GI-275 Question

[LANCECASPER]

I don't like the idea of the hardware and software backing up the same hardware and software. I've seen panels with just two GI-275s and that's it. Having one backing  up the other would scare me. Especially after a new software release. That doesn't strike me as a real back-up solution and how they ever got that approved is beyond me.

Here's one where two GI-275s failed - thankfully he had more instruments (5th post in the thread)

 

[PeteMc]

2 hours ago, LANCECASPER said:

I don't like the idea of the hardware and software backing up the same hardware and software.

Exactly why I have an Aspen and a GI275.  

But the two GI275s do make it easy to convert over the panel and get rid of all the vacuum system and update to digital displays.

  

Edited April 18 by PeteMc

[Pinecone]

On 4/18/2024 at 10:00 AM, jlunseth said:

Because removing the vacuum in some models results in a single point of failure. All becomes dependent on the single alternator and also the single battery.

Except that the individual units (G-5 and GI-275) have their own back up battery.  So you would need to lose the alternator and the main battery and the AI battery.

I may add an IBBS to power the G3X and one nav.

[jlunseth]

13 hours ago, natdm said:

Correct me if I'm wrong (of course) but having two gi275's means he's got an alternator, a battery, and a backup AHRS unit plus 60 minutes of power in each unit (provided the backup batteries were purchased)? I'd think if I lost power and still had a vac system, I'm still landing within the hour. 

When you get the AFSM for the 275 and read it, you find, among other things, that the advertised 60 minutes is actually as little as 30 minutes. I can give you multiple courses where that would not be enough. I can also tell you from actual experience that the aircraft battery, which is supposedly rated for multiple amp hours, may actually give you about a half hour. If you suffer loss of the single alternator you need to drop the gear, because the battery will continue to drain during flight and when you get to your destination, there may not be enough left to lower the gear. You also need to switch the master off, because you may need instruments and radios when you get to your destination, but the single battery will still drain during flight, just not as bad. Now let's say, you are flying from Great Falls over the Rockies to land at KGPI. Or across the route from ABQ to SoCal. Or across the Atlantic from the Bahamas. And you are over a cloud deck, which makes you VFR for now, but you are going to have to shoot some kind of approach in order to safely land. You are going to need time to shoot your approach. Let's say 10 minutes, which is really short for something like an RNAV approach, but maybe you can get vectors and help. That leaves you roughly 20 minutes to get to an airport and the airports are all further than that. Or if you can get to one, you are shooting an approach with no instruments except you manage to get your 275's going. Now what are you going to use for the RNAV or an ILS? Well, that's your GPS that doesn't have a backup battery, so you are glad you remembered to switch off the master and save some power so you can put the approach up and shoot it. Now it is a contest between the life of the remaining batteries and the time it takes you to get through that approach.

What would keep you alive is an AI that operates as long as the engine is going, whether the alternator is working or not, and that relies on a technology other than electricity, of which you may not have enough. That would be a vacuum operated AI, which you took out in your last avionics refit because it was "steam" and you wanted the 7 lbs. of useful load.

This isn't a hypothetical I am giving you. I have flown all these routes. I have had the alternator fail several times, when we (my A&P and me) were installing an aftermarket coupler out of what must have been a defective lot. I have had the alternator fall off into the running engine because of improper installation. None of this has happened in years now, but having actually had it happen it very much affects my decision making.  There must be redundant, non-single point of failure instruments that will continue to operate no matter what, particularly the AI. Sure, electronic tech is nifty, I love my GTN750 and my 275's. But I am not giving up my steam, vacuum operated AI. 

[jlunseth]

@pinecone The G5, which I do not have, apparently has a much longer backup life than the 275. The backup life of the 275, according to my AFMS is as short as 30 minutes. I know from experience that once the alternator fails you will get about a half hour out of the single, 12 volt, house battery even if you switch the master off. When you switch off the master to save power you lose everything except the 275 (or dual redundant 275's). You will now have no more than 30 minutes to find an airport and land, and if you are going to have to shoot an approach you need find that airport in about half your 30 minutes, the rest will be the approach. You are also going to want some of your non-backed up instruments such as your radios and your GPS in order to shoot a safe approach. Everyone would think immediately that they could use the iPad for some functions, and that would be true. Except in some terrain it is not enough. E.g. doing from Flagstaff to Bullhead to Barstow to Palmdale it is necessary to cross several high ridges and then drop several thousand into a valley to find and shoot an approach. Your best defense, actually, is to have so much fuel on board that you can fly out of the weather system you are currently in and get VFR. Why not just have some gear on board that will work as long as the engine is running. If you only think as an East Coast or midwest flyer would think, sure, most places you can find an airport right away quick. Out west or doing a water crossing, no. 

[Ragsf15e]

I agree 30 minutes isn’t enough, but im pretty comfortable with the 3:30-4:30 that I have on two G5s.  I have tested them both many times, and last year flew a 3 hour cross country with both of their CBs pulled.  They still indicated ~45 minutes remaining.  I’m not sure what the right answer is, but I don’t see flying my little m20f through/over weather so bad that it would take me multiple hours to divert to vfr.  That just seems like a day I shouldn’t have flown.

[natdm]

46 minutes ago, jlunseth said:

....

Well all those non-hypothetical hypotheticals definitely make me wonder more about tearing out that vac system.

I have definitely considered a g5 over a 275 for the battery life alone.

[PeteMc]

2 hours ago, jlunseth said:

according to my AFMS is as short as 30 minutes.

I think that's the lawyers talking, not that it isn't a possibility.  But for a battery in good condition and fully charged, I believe you will get the 60+ minutes.   And I'm wondering what it says in the paper work for the G5 since they're both Garmin products? 

[Neshi]

2 hours ago, PeteMc said:

I think that's the lawyers talking, not that it isn't a possibility.  But for a battery in good condition and fully charged, I believe you will get the 60+ minutes.   And I'm wondering what it says in the paper work for the G5 since they're both Garmin products? 

the g5 AFMS states up to 4 hours 190-01112-13_09.pdf (garmin.com) Page 7.

the gi275 does not give an up to range only stating that a green battery icon is at least 60min runtime. 190-02246-12_11.pdf (garmin.com) page 31.

[PT20J]

As I understand it, the difference in the battery time specifications is partly due to the fact that requirements are different for TSO (GI 275) vs non-TSO (G5) instruments. However, it takes a lot more current to run a GI 275 than a G5. According to the installation manuals, the GI 275 draws 0.75A @ 14V and the G5 draws 0.2A @ 14V. That nicer display, brighter backlight, and additional interface capability isn't free. On all the units, turn the backlight down as far as possible when running on battery. 

[Pinecone]

You should be capacity checking your ships battery every annul, so you know the capacity.  
 

if you turn off the master, there should be NO drain on the ships battery.  Or you can load shed and turn off things not needed, leaving only the essentials.   Also, if you turn off the master, once you turn it back on, you have power to your AI. 

another option, an IBBS 

or a backup alternator.  My plane has dual alternators

[201Mooniac]

Just for a reference point, I ran my GI 275 standby AI on the battery for a couple of runs and found it ran for 86 minutes once and 91 minutes the other time.  This certainly isn't as good as the G5 battery but it should get me down.  I would love a standby alternator but I can't seem to get anyone interested in installing one as it seems to require a field approval and those are rather difficult to come by, at least in the local FSDOs.

[jlunseth]

On 4/19/2024 at 5:09 PM, Neshi said:

the g5 AFMS states up to 4 hours 190-01112-13_09.pdf (garmin.com) Page 7.

the gi275 does not give an up to range only stating that a green battery icon is at least 60min runtime. 190-02246-12_11.pdf (garmin.com) page 31.

Honestly, I am not very interested in the “up to” time. That is marketing. Generally, it assumes a new battery and not one that has been in the aircraft for 5 years and many rechargings. I want to know the “down to” time, which is 30 minutes for the 275. I seriously don’t think that is the lawyers talking (caveat, I am one), that is what the engineers found in durability testing and the lawyers then said, well, you need to put it in the AFMS then. What happens if the OAT is -54 dF (have been there) and/or the battery(ies) are old? The other concern is the “system” concern. What if the system created by dual redundant 275’s, for example, develops a software error and the entire system goes to red “X’s”? Although those have been extremely rare, they have happened and some of it has been documented on this site. It got my attention. Don’t get me wrong, I like my 275’s. I love my 750. But I noticed that when certifying aircraft, the FAA insisted on building in non-single-point of failure redundancies. So in the old days, if the King 256 vacuum AI failed there was the electric AI. Not the best backup, I will grant you. But they were thinking “if Plan A goes completely wrong, there needs to be a separate Plan B.” The longer I fly the more I have come to appreciate that concept. If you own one of the 28V dual alternator aircraft perhaps you have a Plan B in the second alternator. But the older single alternator-single battery aircraft  need a separate Plan B. 

I am not trying to pick an argument with anyone, I have met many of the people on this site and like and respect all of them. But I have had the alternator completely fail four or five times, the vacuum once, flown with the Master off and seen what there was left in the single battery when it came time to land, and flown all of these routes that I am talking about, they are not hypotheticals. I am just trying to pass on some wisdom. For the first, probably 8 years I owned my aircraft I did not have a backup AI other than the TC. I have fixed that problem in my own aircraft from advice I read on this site from other more experienced pilots. I am glad I did.

[Hector]

Going through the decision process on backup AI myself. My M20 F is going in for avionics upgrades in a couple of weeks it already has a GI 275 for AI but the HSI is analog. The HSI is getting replaced with another GI 275. Both GNS 430w are getting replaced with GTN 650. The panel mounted 496 will be replaced with an Aera 660. The airplane currently has a backup AI that is vacuum driven. It is the only instrument in the plane that will need vacuum and it just recently started to precess badly so it needs to be replaced. So, struggling with what to replace it with. Another vacuum driven AI, or a digital AI so I can remove the vacuum system. If digital AI then I wanted something that will last longer than the GI 275. Been looking hard at the RCA 2610-3. At 80% brightness it will last 3 hours on its internal battery which is plenty long to get me down alone with the Aera 660 with its own 4 hour battery which I can use for navigation while he master is off. Still have not made a final decision but but leaning towards ditching he vacuum pump and installing the RCA 2610



Sent from my iPad using Tapatalk Pro

[Ragsf15e]

23 minutes ago, Hector said:

Going through the decision process on backup AI myself. My M20 F is going in for avionics upgrades in a couple of weeks it already has a GI 275 for AI but the HSI is analog. The HSI is getting replaced with another GI 275. Both GNS 430w are getting replaced with GTN 650. The panel mounted 496 will be replaced with an Aera 660. The airplane currently has a backup AI that is vacuum driven. It is the only instrument in the plane that will need vacuum and it just recently started to precess badly so it needs to be replaced. So, struggling with what to replace it with. Another vacuum driven AI, or a digital AI so I can remove the vacuum system. If digital AI then I wanted something that will last longer than the GI 275. Been looking hard at the RCA 2610-3. At 80% brightness it will last 3 hours on its internal battery which is plenty long to get me down alone with the Aera 660 with its own 4 hour battery which I can use for navigation while he master is off. Still have not made a final decision but but leaning towards ditching he vacuum pump and installing the RCA 2610



Sent from my iPad using Tapatalk Pro

Another benefit of the rca is completely different software, ahrs type and “aiding” requirements from your gi-275s.  I have looked at that as a great backup option as well.

[OR75]

both the RC2610 and AV-30C seems good options without putting all your eggs in the same basket 

the AV-30C seems more complicated to install and since it has more features  

[Hector]

both the RC2610 and AV-30C seems good options without putting all your eggs in the same basket 
the AV-30C seems more complicated to install and since it has more features  

Yes and it requires pitot-static connection for the AHRS to work correctly. The RCA2610 requires only power and ground.


Sent from my iPhone using Tapatalk

[Neshi]

Went in today as I was working in the area.

Don't know how anybody figures out anything with all those little white wires.

 

 

At least with Voice and networking each of our wires are individually colored.

 

[EricJ]

8 minutes ago, Neshi said:

Went in today as I was working in the area.

Don't know how anybody figures out anything with all those little white wires.

 

 

At least with Voice and networking each of our wires are individually colored.

 

The bigger shops print the wire code on the wires, so they can be identified easily in bundles.   This was done at the factory, too, and the wiring diagrams indicate the wire codes for each wire, which you can match to the wire for a given circuit.

Otherwise you gotta use a buzz box or a fox-and-hound if you get lost, which are much more time consuming.

The local shop that redid my panel printed all of my wires, but then wouldn't give me the drawings for anything that they did (and I'd asked before we even started the project), so it was kind of pointless.    It's something worth asking about while yours is still in the shop.

 

[Fly Boomer]

2 hours ago, Neshi said:

Don't know how anybody figures out anything with all those little white wires.

Pulling wire or building a harness is way easier than tracing a wire after everything is buttoned up.

[Pinecone]

17 hours ago, Neshi said:

Went in today as I was working in the area.

Don't know how anybody figures out anything with all those little white wires.

 

 

I raise you

 

 

[Neshi]

20 hours ago, Pinecone said:

I raise you

 

 

What are you putting in?

[Pinecone]

Easier to answer was it NOT going in.
 

G3X Touch 10" with EIS

G3X Touch 7" (right side)

GTN-750Xi

GTN-650Xi (already had)

G-5 (already had)

GFC-500 with pitch trim and yaw dampener

GTX-345 Remote

PS Engineering 450B

Sirius XM

WX500 Storm Scope

Replacing all the rocker switches with toggle switches

LEMO jacks for the front seats.

USB power on both sides in the front

Cigarette light in rear for O2 concentrator

[Neshi]

Nice the only thing that could make your install better would be to have all the work completed in a day.

[Ragsf15e]

1 hour ago, Neshi said:

Nice the only thing that could make your install better would be to have all the work completed in a day.

Nope, that’ll make it much worse!!