LPV vs LNAV/VNAV — Understanding RNAV Approach Minimums
A complete breakdown of the differences between LPV and LNAV/VNAV approaches, including WAAS, SBAS requirements, decision altitudes, and when to use each type.
Understanding the difference between LPV and LNAV/VNAV minimums is critical for any instrument pilot flying RNAV (GPS) approaches. Both use GPS-based lateral and vertical guidance, but they differ significantly in precision, equipment requirements, and decision altitudes.
Video: “The Difference Between LPV and LNAV/VNAV Approaches” by Boldmethod
What Is an RNAV (GPS) Approach?
An RNAV (GPS) approach is an instrument approach that uses GPS for navigation rather than ground-based navaids like VORs or ILS localizers. A single RNAV approach plate can contain multiple lines of minimums, each requiring different equipment and offering different precision levels:
| Minimum Type | Lateral Guidance | Vertical Guidance | Equipment Required |
|---|---|---|---|
| LP | GPS (WAAS) | None | WAAS GPS |
| LPV | GPS (WAAS) | WAAS Glide Path | WAAS GPS |
| LNAV/VNAV | GPS | Baro-VNAV or WAAS | VNAV-capable GPS |
| LNAV | GPS only | None (step-down) | IFR-approved GPS |
LPV — Localizer Performance with Vertical Guidance
LPV is the most precise RNAV approach type and is often compared to a CAT I ILS in terms of precision — though it is technically classified as an approach with vertical guidance (APV), not a precision approach.
Key characteristics
- Lateral guidance: Angular, like a localizer — the course narrows as you approach the runway, providing increasing precision
- Vertical guidance: WAAS-computed glide path (similar to a glideslope)
- Decision Altitude (DA): Typically 200–250 ft AGL — comparable to ILS CAT I
- Equipment required: WAAS-enabled GPS receiver (e.g., Garmin GNS 480, GTN 650/750, G1000 with WAAS)
- Signal source: GPS satellites + SBAS (WAAS in the US, EGNOS in Europe)
- Angular sensitivity: Gets more sensitive closer to the runway (like an ILS localizer)
- Availability: Subject to WAAS coverage — NOTAM’d when unavailable
How it works
WAAS (Wide Area Augmentation System) uses a network of ground reference stations to measure GPS signal errors and broadcast corrections via geostationary satellites. This improves GPS accuracy from ~15 meters to ~1 meter, enabling the precise lateral and vertical guidance that LPV provides.
In Europe, the equivalent system is EGNOS (European Geostationary Navigation Overlay Service).
LNAV/VNAV — Lateral Navigation / Vertical Navigation
LNAV/VNAV provides both lateral and vertical guidance but with less precision than LPV. The vertical component can come from either WAAS or a barometric VNAV (baro-VNAV) computer.
Key characteristics
- Lateral guidance: GPS-based, fixed-width corridor (not angular) — ±0.3 NM sensitivity throughout the approach
- Vertical guidance: Either baro-VNAV (computed from altimeter setting) or WAAS advisory glide path
- Decision Altitude (DA): Typically 300–400 ft AGL — higher than LPV
- Equipment required: IFR GPS with VNAV capability (baro-VNAV or WAAS)
- Sensitivity: Constant throughout the approach (unlike LPV which narrows)
- Temperature limitations: Baro-VNAV approaches may have cold temperature restrictions (noted on the approach plate)
Baro-VNAV vs WAAS VNAV
- Baro-VNAV: Computes the vertical path using altimeter data — susceptible to altimeter setting errors and non-standard temperatures. Cold weather can cause the aircraft to fly lower than the indicated path.
- WAAS VNAV: Uses satellite corrections for the vertical path — more accurate but still provides LNAV/VNAV minimums (not LPV) if the lateral guidance doesn’t meet LPV standards.
Key Differences at a Glance
| Feature | LPV | LNAV/VNAV |
|---|---|---|
| Lateral sensitivity | Angular (narrows near runway) | Fixed width (±0.3 NM) |
| Vertical source | WAAS glide path | Baro-VNAV or WAAS |
| Typical DA | 200–250 ft AGL | 300–400 ft AGL |
| Precision | Near ILS CAT I | Lower than LPV |
| Cold temp restrictions | No | Yes (baro-VNAV) |
| WAAS required | Yes | No (baro-VNAV option) |
| CDI scaling | Angular (increases near runway) | Linear (constant) |
LNAV — Lateral Navigation Only
For completeness: LNAV is the most basic GPS approach minimum. It provides only lateral (left/right) guidance with no vertical guidance. The pilot descends using step-down fixes and an MDA (Minimum Descent Altitude), not a DA. This is a non-precision approach.
- MDA: Typically 400–600 ft AGL
- Equipment: Any IFR-approved GPS
- Vertical guidance: None — pilot manages descent manually using step-down altitudes
Which Approach Should You Fly?
Your GPS receiver determines which minimums you can use:
- WAAS GPS available and functional → Fly LPV minimums (lowest DA, best precision)
- WAAS GPS with VNAV, but LPV unavailable → Fly LNAV/VNAV minimums
- Non-WAAS GPS with baro-VNAV → Fly LNAV/VNAV minimums (watch for temp restrictions)
- Basic IFR GPS only → Fly LNAV minimums (step-down, MDA)
Always brief the approach plate and check NOTAMs — WAAS/EGNOS outages can downgrade your available minimums.
Practical Tips
- Always check the approach plate box — it lists the required equipment and any notes about temperature limitations or WAAS requirements
- Monitor the GPS receiver annunciation — your avionics will indicate whether LPV, LNAV/VNAV, or LNAV is the active approach mode
- In the Cirrus Perspective (G1000): The annunciation appears in the HSI — look for “LPV” or “L/VNAV” in the approach mode field
- In Europe (EGNOS): LPV coverage is expanding but not universal — always verify availability for your destination
- Brief your fallback: If flying an LPV approach, know the LNAV/VNAV or LNAV minimums as backup in case of WAAS/EGNOS downgrade during the approach