NON-WAAS question

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Feilzer
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NON-WAAS question

Postby Feilzer » Mon Apr 17, 2017 2:59 pm

I am flying my DA-42 (S/N 42.017 with KAP autopilot) since 2005, and fly primarily traditional approaches (VOR/DME, ILS and ADF) and use the GPS primarily for 'en-route' and SID's and STAR's.
Investigating the need (or not) to upgrade to WAAS, I studied the G1000 pilot guide and other documents, but it is not totally clear to me, I am still left with several questions.
I understand that LPV approaches require WAAS.
But, how does the G1000 (RAIM okay and '3D NAV') present LNAV/VNAV approaches?
Will there be any vertical guidance? (albeit to higher minima) , or no guidance on the G1000 and simply use the descent information from the approach plate?

In the orriginal Garmin G1000 Pilot's Guide it states:
"If RAIM is not predicted to be available for the final approach course, the approach does not become active as indicated by the 'RAIM not available from FAF to MAP' messageand the INTEG annunciation flagging".
So, I assume that when RAIM is available, there will be guidance from FAF to MAP.

Question being: is that guidance lateral or both lateral and vertical.

In the Netherlands so far we only have one field with a RNAV approach, but the coming years all field will have to also introduce RNAV approaches.
In other European countries there are already many more GPS approaches.
I noticed that in general different minima are shown for LPV and LNAV/VNAV approaches.
Is the difference: WAAS/LPV and NON-WAAS for LNAV/VNAV approaches (but with guidance)?
I understand that in the U.S. there are already many GPS/WAAS approaches so I assume that there will be a lot of experience with U.S. Twin Star flyers.

Thanks for sharing your experience with me.

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Re: NON-WAAS question

Postby linzhiming » Tue Apr 18, 2017 7:55 am

Feilzer wrote:I understand that LPV approaches require WAAS.
But, how does the G1000 (RAIM okay and '3D NAV') present LNAV/VNAV approaches?
Will there be any vertical guidance? (albeit to higher minima) , or no guidance on the G1000 and simply use the descent information from the approach plate?



You are correct that LPV approaches require WAAS-enabled receivers and availability of the WAAS signal.

Non-WAAS G1000 will NOT support LNAV/VNAV approaches (often called Baro-VNAV approaches) but will support LNAV+V approaches.

LNAV+V approaches are essentially LNAV approaches with advisory vertical guidance and you need to adhere to stepdown fix constraints (which are sometimes ignored in the vertical guidance so watch out for terrain clearance issues in case of stepdown fix constraints!).

In general, LPV approaches have lower minimums than LNAV/VNAV approaches which have lower minimums than LNAV approaches. Please note that there are instances (due to terrain and required obstacle clearance requirements in the procedure designs) for this not to be true.

Whether it makes sense to invest in WAAS-enabled receivers would really depend on your use case requirements on approaches (I think there was a similar thread on this recently). LPV and LNAV minima can be quite close to each other at certain airports whilst they are not at other airports.

Different from FAA requirements whereby a WAAS-enabled GPS is required for sole reliance on GPS for enroute navigation and to be able to plan destination and alternates both based on GPS approaches, this is not a requirement in EUROCONTROL airspace as far as I know. As EUROCONTROL airspace essentially requires BRNAV (RNP5) for almost all enroute operations, this would otherwise mean that you would be unable to fly in EUROCONTROL airspace without WAAS.

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Re: NON-WAAS question

Postby Feilzer » Tue Apr 18, 2017 9:54 am

Thanks a lot for your explanation.
This is really helpfull.
You mentioned that LNAV/VNAV approaches are not supported. But, what does that mean?
How will these be presented on the G1000?
Will it not be possible to choose these approaches to load?
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Re: NON-WAAS question

Postby linzhiming » Tue Apr 18, 2017 10:23 am

Feilzer wrote:Thanks a lot for your explanation.
This is really helpfull.
You mentioned that LNAV/VNAV approaches are not supported. But, what does that mean?
How will these be presented on the G1000?
Will it not be possible to choose these approaches to load?


Correct, you will not be able to load LNAV/VNAV approaches, you would be able to load only LNAV approaches. This is similar to that you would not be presented with any LPV approaches.

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Re: NON-WAAS question

Postby linzhiming » Tue Apr 18, 2017 10:30 am

linzhiming wrote:
Non-WAAS G1000 will NOT support LNAV/VNAV approaches (often called Baro-VNAV approaches) but will support LNAV+V approaches.



I stand corrected on this as I just went through the AFM: Neither LNAV/VNAV approaches nor LNAV+V approaches are supported by Non-WAAS G1000, i.e. only LNAV approaches are supported. (Note: LNAV+V is still an LNAV approach to LNAV minimums but with vertical guidance supplied by the G1000.)

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Re: NON-WAAS question

Postby Feilzer » Tue Apr 18, 2017 10:56 am

I understand. The way you explain it, it is clear to me.
However, how to interpret f.i. The following Jeppesen approach plate:
RNAV (GPS) Rwy 23L (EDDL Dusseldorf)
Which gives both the minima for LNAV/VNAV and for LNAV.
May I assume that this approach will be loaded as a LNAV approach?
Anyway, I will check in the plane if, and how this approach would load.
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Re: NON-WAAS question

Postby Aart » Wed Apr 19, 2017 6:34 am

I am affected as well (non-WAAS G1000), and started to read up a bit on this.

AFAIUI right now the situation is as described above. So you can fly en-route on a non-WAAS G1000, and also fly LNAV approaches. You'll do that without vertical guidance, so basically like you would do any conventional Non-Precision Approach. Apparently the lateral navigation capability of a non-WAAS G1000 is precise enough to fly the current RNAV approaches, but the vertical navigation capability is not..

However, during the coming years (2018-2020) things will be changing because of the introduction of the "Performance Based Navigation" (PBN) and "Required Navigational Performance" (RNP) system. Each country in Europe will introduce this and some are further along than others. See attached info on the plans in the Netherlands as well as general background info.

This PBN/RNP allows for airspace to be used more efficiently by applying tighter lateral limits in airways, arrivals and approaches. Approaches will migrate to "precision" RNP-1 type approaches, as will STARs and SIDS and transitions to en-route. So that involves TMA's. So, rather than just abiding by higher minima, this means that that you would not be allowed to fly above procedures.. The on-board equipment needs to be suitable for more precise navigation (both lateral and vertical) so here is where WAAS (called EGNOS in Europe) comes in. NDB's/VOR's will gradually be phased-out. Some ILS/VOR's will continue to exist, mainly for back-up reasons.

AFAIUI en-route navigation would still be allowed with non-WAAS equipment. Indefinitely? If not, for how long?

Others will undoubtedly know more about this, please correct or chime in!

Introductie PBN in NL 20170111.pdf
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PBN Introduction.pdf
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Re: NON-WAAS question

Postby Feilzer » Wed Apr 19, 2017 10:45 am

Thanks for the additional information.
Today I also received the PBN documentation from the Dutch Diamond dealer including a cost proposal for the WAAS upgrade.
It seems that continuation of IFR flight in Europe in the not to far future makes an upgrade mandatory.
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Re: NON-WAAS question

Postby linzhiming » Wed Apr 19, 2017 11:31 am

Aart wrote:
This PBN/RNP allows for airspace to be used more efficiently by applying tighter lateral limits in airways, arrivals and approaches. Approaches will migrate to "precision" RNP-1 type approaches, as will STARs and SIDS and transitions to en-route. So that involves TMA's. So, rather than just abiding by higher minima, this means that that you would not be allowed to fly above procedures.. The on-board equipment needs to be suitable for more precise navigation (both lateral and vertical) so here is where WAAS (called EGNOS in Europe) comes in. NDB's/VOR's will gradually be phased-out. Some ILS/VOR's will continue to exist, mainly for back-up reasons.

AFAIUI en-route navigation would still be allowed with non-WAAS equipment. Indefinitely? If not, for how long?



I think there is some confusion on this: Enroute operations are generally RNP5, terminal operations are generally RNP1 and LNAV approach operations are generally RNP1 or RNP0.3. All those are supported by the non-WAAS G1000 and it is certified for that. That's "standard RNAV"/"standard LNAV". You see that by the CDI display shifting from "GPS ENR" (RNP5) to "GPS TERM" (RNP1) to "GPS LNAV" (RNP1 or RNP0.3) as you fly an RNAV route, then transition to an RNAV STAR and then an LNAV approach.

Vertical guidance has nothing to do with lateral navigation precision.

RNP AR approaches are not supported but they are not supported by a WAAS-enabled G1000 either. RNP AR approaches generally include RF (radius-to-fix) legs and are not supported by the G1000 in general. There was talk about the G1000 NXi potentially supporting RNP AR approaches.

See page 37 of the AFM at http://support.diamond-air.at/fileadmin ... mplete.pdf which says:

The Garmin GNSS navigation system as installed in this airplane complies with
' the equipment requirements of FAA AC 90-105 and meets the equipment
' performance and functional requirements to conduct RNP terminal departure and
' arrival procedures and RNP approach procedures without RF (radius to fix) legs.
' (RNP1, RNP APCH0.3 LNAV).


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Re: NON-WAAS question

Postby Aart » Wed Apr 19, 2017 2:53 pm

Thank you Wolfgang.

So what you are basically saying is that the only advantage of the WAAS/EGNOS upgrade would be that you get the luxury of vertical guidance on GPS approaches and that you would legally be able to fly to lower minima on most such approaches.

But it does not buy you anything on RNP AR approaches which you cannot fly legally regardless of this upgrade. So the current G1000 is a dead end for AR, and it would take an upgrade to NXi (maybe)?

How can I recognise on an approach plate whether it is an RNP AR one? Just by seeing a RF depicted? Or is there a code/name?

Need to think then before I spend 30k+ on a WAAS/EGNOS upgrade at this point in time..
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