Garmin G5 GPS Clarification

[Davarron]

I'm wondering if one were to lose the GPS signal to the G5, if you would lose the attitude display as well? I could see this possibly happening out west and was wondering if the attitude portion would fail. I see in the manual that the G5 uses GPS and airspeed data to "provide the most accurate attitude information". I'm trying to understand the system more prior to pulling the trigger. Thanks

[carusoam]

I expect that the error handling capability of the G5 would be strong enough to keep operating under less than perfect conditions.  

Throw a flag, so as PIC, you would be aware of the challenge.

See if @TrekLawler is monitoring this Channel... Trek is our Big G contact. But he doesn’t hang out here very often...

Best regards,

-a-

[Steve W]

From Trek's post over at BeechTalk:

The G5 does not require a GPS to work. It works better and to a higher performance level when a good source of GPS is available, but this is not strictly required and users shouldn’t think performance will noticeably suffer if it doesn’t have GPS.

The G5 corrects gyro drift using prioritized sources of data in this order.
1. Internal GPS receiver
2. External GPS from GNS/GTN over MapMX
3. Air data

 

https://www.beechtalk.com/forums/viewtopic.php?f=21&t=131594&start=75

[ArtVandelay]

I’ve turned off my GPS to test this, it was fine.

[bradp]

I have the primary G5 plugged into both the WAAS box and a dedicated antenna.  There's also another antenna in the bezel.  Although it's not tested as a backup the data sources and redundancy from where the attitude information ("solution") comes from is pretty robust.  

[Davarron]

This is all good to know. Thanks for all the info!

[bradp]

Two  advantages of this unit over the Aspen E model are 1) if pitot static goes it relies on gps anyway.  If gps goes it relies on pitot static - so no big Xs if something goes awry.  That’s huge for me. 2) two units two batteries fully redundant- 8-10 hrs of battery life versus 30 min-1 hr.  That inspires more confidence if the electrics go TU

[carusoam]

8-10 hours, really? 

-a-

[Igor_U]

9 hours ago, carusoam said:

8-10 hours, really? 

-a-

Yeah, that got my attention as well, since I'm looking at double G5 install.

I presume his thinking is to run only one G5 (4-5 h battery life) at the time... you could pull out A circuit breaker and keep battery charge on 2nd one.

[bradp]

^^^ That.  Each is 4-5 hours.  Not like you'd actually do that, but it's an option to run one at a time and they are fully redundant. Better than 30 minutes.

[Bob R]

On 4/22/2018 at 7:03 PM, Davarron said:

I'm wondering if one were to lose the GPS signal to the G5, if you would lose the attitude display as well? I could see this possibly happening out west and was wondering if the attitude portion would fail. I see in the manual that the G5 uses GPS and airspeed data to "provide the most accurate attitude information". I'm trying to understand the system more prior to pulling the trigger. Thanks

Not sure if you have an answer to this or not, but the G5 will still have attitude display if you lose the GPS signal to the G5. My G5, will occasional lose GPS signal when descending. Currently it utilizes the internal GPS receiver versus the 530W. I am going to change out the antenna so I can supply the satellite signal, via splitter, to both units. Hopefully this will solve the issue.

Bob

[ragedracer1977]

3 hours ago, Bob R said:

Not sure if you have an answer to this or not, but the G5 will still have attitude display if you lose the GPS signal to the G5. My G5, will occasional lose GPS signal when descending. Currently it utilizes the internal GPS receiver versus the 530W. I am going to change out the antenna so I can supply the satellite signal, via splitter, to both units. Hopefully this will solve the issue.

Bob

Your install is not done correctly.  You don't need a GPS antenna splitter.  Your G5 should get the data from your 530 over the canbus.

[flyingcheesehead]

On 4/22/2018 at 9:03 PM, Davarron said:

I'm wondering if one were to lose the GPS signal to the G5, if you would lose the attitude display as well? I could see this possibly happening out west and was wondering if the attitude portion would fail. I see in the manual that the G5 uses GPS and airspeed data to "provide the most accurate attitude information". I'm trying to understand the system more prior to pulling the trigger. Thanks

Hopefully you've gotten enough clarification, but if you haven't... Allow me to geek out for a moment. 

The gyros that are used by the modern GA glass panels (be it G1000 or all the way down to the G5) are MEMS gyros - MicroElectroMechanical Systems. They're basically gyros in a computer chip, but they actually do move - They're vibrating structure gyros. Basically, electric currents "excite" a small moving part inside the chip so it vibrates, and sensors in the chip can tell when and how it moves.

However, they're not perfect. Like anything else, there is a tolerance... And those errors need to be corrected. Some of that can be done with circuitry, some can be done with software. But, it needs more inputs to know what "correct" is. Using these gyros plus accelerometers (which are also MEMS), magnetometer, GPS, and pitot/static, the unit can correct any errors. If you lose GPS, it can still provide an attitude solution, but after 50-100 hours of flying it might no longer be quite correct.

Using circuitry and software, we can essentially teach it physics, and have it use all the inputs available at the time to come up with an attitude solution. The known relationships between attitude, AoA, lift, and the airplane's path through the sky allow all these things to correct each other. This is called a Kalman Filter.

Pretty cool stuff! And one of the biggest things to enable it all was the development of air bags for cars in the late 80's and early 90's, as that is what provided the funding to develop the MEMS accelerometers.

Also, BTW... Why would one be any more likely to lose GPS signal "out west"? It's satellite, so unless you're flying deep down in pretty narrow valleys, I don't think you'd have any problem with getting good enough signal from enough satellites to have a good position. The existence of RNAV(GPS) approaches into places like Aspen and Jackson Hole demonstrates that.

[EricJ]

1 hour ago, flyingcheesehead said:

Hopefully you've gotten enough clarification, but if you haven't... Allow me to geek out for a moment. 

The gyros that are used by the modern GA glass panels (be it G1000 or all the way down to the G5) are MEMS gyros - MicroElectroMechanical Systems. They're basically gyros in a computer chip, but they actually do move - They're vibrating structure gyros. Basically, electric currents "excite" a small moving part inside the chip so it vibrates, and sensors in the chip can tell when and how it moves.

However, they're not perfect. Like anything else, there is a tolerance... And those errors need to be corrected. Some of that can be done with circuitry, some can be done with software. But, it needs more inputs to know what "correct" is. Using these gyros plus accelerometers (which are also MEMS), magnetometer, GPS, and pitot/static, the unit can correct any errors. If you lose GPS, it can still provide an attitude solution, but after 50-100 hours of flying it might no longer be quite correct.

Using circuitry and software, we can essentially teach it physics, and have it use all the inputs available at the time to come up with an attitude solution. The known relationships between attitude, AoA, lift, and the airplane's path through the sky allow all these things to correct each other. This is called a Kalman Filter.

Pretty cool stuff! And one of the biggest things to enable it all was the development of air bags for cars in the late 80's and early 90's, as that is what provided the funding to develop the MEMS accelerometers.

Airbags were one of the killer apps that drove the economy of scale to make MEMs accelerometers cheap.   There were all kinds of crazy MEMs devices being developed in the 80s when the technology was first becoming more widely available, but MEMs gyros and accelerometers now give of us accurate AHRS systems for <$15.   It's crazy.   In the late 80s I worked on a DARPA program where we used GPS and a strap-down inertial navigator in a Gulfstream I to generate aux data for a radar imaging system, and it was a big rack-mounted system that cost a massive amount of money.  My stratux has all of that now, an AHRS and a WAAS GPS receiver, for <$50 and it's tiny and it'll run for hours on a cheapie battery.   Crazy stuff.

1 hour ago, flyingcheesehead said:

Also, BTW... Why would one be any more likely to lose GPS signal "out west"? It's satellite, so unless you're flying deep down in pretty narrow valleys, I don't think you'd have any problem with getting good enough signal from enough satellites to have a good position. The existence of RNAV(GPS) approaches into places like Aspen and Jackson Hole demonstrates that.

We have constant NOTAMs out here for GPS outages because they do interference and jamming testing and probably a lot of other crazy stuff with the system.   I've only personally noticed a loss of GPS once, and they'd like people to notify ATC if they do lose GPS because it helps them with the testing.

 

[Bob R]

I just looked at the G5 configuration. Noticed that the internal GPS was enabled so I disabled it since there is no direct antenna connection. Noticed a couple of other issues as well so I’m hoping this resolves the issue(s). So much for a “Certified Garmin Installer” knowing what they are doing along with screwing up pins so the CDI doesn’t work. I hate to point fingers, but OBS/CDI was working before *Lasar” installed the G5 and broke my old vacuum attitude indicator in the process. Oops!! Did I say that in my outside voice?

[flyingcheesehead]

20 hours ago, EricJ said:

We have constant NOTAMs out here for GPS outages because they do interference and jamming testing and probably a lot of other crazy stuff with the system.   I've only personally noticed a loss of GPS once, and they'd like people to notify ATC if they do lose GPS because it helps them with the testing.

Hmmm. I've seen plenty of those NOTAMs for the coasts as well. 

Only place I haven't seen them for yet is here in the midwest!