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UK CAA heel dragging on GPS approaches, including LPV (merged)

ince 2003, all of the newly released GPS units have been installed in the US via an STC with an Approved Model List

The key is in the words "newly released", however.

AFAIK the non-W GNS430/530 did not have an AML STC, so most of those would have been done under the 337 / Field Approval process, to get legal GPS/RNAV capability.

And under EASA it was eventually a Minor Mod.

Maybe nobody was installing these in the USA, but lots were installed in Europe, right up to their discontinuation by Garmin. They became fairly cheap, especially when a certain retailer was selling them directly

Garmin never permitted them to be sold alone, without an installation, and while this could be circumvented (certain US avionics installers do sell the stuff direct, sometimes with an "experimental aircraft" wiring harness ) the only official way to get them alone was to buy a used one.

Would anyone with a brain actually fly an NDB approach other than by using a GPS if they have one?

Only on a JAA IR flight test, or similar.

The airlines fly them using their FMS (i.e. RNAV) but they have varying rules on what to do with the ADF. One commuter airline pilot told me they ignore the ADF but the NDB must not be notamed INOP. Others have said they need to tune in the ADF for "monitoring". One told me (with a smile) they are supposed to go around if the ADF indication goes out of tolerance.

or (3) it could be an engineering package generated by a DER authorized to work on the job

That is the process used in Europe nowadays to sidestep the non-cooperation of the NY IFU. Unfortunately it is pricey (I was quoted £1.5k+VAT for a pointless DER package for the TCAS installation, though some can be done for a few hundred quid) and it does not deliver the AFMS which you must have to fly GPS approaches legally. I have made enquiries with US contacts and while it is possible for a DER to produce an AFMS, very few of them have the authorisation. Certain avionics shops that use the DER route to get the 337 filed are/were delivering the finished install without an AFMS and of course the customer doesn't notice.

Thanks for the correction Silvaire - will do when I get back home.

Anyway, LPV would be great but I think it will be many years if ever before today's non-instrument GA airfields get any kind of IAP, never mind LPV, due to the mandatory-ATC requirement. Various people have tried to have a go at it, and some encouraging noises came out of meetings with the CAA over the years, but nothing happened.

What would be good would be a means of flying a DIY-LPV approach (on autopilot) and while it is fairly easy to work out how to do that, it will never ever be legal.

Shoreham EGKA, United Kingdom

No. Many people have made that mistake. The 430W cannot be just screwed into the panel (like many thousands were). Such an install is not even legal for IFR enroute.

I don't believe that. Procuring a GNS430W is not simple and I do not know a shop that would just install it without the paperwork. It's not a simple job after all. Maybe such installs exist but that must be a rare thing. I checked the AFMS that I received as part of the GNS430W installation and it clearly mentions LPV among all the other methods and explicitly approves the use of coupled AP. I consider myself to be properly equipped and licensed for LPV approaches.

Even flying into Europe, I have never come across a case myself where the airport I am going to, which must have Customs, and is IFR capable, doesn't have an ILS but does have a GPS approach (of any kind, never mind LPV).

I mentioned this before: Germany has a lot of airfields that match exactly those criteria. Very few GA airfields have an ILS due to the cost but a large number are desperate to get an instrument approach because their raison d'être is usually to serve the local businesses and those companies demand an IAP.

Here in the UK, many of the old GNS430s just "went in".

It is easy to install in a basic way, because it can be used as an analog GPS i.e. analog deviations etc - not ARINC 429 which is what you would use to control a modern autopilot. There are ready-to-eat wiring diagrams for wiring it to a CDI or HSI, so all the stuff which worked before works afterwards, the same way. These wiring diagrams are intended to allow installation without much functionality understanding - necessary in the wider marketplace IMHO.

One installer I know who put in loads of them didn't used to connect up the HSI course pointer outputs to the GPS, so the OBS bearing has to be set separately on the GPS. This is also fairly common.

I agree few of the GNS430W went in that way, but not many people would install the W unless they had a specific IFR requirement, given the price of used non-W units.

In the past I got quite a few avionics quotes, including a complete GNS430W+GNS530W refit of my TB20, which were quoted on the basis of "all certification is the customer's responsibility".

I think Germans stick to the rules a lot more Keeps certain avionics firms (e.g. one named after a nearby town) in business!

Are there many German airports which have Customs and whose only IAP is a GPS one? That was one of the criteria I used in the past to decide whether the KLN94 legality was worth sorting out, because if the airport has a VOR or NDB IAP, that can be flown with any GPS without any approvals, so long as you "carry" the VOR and ADF boxes.

Shoreham EGKA, United Kingdom


Here in the US, we are only permitted to fly the final approach segment of a ground based approach with the associated VOR or ADF equipment and the ground station must be in operation. The GPS may only be used for situational awareness. In practical terms, this means that the appropriate navigation equipment must be installed, operating, and displaying the course deviation information on a CDI/RMI/ADF indicator. If the latter conditions are met, for example on a #2 VOR, the GPS course data may be presented on a #1 CDI and interfaced to the autopilot. However, in this instance, if the #2 CDI ... indicates that the approach is outside of the required parameters, the approach must be abandoned, even if the GPS indicates on course. If the procedure has a GPS overlay then the title will be something like "NDB or GPS RWY 12". With overlay approaches, the NDB does not need to be operating and the equipment does not need to be installed in the aircraft. Originally, most GPS procedures in the US where overlay approaches, but now they have been largely eliminated as RNAV (GPS) procedures have been added. With WAAS, almost all straight in GPS approaches have vertical guidance via a glideslope including either a LPV , LNAV/VNAV. Where the procedure doesn't have official vertical guidance because there is just a LNAV option, the WAAS GPS units provide an advisory vertical guidance (not official GS) that is permitted to be used between the FAF and the MDA, but never below the MDA as cumulus granite or other obstacles may be on the glidepath. The advisory vertical guidance (annunciated as LNAV+V) works in every respect as a normal glideslope and a capable autopilot will couple to it.

KUZA, United States

The GNS430W STC includes a PDF file that merely has to be printed out by the installer. The installer hand writes in the N number on the title page and checks a few appropriate boxes. The document is not character based and can't be easily modified. It also includes the FAA approval signature already on the document image. I did an OCR of the document that I use from time to time to include text portions in posts.

KUZA, United States


Looks to me like the applications for LPV approaches are being driven by low-end commuter ops e.g. Islanders? That is the business which drove the Alderney one.

These knackered old heaps avoid hazardous weather by flying below it, and are used to serve the islands, from coastal mainland airports where that kind of flying works OK.

There is very little GA activity at these places.

Shoreham EGKA, United Kingdom

Had to do a plain old ILS back into Oxford tonight.

I think GPS approaches give places that don't want to spend the money on an ILS the ability to add "precision non-precision" approaches.

Even an LNAV+V in my experience could be flown to the threshold.

EGTK Oxford

I think GPS approaches give places that don't want to spend the money on an ILS the ability to add "precision non-precision" approaches.

LPV is officially a precision approach (definition: lateral + vertical guidance) and is identical to an ILS CAT I. There is nothing an ILS CAT I can do that an LPV approach couldn't.

I know. I was referring to LNAV and LNAV/VNAV which are very accurate even though not actually precision.

EGTK Oxford

The fundamental problem in the UK is that the CAA can't stand new technology and only tolerate ILS and MLS and CAT3 because the airlines insist and they can't bully the airlines

Gloucs, United Kingdom
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