Well, if pretty experienced pilots can’t even figure it out, what hope is there for the likes of me or Jo Blo? Sounds like an abbreviation soup and a safety hazard. There should be only two approaches – one with vertical guidance and one without, no? Just dump the rest and clean up in the soup.
I am with you! Lets dump VOR, NDB, ILS, Localizer, SDF, LDA, GPS, ILS BC, RNAV (RNP), RNAV (GPS) LNAV/VNAV, LNAV and just keep LPV and LP. 
There should be only two approaches – one with vertical guidance and one without, no?
Your suggestion is about to be implemented 
Forthcoming “re-classification” of all operations will treat an approach procedure operation (RNP APCH and RNP AR APCH alike) as either a 3D operation or a 2D operation (depending on how you fly it).
either a 3D operation or a 2D operation (depending on how you fly it).
You mean – if you fly it incorrectly, you will end up taking up just two dimensions
Bookworm – what are the criteria in Europe for Garmin (or Jepp) deciding whether to offer (or not) the LNAV+V mode?
AFAIUI, the Garmin picks the most precise approach (as in lateral precision, not precision approach). Only then does it decide whether or not to provide an NPA with a +V glideslope.
So the problem is in essence the same as for the LP approaches. If an LNAV approach (which displayed a +V) is replaced by either an LP or a LNAV/VNAV without the appropriate flag, it decides that you’re not meant to get a glideslope and doesn’t offer a +V.
QuoteFrom what you say, the advisory glideslope may be suppressed only at the large airports which have had the LNAV/VNAV approach designed.
It’s not confined to “large airports”. Cambridge has an LNAV/VNAV.
Exactly. You are more than just an uniDimensional HDGing pilot, Peter ….
Bookworm,
As it stands today for the Garmin WAAS navigators, if there is any vertical guidance provided by the approach, either an LPV or LNAV/VNAV, if the vertical integrity criteria is not met, the approach downgrades to a LNAV without any vertical guidance. Advisory vertical guidance (+V) is only applicable on approaches that the only straight in minimum charted on the procedure is LNAV. It requires the same vertical integrity as LPV with a DA of 250 feet or greater or a LNAV/VNAV minimum. Also, as of today, the Garmin WAAS navigators don’t support +V when an approach has an LP minimum charted although they are expected to add support for LP+V sometime in 2014. If the lateral integrity criteria is not met for an LP approach, it will also downgrade to LNAV.
Whether or not a Garmin WAAS GPS supports +V on a given approach is left up to Garmin, although there are now exceptions to this. There are some countries who don’t authorize +V on their approaches and Garmin will honor that. There is an error in the main software for LNAV and LNAV/VNAV approaches when the final approach segment is 7.0 NM long or greater. These approaches have been eliminated from the database with vertical guidance and only provide LNAV without +V as a work around to the problem. In the US, certain RNAV NPA approaches have been flight tested and found to have obstacles in the visual segment that are incompatible with +V and have had the VDA (Visual Descent Angle) removed from the charts and a note added “Descent Angle NA”.
My understanding is that the Garmin Navigators only provide one coding for each approach in the database, although others may be charted. So if an approach contains a LPV, LNAV/VNAV, or LNAV option, only the coding for LPV will be in the database. For LNAV/VNAV and LNAV, only the LNAV/VNAV is coded. If LNAV is coded, it will also be coded with +V or not as appropriate. For LP and LNAV, only LP is coded. All downgrades are to LNAV without +V. In the US, we may fly to any of the procedure minimums as long as one of equal or higher accuracy is annunciated. So with LPV annunciated, I can fly to the LPV DA, the LNAV/VNAV DA, or the LNAV MDA. With LP annunciated, I can fly to the LP or LNAV MDA. In most cases the lowest minimums are available with the highest accuracy procedure, but not always. Very occasionally, the LNAV/VNAV has a lower DA than the LPV. Much more often, the LNAV has the lowest minimums, particularly visibility wise. Particularly when there are close in obstacles or obstacles in the missed approach path, the LPV DA may be forced back and up along the final approach course, putting the obstacle in the visual segment or missed approach segment. With the LNAV, one can take advantage of crossing over a step down fix and then continuing to a lower MDA. Also, a vertically guided path with a DA requires that descent below the DA while initiating the missed approach has to take obstacles into account that level flight at the MDA doesn’t.
Great explanations – thanks!
This is very thought-provoking because – for Europe – it really reduces the utility of a “W” GPS. I would class Cambridge as a “big” airport because it takes sizeable jets and maybe even 737 type stuff. But if the fact that Cambridge and similar places have approaches designed which prevent the LNAV+V functionality, and given there are almost no LPV approaches, what is the point of a “W” GPS?
It would be truly bizzare if we got mandatory PRNAV (which in practical/regulatory terms – the AFMS – can be met only with an upgrade to a “W” GPS) and had to spend money on the gear, but got very little use out of it for flying approaches.
QuoteThis is very thought-provoking because – for Europe – it really reduces the utility of a “W” GPS.
The LNAV/VNAV issue is either fixed or will be fixed fairly soon.
For anyone who ‘s further interested in all that stuff, I can recommend John Eckalbar’s Instrument Flying Update. It’s phenomenal – even though it’s now almost 8 years old, it has all about the differences between LNAV, LNAV+V, LNAV/VNAV, APV, LPV, WAAS and the likes, including numerous real world examples. Shows how many years Europe is “behind” the US with these things…
Just checked: that book is available as a Kindle eBook too, so can be read on a Kindle – or iPad (Kindle app)
