Van's Air Force
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built-in gps
- Thread starter 1bigdog
- Start date
Actually, you need an actual external GPS - the hockey puck is more than antenna, it is the GPS reciever as well.
Canadian_JOY
Well Known Member
Take a look at Grand Rapids Technologies EFIS products - they use an external GPS antenna (supplied with the EFIS) to provide GPS position data which interacts with the flight-planning software within the EFIS. Makes for a nicely integrated solution.
Also, with GRT's Adaptive AHARS one can buy the GNSS option which installs a multi-constellation satellite navigation system in the AHARS. Again, plug in the supplied external antenna and you now have a system which can receive position data not just from the American GPS system but also from GLONASS and several other satellite constellations. Helpful for those times when the US military intentionally degrades GPS accuracy, or for those times when somebody else jams GPS.
Also, with GRT's Adaptive AHARS one can buy the GNSS option which installs a multi-constellation satellite navigation system in the AHARS. Again, plug in the supplied external antenna and you now have a system which can receive position data not just from the American GPS system but also from GLONASS and several other satellite constellations. Helpful for those times when the US military intentionally degrades GPS accuracy, or for those times when somebody else jams GPS.
You also need an external antenna (GA 26C) for the G3X. Unlike the G5, Aera 660 etc, the G3X does not have this antenna built in. Alternatively you can pull the position data from an external source (GTN 625 etc) but I would still want an antenna directly connected to the G3X for redundancy.
Tom.
Tom.
Just to be clear, NONE of the gps systems mentioned in this thread are approved for primary navigation under IFR.
good point
Hi Bob,
It's an important point. Mine is being built as an IFR platform so I have yet to decide on the legal navigator (either GTN650 or IFD440). I simply didn't know some had the option for providing their own internal source which would be a useful backup in this case.
When I looked at the Dynon and AFS manuals both appear to use a similar external GPS and then using that data stream within the EFIS. They certainly look like external GPS's by just looking at the wires to the "antenna". The G3X however calls it a "built-in GPS" so I don't know if that's just marketing speak. More research.
Hi Bob,
It's an important point. Mine is being built as an IFR platform so I have yet to decide on the legal navigator (either GTN650 or IFD440). I simply didn't know some had the option for providing their own internal source which would be a useful backup in this case.
When I looked at the Dynon and AFS manuals both appear to use a similar external GPS and then using that data stream within the EFIS. They certainly look like external GPS's by just looking at the wires to the "antenna". The G3X however calls it a "built-in GPS" so I don't know if that's just marketing speak. More research.
Canadian_JOY
Well Known Member
Michael - in reality, it doesn't matter if the GPS chipset is in the antenna puck or within the EFIS. No matter how you cut it, there's better than an even chance that anything you install in the panel will be shaded from a clear view of the sky, thus even if it has a fully self-contained GPS it likely will need an external antenna to get the required view of the sky.
Also, since you're in Canada, be aware that you'll need more than a GTN650 or IFD440 in order to be IFR-legal. You'll need to add another NAV source (like an SL30 or similar). The way the Canadian regs are written, you have to be able to get back on the ground after the GTN or IFD fails - we aren't allowed to say "oh, the GPS inside the box failed but I can still use it as an ILS receiver" - we have to have a completely separate alternate source of navigation guidance.
As for using the "built in" GPS equipment in the EFIS as a back-up, well, that's a great idea, and I would add they often provide huge situational awareness benefits as they drive the very powerful moving map features on today's big-screen EFIS systems. I often have the map up on one of my EFIS screens even though the airplane is being driven around the sky based on the information coming from my certified GPS navigator.
Also, since you're in Canada, be aware that you'll need more than a GTN650 or IFD440 in order to be IFR-legal. You'll need to add another NAV source (like an SL30 or similar). The way the Canadian regs are written, you have to be able to get back on the ground after the GTN or IFD fails - we aren't allowed to say "oh, the GPS inside the box failed but I can still use it as an ILS receiver" - we have to have a completely separate alternate source of navigation guidance.
As for using the "built in" GPS equipment in the EFIS as a back-up, well, that's a great idea, and I would add they often provide huge situational awareness benefits as they drive the very powerful moving map features on today's big-screen EFIS systems. I often have the map up on one of my EFIS screens even though the airplane is being driven around the sky based on the information coming from my certified GPS navigator.
Unfortunately, no
The FAA makes a distinction between an approved / certified position source and an approved navigator. A navigator is much more than just the latitude / longitude / altitude. It's also a certified database, certified display, certified CDI output, etc.
A manufacturer could theoretically build an approved navigator around such a position source, but by itself - even connected to an excellent non-TSO / VFR navigation system - it isn't enough. Necessary, but not sufficient.
The FAA makes a distinction between an approved / certified position source and an approved navigator. A navigator is much more than just the latitude / longitude / altitude. It's also a certified database, certified display, certified CDI output, etc.
A manufacturer could theoretically build an approved navigator around such a position source, but by itself - even connected to an excellent non-TSO / VFR navigation system - it isn't enough. Necessary, but not sufficient.
GalinHdz
Well Known Member
Legal IFR in Canada
Hi Canada Joy,
Yes, I'm aware of the legal requirements and SL30 is part of the planned list for the NAV. My initial question was out of ignorance because I didn't realize the bulk of the big names in EFIS had GPS capabilities on-board. I thought they all needed an external GPS source, such as a GTN or IFD. Having the option to simply add an accessory to the EFIS is purely to provide backup. I will have VOR (plus other redundant capabilities).
Thanks.
Hi Canada Joy,
Yes, I'm aware of the legal requirements and SL30 is part of the planned list for the NAV. My initial question was out of ignorance because I didn't realize the bulk of the big names in EFIS had GPS capabilities on-board. I thought they all needed an external GPS source, such as a GTN or IFD. Having the option to simply add an accessory to the EFIS is purely to provide backup. I will have VOR (plus other redundant capabilities).
Thanks.
Virtually all the EFIS boxes have, or can have, an inexpensive, internal or hidden external, non-TSO?d for IFR, GPS. This is more than window dressing. Some EFIS units use gps data to ?aid? the attitude solution. Some EFIS units use gps data as a critical input if pitot data fails. You owe it to yourself to find out how your proposed efis works.
Canadian_JOY
Well Known Member
Bob raises an excellent point with respect to understanding how your EFIS derives its attitude solution, especially in the event of a plugged pitot, a very real possibility. In the heyday of the D100 EFIS family Dynon came up with a software update that allowed the EFIS to switch over to velocity data provided by an external GPS in the event pitot was lost. That was a big improvement because a big bug lodged in your pitot would previously have caused the attitude indication to become unreliable.
The bottom line in this equation is you'll have a certified navigator and a redundant NAV receiver so you will have met the minimum requirements for IFR. Those are the "big" check marks on the avionics design checklist. Now
you have the fun of working on all the smaller check marks. You're off to a great start.
When it comes to "bang for buck" adding those inexpensive GPS receivers to the EFIS usually represents a disproportionately-large gain in functionality. The decision to add that functionality at low cost becomes almost a no-brainer. Until the day when you realize you're out of communications ports and that GPS is using a port that you really, really need. That's when the real fun begins!
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