FAA Instrument Flight Instructor (FII)Instruments and SystemsHard
A CFII is explaining WAAS-based approach types to an instrument student. Which statement correctly distinguishes an LPV approach from an LNAV approach?
- ALPV provides lateral and vertical guidance to a decision altitude, similar to an ILS, using WAAS augmentation
- BLPV and LNAV both use barometric vertical guidance derived from the altimeter setting
- CLPV is only usable by aircraft with a flight director, while LNAV requires only a basic GPS receiver
- DLPV provides lateral guidance only, while LNAV provides both lateral and vertical guidance
Show answer & explanationAnswer & explanation
Correct answer: A. LPV provides lateral and vertical guidance to a decision altitude, similar to an ILS, using WAAS augmentation
LPV (Localizer Performance with Vertical guidance) uses WAAS to provide precision-like lateral and vertical guidance down to a decision altitude (DA), much like an ILS. LNAV is a lateral-only approach flown to an MDA with no vertical path guidance from the navigation system.
Why the other options are wrong
- B. LPV vertical guidance is WAAS-based satellite guidance, not barometric.
- C. A flight director is not a certification requirement for flying LPV; a WAAS-capable receiver is required.
- D. This reverses the capabilities — LPV, not LNAV, provides vertical guidance.
LPV vs. LNAV Approaches
LPV (Localizer Performance with Vertical guidance) uses WAAS to provide precision-like lateral/vertical guidance to a DA; LNAV provides lateral-only guidance to an MDA.
- LPV requires a WAAS-capable GPS receiver
- LPV minimums can rival ILS (as low as 200 ft AGL)
- LNAV/VNAV uses barometric VNAV, different from LPV's WAAS vertical guidance
Memory trick: LPV = 'Like Precision Vertical' — flies just like an ILS.