A pilot is planning an IFR flight to an airport with a published RNAV (GPS) approach. The approach chart shows both LNAV/VNAV and LNAV minimums. The pilot's aircraft is equipped with an IFR-approved GPS that has WAAS capability. Which minimums are the pilot authorized to use?
- AOnly LNAV/VNAV minimums, as they provide vertical guidance.
- BBoth LNAV/VNAV and LNAV minimums, provided the WAAS system is operating correctly.
- CNeither, as a separate baro-VNAV system is required for LNAV/VNAV minimums.
- DOnly LNAV minimums, as WAAS is not required for LNAV.
Show answer & explanationAnswer & explanation
Correct answer: B. Both LNAV/VNAV and LNAV minimums, provided the WAAS system is operating correctly.
An IFR-approved GPS with WAAS capability provides both lateral and vertical guidance. Therefore, a pilot with such equipment can utilize both LNAV/VNAV minimums (which offer precision-like vertical guidance) and LNAV minimums (which offer lateral guidance only) on an RNAV (GPS) approach, provided the WAAS system is functional.
Why the other options are wrong
- A. While LNAV/VNAV provides vertical guidance, LNAV minimums are also available as a less precise option.
- C. WAAS-equipped GPS does not require a separate baro-VNAV system for LNAV/VNAV; WAAS provides the vertical guidance.
- D. WAAS-equipped GPS allows for the use of vertical guidance (LNAV/VNAV) as well as lateral (LNAV).
RNAV (GPS) Minimums - WAAS
An IFR-approved GPS receiver with Wide Area Augmentation System (WAAS) capability allows a pilot to utilize both LNAV/VNAV (lateral navigation/vertical navigation) and LNAV (lateral navigation) minimums on an RNAV (GPS) approach, as WAAS provides the necessary vertical guidance for LNAV/VNAV.
- WAAS provides enhanced GPS accuracy and integrity.
- WAAS enables vertical guidance for RNAV approaches.
- LNAV/VNAV requires WAAS or Baro-VNAV.
- LNAV only provides lateral guidance and can be flown with non-WAAS IFR GPS.
Memory trick: WAAS WINS: Vertical guidance With All Accuracy Standards!