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Does Anyone in the UK Get Vertical Guidance from their GTN650/750?

Clearly there is no FAS DB, as such, to load.

My theory is that they might recreate one from available data, and the data is readily available from the AIP.

The LOI logic isn’t built into the FAS DB. The FAS DB is actually rather simpler than maybe some people give it credit for. If they fill every field of the FAS DB, including HAL and VAL, I can’t really see why LOI wouldn’t be the same logic, if they wanted to be.

To answer Tone’s question, I believe that switching off the LNAV/VNAV slope is just one flag in the database.

EGKB Biggin Hill

I don’t know about the GTN units but on the GNS430W it is necessary to check that you actually have WAAS / EGNOS enabled….you should see a D next to the satellite status on the relevant page…

YPJT, United Arab Emirates

Technically one should do that on any 146() equipment, but a rule more honoured in the breach than the observance, I fear.

EGKB Biggin Hill

The OP should also check that EGNOS had been selected on the SBAS page

YPJT, United Arab Emirates

The OP should also check that EGNOS had been selected on the SBAS page

Thanks Anthony, it certainly is.

Thanks to the information on the previous pages I’ve now concluded that the GTN is indeed set up correctly, and the reason that UK RNAV approaches with LNAV/VNAV mimima are only showing up as LNAV are down to the CAA restrictions.

Last Edited by TonesTaxis at 08 Dec 14:08
United Kingdom

Join the queue of those of us rolling our eyes and making tutting sounds in the general direction of the CAA.

EGKB Biggin Hill

I have to say though, I’m surprised that it’s not more widely publicised that this feature has been downgraded by the CAA.

The only official reference I can find to this is from CAP773, section 2.7.3;

“WARNING! At the time of writing this document (Autumn 2014), the use of SBAS to provide augmentation for the VNAV element of a notified LNAV/VNAV approach is not permitted in the UK. Notwithstanding any certification for RNAV VNAV approach operations using SBAS, aircraft which are not certified for the use of barometric VNAV data are currently precluded from flying approach operations to LNAV/VNAV minima.

These aircraft are not authorised to continue RNAV approach operations below the
published LNAV-only minima."

However (to me at least) this doesn’t clearly suggest to a potential buyer of a GTN avionics package that the vertical guidance wouldn’t actually be available! Just that one would fly to the higher LNAV minima.

Last Edited by TonesTaxis at 08 Dec 14:23
United Kingdom

It is a remarkable bit of Gold Plating over the top of any other state I am aware of. And it significantly impacts safety. The CAA should be ashamed of themselves. I doubt they are.

EGKB Biggin Hill

Timothy wrote:

It is a remarkable bit of Gold Plating over the top of any other state I am aware of. And it significantly impacts safety. The CAA should be ashamed of themselves. I doubt they are.

It would make some kind of sense if the CAA had requested that the GPS box simply ignored the VNAV part. Then the approach would be LNAV+V and it wouldn’t matter if the glide path didn’t agree with the Baro-VNAV glide path as it would be advisory anyway and all stepdown altitudes would still apply.

ESKC (Uppsala/Sundbro), Sweden

What is interesting is that Jeppesen (or Garmin) actually disabled the GS guidance for UK airports, to implement the CAA ruling.

Administrator
Shoreham EGKA, United Kingdom
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