A pilot is flying an RNAV (GPS) approach with LNAV/VNAV minimums. The aircraft is equipped with WAAS. During the approach, the GPS system indicates 'LNAV+V' as the active mode. What does this indication signify regarding vertical guidance?
- AThe system is providing advisory vertical guidance, but it is not approved for LNAV/VNAV minimums.
- BThe system has reverted to LNAV-only guidance due to a WAAS signal degradation.
- CThe system is providing approved vertical guidance, allowing descent to LNAV/VNAV minimums.
- DThe system is providing LPV guidance, which is the highest precision available.
Show answer & explanationAnswer & explanation
Correct answer: A. The system is providing advisory vertical guidance, but it is not approved for LNAV/VNAV minimums.
The 'LNAV+V' indication means that the GPS receiver is using WAAS to provide advisory vertical guidance, but this guidance does not meet the stringent requirements for approved LNAV/VNAV or LPV minimums. Therefore, the approach must be flown to the LNAV minimums (MDA), and the 'V' is for advisory purposes only.
Why the other options are wrong
- B. While WAAS degradation can lead to mode changes, 'LNAV+V' specifically means advisory vertical guidance, not a complete reversion to LNAV-only due to degradation unless other annunciations are present.
- C. Approved vertical guidance for LNAV/VNAV minimums would typically be indicated by 'LNAV/VNAV' or 'LPV' active modes, not 'LNAV+V'.
- D. 'LPV' is a distinct mode with higher precision, indicated as 'LPV', not 'LNAV+V'.
LNAV+V Indication
The 'LNAV+V' annunciation on a WAAS-equipped GPS receiver during an RNAV (GPS) approach indicates that the system is providing advisory vertical guidance. This guidance is not approved for LNAV/VNAV or LPV minimums; the approach must be flown to LNAV (MDA) minimums.
- LNAV+V = advisory vertical guidance.
- Not approved for LNAV/VNAV or LPV minimums.
- Approach must be flown to LNAV minimums (MDA).
Memory trick: Plus V Means Advisory, Not Approved Descent.