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RNAV approaches: one-page summary
FAA procedures (AIM). Explanations, worked examples and practice: pilotscafe.com/deciphering-rnav-approach-minimas/
The four kinds of minima
| Line | Guidance | To | Needs |
|---|---|---|---|
| LPV | Lateral + vertical, angular | DA | WAAS, LPV approved |
| LNAV/VNAV | Lateral + vertical | DA | WAAS (Class 2+) or baro-VNAV |
| LP | Lateral, angular | MDA | WAAS, LP approved |
| LNAV | Lateral | MDA | Any approach-approved GPS |
LP appears only where no vertically guided line can be published, so never with LPV or LNAV/VNAV, and isn't a fallback from LPV. WAAS units certified before TSO-C145b/C146b may lack LP. Circling may be below LNAV/VNAV, never below LNAV.
Which line you may fly
The AFM or supplement lists the approach types. On the approach, a WAAS receiver annunciates the best line available; you may use it or a higher one. The supplement describes how it reports a downgrade.
DA lines and MDA lines
- DA (LPV, LNAV/VNAV): follow the path. Stepdowns on final don't apply. At the DA, continue only if you meet 91.175(c); otherwise go missed.
- MDA (LP, LNAV): stepdowns on final apply. Level off at the MDA. Descend only when you meet 91.175(c); you shouldn't before a charted VDP (V). Missed approach at the MAP.
- LNAV+V, LP+V: advisory glidepath only. The MDA is still an MDA, and the stepdowns still apply.
Failures on final
- Vertical flag only (LPV, LNAV/VNAV): you may use the LNAV minima if your rules allow changing the approach after starting it. Already below the LNAV MDA: go missed unless you meet 91.175(c).
- Lateral alarm on an LP approach: go missed.
- RAIM alarm, non-WAAS GPS: before the FAF, don't descend; fly to the missed approach point and go missed. After the FAF: climb and go missed.
Chart notes
| RNP APCH - GPS | An RNAV (GPS) approach; GPS required |
| RNP AR APCH, Authorization required | RNAV (RNP): FAA authorization required, no exceptions |
| RF, RF required | Radius-to-fix leg: only if your avionics list RF |
| Uncompensated Baro-VNAV … NA below −XX°C or above XX°C | RNAV (GPS): LNAV/VNAV line not usable. RNAV (RNP): whole approach not usable |
| Snowflake and a temperature | Cold Temperature Airport: correct altitudes at or below that temperature (AIM 7-3) |
| Baro-VNAV NA | LNAV/VNAV line for WAAS only |
| Use XXX altimeter setting… increase… | Remote setting: higher minima, no baro-VNAV |
| Negative W | WAAS vertical outages not NOTAMed: plan LNAV or circling |
| DME/DME RNP-0.3 NA | Not for an FMS relying on DME/DME |
| Abroad: RNP RWY 24; RNP RWY 24 (AR) | ICAO titles for RNAV (GPS) RWY 24; RNAV (RNP) RWY 24 |
Before you go
A GPS approved for IFR approaches, and an approach that loads by name from a current database (or an expired one, if you verify the procedure hasn't been amended). Check GPS and WAAS NOTAMs. Without WAAS: RAIM for your ETA, and another approved means of navigation for the route.
Alternates when GPS is your only approach navigation
- Non-WAAS (FDE, RAIM prediction): a GPS approach at the destination or the alternate, not both. Plan LNAV or circling (LNAV/VNAV with approved baro-VNAV).
- WAAS: GPS approaches at both. Plan LNAV or circling, with nonprecision alternate weather (LNAV/VNAV with approved baro-VNAV). On arrival, fly LPV if annunciated.