Autopilot upgrade

[etv100Fly]

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

[Skywalker]

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

[patrolpilot]

Originally Posted by etv100Fly

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 L

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.

[Learjetter]

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

[patrolpilot]

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.

[Learjetter]

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.

[mshac]

Originally Posted by etv100Fly

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

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.

[patrolpilot]

Originally Posted by mshac

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.

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.



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.

[mshac]

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.

[sunnysky]

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.

[GAdams]

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".

[rmorris]

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.

[Jjavitt]

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?

[Galvine]

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

[YankeeClipper]

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.