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Garmin / Avidyne / Jeppesen +V Advisory Glidepath / Glideslope, does it ever breach stepdown fixes, and does it exist for non-GPS IAP airports?

I checked the database for the GNS430W / GTN / G1000. The two RNAV (GNSS) procedures at EGKA have LNAV+V, and of course the two NDB procedures do not. I also understand that you are supposed to get an LPV next year. That will bring you into the 21st Century.

KUZA, United States

It is EGKA. The 20 approach is April 2012.

Apparently the UK CAA is banning (from the Jepp database) all LNAV+V approaches which have an obstacle below the MDA. This is self evidently stupid because you are not supposed to descend below the MDA! I don’t know how many there are or indeed if there are any in the UK and the only example I can find discussed is the same old one which was mentioned in the April 2014 US IFR Magazine article (Sydney, N23 airport code, USA) which does have an obstacle below the MDA on runway 07.

I also understand that you are supposed to get an LPV next year. That will bring you into the 21st Century.

Haha… that’s if a lot of things “happen”…

Last Edited by Peter at 26 Aug 14:02
Administrator
Shoreham EGKA, United Kingdom

Peter,

The FAA is also removing the +V if an LNAV or LP procedure has significant obstacle issues below the MDA, The flight test crew attempts to fly the procedure at a 1 dot fly up indication and if they get a TAWS warning or observe that the obstacles don’t permit a safe descent along the VDA (Visual Descent Angle), they will make a note in the test results that the VDA is not to be charted and that a note “Descent Angle NA” be added to the chart. This will take years to be reflected in all the affected procedures in the US. Fortunately, most approaches that have just an LNAV and or LP MDA will not end up with this note. Obstacles can be found in the 20 to 1 visual segment evaluation, but if they are far from the center of the flightpath or just minor penetrations, they don’t necessarily present a hazard for an aircraft flying the advisory glidepath below the MDA.

For those not familiar, the LP (Localizer Performance) is a SBAS (WAAS or EGNOS) procedure that provides lateral guidance identical to the LPV lateral guidance and is used when the approach does not qualify for LPV and offers a lower MDA than the LNAV option due to its more precise path and smaller obstacle evaluation area. We have about 550+ of these in use in the US.

KUZA, United States

BARO-VNAV capability is rarely found on smaller bizjets. Mostly Falcon/Challenger and upwards and airliners can do it.

It’s there on Collins Proline 21 as fitted to the CJ series and the later King Airs

Darley Moor, Gamston (UK)

Here is an extract from April 2014 IFR Magazine – authorised from the publisher

Last Edited by Peter at 26 Aug 15:55
Administrator
Shoreham EGKA, United Kingdom

I am guessing there is a difference between TERPS and EU-OPS or PANS OPS regarding procedure design and the VDP?

There are some fairly important issues in other areas (circling notably), so be sure we are comparing like with like.

London area

I don’t think either of them suggests flying below the MDA if you can’t see the runway

Administrator
Shoreham EGKA, United Kingdom

In the US, the TERPS were never designed to provide a clear path from the FAF to the runway on a non precision approach. After passing the FAF, the only criteria is that the obstacle clearance surface must be clear of obstacles. The FAA recommends that a Constant Angle Non Precision Approach (CANPA) profile be flown by Turbojet aircraft instead of the dive and drive method because of its safety advantages. CANPA is also termed CDFA NPA (Constant Descent Final Approach). However, the CANPA method requires that in addition to meeting TERPS criteria, the visual segment below the MDA needs to be clear of obstacles. For airports that the airlines fly into, the specific runways and approaches often meet the additional criteria in the visual segment, but for a good number of approaches into US General Aviation airports, these criteria are simply not practical. For this and for other reasons, the CANPA method does not always apply to the light piston crowd, That is what is discussed in detail in the IFR article.

KUZA, United States

bq. BARO-VNAV capability is rarely found on smaller bizjets. Mostly Falcon/Challenger and upwards and airliners can do it.

It’s there on Collins Proline 21 as fitted to the CJ series and the later King Airs

But are you sure that it is certified for approach? We have tro Proline equipped aircraft in our fleet and they are not approved for BARO-VNAV approaches. Also the Honeywell equipped Citations that I fly have barometric VNAV (which works all the way to the ground if necessary) but it is only approved for enroute and terminal navigation, not for approach. The scale of the “VNAV glidesloope” is fixed at 500ft and it cannot be coupled to the flight director and autopilot.

EDDS - Stuttgart

Funny we should be talking about this topic, just as the FAA sends round this by email.

Apparently, Garmin had a “feature” in their firmware which caused a division by zero error when the approach with a zero slope was seen. So they just disabled all such approaches. This was fixed in v5.10.

Isn’t that the same version in which they “fixed” the crossfill protocol to stop 3rd party add-ons working?

Last Edited by Peter at 26 Aug 20:21
Administrator
Shoreham EGKA, United Kingdom
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