anybody using two GI-275s to drive an Autoflite IIIB (Century IIB)?

[Velvet_Hammer]

So it turns out Garmin GI-275's will drive the legacy 2-axis Century/Piper autopilot in my Archer; so I'm getting a local shop to quote me on installing two GI-275's to replace my DG and AI, along with a GNX-375 navigator; that combination will command the autopilot to fly RNAV and LPV approaches, procedure turns, etc.

Anybody have this setup driving a legacy autopilot? Looking for feedback if so.

 

[bkspero]

I just had 2 GI-275s installed replacing the AI and DG, and connecting to a Century IIB and GNS-530w navigator. Installation was completed last November and still isn't right. The 275 STC requires the installation of a relay in the power line of the IIB. That relay is intended to shut off the autopilot in the event of a problem with one or both of the 275s.

What I am seeing is that randomly the 275s report an instantaneous error and then correct themselves. But once the power is shut off to the autopilot for that instant it must be turned back on manually. The shop isolated the problem to the 275s by connecting the relay coil directly to ground (rather than grounding through the 275s). This keeps the relay coil energized. If the relay or the autopilot were faulty the shutdowns would have continued. But they did not. So the only other possible cause is the 275s.

Garmin Dealer Tech Support has been dismal. There are error log files recorded on the units, but they are password protected and can only be read by Garmin. Mine went into them in mid December and despite 4 follow up emails and 3 follow up calls from the dealer to Garmin, no response has been forthcoming. I've tried Garmin customer Tech Support and get nonsensical responses like "there is no way that a 275 can interrupt power the the autopilot" or "the autopilot must be defective".

When it's working, the IIB interacts well with the 275s. But I can't trust to use it in IMC if the 275s are going to randomly shut down the autopilot without warning.

 

[Velvet_Hammer]

Wow - thank you for the feedback - I appreciate the background and info. How is the IIB with GPSS inputs? Is it reasonably precise?

 

[bbarrett]

I have two GI-275s and a Century IIB. The GPSS emulation is amazing, considering the Century is as old as it is. Holding patterns, turns in the course, and approaches are all very smooth. I have not had the random disconnect problems mentioned above. I have the an in-line relay as well, and it works if I hit the autopilot disconnect soft key on the 275 or if I power down the ADI 275, but has otherwise never disconnected.

On a new install, definitely have them add a physical switch for switching between GPSS and HDG mode. The new software layout is better than it used to be, but every time I’ve had to switch back and forth, it was at a point where I wanted to do it right now, with minimal mental energy. We retrofitted the switch after the 2.40 software came out and it was a nice improvement.

 

[bkspero]

...How is the IIB with GPSS inputs? Is it reasonably precise?

My experience when the autopilot is operating is consistent with bbarrett's. GPSS works as it should holding the GPS track in both turns and straight lines.

I also second his recommendation to get the GPSS/Heading switch installed rather than relying on the menu system to make that switch. Prior to the v2.4 firmware it had taken a button push (or screen swipe) and 4 or 5 soft button pushes (i.e., screen taps) to make the switch from Nav mode to Heading mode. Imagine doing that in IMC on an instrument approach in turbulence first having to switch from Enroute Nav mode to Heading mode for vectors to final, then back to Nav mode once established on the approach. Firmware v2.4 simplified that to a button push (or screen swipe) and 1 or 2 soft button taps and introduced the option of a panel switch as a kludge to overcome the clumsy menu system altogether on these units. BTW, don't rely on the GI-275 Pilot's Guide or AFM supplement for information on these changes, as, at least the v2.4 guide/supplement are wrong and show the old, superseded, menu choices to make this changeover. Better to just pay for the switch to be installed.

One other caution. There are times you need to know the reciprocal of your current heading. You can do the math in your head, but that takes processing power that can be beneficially used elsewhere when flying (again, particularly in IMC). I was trained to look at the base of the DG compass rose (opposite to the heading being flown) and read it off directly. You can't do that with the 275 in HSI mode. For some reason Garmin decided to obscure the bottom of the compass rose so you can't directly read the reciprocal heading. A small issue, but aggravating. My kludge was to leave the Nav2 CDI in the panel and connected so I can read reciprocal headings from it's compass rose.

Finally, see what you can find out about the need for databases. Garmin is telling me that I must have a NavData database installed (at about $300/yr). The units seem to be working without it in ADI/HSI (not HSI Map) modes. They are giving a synthetic vision alert on every startup even though I didn't buy the synthetic vision option, but that is unrelated to missing NavData. You will also need to install a terrain database (or get a small but continuous TERR alert on the screen). Neither the Pilot's Guide nor the AFM supplement contain a comprehensive description of what databases are required for each combination of functions, and, as with everything else, Garmin Tech support has not been helpful.

 

[bbarrett]

The 275s have the same map data as the GTN 650: Navigation Data, Obstacles, SafeTaxi, and Basemap. My understanding is that the units will function without databases, except for the moving map bits, but I haven't tried it. I did have to change the bundle I needed from when I just had the GTN650 to one that covers multiple units, but it wasn't significantly more per year. You probably will have to buy a database every 5-10 years to get the magnetic reference data updates, but I could be wrong there, too.

The reciprocal math thing is definitely real. I left the Nav2 CDI installed as well, not because of the reciprocal thing, but because being able to only display one CDI at a time seemed unfortunate.

 

[Velvet_Hammer]

Interesting -- I bet future software updates will fix the "glitch" of not being able to see the heading reciprocal on the HSI. I'm not a fan of how much information they've crammed into the displays (my main goal is to have a GPS navigator talk to my existing autopilot) and I imagine there will be additional declutter options as pilots speak up.

 

[Tantalum]

Our club's nice duchess has a set up similar to this. It works great!

I usually like hand flying but on this last trip I gave the auto pilot a ton of use and it worked fantastic

It's no GFC500 but damn they got pretty close amazing how well it works relative to how old the Century is

You can see below the two GI 275 and over on the right the century III with all the modes clicked on

 

[Mtns2Skies]

Our club's nice duchess has a set up similar to this. It works great!

Why do you have so many nice twins accessible to you? Around me there are only ratty-ass expensive Seneca II's that climb and cruise slower than my 180... so they don't make a lot of sense for me to shell out $400/hr to rent them.

 

[Tantalum]

Why do you have so many nice twins accessible to you? Around me there are only ratty-ass expensive Seneca II's that climb and cruise slower than my 180... so they don't make a lot of sense for me to shell out $400/hr to rent them.

Plus One is a fantastic club. The planes are lease back and you have your pick of ratty-A$$ planes up through the nicer ones. This one rents for $295/hr hobbs time, wet (). And outside of a few obvious common sense rules they're pretty laid back

The one in the pic is one of the nicest planes in the club, overall. Owner keeps it in a hangar and it's on a battery minder. He also flies it himself personally, so that helps with general maintenance and upkeep. We've got a Debby, G1000 182, and a few Cirrus, all <=G3 and in my opinion way the hell over priced, especially for a 430/avidyne plane

You've also got your run of <$110-$130/hr analog beater "holy crap this thing flies?" 172 in the club. So something for everyone


I have zero affiliation with them outside of being a happy customer, but I invite you to check out their fleet, most of the planes are at MYF but they have a few at CRQ, RMN, and SEE https://www.plusoneflyers.org/montgomery-fleet/

 

[Mtns2Skies]

Plus One is a fantastic club.

You need to take advantage of that 170

 

[Tantalum]

I don't have my tail wheel!

 

[vontresc]

Do you have a radio coupler? Our archer has the DG wired directly to the piper autocontrol (Century IIb). In digging through the Garmin install docs, the 275 is not able to drive the Century without the Radio Coupler.

 

[MajorTurbulence]

I have two GI-275s and a Century IIB. The GPSS emulation is amazing, considering the Century is as old as it is. Holding patterns, turns in the course, and approaches are all very smooth. I have not had the random disconnect problems mentioned above. I have the an in-line relay as well, and it works if I hit the autopilot disconnect soft key on the 275 or if I power down the ADI 275, but has otherwise never disconnected.

On a new install, definitely have them add a physical switch for switching between GPSS and HDG mode. The new software layout is better than it used to be, but every time I’ve had to switch back and forth, it was at a point where I wanted to do it right now, with minimal mental energy. We retrofitted the switch after the 2.40 software came out and it was a nice improvement.

I have a Century 2B (Piper Autocontrol 3B) being driven through my Aspen connected to a 430W. The issue with the switch needed for going from heading to GPSS or back is accomplished by pressing the GPSS button on or off on the Aspen. When off, it goes back to heading mode. Of course, the legacy Century includes a switch that one leaves in heading mode throughout the process. So if I understand the problem, there is no such ability on the 275, and thus the need for an added switch somewhere.

It is nice that there is another option with the 275 to get attitude data to interface with the century autopilot since that is not available with the G5.

 

[bbarrett]

The installation manual assumes you have a radio coupler, for sure, but I think by comparing the Century IIB install manual and the GI275 manual, you could figure out how to wire without a coupler.

That said, 1C388M couplers are not very expensive ($300?) on eBay and the avionics shop is going to have all the wire bundles involved in installing the coupler open as part of the 275 install. So if you have space in your panel, now might be a good time to add a coupler.

 

[Velvet_Hammer]

Do you have a radio coupler? Our archer has the DG wired directly to the piper autocontrol (Century IIb). In digging through the Garmin install docs, the 275 is not able to drive the Century without the Radio Coupler.

Yes I do, and yes you are correct -- the radio coupler has to be present for the 275s to drive the Century.

 

[Velvet_Hammer]

So I got one quote back from a local shop here in NorCal; to install 2x GI-275s, and a GNX-375, and the necessary relays to connect it to my existing Autoflite IIIB they've quoted me $39,000, before tax. About half of that is labor; full retail pricing on the hardware. This seems high but I'd be the first time they've done this kind of install with a legacy AP. I'm looking around to find a couple shops that have actually done this install before.

 

[asicer]

So I got one quote back from a local shop here in NorCal; to install 2x GI-275s, and a GNX-375, and the necessary relays to connect it to my existing Autoflite IIIB they've quoted me $39,000, before tax. About half of that is labor; full retail pricing on the hardware. This seems high but I'd be the first time they've done this kind of install with a legacy AP. I'm looking around to find a couple shops that have actually done this install before.

For that much, you can install 2x GI-275s, rip out your old autopilot and install a modern digital 2/3 axis AP like a TruTrack, Trio or maybe even a GFC500 depending on whether your airframe is on the AML (you said "Archer", so you're probably good). Heck, that could even buy a full-boat flat screen Dynon setup.

Also, isn't AutoFlite rate-based rather than attitude-based? Or did you mean AutoControl IIIB (which is really a 1-axis Century IIB)?

 

[Velvet_Hammer]

For that much, you can install 2x GI-275s, rip out your old autopilot and install a modern digital 2/3 axis AP like a TruTrack, Trio or maybe even a GFC500 depending on whether your airframe is on the AML (you said "Archer", so you're probably good). Heck, that could even buy a full-boat flat screen Dynon setup.

Also, isn't AutoFlite rate-based rather than attitude-based? Or did you mean AutoControl IIIB (which is really a 1-axis Century IIB)?

Autocontrol IIIB is what I meant, which yes is the Century II one-axis autopilot. A friend had two G5s, GPS175, and a GFC550 installed for around $31k, so that's definitely a consideration. I really prefer the GI275s but at these prices...I'd rather install a GPS175, connect it to the existing CDI, and let that be enough until I'm ready to upgrade to something faster.

 

[cowman]

I did this last year. Piper autocontrol III/ 530w. The shop doing the install didn’t know they had to have an interface box between the gi-275s and the old autopilot. They attempted to cobble their own, not knowing a company called Deklin makes one.

They comped me the extra labor but I was down for a lot longer than anticipated and we’re still working out bugs although the system works pretty well now. In 20/20 hindsight I might have held off or saved up and just replaced the legacy autopilot at the same time but these things aren’t exactly cheap so there is that….

 

[Velvet_Hammer]

In 20/20 hindsight I might have held off or saved up and just replaced the legacy autopilot at the same time but these things aren’t exactly cheap so there is that….

I had a talk with another shop nearby today, and it's clear they don't really want to take on this kind of work; they'd all rather just sell and install the new Garmin stuff (which I get). I'm leaning towards just leaving the autopilot alone, and installing a GNX375 and GI275 as CDI/MFD.

 

[asicer]

I had a talk with another shop nearby today, and it's clear they don't really want to take on this kind of work; they'd all rather just sell and install the new Garmin stuff (which I get). I'm leaning towards just leaving the autopilot alone, and installing a GNX375 and GI275 as CDI/MFD.

Where are you located? There's a ton of variables, including where you take the plane, but based on what other members here have done, my wild guess is $12k to install a GNX375, $8k for a pair of G5, add $2500 to upgrade those to GI275, $8k to install a TruTrak (AeroCruze 100), add $7k to upgrade to GFC500 and another $4k to add a trim servo.

 

[Velvet_Hammer]

Where are you located? There's a ton of variables, including where you take the plane, but based on what other members here have done, my wild guess is $12k to install a GNX375, $8k for a pair of G5, add $2500 to upgrade those to GI275, $8k to install a TruTrak (AeroCruze 100), add $7k to upgrade to GFC500 and another $4k to add a trim servo.

I'm in Northern California. Your estimates (~$40k) are about right. As the day has worn on, I'm pretty sure I'm going to just add a GNX375 and the GI275 CDI; I'll keep my mechanical CDI as an indicator for NAV2 and remove the VOR indicator. I'll keep my gyro AI and DG and leave the autopilot alone for now. My mission in this airplane will generally only include light IFR into/out of marine cloud/fog layers on the coast or in SoCal.

 

[AA5Bman]

So I got one quote back from a local shop here in NorCal; to install 2x GI-275s, and a GNX-375, and the necessary relays to connect it to my existing Autoflite IIIB they've quoted me $39,000, before tax. About half of that is labor; full retail pricing on the hardware. This seems high but I'd be the first time they've done this kind of install with a legacy AP. I'm looking around to find a couple shops that have actually done this install before.

Thats insane. For more than $10k less than that I did a whole panel, 275, 650xi, new transponder, new audio panel, new GNC255, new VOR indicator for my #2, all coupled to a Century IIB. The GPSS from the GI275 drives the Century IIB flawlessly.

 

[Velvet_Hammer]

Thats insane. For more than $10k less than that I did a whole panel, 275, 650xi, new transponder, new audio panel, new GNC255, new VOR indicator for my #2, all coupled to a Century IIB. The GPSS from the GI275 drives the Century IIB flawlessly.

Yep, that's closer to what I was expecting. Who did the work for you (and when)?