WAAS = OFF and RAIM check with GTN XI?

[Ibra]

Hello, 

In GTN XI, does anyone know how one checks GPS status? selects SBAS provider? get RAIM prediction? disable +V?

I would have expected these to work,

Home -> System -> GPS status -> SBAS
Home -> Utilities -> RAIM prediction -> “compute RAIM”

However, I can't find these in the menu? I was scratching my head in the hold trying to disable +V vertical guidance with no luck (it seems these options are not available when one receives WAAS augmentation)

 

Edited March 13, 2024 by Ibra

[PT20J]

I'm not clear what you are asking  I tried the paths you listed and I can select/turn off SBAS systems and do a RAIM check on the simulator.

I don't know how Garmin computes +V but it appears to use GPS without SBAS. This would work because it doesn't need precision-level accuracy.

What I noticed is that if I turn off SBAS, the PROC catalog for an airport changes LPV approaches to LNAV+V.

I don't think there is any way to disable +V. You can just ignore the GP and if the GFC 500 is in NAV rather than APR, the FD and autopilot will ignore it.

[PeteMc]

They are not in one place.  From the Home Page:

GPS Status = System > GPS Status

SBAS = System > GPS Status > SBAS (upper left on the Status page)

RAIM = Utilities > RAIM Prediction > Enter Wpt/Airport, Date & Arrival Time

No idea what +V is.  LNAV+V ???  Not something I would think you could disable and not sure why either.  What exactly are you looking for?

 

 

Edited March 14, 2024 by PeteMc

[Ibra]

Yes all the steps above work in GTN NXI/TXI simulator, I was referring to the steps in navigator while flying the aircraft, those menus just vanish whole airborne, I will do a screenshot next time I fly my friend aircraft...then they re-appeared inside the hangar 

15 hours ago, PeteMc said:

No idea what +V is.  LNAV+V ???  Not something I would think you could disable and not sure why either.  What exactly are you looking for?

The examiner wanted to disable +V in LNAV+V so that his student can fly 2D procedures like in the old days: counting distances & altitudes, he also wanted RAIM prediction...

I am not sure why one would disable augmentation or advisory glide in real life? I was told one need to tick EGNOS and untick WAAS while flying RNP in Greenland, honestly, if one need LPV minima there they are pretty much dead LOL 

Edited March 14, 2024 by Ibra

[Ibra]

17 hours ago, PT20J said:

What I noticed is that if I turn off SBAS, the PROC catalog for an airport changes LPV approaches to LNAV+V.

In G430W to an airport that has LPV & LNAV:

- If you disable SBAS 2nm before FAF while in TERM, you get LNAV+V using NAVSTAR only, as you said it's computed on GPS only 

- If you disable SBAS after LPV annunciation, it treats the lack of SBAS as integrity loss for an LPV, then fallback to LNAV without advisory glideslope 

In GTN XI, it seems one can't do RAIM, SBAS = OFF and can't disable official/advisory slopes 

Edited March 14, 2024 by Ibra

[PT20J]

2 minutes ago, Ibra said:

In G430W, if you disable SBAS 2nm before FAF, you still get LNAV+V using NAVSTAR only 

If you disable SBAS at FAF with LPV annunciation, it fallback to LNAV and ditch +V 

OK, but why would you want to do that? And, do you really want to be changing the navigation system at the FAF?

[Ibra]

11 minutes ago, PT20J said:

OK, but why would you want to do that? And, do you really want to be changing the navigation system at the FAF?

It seems to be a requirement for IFR exams here:

- You have to fly 2D CDFA without any slope and 3D precision on official slopes (ILS/LPV)

- You have to do RAIM computation at ETA in case SBAS is not available (it's a piece of theatre, I don’t think anyone has died because of lack of sattelites )

GTN XI seems to prevent both possibilities 

Edited March 14, 2024 by Ibra

[PT20J]

1 minute ago, Ibra said:

It seems to be a requirement for IFR exams here:

- You have to fly 2D CDFA without any slope and 3D precision with official slope

- You have to do RAIM computation at ETA (it's a piece of theatre, I don’t think anyone has died because of lack of sattelites )

GTN XI seems to prevent both possibilities 

Ah, I see.  You might talk it over with whomever will do the exam. If the avionics won't do it, it seems unreasonable to require it. 

[Ibra]

34 minutes ago, PT20J said:

If the avionics won't do it, it seems unreasonable to require it.

If it's not broken don't fix it 

I can't see why on earth flying +V while above MDA (or 2D MDAs) is problematic? I get it's advisory, it does not mean he should disable it 

Looking at recent mannual for latest units, it seems impossible and avionics won't let hime do it...I think my friend is going to get fried next week on NDB or VOR/LOC with distance and timer, let's hope he will not get to disable ground speed, wind vector, flight path vector, track diamond as they make flying non-precision easier (aka safer)

 

 

 

Edited March 14, 2024 by Ibra

[PeteMc]

3 hours ago, Ibra said:

those menus just vanish whole airborne,

3 hours ago, Ibra said:

The examiner wanted to disable +V in LNAV+V so that his student can fly 2D procedures like in the old days:

I'm pretty sure those menus are still there.  Seeing your GPS Status and RAIM Prediction are pretty important.  I'll try and remember to check on my box too.

And are there no VOR or plain RNAV approaches anywhere near you?  But even if you still had the V needle, if you do a step down the needle will just go off to the  top.  Sure it will come back when you reach the next stepdown, but you should still be able to demonstrate a basic RNAV approach without Vertical Guidance.  (Bet the DPE doesn't let the Private checkrides use an EFB either... )

 

 

[midlifeflyer]

I don’t know about the others, but if you are using ForeFlight, tap on Navlog from Flights, and you will see the RAIM check.

[Ibra]

41 minutes ago, midlifeflyer said:

I don’t know about the others, but if you are using ForeFlight, tap on Navlog from Flights, and you will see the RAIM check.

Thanks for this, I will give it a try next time using ForeFlight (seems quicker than using websites)

Edited March 14, 2024 by Ibra

[midlifeflyer]

15 minutes ago, Ibra said:

15 minutes ago, Ibra said:

Thanks for this, I will give it a try next time using ForeFlight 

The advantage when doing it in the GTN is that you can do it enroute. although the chance of a enroute change is very small. It’s a prediction after all.
 

In the GTN, it’s in the Utilities menu.

 

Edited March 14, 2024 by midlifeflyer

[Ibra]

Yes I see the menu in simulator/trainer, it was missing in aircraft when flying* (I will get a screenshot)

*I do see it in older GTN and GNS, it’s on 650XI v20. where it’s no longer there 

Edited March 15, 2024 by Ibra

[midlifeflyer]

2 hours ago, Ibra said:

Yes I see the menu in simulator/trainer, it was missing in aircraft when flying* (I will get a screenshot)

*I do see it in older GTN and GNS, it’s on 650XI v20. where it’s no longer there 

The button not there at all, or just greyed out? 

I haven’t seen anything, and have only needed RAIM prediction in one airplane I’ve flown in the past 10 years (used it last week) but I can almost see them removing it. If we are using RNAV routes for navigation, we need enroute RAIM prediction.  So tools like ForeFlight, FltPlan.com, and Garmin’s own  make more sense these days than one in which you might have to check a series of waypoints one at a time.

Edited March 15, 2024 by midlifeflyer

[PT20J]

If you really need a non precision approach without vertical guidance, you could select a localizer approach.

[midlifeflyer]

2 hours ago, PT20J said:

If you really need a non precision approach without vertical guidance, you could select a localizer approach.

True, but for things like a checkride or IPC, you currently need two nonprecision approaches using different systems. There are a few options (NDB, VOR, LPV with minimums >250) but sometimes it’s just more efficient to turn off SBAS. Plus, even above 250, there’s an element of reality in not having a glidepath or pretending there’s a “GS Unreliable” NOTAM for the ILS. And, for the surprise (but important) factor, there’s the pilot who doesn’t notice that LNAV is the only thing annuncuated.

Edited March 15, 2024 by midlifeflyer

[PeteMc]

1 hour ago, midlifeflyer said:

you currently need two nonprecision approaches using different systems

Is that still true, at least here in the US?  I thought they had changed that if the plane did not have a VOR/LOC/ILS receiver, the DPE could do different types of approaches with the GPS.  The point was to just demonstrate the ability to fly the different types and it did not need to be GPS vs Ground Based any more.  (Thought I read this actually changed quite a few years ago.)

[Ibra]

4 hours ago, PT20J said:

If you really need a non precision approach without vertical guidance, you could select a localizer approach.

Yes, ATC could disable GS with flip of button in tower or pilot can tune on CDI/VOR without slope, the catch is that LOC procedures here tend to require DME/ADF (at least when examiners are around ) for FAF/MAPT: it’s more efficient to enable & disable glide from WAAS navigator (*), do LPV then LNAV without having to go into a big airport that has an ILS/LOC 

The funny part is that for non precision approach some examiners accept “timed NDB” or “timed VOR” where you fly vertical speed on dead reckoning with stopwatch, however, they can’t get along with “LNAV+V” and want +V disabled, go figure !

(*) You still need to plan for non-GPS or have good weather at alternates 

Edited March 15, 2024 by Ibra

[midlifeflyer]

44 minutes ago, PeteMc said:

Is that still true, at least here in the US?  I thought they had changed that if the plane did not have a VOR/LOC/ILS receiver, the DPE could do different types of approaches with the GPS.  The point was to just demonstrate the ability to fly the different types and it did not need to be GPS vs Ground Based any more.  (Thought I read this actually changed quite a few years ago.)

There is a possible change pending.sorry, but my latest article is behind a paywall.

 

 

Edited March 15, 2024 by midlifeflyer

[PeteMc]

3 hours ago, midlifeflyer said:

There is a possible change pending.sorry,

I did some digging.  No change yet, but I believe there is about to be a change where you can use various GPS Approaches for the Checkride. (Which maybe is what you're implying too.)  And the change awhile ago I think was that you can use a LPV Approach in lieu of an ILS/Precision *if* the DA is below 300ft. 

 

 

 

 

[midlifeflyer]

10 hours ago, PeteMc said:

I did some digging.  No change yet, but I believe there is about to be a change where you can use various GPS Approaches for the Checkride. (Which maybe is what you're implying too.)  And the change awhile ago I think was that you can use a LPV Approach in lieu of an ILS/Precision *if* the DA is below 300ft. 

 

Yes. That change is in part what the article is about and the 300’ is in the excerpt of the ACS I posted (I mistakenly said 250 earlier). ”About to be” is a matter of perspective. The proposed rule and draft ACS have been around since December 2022. 

The proposed revision’s distinction for ACS purposes between precision and nonprecision would be whether the approach has official vertical guidance. For example, LPV would be precision, LP+V, nonprecision . And it replaces the two based on  “different systems” with being based on different tasks accomplished. The draft is available at https://downloads.regulations.gov/FAA-2022-1463-0034/content.pdf 

 

Edited March 16, 2024 by midlifeflyer

[airdogalpha]

I hope this is the correct thread.  Pls forgive me if is not.     I was flying my TXI, connected to a 750 today on a RNAV rwy 07 CYXX approach.      I joined the IAF at 3000 feet,   roughly nine miles back.    airplane flew it perfectly.   It confirmed LPV,     and captured the glide slope advisory.    The weird thing was the Diamond (advisory gS) was grey the entire way down to minimums, normally this is magenta.   (did it lose WAAS?)     I have never had this before.  I hunted and searched the txi and GTN manual.  Did word searches... I came up with nothing.  Anyone have any idea?         

Edited March 16, 2024 by airdogalpha

[PeteMc]

I believe Gray would indicate the CDI/VDI Preview mode. 

I don't have a TXI, but the manual says: For ILS and GPS approaches, the VDI provides a preview of glideslope or glidepath deviation.  

 

[midlifeflyer]

13 hours ago, PeteMc said:

I believe Gray would indicate the CDI/VDI Preview mode. 

I don't have a TXI, but the manual says: For ILS and GPS approaches, the VDI provides a preview of glideslope or glidepath deviation.  

 

That’s true for a number of Garmin PFDs.