337 autopilots

[Roger]

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.

[tropical]

Originally Posted by Roger

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.

[skymstr02]

Originally Posted by Roger

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.

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

[Rick Gardner]

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

[Roger]

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..

[Rick Gardner]

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!

[SteveG]

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.

[Rick Gardner]

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.