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Need help understanding IFR Navigators

R7237

Well Known Member
I might be showing my ignorance, but here goes:
What does an IFR navigator (like GPS-175) provide that a WAAS GPS (like SV-GPS-2020) does not,, other than TSO certification?
I am building the panel on an RV-12iS build as an EAB that I want IFR capability to use for Trainning purposes. I can add a nav radio (like Val NAV 2k) and take care of ILS/GS/VOR, but am trying to decide the need for a GPS-175 vs just using the SV-GPS-2020. Obviously price is the concern ($4250 vs $500). The airplane will have an autopilot.
Does the GPS-175 allow for RNAV approaches that the SV-GPS-2020 does not?
The airplane will have an AFS-5500 as the primary flight EFIS and the Dynon SV autopilot.

Thanks in advance.
 
Your AFS display will not have the capability to load approaches, pure and simple, whereas the GPS-175 will. Keep in mind that the GPS-175 is a full-fledged GPS navigator unit, whereas the SV-GPS-2020 is simple a GPD receiver puck whose sole purpose is to provide position data to a compatible EFIS screen.
 
The Garmin adds enroute and terminal IFR navigation and GPS based approaches. Whereas, the Dynon hockey puck only gives you an ADS-B out position source and VFR Navigation.

You could file and fly IFR with ILS/VOR. But, once you fly IFR GPS, you'll be hooked. Especially with some cool glass, like the Skyview system.
 
Download the Garmin user guide and it describes all the self testing the 175 does in the background. It will give alerts and even cancel approaches if anything is amiss. Lot of stuff going on in that little box. If you want to do IFR training the 175 will also simulate an ILS approach with dire warnings of for training purposes only. The Dynon system needs a GPS reference and the 2020 works well with it. $500 well spent.
 
Download the Garmin user guide and it describes all the self testing the 175 does in the background. It will give alerts and even cancel approaches if anything is amiss. Lot of stuff going on in that little box. If you want to do IFR training the 175 will also simulate an ILS approach with dire warnings of for training purposes only. The Dynon system needs a GPS reference and the 2020 works well with it. $500 well spent.

Would you recommend I install both the SV-GPS-2020 and the GPS-175?
I figured with an ARINC adaptor, I would provide the GPS data from the GPS-175 to the AFS 5500 and the SV-GPS-2020 would don't be needed,,,, GPS data to the transponder as well.
 
Would you recommend I install both the SV-GPS-2020 and the GPS-175?
I figured with an ARINC adaptor, I would provide the GPS data from the GPS-175 to the AFS 5500 and the SV-GPS-2020 would don't be needed,,,, GPS data to the transponder as well.
In aviation I am a belt & suspenders kind of guy so IMHO yes.

The 2020 is a simple connection for your transponder and you can have the 175 as a backup. You have to connect the 175 directly to your transponder (not through the SkyView/AFS) for it to be used as an ADS-B source. But that is the great thing about experimental, you can do whatever is best for you.

FWIW I have the exact same setup but with a G430W instead of the 175.

:cool:
 
Would you recommend I install both the SV-GPS-2020 and the GPS-175?
I figured with an ARINC adaptor, I would provide the GPS data from the GPS-175 to the AFS 5500 and the SV-GPS-2020 would don't be needed,,,, GPS data to the transponder as well.

You do not need the GPS-2020 if you have the Garmin GPS 175. The Garmin can supply the signal for ADSB out. But you would still need a GPS source for the AFS. You could however, get by with a SV-GPS-250 (instead of the 2020) for the AFS display. The GPS 250 can be found used for about $50 from those upgrading, so you could save some money that way. I don't think you can use the Garmin 175 GPS signal for the AFS 5500.
 
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It sounds like you have already purchased an EFIS, but, if not, maybe you should look at GRT. They have a beta-test going with gps approaches using their $500 gps intended for adsb-out use, plus all the rest of the software and databases inside an HX EFIS (not sure if their newer efis units also support this). There is no TSO, and they clearly state this is for practice use under vfr. Any approval for ifr use is up to the owner to obtain.
 
It sounds like you have already purchased an EFIS, but, if not, maybe you should look at GRT. They have a beta-test going with gps approaches using their $500 gps intended for adsb-out use, plus all the rest of the software and databases inside an HX EFIS (not sure if their newer efis units also support this). There is no TSO, and they clearly state this is for practice use under vfr. Any approval for ifr use is up to the owner to obtain.

Already have the AFS 5500, otherwise would consider it.
 
You do not need the GPS-2020 if you have the Garmin GPS 175. The Garmin can supply the signal for ADSB out. But you would still need a GPS source for the AFS. You could however, get by with a SV-GPS-250 (instead of the 2020) for the AFS display. The GPS 250 can be found used for about $50 from those upgrading, so you could save some money that way. I don't think you can use the Garmin 175 GPS signal for the AFS 5500.

Two points:
- Yes, you still need the GPS-2020 or GPS-250 if only for backup.
- Yes, perfectly ok to use the GPS-250 instead of the GPS-2020 if you are using the Garmin box for the serial GPS output to the XPDR for ADS-b out. I did this on my current RV-8 (GTN-650 with dual SkyView HDX displays). As a side benefit, the GPS-250 position locks much faster than the GTN-650 and I told faster than the GPS-2020. It is not WAAS, so may differ from the GPS-250 by a couple of feet (in other words no practical difference as you don?t use either for IFR approach).

Carl
 
Two points:
- Yes, you still need the GPS-2020 or GPS-250 if only for backup.
- Yes, perfectly ok to use the GPS-250 instead of the GPS-2020 if you are using the Garmin box for the serial GPS output to the XPDR for ADS-b out. I did this on my current RV-8 (GTN-650 with dual SkyView HDX displays). As a side benefit, the GPS-250 position locks much faster than the GTN-650 and I told faster than the GPS-2020. It is not WAAS, so may differ from the GPS-250 by a couple of feet (in other words no practical difference as you don?t use either for IFR approach).

Carl

Very helpful information. Thanks for taking the time to respond.
 
I will have to look to be sure but I believe the GPS 250 is WAAS but is not certified to the same level as those required for ADSB and IFR navigation. Because of that it reports different SIL and SDA values but I think the position will report the same as the GPS 2020.
 
I struggled with this very question too. Hopefully, given the title of your post, you will find the following helpful. If you already understand the difference, just go to the next post!

Before the advent of GPS, pilots used approach plates as directions for the approach and flew an approach by tuning in the initial fix on the VOR receiver, flying to it, then tuning the next fix and so on. There were no graphics and you learned to picture your position in your head.

A GPS receiver ?knows? where it is located (your present position) and virtually all have a database so it can present a map to show you your location and the location of nearby objects (roads, towns, airports etc).

A GPS navigator has the above functionality and an expanded database. Like other GPS receivers, with its database, it ?knows? the location of navigation points (VORs, intersections, runways, etc) which are commonly called waypoints. But its database also contains approach data. A requirement of GPS approaches is that the approach must be contained in the database and that there is automatic sequencing of the waypoints in an approach. So when you load and activate a GPS approach, the navigator will provide guidance to the initial fix and when you get there it will automatically sequence to each fix in the approach. This is why a GPS navigator is needed to fly GPS approaches.

A GPS receiver, even a WAAS receiver, does not have the database to provide automatic sequencing. WAAS adds more precision to the location information of a GPS receiver and that is why a WAAS GPS navigator is required for LPV approaches. The extra precision is needed for ADSB also.

Garmin revolutionized navigation with the GNS430 about 20 years ago. They combined a nav, com and GPS navigator in one box and they use the GPS to not only fly GPS procedures, but also to fly VOR and ILS procedures, switching to the VOR or ILS receiver for the segment from the final approach fix to the runway. This makes the setup and procedure for flying every kind of approach identical, simplifying workload.

My understanding from the install manual, is that a GPS175 has the capability to provide GPS location to an EFIS like your AFS- 5550. This will be a RS232 serial link. With this you do not need a separate GPS for your EFIS although you may want one for redundancy. It also will provide GPS ARINC data to your EFIS which provides longitudinal and vertical steering. It also has the Garmin propriety GPS information for Garmin ADSB out solutions.

Typically you will control your SV autopilot from your AFS-550. However most installations usually provide a redundant mode to control an autopilot directly. I think this is done with the Dynon autopilot control panel and it will use the RS232 GPS data as well as the GPS ARINC data.

Jim Butcher
 
I struggled with this very question too. Hopefully, given the title of your post, you will find the following helpful. If you already understand the difference, just go to the next post!

Before the advent of GPS, pilots used approach plates as directions for the approach and flew an approach by tuning in the initial fix on the VOR receiver, flying to it, then tuning the next fix and so on. There were no graphics and you learned to picture your position in your head.

A GPS receiver ?knows? where it is located (your present position) and virtually all have a database so it can present a map to show you your location and the location of nearby objects (roads, towns, airports etc).

A GPS navigator has the above functionality and an expanded database. Like other GPS receivers, with its database, it ?knows? the location of navigation points (VORs, intersections, runways, etc) which are commonly called waypoints. But its database also contains approach data. A requirement of GPS approaches is that the approach must be contained in the database and that there is automatic sequencing of the waypoints in an approach. So when you load and activate a GPS approach, the navigator will provide guidance to the initial fix and when you get there it will automatically sequence to each fix in the approach. This is why a GPS navigator is needed to fly GPS approaches.

A GPS receiver, even a WAAS receiver, does not have the database to provide automatic sequencing. WAAS adds more precision to the location information of a GPS receiver and that is why a WAAS GPS navigator is required for LPV approaches. The extra precision is needed for ADSB also.

Garmin revolutionized navigation with the GNS430 about 20 years ago. They combined a nav, com and GPS navigator in one box and they use the GPS to not only fly GPS procedures, but also to fly VOR and ILS procedures, switching to the VOR or ILS receiver for the segment from the final approach fix to the runway. This makes the setup and procedure for flying every kind of approach identical, simplifying workload.

My understanding from the install manual, is that a GPS175 has the capability to provide GPS location to an EFIS like your AFS- 5550. This will be a RS232 serial link. With this you do not need a separate GPS for your EFIS although you may want one for redundancy. It also will provide GPS ARINC data to your EFIS which provides longitudinal and vertical steering. It also has the Garmin propriety GPS information for Garmin ADSB out solutions.

Typically you will control your SV autopilot from your AFS-550. However most installations usually provide a redundant mode to control an autopilot directly. I think this is done with the Dynon autopilot control panel and it will use the RS232 GPS data as well as the GPS ARINC data.

Jim Butcher

EXACTLY what I needed. This was very helpful. I figured my ignorance was based on my not having spend the time and money getting my IFR certificate, but when I discuss with friends that had their IFR, they were not well informed about the different types of GPS approaches. Their response was "if you want to fly IFR, you need a NAV radio for ILS/GS". Amazes me the resource VAF provides. Thank you Jim for the response.
 
I will have to look to be sure but I believe the GPS 250 is WAAS but is not certified to the same level as those required for ADSB and IFR navigation. Because of that it reports different SIL and SDA values but I think the position will report the same as the GPS 2020.

Correct. The 250 is WAAS but not permitted for ADS-B out. Not mentioned above is that an IFR GPS navigator does not have to be WAAS - though support for those older units is waning.
 
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I struggled with this very question too. Hopefully, given the title of your post, you will find the following helpful. If you already understand the difference, just go to the next post!

Before the advent of GPS, pilots used approach plates as directions for the approach and flew an approach by tuning in the initial fix on the VOR receiver, flying to it, then tuning the next fix and so on. There were no graphics and you learned to picture your position in your head.

A GPS receiver ?knows? where it is located (your present position) and virtually all have a database so it can present a map to show you your location and the location of nearby objects (roads, towns, airports etc).

A GPS navigator has the above functionality and an expanded database. Like other GPS receivers, with its database, it ?knows? the location of navigation points (VORs, intersections, runways, etc) which are commonly called waypoints. But its database also contains approach data. A requirement of GPS approaches is that the approach must be contained in the database and that there is automatic sequencing of the waypoints in an approach. So when you load and activate a GPS approach, the navigator will provide guidance to the initial fix and when you get there it will automatically sequence to each fix in the approach. This is why a GPS navigator is needed to fly GPS approaches.

A GPS receiver, even a WAAS receiver, does not have the database to provide automatic sequencing. WAAS adds more precision to the location information of a GPS receiver and that is why a WAAS GPS navigator is required for LPV approaches. The extra precision is needed for ADSB also.

Garmin revolutionized navigation with the GNS430 about 20 years ago. They combined a nav, com and GPS navigator in one box and they use the GPS to not only fly GPS procedures, but also to fly VOR and ILS procedures, switching to the VOR or ILS receiver for the segment from the final approach fix to the runway. This makes the setup and procedure for flying every kind of approach identical, simplifying workload.

There are also, as noted, a lot of things going on inside a TSO'd GPS navigator, such as RAIM computations, and so forth, that may or may not be part of a non-TSO'd device. AND, the database itself that is used by a certified box is, itself, certified.
 
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