EGNOS and LPV

[SunnyDayInWiltshire]

** UPDATED IN LIGHT OF REPLIES THAT FOLLOW, so some of the replies later in the thread may no longer make sense.

I confess to bring a bit confused about the current state of EGNOS (the European equivalent of WAAS) and do did some research. Are my assumptions below correct and have I missed anything obvious?

1) An aviation GPS receiver is more sophisticated than a car SatNav, including features such as RAIM which double check the integrity of the signal received. Often GPS receivers are connected to other instruments such as a CDI or HSI, this being a requirement if used for IFR flight.

2) EGNOS provides extra information to a GPS receiver which allows it to achieve accuracy of 1-2 metres compared to the normal 19 metres, both horizontally and vertically. This is a wide-area augmentation system that is more accurate than and not the same as Differential GPS (as explained in approved for "Safety of Life" applications such as aviation approaches in March 2011. It covers all European countries and even parts of North Africa

5) Most UK GPS approaches are classed as a non precision approach and don't provide a glide slope - they are similar to an NDB/DME or ILS localiser only. EGNOS is NOT required for this type of approach. Navigation equipment to handle these Non Precision Approaches can often be installed as an EASA minor mod.

6) A more sophisticated GPS approach is called an LPV which also provides a glide slope just like an ILS. These all require EGNOS to be fitted to be used legally. If the EGNOS signal is not received then the GPS approach cannot be used. Most GPS LPV installations would require a very expensive Major Mod, but Garmin has obtained generic approval for their GTN series which means they can be installed for LPV as a minor mod only (see detailed reply below) Today there is only one in the British Isles today at Alderney - next is Southampton in March, while France now has four (see list)

7) An IMC rated private pilot probably legally may require further training to use a GPS or LPV approach, regardless of which this might be sensible

8) Fitting an EGNOS capable GPS such as the 430W is not normally a Major Mod, for non-precision approaches, but for LPV would require one and be ludicrously expensive. Garmin has obtained a generic EASA approval for their GTN 750/650 series which means they only require a minor mod.

9) LPV and GPS approaches are available to EASA and Annex II IFR capable aircraft, (not to Permit or VFR only)

10) Unlike in the US, in Europe all GPS approaches must be manned by full ATC service (not a FISO or A/G) when used, but needn't have radar. This will limit the rollout of GPS approaches outside those which already have some form of instrument appriach today.

Thanks in advance

SD

*Editted to incorporate clarifications and corrects from later replies 19/2/12

[Sir George Cayley]

Well I'd say that's a good attempt. But there's many more in the know posters who'll be along soon.

It will be interesting to see if those airports like Gloucester that have a non precision GPS approach will upgrade to full LPV?

SGC

[mm_flynn]

Broadly OK.

Point 5 is not true, you do not need EGNOS or a W capable receiver for normal GPS approaches (GPS approaches have been legal in the UK for some time before the EGNOS SOL signal was available). However, Point 6 Should highlife that the EGNOS signal is required for LPV approaches.

Point 7 - I believe for a Greg operator you are supposed to have differences training on this. Although I am not sure (I certinly made a point to get a sign off in my last renewal)

Point 8 - I am not sure this is true for G reg (and virtually any avionics install could be described by the man on the street as 'ludicrously expensive')

[smitn05]

HI SD

A few things to throw into the mix that may help, or possibly may confuse you some more!!

On point 1 you say often a CDI / HSI is interfaced to the GPS. In fact to be able to certify the GPS functionality for IFR use (and hence carry out things like LPV approaches) a CDI / HSI is a requirement.

On point 5, WAAS capable equipment is required for LPV approaches but NPA approaches can be carried out on non-WAAS GPSs. Many aircraft have been approved to fly NPAs by showing the installation is compliant with the information contained within CAA publication CAP773, although in recent weeks this method of approving NPAs has been recinded on new applications.

On point 8, things get interesting. The installation of a GNS430W (single unit only, dual installs are always STCs) can be carried out via EASA Minor change. Previously (until LPV) this could also include the IFR approvals for the GPS for BRNAV (Enroute) and NPA operations either as part of the Minor change or as a retrospective Minor change (to remove an existing GPSs 'VFR only' restrictions). Part of this IFR approval includes checking that the GPS has a CDI installed with mode selection annunciation, that it is connected to an encoded altitude source as well as checking software levels on the unit.

However, currently to approve a GPS installation for LPV operation is via an EASA Major change (STC). For something like a GNS430W this could be considered the ludicrously expensive part of the work

To muddy the waters further, the new touchscreen GTN750 / 650 units (GNS series replacements) were decreed by EASA to require an EASA Major change for every installation. Garmin realised that this effectively killed the possibility of sales in Europe of the new units and set about validating the FAA AML STC with EASA, thus allowing a pre approved EASA Major change to be used to install this equipment. This has now been granted by EASA for hundreds of aircraft types and this STC includes IFR approvals including LPV, with the caveat that an EASA Minor change should also be carried out for each airframe type to cover off the non-generic parts of the modification.

This effectively means that LPV approving a GTN series unit is via a free Garmin provided STC with purely a relatively cheap EASA Minor required to be paid for to install it, whilst the GNS series unit would require a Minor to install it but a chargeable STC to LPV approve it - simplez huh!!

I would suggest a call to your friendly DO / Installer to get prices etc as you can see its not that straightforward, the guys at Fairoaks have a lot of experience in getting through the certification maze.

Hope this has made it all crystal clear !!!!

[SunnyDayInWiltshire]

Thanks for the detailed and informative replies. For me, this is Pprune working at its best to inform pilots through its combined expertise

I've updated the original post based on the replies to date to make it more accurate for subsequent readers

A couple more questions though:

1) while advisable, is it really legally required to have additional training to be allowed to use an LPV approach? An IMC pilot may not have tried all the various types of approach during training, eg I have never made a VOR/DME approach, but would still be legally allowed to do one.

2) German EGNOSS approaches are all APV Baro according to this document, which implies that EGNOSS is required to use them. Here in the UK, Cambridge airport also announced an APV Baro GPS approach. So are all non LPV approaches APV Baro and if so, why do only German ones require EGNOSS?

Thanks again for the helpful replies so far.

SD

[peterh337]

1) No.

Advisable, of course, but then knowing what all the knobs in your plane do is very advisable

And you need to have a much deeper knowledge of "knobs" to fly GPS/LPV than to fly an ILS for example.

Most pilots who fly behind an IFR GPS don't understand how to drive it to the full. That is fair enough if you are not using the extra modes. For example I never bothered to learn the full GPS RNAV approach + missed approach waypoint sequencing (or not sequencing) peccadiloes of mine until recently. For LPV ops you do need to read the manual and learn it.

2) No idea what that means. All LPV approaches do need EGNOS (WAAS in the USA).

There is a level below "full LPV" whereby the GPS shows a "glideslope" which is not the actual ILS-like LPV glideslope but is in fact the continuous descent profile depicted on the approach plate. And with suitable avionics this too can be flown using an autopilot, like an ILS. The minima are the nonprecision published minima. The benefit of this is that you get continuous vertical guidance. You need EGNOS for this too.

I don't follow the details of this stuff because my GPS is RNAV approaches only, and it would cost me about £20k-40k to get LPV (or PRNAV for that matter).

[Gulfstreamaviator]

LNAV / VNAV

Is the level below LPV.

The Slope is based on the FAF, and the threshold.

Note the relevent mins are different, do not confuse.

glf

[peterh337]

I have just looked up the EGSC 05 and 23 RNAV approaches and the minima are the same on LNAV/VNAV and LNAV/CDFA.

Maybe that is a coincidence?

But if the slope is based on what you should be flying on a CDA approach, why would the minima be different?

Maybe we have wires crossed.

[bookworm]

There are three levels of minima:

1) LPV, which must use SBAS (EGNOS) for vertical guidance.

2) LNAV/VNAV can in principle derive its sub-LPV-precision vertical guidance from either BaroVNAV or SBAS (EGNOS). I don't think that the SBAS flavour is yet incorporated into the relevant EASA AMC though. So in practice most such approaches are flown using BaroVNAV

3) LNAV has no proper vertical guidance. However, an SBAS (EGNOS) will display the advisory glideslope as "LNAV+V". But your minima are the same as for the LNAV only non-precision approach, with no "credit" for the glideslope.

Heathrow 27L has LNAV/VNAV minima that are lower than the plain LNAV minima by 120 ft.

[IanSeager]

1) An aviation GPS receiver is more sophisticated than a car SatNav, including features such as RAIM which double check the integrity of the signal received. Often GPS receivers are connected to other instruments such as a CDI or HSI, this being a requirement if used for IFR flight.

Yup

2) EGNOS provides extra information to a GPS receiver which allows it to achieve accuracy of 1-2 metres compared to the normal 19 metres, both horizontally and vertically. This is a wide-area augmentation system that is more accurate than and not the same as Differential GPS (as explained in approved for "Safety of Life" applications such as aviation approaches in March 2011. It covers all European countries and even parts of North Africa

Yup

5) Most UK GPS approaches are classed as a non precision approach and don't provide a glide slope - they are similar to an NDB/DME or ILS localiser only. EGNOS is NOT required for this type of approach. Navigation equipment to handle these Non Precision Approaches can often be installed as an EASA minor mod.

Strictly speaking, all RNAV (GPSS) approaches are non-precision, even those with vertical guidance. That has more to do with the ICAO definition of a precision approach than anything else though. A WAAS/EGNOS enabled GPS will pick up a glideslope on an LNAV approach if it has been coded. This will enable you to fly a continuous descent to the MDA. You can fit a GTN650 or GTN750 to an EASA aircraft with an existing STC and a minor mod.

6) A more sophisticated GPS approach is called an LPV which also provides a glide slope just like an ILS. These all require EGNOS to be fitted to be used legally. If the EGNOS signal is not received then the GPS approach cannot be used. Most GPS LPV installations would require a very expensive Major Mod, but Garmin has obtained generic approval for their GTN series which means they can be installed for LPV as a minor mod only (see detailed reply below) Today there is only one in the British Isles today at Alderney - next is Southampton in March, while France now has four (see list)

To fly an LPV approach you need the kit and the correct flight manual supplement. For the GTNs you only need the minor mod (Garmin included LPV in the FMS) - for a 430W or 530W you will need an STC unless you fly a Beechcraft (GAMA Engineering has an STC for Beechcraft piston aircraft and I think the King Air. - I understand it is working on an STC for some Piper aircraft too. That STC has the FMS)

7) An IMC rated private pilot probably legally may require further training to use a GPS or LPV approach, regardless of which this might be sensible

I don't know about a legal requirement, but it would obviously be very sensible.

8) Fitting an EGNOS capable GPS such as the 430W is not normally a Major Mod, for non-precision approaches, but for LPV would require one and be ludicrously expensive. Garmin has obtained a generic EASA approval for their GTN 750/650 series which means they only require a minor mod.

Yup

9) LPV and GPS approaches are available to EASA and Annex II IFR capable aircraft, (not to Permit or VFR only)

…and to N reg of course

10) Unlike in the US, in Europe all GPS approaches must be manned by full ATC service (not a FISO or A/G) when used, but needn't have radar. This will limit the rollout of GPS approaches outside those which already have some form of instrument approach today.

Full ATC (at destination) is certainly required in the UK (apart from at some discreet approaches - and for discreet read private). That is not the case everywhere else in Europe, certainly not France.

HTH

Originally Posted by peterh337

I don't follow the details of this stuff because my GPS is RNAV approaches only, and it would cost me about £20k-40k to get LPV (or PRNAV for that matter).

That seems like a lot of money to get a GTN650 or 430W fitted

Ian

[wigglyamp]

Excessive cost.

I think a fully-integrated GTN650 in peter337's TB would cost between £11k and £13k + VAT - significantly less than he imagines. He doesn't need an EFIS H.S.I for Prnav and certification is covered under the FAA AML to include LPV.

[peterh337]

10) Unlike in the US, in Europe all GPS approaches must be manned by full ATC service (not a FISO or A/G) when used, but needn't have radar. This will limit the rollout of GPS approaches outside those which already have some form of instrument appriach today.

Not actually true but de facto true

The UK CAA, and I believe any other European CAA, does not mandate ATC sitting in the tower of the IAP destination airport.

What is mandated is an approach controller "somewhere".

In the USA, the ability to fly approaches to unmanned airfields is dealt with by having a nearby approach controller. He is paid by the FAA which is in turn paid by fuel taxes etc. So the airfield with the IAP does not get billed for the service.

The same could be done in the UK but because we have privatised ATC, the employer of the approach controller will send a bill to the said airfield. The level of billing (e.g. the pro-rated NATS overhead of an ATC desk) is very high (6 figures a year, plus) and almost no "GA" airfield would be able to afford it, relative to the extra traffic it "might" generate.

An example is Biggin Hill which gets an approach radar service from Thames Radar, and gets billed for that. This is why Biggin plates say that the procedural service is available only if Thames Radar is not operating Presumably Thames bill Biggin at a flat annual rate so Biggin wants to get its money's worth Biggin is not a great example because they do have ATC in the tower, but Walney Island EGNL is a better one, where the on-airport man is a FISO and the approach controller is remotely located (and in paid by BAE, I believe).

So the chances of GPS approaches spreading to places like Goodwood are very slim. On top of that you have approach design costs, etc.

To make a breakthrough in this, one would need to permit non-ATC (basically AFIS or A/G) people to do approach scheduling, and that would be a very hot potato politically. It would be fiercely resisted, due to undermining ATC pay scales etc.

That seems like a lot of money to get a GTN650 or 430W fitted

I think a fully-integrated GTN650 in peter337's TB would cost between £11k and £13k + VAT - significantly less than he imagines. He doesn't need an EFIS H.S.I for Prnav and certification is covered under the FAA AML to include LPV.

It would be a lot more by the time one rips out the KMD550 MFD (which is not Garmin-compatible in the OBS mode) replaces it with something else, and sorts out all the other loose ends.

Also I would not install the GTN product because it is too new, is totally unproven in terms of long term reliability, and has firmware bugs which need to be worked out.

If pressed I would put in a GNS430W and perhaps one of the Avidyne MFDs (avoiding the one which is barely visible in sunlight - EX500 or EX5000?).

Or more likely wait till the GTN products have been out for a lot longer.

A 430W by itself is too small to fly with, IMHO. It needs an MFD. It is like my old KLN94 in terms of functionality (and a useless small screen) except that it is PRNAV approvable and can support LPV. The GTN650 is not much bigger; it still needs an MFD.

The bottom line is that GPS approaches are not operationally relevant in the UK and anywhere else I fly to, LPV far less so, and PRNAV is not mandatory (yet) for enroute airspace.

[bookworm]

The UK CAA, and I believe any other European CAA, does not mandate ATC sitting in the tower of the IAP destination airport.

And conversely, the FAA does mandate approach control, but as you say, the ATC is provided remotely. There's no real difference, apart from the willingness of the taxpayer to pay for it.

In France, IAPs to unmanned fields are routine, with a remote approach control (often seems to be the SIV).

In Germany, at class F fields, approach is remotely provided but an AFIS is required on the field as well.