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STEC 30A oscillating; 1/2 standard rate turns


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I'm close to purchasing a nice 65 M20E. I took it for a test flight with an instructor today (the owner lost his medical) and when we engaged the STEC 30 AP with Alt hold, it didn't perform as I expected. In wing leveler mode, it would rock left and right every 20 seconds or so. In heading mode it would only turn at half standard rate. What's the range, as far as repair/service cost, I should expect to get it fixed? 

Any advice is very appreciated. 

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I'm close to purchasing a nice 65 M20E. I took it for a test flight with an instructor today (the owner lost his medical) and when we engaged the STEC 30 AP with Alt hold, it didn't perform as I expected. In wing leveler mode, it would rock left and right every 20 seconds or so. In heading mode it would only turn at half standard rate. What's the range, as far as repair/service cost, I should expect to get it fixed? 

Any advice is very appreciated. 

You'll need to call a shop and find out what the going yellow tag cost is these days. At one point it was around $1,500 for a computer box to be repaired and tagged. I think the employees bought out the company and I am sure they have a new price structure.

You might be dealing with a servo issue as well. Did you run through the STEC pre-flight check procedure? Will verify the AP is operating correctly. Here is a link to the manual, starts around page 20. http://bayareaaeroclub.org/b2/wp-content/uploads/manual-501ER-SYSTEM30autopilot.pdf

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While I cannot answer what it will cost to get it fixed, If the owner/ owners' avionics shop were to run the servo motor's in both directions for a minute and clean the armatures, the rocking will stop. This is a fix given to me a number of years ago by Stec. He will need to make up a sub min. D connector to plug a 12 v. source into. I cannot remember what the pinout is, but I believe I posted an STEC install manual here a while back that would have it.

 

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1 hour ago, mike_elliott said:

While I cannot answer what it will cost to get it fixed, If the owner/ owners' avionics shop were to run the servo motor's in both directions for a minute and clean the armatures, the rocking will stop. This is a fix given to me a number of years ago by Stec. He will need to make up a sub min. D connector to plug a 12 v. source into. I cannot remember what the pinout is, but I believe I posted an STEC install manual here a while back that would have it.

 

Get this done first... you'll have to disconnect the push rod from the roll servo in the wing, and then hook up a variable voltage power supply to the D-sub test harness and exercise the servo in both directions.  This helped mine recently.

If that fails, I'd try calling Autopilots Central in Tulsa as they have developed their own in-house repair specs/procedures and can do a lot of work much cheaper than STEC will charge.  

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Thank you very much. I will share the recommendations with the current owner and see if he is willing to get it done by the local avionics shop. I hope that fixes it, because otherwise it's a very nice plane. 

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  • 3 weeks later...

My STEC 30 w/Alt Hold also only does half standard rate turns in HDG mode (hooked up to King HSI 525 heading bug).  I have GPSS and it will do full STD rate turns when following the GPSS turns at waypoints.  No idea why HDG mode only does half.  I chalked it up to an internal setting or unknown gremlins and moved on because everything else works fine and I don't want to mess with it.

The rocking back and forth would concern me though, mine is rock solid on altitude and heading / track.

You have an MSC right there in Portland (Troutdale) - recommend a thorough pre-buy of the E model.  And then you can give me a recommendation on their shop too!  I just moved to Spokane and was thinking of taking mine to the Troutdale MSC for annual this summer.

Rags

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Advanced Aviation did my fuel tanks.  Greg was great to work with.  Work Completed on time as promised. As Greg and I were doing the paperwork, his guys were pulling the interior to get started. I would highly recommend them.  Greg took me to Portland airport and picked me up for connections to the airlines.

 

Ron

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