What is LPV?

[Hardy Heinlin]

What is LPV?

Edit: Ah, this https://en.wikipedia.org/wiki/Localizer_performance_with_vertical_guidance

[tango4]

Something not very seven four seveny I guess:

[emerydc8]

I learned it and then forgot it. Now, I just remember that it doesn't apply to us and we can't use those minimums.

[Hardy Heinlin]

The airport has no localizer anyway. Does "localizer performance" mean "GPS performance" in RNP language?

[emerydc8]

Speaking of published minimums, here's something that you only see in Europe and only with Category C and D non-ILS landing minimums -- Converted Meteorological Visibility (CMV). Look at the approach plate for Amsterdam below. If the reported visibility is only 1600m, can you do the VOR approach at night if you don't have HIALS and HIRL? Just looking at the plate you might say no. Using the conversion chart gives you a CMV of 2400m. So you are good to go!





Here's more information and another example:

[tango4]

The airport has no localizer anyway. Does "localizer performance" mean "GPS performance" in RNP language?

LPV means that it is an RNAV approach that is basically equivalent to a Localizer with vertical guidance, and so you will get minima very close to a CAT I ILS, without the maintenance cost of the antennas.
It is mostly a marketing term...
You will frequently find 3 types of minima on your RNAV approach, that you can use depending on the equipment you have and whether you are trained for it or not. These are LNAV, LNAV/VNAV, LPV.
LNAV is just lateral guidance.
LNAV/VNAV is lateral guidance and vertical guidance coming from the aircraft VNAV capability.
LPV is localizer AND vertical guidance coming from the SBAS (EGNOS in Europe), so more precise.


I don't know if there are any 747 that are LPV compatible. Perhaps the -8, or those with the Next Gen FMC ?


And did not know about CMV, thanks for the info Jon !




Charles

[Hardy Heinlin]

Understood. But what is LNAV in this context? I thought it may be coupled with a certain RNP value. The term "LNAV" alone says nothing about the current actual navigational precision; the FMC's position update mode could be single IRS, mixed IRS, radio updating with DD, VD etc., or GPS ... whereas VNAV can always and only refer to barometric air data.


|-|ardy

[tango4]

Well, pilots may be better suited to answer that question, so guys please correct me if I'm wrong.
It is indeed coupled with RNP values.
During the initial approach phase it is RNP1.
When on the final approach, it is RNP 0.3 for all those procedures.
For the LPV, the lateral guidance should be theoretically more precise thanks to EGNOS, but you still are RNP 0.3.
RNP 0.1 is for RNP AR (authorization required) procedure and can be for some segments only.


I'd be really interested to know if I wrote some mistakes here, so any inputs from someone more knowledgeable is appreciated.


Charles

[Britjet]

The -400 can't do LPV - I don't know about the -800. To use LPV you need extra on-board receivers to monitor the WAAS system,.
Edit - deleted this section as it was bo88ox..but what I wanted to say is that flying an approach such as a VOR, using on-board LNAV, is not the same thing as flying an approach which is labelled "LNAV". The former just makes flying the approach easier, but still requires the raw data (e.g. VOR) information to be monitored.
US (Terps) naming tends to be different from EU or ICAO naming. (Which is where I lose the plot slightly!).
Peter

Edit...noting Jon's comments about adding 50 feet to minima - my BA manual states that if an approach is defined as "LNAV' only, it already has an additive margin built into the minima, so there is no need to add 50 feet. If it is "LNAV/VNAV' then an extra margin would be appropriate, (apparently). I'm unsure if this applies generically, though.

[DougSnow]

CMV just isnt in Europe, check out the RJAA VOR 16L (Jepp 23-1 dtd 8 Apr 16)

[Britjet]

This might help explain the methods used to fly the various approaches....quote....

LNAV or LNAV/VNAV Minima

A problem with the development of PBN terminology is that aerodrome operating minima are listed under headings which refer to aeroplane autopilot modes specific to Boeing aeroplanes. In fact minima titled LNAV or LNAV/VNAV refer to the way in which an approach was designed, not the autopilot modes required to fly it. Unfortunately, pilots sometimes see a minimum specification labelled 'LNAV' and assume they have to use that MCP mode.

An approach designed for LNAV-only is a conventional NPA, but using RNAV as the lateral-guidance medium. LNAV/ VNAV minima imply an approach is designed as an RNP APCH. But one approach can have both LNAV minima, for the simple case, and LNAV/VNAV minima for the RNP APCH case. The difference in the minima arises from the use of different obstacle-assessment criteria. In some cases LNAV/VNAV minima can be higher than LNAV-only.

Confusion arises because all fleets fly FMS database approaches using VNAV. It is perfectly acceptable to fly an approach which only has LNAV minima (e.g. BDA 12, BOD 05 & 23) using VNAV, providing the appropriate (fleet- specific) procedures are used, with the LNAV minima. But if LNAV/VNAV minima are provided, they should be used if VNAV is being used. An analogy would be flying a VOR database approach using the FMS: pilots would use the VOR minima, even though it would be flown using VNAV.

[tango4]

Hi Peter and thanks for your input.
I was about to ask a clarification in your first post but i see your already edited that !
If I am correct the difference between let's say a VOR DME approach and an equivalent RNAV approach with LNAV minima is that in the second case, you should verify RNP 0.3, while in the first case, the LNAV autopilot mode is just a help, and lateral accuracy is provided by monitoring RAW data.
In both cases you will probably fly it using LNAV/VNAV autopilot modes.
But for me if an approach is published with LNAV and LNAV/VNAV minima, the lateral accuracy in both cases is the same at RNP 0.3.


But this is clearly a can of worm... We were forced to suspend the use of the RNAV 27 at LFPB due to many incidents with pilots flying things they were not supposed to, not capturing the axis, not descending on the approach and so on.
A new one is being re designed with some restrictions. I spent a whole afternoon in a Falcon 2000 FFS testing many scenarios on this new procedure, which was real fun ! I had the opportunity to land it (no, I was not playing, it was for work...  ) and holy crap, I guess I flew too much PSX in the recent months. Definitely not the same animal !

[emerydc8]

CMV just isnt in Europe, check out the RJAA VOR 16L (Jepp 23-1 dtd 8 Apr 16)

Good catch. I see JAR-OPS uses it too.