Autopilot upgrade
 

Hell members! Anyone installed a new autopilot in there plane with a current STC? I see a lot of units available but no STC. Looks like either going rouge or nothing. Thoughts? Thanks Capt Leo:cool:

Hi
I have in my 1979 .P337 H model, N88TN .Stec 55 X with STC and its coupled with G-500 And GTN 750/650 and working great and fly Flawless ILS/RNAV approaches
Dennis

Does your airplane currently have an autopilot?

I mention this because the airplane I just bought has the Cessna 400A and I was impressed with its performance. There have only been two previous owners of this '77 airplane. The fellow I bought it from, the second owner, said the AP was not working very well when he purchased it, so he took it to Autopilot Central in Tulsa. A few days later it was as good as new. He suggested that I schedule a stop there every two years as he as done, for a tuneup and tweaking. Given the performance on my journey home, I think I will take that advice as it worked as well as the brand new airplane I flew in '77.

Waiting for the recent tropical weather to clear across my flight path, I filled out the Garmin GFC-500 STC Interest and Canidate Aircraft Application forms. I just assumed it wouldn't work that well as every seller I had talked to lead the subject "About the autopilot,..." Seems, I might have jumped the gun.

Another idea for “upgrade”?
 

Question for the gurus:
My 337G model has a 400A (Af530) installed. Has anyone installed the 400B (AF550), say as removed from a Cessna 210, in a 337?

I’ve got 400A manual, would anyone have a 400B manual available so my shop technicians can compare the wiring diagrams, part numbers for servos, etc for compatibility?

-LJ

Look in the AFM Equipment list and see if the "B" was offered. Another source would be Autopilots Central just NE of you. The boss man told me that the B would outfly the STEC 55 as it uses torque motors for control input, very smooth.

My equipment list shows all manner of 400 options, but no 400B. Back to the idea of getting DER approval to interface Garmin to 400A.

I have an STEC 60-2 with electric trim that works pretty good, but I know they cost too much to buy new and install.

LOTS of options if you're willing to "go rogue"!!!

Speaking of "going rogue" there is an Aztec near me that had dual Dynon Experimental glass panels and engine monitors installed. It looks great and according to the owner, works great as well. He makes no attempt to hide it, and the planes been flying like this for almost eight years now. YMMV.

You can install an experimental A/P or otherwise non-approved but expect to spend a lot of time as a "test pilot" tweaking all the settings. And when you go to sell the plane, it could be an issue. But hey, its only time and money, right? ;)

If you want to stay legal AND stick to a budget, why not buy a complete system from one of the guys on here parting out 337's then send it to Autopilots Central for OH? My guess is your cost would be a fraction of buying a new certified AP.

skymaster autopilots again
 

Hello All.
Im a little confused. Skywalker posts he has an Stec 55 installed with an STC ?
As far as i'm aware, there is still no STC for the upgrade of a 337 autopilot??
For the last 38 years I have owned GBFGH, a Skymaster G model.
Its got the Navomatic 400A installed which has worked brilliantly over the years.
However, now, im having issues and nobody in Europe seems able to repair it.
( for years Pete Sommers helped me , but sadly is no longer with us )
Im certainly prepared to spend the money to fit an up to date unit .
So are all these guys you read about fitting new autopilots to Skymastes doing so illegally.

I think that would be the case if the 400A was in great condition. In that the airplane is being parted, that is probably not.

There are only two STC'd autopilots (current), both GeneSys (STEC). The GeneSys online STC list breaks them down. It is a large document. I've attached the pages that cover the Skymaster. The 336 is not addressed at all. The STC list was updated on 7/21/22; there were no changes to the C337 listings.

Here are the systems for the G, my airplane, and the prices. GeneSys has not updated the prices yet; they are for 2021.

Attachment 2728

The systems listed are all rate-based autopilots, and altitude preselects are unavailable. I've spoken with GeneSys and three shops, and they all have suggested the same; the 55X or 60PSS end up about the same. There are some small differences but talk to your installer.

When adding trim, "AP" is for the autopilot only. Adding it to the aircraft is the additional "AC" amount. The shops recommend removing the Cessna trim, if you have it, and going with the GeneSys trim. I agree, as if the control yoke button fails, that alone is $1K if you can find it.

All three shops were upfront with me, saying to remember these are not digital autopilot, and they will not be as smooth as a 400A that has been maintained. These are from customer comments. They also expected labor to be the same as the base equipment charge. APC suggested the 55X with both aircraft and autopilot trim, but given my 400A, I continue to maintain it as long as possible because I would not get a return on the installation given the age of the airplane. Once it goes out, it becomes a financial decision, and we each have different considerations.

My only comment is that Altitude Preselect IS available because I have it with my 60-2. The ST360 digital altitude and vertical speed preselect panel adds both capabilities.

55x
 

I am installing a 55X in my 1969 D model without the electric trim. My airplane doesn't have electric trim now and I think I can move the trim wheel when the annunciation says I must. I have dual Aspen's with the autopilot interface so allegedly I will get Altitude pre-select. I am removing the 300 autopilot. One of the criteria for installing the 55X was certain brackets must be in the aircraft to support the new servos. As it turns out the Cessna 300/400 series autopilots used the bracket that's required. You can call Cessna and they will confirm you have the proper bracket in your airplane which was factory installed. For those of you with STOL airplanes S-Tec has an issue with how to mount the servos. It can be done and has been done with more than a few using the S-Tec 65. I don't know about the 55X and STOL wings modification. It might be a Robertson STOL thing. I don't know for sure. Bottom line is there will be no digital autopilot with an STC from most any manufacturer for the 337. If you are going Rogue look at the paperwork for the Century autopilots. They are STC'd for every Skymaster model but the 337D. You do see them on eBay once in awhile and those good old boys will overhaul them and give you an STC for a reasonable price. I didn't go that way simple because the STC didn't apply to the D model and they wouldn't add it. "To much work fussing with the FAA".

Gi275?
 

Here an interesting twist... the Navomatic 400 requires the origin vacuum based AI. So, when I installed my dual G5s, I kept all the vacuum stuff and moved old AI over on panel. But I think the GI275 can emulate the output from that vacuum AI...

Shame we can't get a low cost a/p like TruTrak or Trio, like the single engine guys.

Is there a group of 227 owners lobbying STEC for a 3100 upgrade path?
 

Now that we are in a place where no new replacement parts exist for STEC 60's and 65's, the only path forward seems to be an STC to upgrade to the Garmin 3100.

Is there a group of owners currently engaged with Garmin on this?

We heard last spring that Garmin has announced they are going forward with the STC for the GFC 600 Autopilot for the Skymaster.
We haven’t heard much since.

So I have reached out to both STEC and Garmin to learn more.

STEC told me they have no plans to get the STEC 3100 series digital AP approved for the Skymaster.
.
Garmin however did say they are going to pursue the GFC 600 AP for the Skymaster.
They told me it was scheduled to begin in 2026.

That’s great news. It’s an awesome autopilot: digital, envelope protection, Level button etc.
I feel it’s a real safety feature. I have added my name to the list as a buyer.

That’s what I know at this point.

Greg

Tune in next week when our heroes hear an entirely different story from exactly the same sources...

All quasi humor aside, thank you for looking into this. I've contacted them both as well several times and while I do get a different story each time, it does seem that progress marches slowly slowly forward. At least for Garmin. STEC has been saying for quite some time now that they are just not interested. For what it's worth I'm not that interested in them either, so the feeling is mutual.

Anyway, back to Garmin, it does seem as though the path the progress involves constant nagging. It might be my turn again in 6 months.

Anyone heard any updates? Would be a pity if these aircraft were relegated to VFR or light IFR.

I also haven’t heard anymore.

I do need an AP upgrade

Either STEC 55X now or keep waiting

Greg

Just got off the phone with Garmin.

They are currently in S/W dev for the Skymaster. No physical implementation yet. Once they get to the H/W stage they estimate about 1-2 years what with further R&D and FAA to get through.

I asked if they would usually see an actual product materialize (eventually) once they've gotten to the development phase they are currently in. He said that unless they just can't make it work right or the FAA won't cooperate it usually does materialize. Given that other aftermarket APs have, I see no reason why Garmin couldn't. They have multiple products which operate at multiple levels of servo size/strength.

Thanks for calling
I was sure hoping ready for installation in 2026. Looks like exactly that, wishful Thinking

Might be a little wishful, perhaps. I'm also wishful that it will be less than an STEC 55x, especially since they weren't making any more parts for it last I spoke with those folks. It might even be discontinued at this point.

There was talk a while back about deposits for 3100s, but if that has been certified for our planes Genesys is awful coy about it.

Fingers crossed for the 600. Would have preferred attitude-based, but who knows--maybe the newer software will resolve that. And having one fewer point of failure isn't a bad thing. Could possibly lose the vacuum pump at that point ... I think.

Thanks for the calls to Garmin. I went by every autopilot booth at Oshkosh this last '24 summer. Tried to not say anything here for fear of perpetuating rumors. But I'll speak up anyway.

Nil results across the board except:

1) STEC would take a deposit for the 55x at the show and energetically said it still was in production. They feel there is 5 more years of life left in the product and weren't planning on cancellation anytime soon. 3100, no go.

2) Garmin acknowledged interest in 337 airframe. Used the phrase "it's in the sandbox" (whatever that means). However they were more focused on airframes that could generate higher revenue/higher numbers. In particular, at the time, alot of focus on beefing up the citation fleet. On a positive note however, it is their plan to eventually get the GFC certified across all GA models and are committed to "full" GA buildout eventually.

Trio was a little intrigued in 337 airframe due to inline thrust. Also, a lean towards "orphan airframes" (Gruman AA-5, Cessna 190). They volunteered that some of what is going on is that FAA was more liberal about mathematical modeling and reporting from manufacturers as well as grouping similar airframes together to expedite the "new equipment to market" process....until the whole Boeing debacle. Now they have pumped the brakes.

So, fork in the road. Grab 55x now. Or hope for GFC and that nothing de-rails approval for 337. I'm still undecided....er, hopeful.

Autopilot upgrade vs GTN exchange for Xi’s
 

I am in the midst of getting some panel updates. Going from a single Aspen Legacy 1000 PFD to 2000 Max PFD/MFD wtih two AV-30’s for backup AI’s to pull vacuum gauges. Current AP is an S-Tec 65 with a remote annunciator and remote ST 361 controller. It works very well with the Aspen and a pair of GTN 650’s. Garmin still has some incentives to exchange the two 650’s for new platform 650Xi’s. Anyone flown with both and how much better is the Xi platform than the original? I do not plan to sell this airplane and probably have at best, 13 years of flying left. If I elect to reduce some cost for this year’s work, I can either just upgrade the GTN’s and keep the S-Tec 65, or keep the GTN’s and swap the 65 for a 55X. Anyone have the S-Tec Yaw Damper? I am told it’s not needed for Dutch roll stability on a 337. Which pathway would you consider first, the autopilot or upgrade the GTN’s. Not sure how much better a 55X is than my 65. Disappointing to continue to hear that we are not getting a look from any of the digital manufacturers. Meanwhile, old models with much lower production runs, like the Cessna 303 (only 287 were ever built) are getting STC’s for them. Guess you have to know someone. Just curious to hear some thoughts. Thx

Keep in mind that Genesys keeps threatening to stop supporting the 55x. Two years ago when Covid-related supply chains were stirring up panic (and prices) they said (by phone anyway) that they were going to stop making new parts for it.

As for the 650xi--never heard of it but pretty sure it isn't on the radar for Garmin to add to their AML. They recently stated that they're currently working on the software, and would likely implement (once the bugs are squashed) as a GFC 600. That would be nice as I think it's an attitude-based platform.

Autopilot upgrade vs GTN upgrade
 

Thanks. All the components of my S-Tex 65 work on the 55X so I only need the main control box. They’re not super pricey for certified used units. I was just wondering if it was even worth the hassle/expense of swapping. The same with the Garmin nav setup. I currently have two GTN 650’s but wonder if I should exchange them for 650 Xi’s while they’re still giving a relatively good price to upgrade them? I’m looking to get 10-13 years out of this panel with hard IFR capability and then call it a day. I’m even considering adding an old KN 63a and radar altimeter. We have been told to expect a move to Alaska sometime this year. With the many mountains and frequent low vis on the coast, I want all the relevant upgrades and redundancy I can pack into that thing. Not sure the 55X swap is worth it and not sure the GTN 650 gps to 650 Xi gps is worth it.

I reached out to Garmin again about the GFC 500 AP

They said “no new news, still no sooner than 2026, but we do still plan on covering it… cheers “


FYI

Let’s hope, based on aircraft weight and performance that they actually do with the GFC 600 and not the 500. If they do come through on a solution.