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LPV, LNAV/VNAV, APV, baro-VNAV, +V (merged)

Some non precision approaches (i.e. those without vertical guidance) have a "suggested" glidepath and are supposed to be implemented in the GPS navigator database as LNAV+V. For such approaches, there should be a glideslope signal for the autopilot.

Now I have an up to date GNS430W but I have yet to find an airport where it would give me LNAV+V and show the glidepath so that I can couple the autopilot.

Has anyone done this in Europe/Germany? I recall something that Garmin/Jeppesen chose to not enable them over here. My GNS430W firmware is at 3.1 (going to be 5.0 next week).

What about other navigators? Obviously such approaches would be much easier to fly than having to roll your own glidepath. I usually prefer letting the airplane do what it can and spend my attention on monitoring everything. The more I do myself, the less attention I can put on monitoring and crosschecking.

I am not familiar with the GPS approach terminology (I know of only GPS/RNAV, and LPV, which are both well known even though the latter is almost nonexistent in Europe) but there is a mode on the GNS/GTN boxes whereby the "continuous descent" profile (a straight line FAF-MAP) seen on many/most Jepp plates is available as an advisory "glideslope" and the box can output a VNAV deviation signal to a CDI (or HSI etc) and thus to an autopilot.

I recall reading reports from some UK pilots who got this working.

Obviously it has to be coded in the database.

Some handhelds e.g. a Garmin 496 offer an "ILS" function which does more or less the same thing but terminates at some height (1000ft?) AGL to stop you using it in a real emergency. One day I mean to test this on mine...

That's all I know.

Administrator
Shoreham EGKA, United Kingdom

What about other navigators?

The Honeywell avionics of our Citations are able to do that, but the link to autopilot/flight director is disabled in German/European installations. What we get though is a "raw data" glideslope indication which is a lot better than nothing.

EDDS - Stuttgart

but there is a mode on the GNS/GTN boxes whereby the "continuous descent" profile (a straight line FAF-MAP) seen on many/most Jepp plates is available as an advisory "glideslope" and the box can output a VNAV deviation signal to a CDI (or HSI etc) and thus to an autopilot.

That's exactly what the GNS/GTN boxes do and it is part of the Jeppesen supplied approach database. Here's a Garmin blog article. Jeppesen used to block the +V component in the European database but when I asked them about it, they told me this limitation was lifted ca. 2 years ago.

Someone told me yesterday that Straubing EDMS has it now enabled but I was not able to find it last time I went there. The GNS simulator is too old it seems (there is a way of injecting a current database but that didn't help either). I will try it again next week and wonder if there's something I have to enable/configure for these approaches to show up.

LNAV+V would be an extremely handy tool to do RNAV approaches below the MDA, aehm I mean to reduce pilot workload and make sure to go around on reaching MDA...

LNAV+V would be an extremely handy tool to do RNAV approaches below the MDA

I'd be a little careful, because on a nonprecision IAP the obstacle clearance is not assured on a "glideslope" trajectory flown beyond the MAP (all the way to the runway) the way it is on a precision IAP such as ILS or LPV.

But I know you knew that

The Honeywell avionics of our Citations are able to do that, but the link to autopilot/flight director is disabled in German/European installations. What we get though is a "raw data" glideslope indication which is a lot better than nothing.

That's outrageous, surely...

It that an AOC requirement?

I suppose if they mandated a 30cm spike in the yoke, pointing at your chest, you would do your balanced runway calcs more carefully, too.

Administrator
Shoreham EGKA, United Kingdom

I am sure it works but most German LNAVs where the +V would operate also have a LNAV/VNAV so that will be used if the system is able to.

EGBJ has an LNAV that gets a +V so can be flown coupled.

EGTK Oxford

On Proline 21 equipped aircraft with the FMS3000 every airfield has a "visual" approach in the database which adds a waypoint at 5 miles on the extended centreline and vertical guidance to the ground at the threshold. This can be coupled and the aircraft will fly it all the way down in vnav mode. In fact the Proline 21 VNAV mode will fly a 3 degree descent to hit the waypoint at a height you specify (or is coded).

Darley Moor, Gamston (UK)

I have a worldwide database on the GTN and GNS530W simulators dated Feb 07, 2013. I could not find any RNAV approaches in Germany that have the LNAV+V. I found them in France, example LFOA and in Peter's home drome EGKA, so it must be a country thing. The equipment is capable of providing the advisory glidepath and it works in every respect like an ILS, so may be used to couple to an autopilot. Of course, as Peter noted, one should not use it below the MDA as there are no assurances that it won't take you through a ridge or trees once you leave the safety of the MDA. In otherwords, you need to descend by visual means from the MDA to the runway.

KUZA

Question to NCYankee:

Would the GNSS530W programme, downloaded today, contain the new (February 2013) database?
If not, where could I obtain the new database from?

YSCB

JasonC wrote:

I am sure it works but most German LNAVs where the +V would operate also have a LNAV/VNAV so that will be used if the system is able to.

If the approach has vertical guidance via an APV such as LPV or LNAV/VNAV, then the vertical guidance is official and may be used to the DH. Below the DH, the visual segment must be clear of obstacles and following the glidepath is expected. However, the advisory glidepath annunciated as LNAV+V will only be available on a RNAV approach that only has LNAV minimums. The Garmin WAAS GPS Units are approved for flying officially vertically guided APV approaches, both LPV and LNAV/VNAV. LNAV+V is a feature and invention of the manufacturer and is not part of the approach evaluation criteria. I have never seen +V indicated on an approach chart, although one can normally guess if it will be provided.

In the US, flying an approach with official vertical guidance is to a DH, and the decision is made at that point. Momentum may carry the aircraft lower than the DH and that is permitted as long as the missed approach has been initiated if the visual criteria is not met. With a LNAV, there is a MDA, and the aircraft must not descend below the MDA until a normal visual descent can be made. Some pilots treat a LNAV+V MDA as a DH and add a small buffer of 50 feet so they don't bust minimums and start the missed approach at that point. The MAP on the LNAV is typically at the runway threshold and the visibility requirement assumes the pilot continues along at the MDA until the runway is identified. By initiating the missed approach at the point where the GS intersects the MDA, the visibility requirement is much higher and in low visibility situations, an unnecessary miss may be required when in fact the approach could be safely completed. For turbojet aircraft, this may be required, but for piston aircraft, much steeper descents to the runway are possible to do safely. Also don't forget on any missed approach initiated at the pseudo DH, one must still navigate to the MAP and follow any turn instructions at that point. A turn too early can have bad results.

KUZA
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