337 autopilots
 

I have a '65 337 that has never had an autopilot. I thought I could use a Century 2000 but the STC doesn't cover '65 or '66 years. How about a recommendation. Would like approach capable, LOC and G/S.

Others know far more than me about this, but by way of guidance you should know that the original auto pilot consisted of electronics and controls on the console, more electronics on the top of the cabin, plus servos and mechanisms on one of the booms (and I think the wings). So my first reaction is that incorporating an autopilot to an aircraft that has never had one may be costly. Perhaps aftermarket autopilots can be installed for less and more knowledgeable people will jump in here and advise you.

Ernie

I have an S-Tec 60-2 in my '77 and it works well...if ya dont mind a little porpoiseing at cruise. I think they run about $10k off the shelf.,,,,installation is, of course, the big bugger.

But BEWARE of the temptation of "affordable" autopilots available on ebay, etc.

I have read in many MANY articles that S-TEC will not support ANY autopilot other than that for which it was purchased NEW. It doesnt matter if you want to install a yellow-tagged autopilot in the same year, and model, S-TEC wont have anything to do with it once it is removed from the aircraft in which it was originally installed.

As always, I could be wrong....it's been known to happen.

But I've read it in a number of independant, "reputable" resources.

Caveat Emptor!!!

Cole

I've heard that before about S-tec. They tend not to hold a steady altitude. Is there a reason for that and are the original autopilots better at altitude hold and tracking course?

Karl

STEC Autopilot
 

I have an STEC 55X in our 76 model and it reallly does not work well at all. I have spent thousands to have the computer, transducer etc. sent to STEC. We had a King KAP140 in out Cessna206 and it worked really well. Now, I am not trying to promote one versus the other but my impression after having both is that the STEC does very poorly capturing laterally and vertically. As usual, the avionics shop says it the autopilot, STEC says its the installation and I say......

Now STEC admits there may be an issue wih the servos and that there is a procedure to clean out the servos.....

Anyone else have this issue?

The only problem I have with my plane is my piece of crap stec 60-2. It is like riding a porpoise at cruise, plus I can't get my altitude pre-select to capture any input data. I typically don't use altitude hold. It works great on the Bug, needle and GPS tracking (GPSS Roll Stearing) and if trimmed corrrectly the plane itself holds altitude, bit the minuite I click on Altitude Hold it start to porpoise. Any help would be appreciated.

Sounds like you have moisture in the static line to the autopilot computer. Dry that out and the problem will go away.

Is the bridle cable tension on the pitch servo tight enough? Sometimes low cable tension will create the porpose effect.

Autopilot
 

Static lines checked, servo motor removed and set to factory torque settings, rigging checked for proper tensions.

My IA advised me to try flying the autopilot with the interior standby static open. I flew first with it closed and the 60-2 hunted 100' +/-, then I closed it and after re-establishing a set altitude, it tracked +/- 20'. Much, much better. So I guess the problem is in the static system, water, etc..

Autopilot
 

OK Thanks, that's a new one. I will try it tomorrow. We are in Cabo San Lucas right now headed fo Puerto Vallarta tomorrow morning and then back to Cancun so there are plenty of miles to try it out (or to continue cursing under my breath about STEC).
Thanks!

I'm quite surprised to read of so many unhappy S-Tec users. I have the older Model 50 and it holds heading and altitude +/- virtually nothing. Occasionally, in turbulence, you'll want to "help" it dampen the initial jolt but it then recovers nicely. I have never seen any tendency to porpoise or hunt. My only negative comment would be that its approach mode is insufficiently sensitive to accurately track a localizer, wandering +/- a half dot or so. I just fly the approach on the heading bug with no problem so it's not any real concern. Assuming the guts of the system are essentially the same across the differing models being discussed, I would have to conclude that precision problems are installation problems or rigging problems based on my experience with the make.

Autopilot
 

Actually m problem is both vertical and lateral. If you set it on HDG mode to intercept an airway it reacts like a drunken sailor. It will blow thorugh it, turn back, go through it again while at the same time porpoising +/- 100 feet. When you do a vertical speed climb to intercept a pre-set altitude it does the same thing, blows through and then begins its usual porpoising. Why go to Disney when you can treat the wife and kids to the same excitement while in the air.....

I have spent thousands of dollars trying to get it fixed. Although I am not a huge King fan, the KAP 140 worked lije it was on rails vertically and laterally. Excelent intecepting ability in both dimensions.

I will try the ALT static to see if that helps the vertical performance.

Back in the goold ole days (when my plane could fly) I found that I could stop the cruise porpoising if I turned off the electric trim.

I would say that perhaps it was a computer interface problem between the old STEC 60-2 and the new Garmin G-500....but I was porpoising before I upgraded.

I hold lateral course flawlessly with great cross wind compensation.

I have an ancient analog altitude pre-select....by that I mean that I have individual verticle mechanical dials that I use to input Baro, desired altitude, and desired verticle rate. Its primitive, but it works very well.

My only other nag is GS Intercept. In my bird, when I set it to intercept the glide slope I expect to hear a klaxon horn followed by an announcement over my intercom to "Dive! Dive! Dive!" cuz she immidiately pushes forward about 15 degrees nose down. :eek:

Fortunately, my thumb never strays too far from my Autopilot Disconnect button when I am below 3k

I have no doubt that my issues are some adjustment that needs tweaking.

But for now...I have other priorities.
Cole

I hope by the time I purchase one for my Skymaster, the problem will be determined. Considering the amount of the purchase and to have installed, I think I should be able to at least track a course and hold altitude in smooth air. I can understand if the porpose problem existed in turbulent air.

Karl