Old autopilot on its last legs?

[@rollandsicard1628]

Test the Pitot Static system for leaks. Replace the Altitude Hold canister. Then Alt Hold should work properly. Regarding Glideslope coupling, check that GS signal is getting from Garmin to coupler. If so, replace coupler. Then retest GS coupling.

[@Allegan49010]

In our 79 C210 we used our old Cessna 400B auto pilot with a Garmin 430, surprisingly it worked well with our steam gauges...sure saved the dollars!

[@WingsOverTO]

Yeah that’s the setup that I had before I upgraded my panel: a GNS430w with steam gauges driving the AP.

[@user-xj3vk9hr7p]

I added GFC500 in my Piper Arrow 2 years ago and it's been the best investment. Single pilot IFR is amazingly simple when combined with Garmin GPS (I have GNX375) along with dual Garmin G5s. I fly holds at cruise speed and this thing is on rails. Unbelievable accuracy, precision and no reliability issues with it. I actually had mine installed in Oshawa at Enterprise Aviation. Not cheap, but definitely worth every penny.

[@WingsOverTO]

Oh nice, those are the same guys I used to do my panel upgrade.

[@adfa5288]

Bite the bullet and install a GFC500 This thing is amazing You will get your moneys worth specially in IMC Plus the VNav functionality is amazing

[@terrypedersen7]

If you plan on holding onto the plane the GFC500 is the way to go in my opinion before dumping more money into a losing cause. As far as holding off until Trio adds the STC for your plane to their list I wouldn’t entertain that. I have a Trio in my 182 and it works ok but I believe the Garmin support and functionality with your current Gamin equipment is worth the extra investment. There are so many aviation shops around that can provide services. The only reason I ended up with a Trio was the timing as I believe it was in 2016 when I did the panel upgrade and Garmin didn’t have the options then. Basically the same reason I went with an Aspen PFD at the time. Now Trio has approval for integrating the units so that’s where I am at now. The Trio went back to California for upgrades and currently waiting for re-wiring and install to see how it pairs. Essentially it will allow for altitude capture and heading selection on the Aspen instead of everything being selected on the Trio. I was contemplating switching to a GFC at some point but now with the integration that has currently been taken off my list.

[@WingsOverTO]

Thanks, Terry. I totally agree that the GFC is a fantastic system and I'd much rather have that than trying to retrofit an older system or waiting for the Trio. I just wish the cost wasn't so high! It seems every year since I bought the plane I've ended up dropping a good chunk of money into it, and I was hoping 2024 wouldn't be like that. :)

[@Marauder92V]

First, I see you still haven’t stuck that snubber in your JPI 900’s MP line. 😂 If mine jumped around like that I’d go crazy. As for the AP. Does your Century have a pressure transducer for altitude hold? If so, the problem may be in the pressure transducer or the static line going to it. If you have a generic email node linked to your channel, I’ll send you a picture of what it looks like. Also, considering you are having intermittent glide slope issues, your altitude hold and glide slope coupling may be a related problem in the computer of the autopilot. On my Aspen and I suspect the same goes for your Century, there is no link between your altitude hold function on the autopilot and the altimeter. In other words, the GI-275 is just showing you losing or gaining altitude. The issue is in the AP. It might be worthwhile having another shop look over the installation. Sometimes a shop isn’t as familiar with the analog world.

[@WingsOverTO]

Hey there, thanks for writing. You can email me at [e-mail] . Thanks very much. There is a shop not too far from here that has a bench test setup for the Century III (and in fact they did repairs to my autopilot before I bought the plan back in 2020), so I'll probably fly down there and have them take a look at it.

[@deansiracusa3966]

Chasing down issues with analog autopilots and modern digital avionics is a pain. I had a similar problem with a Century 2000 system, but in my case it was a more apparent vertical oscillation, up and down. I took it to Century and spent thousands and they only slightly fixed it. Frustrating thing is that it wouldn't do it all the time. Just occasionally. Century spent much of their time overhauling servos and making adjustments to the head unit.

[@WingsOverTO]

Yikes, that sounds brutal. For that cost and level of frustration and the mediocre result, it might be better for me to just bite the bullet and upgrade to a GFC 500.

[@fargoaerials3456]

Your AP altitude hold works just as well as mine in my Comanche. In my case, though, i have an alt hold by S-TEC which is separate from the navigation AP. doesn't make life easier. Ive thought about dumping $$$ into the issue, but its just easier to hand fly most of the time. One other thought. Just for diagnostic purposes, have you tried selecting your alternate static source?

[@WingsOverTO]

I haven't tried the alt static source, but given the GI275 seems be getting the right altitude, and the GPS altitude also shows a climb, I think it's probably not the source. Still, I'll give that a shot next time I'm up. Thanks!

[@fargoaerials3456]

@@WingsOverTO thanks for adding. To my data points!

[@amendippanesar]

Sounds like an upgrade to the GFC500, although it won't be cheap, might be it. Any other options?

[@WingsOverTO]

Sadly that is the only modern option certified for my plane. I could try to find something a bit older but doesn’t seem worth it.

[@amendippanesar]

@@WingsOverTO Understood

[@Cess08van]

Why wait to do tomorrow what you can do today! Single pilot workload, and you’re not content with current install. Go with the GFC500 for your conscious sake.

[@WingsOverTO]

It would be great to do that. I just wish it wasn't so bloody expensive!