS altitude at the outer marker (OM) or designated fix. This is the minimum altitude for GS interception after completion of the procedure turn. On precision approaches, the glideslope (GS) intercept altitude is illustrated by a zigzag line and an altitude. The ACG offers the following additional distinction: On non-precision only approach procedures, the approach track descends to the MDA or VDP point, thence horizontally to the missed approach point. Stepdown fixes may also be provided between the FAF and the airport for authorizing a lower minimum descent angle (MDA) and are depicted with the fix or facility name and a dashed line. When no FAF is depicted, the final approach point is the point at which the aircraft is established inbound on the final approach course. On non-precision approaches, the final segment begins at the Final Approach Fix (FAF) which is identified with the Maltese cross symbol. The Aeronautical Chart User’s Guide also explains: Intercepting the glide slope at this altitude marks the beginning of the final approach segment and ensures required obstacle clearance during descent from the glide slope intercept altitude to the lowest published decision altitude for the approach. This point marks the PFAF and is depicted by the ”lightning bolt” symbol on U.S. The ILS glide slope is intended to be intercepted at the published glide slope intercept altitude. Instrument Approach Procedure (IAP) Charts includes a note that explains the situation: But if you’re flying the LOC-only procedure, the FAF is at ELWHA, marked by the Maltese cross, another 3.3 nm along the final approach course and 1000 ft lower.ĪIM 5−4−5. For example, the profile view for ILS or LOC RWY 08 at KCLM marks the beginning of the final approach segment for the ILS with the lightning bolt at OCUVI. Sometimes an approach has different FAFs for variations of the same procedure. The profile view does not include the familiar “Maltese cross” that marks the FAF on charts for procedures that include minimums for both a full ILS (a precision approach with a glideslope) and a localizer-only, nonprecision approach to an MDA, as on the ILS RWY 20 at KPWT.īut because the chart for KLWS is only for a precision approach, it doesn’t have a charted “final approach fix.” Here’s a question that came up recently during a presentation that I gave to a group of IFR pilots:
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