S

Sid Lambert

Well Known Member
This topic has been discussed but I can't find any definitive information on the subject.

Is it lawful and/or possible to use the GRT GPS with waas to shoot a precision approach?

I am starting to buy pieces of my panel and think waas is the way to go but I'm trying to save money as well. This would save the GNS-430W purchase if it were possible.

In mind for IFR related pieces...
GRT w GPS and XM Weather
SL-30 no analog CDI
TruTrak ADI II

I'm opening to flaming... I mean opinions but would like fact as well.
 
Sid Lambert said:
Is it lawful and/or possible to use the GRT GPS with waas to shoot a precision approach?
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In mind for IFR related pieces...
GRT w GPS and XM Weather
SL-30 no analog CDI
TruTrak ADI II
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Get the 430W! I'm not sure if the GRT GPS has the GPS/WAAS IFR procedure waypoints in the database, but even if it does it still would not have the TSO C129/146a paperwork and would probably make it NOT legal if you were ramped checked after an approach with it only in IMC. As with so many things with the FAA (and government in general) it's all in the paperwork, no matter what the hardware can do.
 
I think so

There are many varying opinions, but after searching around the web I reached the conclusion that as long as the unit has suitable accuracy monitoring and warning (RAIM equiv) and a current data base, it's ok in a homebuilt.

I have more to say about it, but I'll await the flaming.
 
Transporter said:
See http://members.eaa.org/home/homebuilders/faq/Equipping a Homebuilt for IFR operations.html for the EAA opinion regarding GPS.
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So for Transponders and GPS, the equipment must "must meet the performance requirements of the applicable TSO" and "if the equipment is not built under a TSO authorization, it is up to the owner/operator to verify and document that the equipment performs within the required specifications." It think GRT will say it meets TSO but I bet they will NOT give you documentation verifying that so you will be on your own.

Much easier and more comforting (at least to me) to just get something built under a TSO for GPS and Transponders.
 
Good information in the posts above - there is a lot of variability of opinion. In addition to that, the GRT WAAS GPS hasn't been released yet, so it's hard to tell how it fits in for sure. I'm looking forward to seeing my first one and finding out how they plan to handle databases and the like. Based on GRT's track record, it will come out when they feel it's ready, and not before!

Paul
 
Good question, but first..

Before you get to the question of precision WAAS approaches with GRT, you have to decide if it's even legal to use the GRT (with internal GPS) for IFR at all. I'm not talking about using it like a handheld, but filing "/G" based solely on the GRT and not on a (for instance) 430/530.

IMHO, it is not legal. I won't rehash the excellent responses above because they are mostly dead on. Either it must be TSO'd or it must meet the standards and you would have to determine that (I believe this implies actual testing) and probably make appropriate log entries to support and attest, etc. Based on some exchanges I've had with GRT, that is simply not possible to do with any honesty. BTW, RAIM is a major part of the requirements, but not all of it. From what GRT told me, they don't even support all the required aspects of RAIM.

I have a GRT dual screen setup and I wish I could file /G, but I don't believe I can (without a certain, risky, amount of indefensible exaggeration).

Finally, I see nothing in the regulations to support the idea that the Experimental category is any differently regulated in this area.

Good luck with that!
 
hevansrv7a said:
I have a GRT dual screen setup and I wish I could file /G, but I don't believe I can (without a certain, risky, amount of indefensible exaggeration).
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I actually agree with you, which is why I personally drive my GRT dual screen with a certified 430 system....since we really don't know anything about the (future) GRT WAAS GPS, I reserve judgment based on additional data - but for now, I prefer to keep a known IFR GPS engine to drive my integrated system.

Paul
 
Paul, with that being the case, why not get a dynon and 430W if the internal GRT GPS is somewhat questionable for IFR which I definitely plan on?? GRT is great but Dynon seems significantly cheaper if you're going to use cerified external GPS??

I am a long way from building my panel so know very little about this hence the question, not a GRT flame in any way.

Thanks.
 
I'm sure Paul can answer with more authority on this but my understanding is the GRT requires no outside assistance to keep itself stabilized. The Dynon requires air speed from the pitot to keep itself stabilized. Others use GPS.

So for heavy IFR the GRT would potentially be the best of the experimental EFIS systems since it does not rely on external information.

I'm riding a 3 way fence with Dynon, AFS and GRT right now.

grantcarruthers said:
Paul, with that being the case, why not get a dynon and 430W if the internal GRT GPS is somewhat questionable for IFR which I definitely plan on?? GRT is great but Dynon seems significantly cheaper if you're going to use cerified external GPS??

I am a long way from building my panel so know very little about this hence the question, not a GRT flame in any way.

Thanks.
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I had a discussion with GRT on this topic a while back. They were quick to point out that the current GPS has WAAS (just like a lot of handhelds). What it doesn't have, and what the new one will, is RAIM.

Then there's also the issue of the DB which I presume their long discussed option for Jeppesen data would address.

Bob
RV-10 #40105
 
grantcarruthers said:
Paul, with that being the case, why not get a dynon and 430W if the internal GRT GPS is somewhat questionable for IFR which I definitely plan on?? GRT is great but Dynon seems significantly cheaper if you're going to use cerified external GPS??

[\QUOTE]


I talked a bit about this in a thread the other day:

http://http://www.vansairforce.com/community/showthread.php?t=24375


The bottom line is that I believe the GRT to be a very stable, highly reliable system that is much more fully integrated than the Dynons. I think that the DYnon is an excellent gyro replacement unit, but I like and understand the AHRS design of the GRT and am very comfortable with it in IFR.
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Sid Lambert said:
So for heavy IFR the GRT would potentially be the best of the experimental EFIS systems since it does not rely on external information.

I'm riding a 3 way fence with Dynon, AFS and GRT right now.
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I think we need to take a system approach here. The EFIS is a very important part of the avionics system, but it's still only a part. The suitability of each different vendor's EFIS for IFR depends on what you expect it to do within the context of the system.

For example: If I want the EFIS to display flight instrument and engine monitor data, any will work. If I want it to act as a HSI, all of the "big three" will work, although you might need ARINC429 converter options. If you want the EFIS to act as an approach certified GPS/FMS and file /g, I think you're limited to Chelton and Garmin, at least at the moment.

My thought is that I want an EFIS to display flight and engine data and have a HSI. I will leave determination of nav and approach data to the certified boxes, e.g., SL30, G480, etc.

IMHO, the big differentiation comes when you want to add a moving map, multiple screens and an autopilot. GRT has the most flexible system that integrates well ("plays well with others"). AFS and Garmin have the best screens in terms of size, resolution and brightness. Enigma is the lowest cost, particularly for VFR installations.

It's nice to have choices.

TODR
 
GRT IFR

I started out with a dual GRT Sport with GPS in my 9A. I am currently waiting for Stark to ship my 430W and 106 GS indicator so I won't have to wonder if I'm legal anymore. I love the GRT system and am glad I installed it.

Joe Ramotowski
 
the_other_dougreeves said:
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For example: If I want the EFIS to display flight instrument and engine monitor data, any will work. If I want it to act as a HSI, all of the "big three" will work, although you might need ARINC429 converter options. If you want the EFIS to act as an approach certified GPS/FMS and file /g, I think you're limited to Chelton and Garmin, at least at the moment..
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Only Garmin unless you mate the Chelton with the Freeflight 1101 GPS. The Freeflight 1101 is an optional ($$) add-on component to the Chelton EFIS. Without the optional 1101, you CANT file /g with the basic Chelton and the built in GPS-IMHO.
 
grantcarruthers said:
Paul, with that being the case, why not get a dynon and 430W if the internal GRT GPS is somewhat questionable for IFR which I definitely plan on?? GRT is great but Dynon seems significantly cheaper if you're going to use cerified external GPS??

I am a long way from building my panel so know very little about this hence the question, not a GRT flame in any way.

Thanks.
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Grant,

You first have to make the distinction between a "flight" instrument and a navigator. The current generation of EFIS for the most part, with the exception of the G900X, are "flight" instruments. And then there are TSO'd GPS are navigators. Even in the G900X, the EFIS and the navigators are separate line replacable units (LRUs). Only the screen/interface integrates them together.

The inclusion of basic GPS systems in EFIS does not make them full fledged navigators. Basic GPS engines are so inexpensive nowadays that it cost very little for a manufacturer to add it to their EFIS in order to increase the perceived value. The EFIS needing or not needing GPS aiding has little to do with its applicability as an approved navigation device or a good IFR platform. GRT/AFS, etc put all the pieces together for a reliable and stable flight instrument, but you still need an approved GPS navigator to navigate with WAAS in the national airspace system. The GPS included with most EFIS systems is not suitable for this task-IMHO.

Once you start flying IFR, and doing GPS approaches, the distinction will become clear.
 
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bcondrey said:
I had a discussion with GRT on this topic a while back. They were quick to point out that the current GPS has WAAS (just like a lot of handhelds). What it doesn't have, and what the new one will, is RAIM.

Then there's also the issue of the DB which I presume their long discussed option for Jeppesen data would address.

Bob
RV-10 #40105
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And remember there are two kinds of RAIM. There is RAIM - FD (TSO-C129) and RAIM - FDE (TSO-146/a). Which one will GRT support? In my opinion, none of the GPS built in to any of the experimental EFIS, except Garmin 900x which is basically a headless 430w, are suitable for IFR navigation. Most however are suitable for IFR flight. If you don't see the distinction, hurry up and get that IFR rating:eek:
 
There are two questions here:

1 - Is this legal? - In Australia it is a little more clear cut. In the US might be open to interpretation. In addition, legal is the bare minimum requirement. It doesn't necessarily imply safe or ideal.

2 - Legal or not, is the pilot prepared to fly it in IMC to minima? - The first step to deciding this is to get educated about what TSO compliance entails. One good place to start reading is here -> http://www.casa.gov.au/download/CAAPs/ops/179a_1.pdf. The FAA may have a similar document but I am not aware of US documentation.

I don't own anything GRT in my panel, but my personal view is that GRT and other experimental or not TSO'd GPS units do not meet my comfort level for approach to minima. Having a WAAS compliant GPS is a very small part of the equation. Navigation above LSALT, no problem with Jeppesen database and RAIM. Approaches non-precision or precision no. Thus question 1 is largely irrelevant to me.

One of the biggest questions in my mind with all these EFIS units is that of pilot "certification" of firmware upgrades. How can you be sure that when you upgrade your EFIS to the very newest whiz-bang code and head off into IMC that something is not going to fail during an approach or any other flight phase? Are you going to retest your panel under the VFR? I will. And from time to time this may mean I do not upgrade my EFIS as soon as new firmware is available.

Richard
RV7A - Finishing
 
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Garmin as Navigator, GRT as a Display....

Just to make sure that people don't misunderstand me, here's how I consider the various parts of my system:

My GRT is an outstanding attitude platform and navigational display. I ave done a LOT of research, including what EAA has to say on the subject, and I do not believe that the display for the GPS system needs to be TSO'd. Some will disagree - forever - and some will agree.( As a matter of fact, you can probably find two FSDO's that would disagree and get them fighting between each other - might be fun!) The GRT also fully integrates systems monitoring functions and fuel calculations, as well as adding situational awareness calculations based on navigation and systems data (such as fuel state at various waypoints, winds aloft affect on ETA's, MPG, SFC, etc....) to increase situational awareness. In addition, it provides some very well thought out display methods for instrument approach guidance (Highway in the Sky) along with more traditional (needles o bars) guidance. Fly the HITS once, and you'll know how easy it is - and since it is driven from the exact same data as the needles, it is plenty reliable.

My Garmin 430 is a fully TSO-compliant and certified GPS navigator which uses the GRT to display it's data.

My TruTrak Pictorial Pilot is a great autopilot which integrates exceptionally well with the GRT EFIS and serves (as well) as a back-up flight instrument and attitude platform. For additional redundancy, I have a second GPS (non-IFR) which can drive the EFIS in an emergency situation (the 430 goes up in smoke for instance).

On top of all of these devices, my Garmin 396 provides yet a third GPS (non-IFR certified) and all of the valuable weather information.

The 430, GRT, and 396 all provide navigation information, the 430 being the only legal one for IFR, and the 396 being second in usability. Of course, that is at the current time. Software is always being updated and improved for the GRT. One nice feature f the GRT is that I can run an internal Flight plan that is different from the external plan provided by the 430, and compare the two for alternate routings.

It's all about situational awareness - the GRT provides and excellent system approach to integrating all of the available data - and makes a great display for the 430 data!

Paul
 
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