RNAV APPROACHES

RNAV approaches are approaches using an IFR certified GPS installed in your aircraft which gets updated every 28 days.

LPV vs. LNAV/VNAV vs. LNAV are not types of approaches. They are minimums with RNAV approaches. Hence, the correct terminology is “RNAV approach to LPV minima.”

For simplicity, and to gain an overview, it is fair to think of LPV approaches as ILS approaches and the LNAV approaches as VOR approaches.

If you’re an instrument rated pilot you will most definitely be familiar with the words “LPV Magenta!” I just came across this fantastic article written by Sarah Fritts of thinkaviation.net.

Sarah’s article breaks down the differences between various GPS approaches that are flown to LPV, LNAV/VNAV and LNAV minimums.

RNAV APPROACH TO LNAV MINIMAS

“LNAV approaches” are the most basic of RNAV approaches and as such they usually have the highest minimums. They require no special avionics except a IFR certified installed GPS receiver. Simple C172s with steam gauges and a G430 could use these approach minimums.

Think of LNAV-only approach minima as the equivalent to a Localizer or VOR approach. It’s missing the vertical component just like localizer approaches with no glideslope.

RNAV APPROACH TO LNAV/VNAV MINIMAS

“LNAV/VNAV approaches” are for aircraft with vertical navigation capability. The vertical guidance is generated internally by barometric settings which is why you see alternate instructions in the notes if you don’t have local altimeter setting or it’s too cold.

A LNAV/VNAV approach is a GPS version of an ILS approach. It will give you a glidepath indication on your attitude display.

You have to check RAIM for these approaches. You can check RAIM before you take off on the FAA website. Your IFR GPS will monitor RAIM throughout your flight.

RNAV APPROACHES TO LPV MINIMAS

LPV approach minimas are available for WAAS equipped aircraft only.

WAAS, or SBAS in Europe, equipped aircraft have the ability to receive correction signals from the “space segment” of the WAAS system. The “space segment” gets input from the “ground segment”. The ground segment is composed of Wide Area Reference Ground Stations. These stations are precisely surveyed stations. The ground stations talk to the Wide Area Master Stations which then tell the satellites if they are sending accurate signals. All these pieces talk to each other and constantly update each other.

The main visual indication that’s different when flying a LPV approach, in comparison to the LNAV and LNAV/VNAV approaches, is that you will have some indication on your PFD that you are “ready for LPV”.