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This approach shows two sets of minimums that both have vertical guidance with a Decision Altitude (DA). What is the difference between LNAV/VNAV and LPV, and why does LPV have lower minimums?

KFXE RNAV 26 Approach plate

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There's an FAA paper on RNAV approaches that explains the differences between LP, LPV, LNAV and LNAV/RNAV approaches. I made a table for my own reference but since StackExchange doesn't allow tables (AFAIK) here's a summary:

  • LP: no vertical guidance; WAAS required; MDA for minimums
  • LPV: vertical guidance; WAAS required; DA for minimums
  • LNAV: no vertical guidance; WAAS not required; MDA for minimums; requires RAIM integrity if WAAS is not available
  • LNAV/VNAV: vertical guidance; WAAS or baro-VNAV required; DA for minimums; requires RAIM integrity if WAAS is not available (i.e. if using baro-VNAV); possible temperature restrictions if using baro-VNAV

The difference between LPV and LNAV/VNAV is that although they both have vertical guidance, LPV was intentionally designed to be very similar to an ILS approach with an increasingly sensitive glideslope whereas LNAV/VNAV was not. Other answers have additional comments about LNAV/VNAV having been designed earlier and for different equipment which would certainly make sense.

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    $\begingroup$ The difference in required equipment is the reason why LPV approaches can have lower minima. GPS with WAAS (needed for LPV) provides true altitude, quite precisely, and does not require any setting. On the other hand LNAV/VNAV can be flown on barometric altimeter only and that requires setting and even when set properly has systemic temperature-dependent error, so it is not as reliable and consequently the decision altitude has to be higher. $\endgroup$ – Jan Hudec Sep 12 '14 at 20:05
  • $\begingroup$ LPV is not considered a precision approach. It is an APV, approach with vertical guidance that doesn't meet precision approach criteria. See page 7-2 of you Jepp Instrument/Commercial book. $\endgroup$ – user11580 Oct 5 '15 at 3:06
  • $\begingroup$ @Jobuck I just saw that your answer was converted to a comment, whcih is why it popped up again for me. Apologies for repeating the same points again. $\endgroup$ – Pondlife Oct 6 '15 at 20:07
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LNAV/VNAV approaches were originally designed for larger, more sophisticated turbine aircraft utilizing onboard Flight Management Systems (FMS). These types of approaches uses barometric altimeters and ground radio equipment to compute a descent path and add vertical guidance to an existing non-precision approach.

An LPV approach still provides vertical guidance but is not a precision approach. In this type of approach WAAS GPS satellite and ground-based data are used to provide the aircraft with the vertical descent information.

Usually a WAAS approved GPS navigator, like the Garmin 430w, is capable of flying both LPV and LNAV/VNAV approaches.

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  • $\begingroup$ When you say that LNAV/VNAV was "originally designed for..." does this mean that they are now being used by smaller airplanes too? $\endgroup$ – Lnafziger Jan 16 '14 at 15:34
  • $\begingroup$ @Lnafziger, if a smaller plane is equipped with a WAAS GPS, then yes, they could fly the LNAV/VNAV approach as well, but generally, a WAAS GPS would qualify them to also fly an LPV which provides a lower minimum and would be the likely choice as a preferred approach. If there is not an LPV available then and LNAV/VNAV could be flown. An aircraft equipped for LNAV/VNAV most likely could not fly an LPV. $\endgroup$ – Magnetoz Jan 16 '14 at 15:42
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    $\begingroup$ Got it, but are there GPS's for smaller airplanes (like maybe the G1000 or similar advanced cockpits) that can do LNAV/VNAV approaches? $\endgroup$ – Lnafziger Jan 16 '14 at 15:55
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    $\begingroup$ I don't know the answer to that, but I would guess no. A barometric altimeter and an FMS are usually required and not too many light general aviation aircraft are equipped with such expensive equipment. One could certainty modify a Cessna 172 to comply, but I can't think of any aircraft that came from the factory with the necessary avionics. $\endgroup$ – Magnetoz Jan 16 '14 at 16:27
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    $\begingroup$ That's right. Its called Baro-vnav and here's the Advisory Circular with guidance for operators conduction approaches. faa.gov/documentLibrary/media/Advisory_Circular/AC%2090-105.pdf $\endgroup$ – Magnetoz Jan 16 '14 at 16:44
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LPV is a higher precision approach requiring equipment beyond what is needed for LNAV/VNAV. In particular you need dual WAAS recievers in a certified installation. The improved guidance is what allows the lower DH. See this link for more information.

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    $\begingroup$ Are dual receivers really required? I haven't heard that before, do you have a reference to a regulation or something that says that? $\endgroup$ – Lnafziger Feb 18 '14 at 15:47
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    $\begingroup$ Any update? I've never seen a dual nav requirement for LPV either. $\endgroup$ – egid Mar 24 '15 at 6:07
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. A LPV approach can provide WAAS vertical guidance as low as 200 feet AGL. LNAV/VNAV approaches also provide approved vertical guidance and existed before the WAAS system was certified. At that time, only aircraft equipped with a flight management system (FMS) and certified baro-VNAV systems could use the LNAV/VNAV minimums. Also the design of an LPV approach incorporates angular guidance with increasing sensitivity as an aircraft gets closer to the runway. (This is intentional to aid pilots in transferring their ILS flying skills to LPV approaches).

http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/library/factsheets/media/RNAV_QFacts_final_06122012.pdf

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LPV - Localizer Performance with Vertical Guidance is some kind of enhanced satellite navigation with an required accuracy of 16 meters in the horizontal and 20 meters in the vertical plane during 95 percent of the time, achieved by multiple special GPS (WAAS) receivers. Obviously this accuracy allows to reduce the minima on the approaches.

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In order to get the LPV minima you need:
1 - An approach certified SBAS/WAAS capable receiver
2 - That the GPS+SBAS signals are good enough for LPV approach (horizontal and vertical protection levels low enough)
If you have an approach certified GPS receiver without WAAS, then no LPV/LP for you, but there are still the possibility of getting a VNAV or a pure LNAV approach depending on your installation and GPS signal quality.
In essence you will always automatically get the best minima possible. The receiver will tell you which one automatically.
Look up the documentation for your GPS receiver.
Dual receveivers are NOT required !
There is also the possibility of getting an LPV, but with a higher DH/same visibility if the signal quality is within LPV250 but outside LPV requirements.

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Read below with a grain of salt, as I'm not a CFII.

From what I understand, there are no "precision" GPS approaches, aside from CAT1,2,3.

LPV is more accurate, uses WAAS, and means LP with vertical guidance.

LNAV/VNAV is an older tech, and was originally designed before WAAS was available. Before WAAS, aircraft with flight management/director systems were equipped to fly LNAV/VNAV. The VNAV portion consisted of Baro-VNAV equipment requirements. Nowadays, you can buy some newer aircraft equipped with Baro-VNAV, or fly those approaches with capable WAAS GPS.

Either way, you should read your aircraft manual and check it's equipment and what approaches it's qualified for.

Here's a link to more info I found.

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    $\begingroup$ LPV is precision and is comparable to ILS in terms of minimums. $\endgroup$ – egid Mar 24 '15 at 6:08

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