well….NAV .accuracy downgrade message …..check trajectory :-)…donno I dont have a fancy GTN ;-)
For going missed with turn right after some altitude
Adding to nerdy questions: how does TSO146 box with SBAS/WAAS switched off know you have crossed your (barometric) altitude terminator, let alone calculate the turn after, especially if it does not have Baro-VNAV feeds 
well…from the internet..:-)
During a GPS approach in which GPS accuracy requirements cannot be met by the GPS receiver for any GPS approach type, the GNS will flag all CDI guidance and display a system message “ABORT APPROACH – Loss of Navigation”. Immediately upon viewing the message, the unit will revert to Terminal navigation mode alarm limits. If the position integrity is within these limits lateral guidance will be restored and the GPS may be used to execute the missed approach, otherwise alternate means of navigation must be utilized.
If the position integrity is within these limits lateral guidance will be restored and the GPS may be used to execute the missed approach
Yes when you get LOI on LPV/LNAV the TSO146 box may still perfectly fly RNAV1 missed laterally but vertically without SBAS/BARO how the heck it can guess where “1500ft altitude before tuning” let alone “calculate turn for HSI” ? not surprising they would recommend dead recon to fly that missed 
well the flight warning computer will trigger an air data warning on your PFD display " check ALT" with an ECAM warning ADIRU 1 fault ;-)… I guess
…just kidding
gallois wrote:
LPV is an APV (approach with vertical guidance) however so is an LNAV + V the difference between the 2 is (short version) that like an ILS the LPV is angular both vertically and horizontally which means they converge to a point in the same way a a VOR does. LNAV + V works like the magenta line.on the GPS and do not converge, therefore they are not as accurate at lower MDH/DH and the vertical path needs barometric pressure which the LPV like the ILS glide slope and therefore loses accuracy with temperature. This I will admit is easier to explain with an image.
LNAV + V is definitely not APV. The LNAV+V guidance is “Advisory Vertical Guidance” and following the +V does not assure that step down altitudes will be complied with nor that there won’t be obstacles along the vertical path to the runway below the MDA. In fact, in the latest versions of the TSO specification, +V may be provided even when outside of an SBAS service volume, as it is only advisory and almost any reasonable vertical path between the FAF and the MDA is acceptable.. LPV is an APV where the vertical guidance provides assurances of obstacle clearance to the runway and step down fixes inside the PFAF don’t apply. Although there is an option for LNAV lateral CDI guidance to be linear, 0.3 NM inside the FAF, it may also be angular at +/- 2 degrees, whichever is lower. All the GPS systems I am familiar with choose the angular option for LNAV CDI deviation (GNS/GTN/G1000/IFD). The LNAV +V does not use barometric pressure to determine the path, it is based strictly on geometry between the FAF at the crossing altitude to the threshold at the TCH. +V is an aid for flying CDFA down to the MDA and not below, LPV is vertical guidance with a GP and a DA.
Graham wrote:
What’s stopping you individually loading the waypoints into the world’s most basic GPS and just flying from one to another, at least for LNAV? You don’t even need to load them. For a simple LNAV like e.g. EGBJ RNP Rwy27, you know that you have an IAF at 10nm long final on a 264 course so you just fly over that at 2,500, stepping down to 2,000’ at a 5nm final, 1,250’ at 3nm and 510’ at 1nm, with the minimum being 600’. You don’t need to load the procedure in the box to do this (practically, I make no comment on legally.)
The comment on legality is specified in the GPS AFMS, under limitations. In US regulation, the limitations section is regulatory and must be followed. The approach procedure must be loaded from the database and the data in the database entry must be current. Several things don’t occur if you just manually enter the approach waypoints, the integrity and alerting does not occur, the CDI guidance is not automatic, missed approach guidance is unavailable
Ibra wrote:
Some of this relevant when considering planning ceiling minima: you don’t give much importance to ceiling on Precision Approach during planning (you know exactly where the runway sits with a guaranteed 3D guidance to 200ft and if there is hole inside some broken 100ft layer for you to see the runway, you can sneak in), however, you can do this for ILS PA but not on LPV PA as you are required to degrade SBAS during planning (not because LPV200 is not precision approach)
The US is going to define LPV with a DA at 250 or lower to be a precision approach. A new AC is in draft form 90-119 and will replace all the previous guidance in the AIM, AC’s 90-100, 90-105, 90-107, and 90-108. Probably won’t be out to late this year or next year. As far as alternate planning, unlike an ILS where GS may be out of service yet the procedure may still be used as a localizer approach with precision lateral guidance, LPV downgrades to LNAV where the allowed lateral guidance is +/- 0.3 NM. So pilots must plan to use the NPA LNAV minimums of 800-2 Although LPV vertical and lateral guidance will have a very high availability, LNAV will be much closer to 100% and does not depend on SBAS even operating.
johnh wrote:
What a lot of ado about nothing (the PBN training requirement, I mean, not the discussion). Flying a GPS/RNAV/LPV approach is the easiest thing in the world, WAY easier than an ILS (and let’s not even think about VOR and NDB). Yes, you have to know about RAIM, and you have to know which buttons to press when.
I do agree that flying an LPV approach is easy and I don’t fly ILS unless absolutely necessary, other than for practice. There is a lot more, however to understanding how the system works. What annunciation do you need and when does it appear. What does it mean if the annunciation is amber? In the US, we also have LP procedures and LP+V annunciations. When is using the LP minimums allowed? We also have TAA (Terminal Arrival Areas). Most of our approaches are T style, many with holds at the center of the T as an IAF/IF. When is the hold required? If you are told to hold, how do you remain in the hold. How do you exit the hold? How do you avoid the hold when cleared straight in. When can you descend in a TAA? What happens if you attempt the missed approach early and press the OBS button? How do you recover from this? If cleared to begin the approach at an IF, going thru the approach selection dialog does not offer this choice, how do you comply? When do you commence a turn on a missed approach, what do you need to do to obtain missed approach guidance, what if you activate the missed approach guidance before you should? What does activating an approach mean and do? What happens if you activate an already activated approach? What happens if you proceed direct to the FAF? How do you load and fly a SID or STAR? How do you enter a complex flight plan with airways. If your system supports it, how do you enter a random hold into your route? How can you determine if you should expect a downgrade for an LPV.
In almost all of these “what’s it doing now” situations, pilots will have a good chance of messing up and becoming confused if they have never been trained and it just happens.
In the US, for part 91 operations, there are no training requirements to use PBN. I cover all this during an IPC. It is my experience that training pilots how to understand and fly PBN takes about 4 hours of ground discussion and a couple of hours doing actual procedures.
Airborne_Again wrote:
For the record, I’m not arguing for PBN training at an ATO. What I’m arguing for is that pilots should read up properly on PBN operations before attempting them. As GA_Pete notes, it is clear from this discussion that not all do.
Very much agree.
