Autopilot issues- S-Tec 30 Alt

[The-sky-captain]

The last couple of flights, while in GPS mode, the plane tracks about 10 degrees to the right. Last flight it "warmed up" and started working after about 1.5 hours. Today was a short flight of an hour or so and never worked correctly. The heading bug and altitude hold works fine. I've had the AP for over 6 years and have never had any issues with it. I have not had any recent maintenance done on the plane that would have affected anything. It worked on a 3 hour trip, last weekend, just fine and was kooky the next day. Any ideas of where to start the troubleshooting? Thx!

[Ron McBride]

When my S-tec 30 was new, it would not work well when cold.  I had to send it back and they rebuilt it.

 

Ron

[Marauder]

The problem sounds electronic in nature. My guess is the roll computer.

[The-sky-captain]

Well, well, well.... It worked fine from the get go on the trip back. I'll dig into it at annual and see what we come up with. I don't think the cold is an issue as it was 70 degrees when I left Louisiana last weekend and I've had it going on 6 winters. Who knows though, if it decides it doesnt like cold weather I guess I'll have to deal with it

[Marauder]

It could be moisture as well as cold. Electronics are funny that way. Condensation on cold metal can lead to issues.

[The-sky-captain]

Interesting, the hangar was VERY humid w lots of condensation on the plane and slab. Something to think about ...

[The-sky-captain]

How could this be addressed? Open up the access panel and warm it up/ air it out on those humid days?

[KSMooniac]

Please keep us updated.  Perhaps putting a big dessicant bag (or bucket) inside your plane while parked in humid conditions might help.

[The-sky-captain]

Good idea Scott!

[Marauder]

You can also use a Golden Rod dehumidifier. The kind found in gun safes. I have them in my cockpit during the winter.

[carusoam]

Desiccant bags work well in a closed / sealed environment...

In an open environment they absorb so much moisture they will be 'used up' in a matter of days...

Their ability to dry air is for small closed volumes.

Fortunately,

What you are trying to achieve is control of relative humidity.

This can be done by removing moisture from the air or increasing the temperature of the air in the plane, or both...

Questions that come to mind...

What's the smallest home dehumidifier available from HD? Put it's drain tube through the bottom of the baggage compartment. It only runs when the humidity in the plane is high...

What's the smallest heater with a fan available from HD? Back when the world was analog, the dad left a light bulb on in his boat to generate heat...

Keep a look out for safety issues. There won't be a prize for lighting a hangar on fire...

Applied chemical engineering!

[carusoam]

http://www.amazon.com/GoldenRod-36-inch-Dehumidifier-7D-36/dp/B005FRG6T2/ref=sr_1_2?s=home-garden&ie=UTF8&qid=1418394171&sr=1-2

Going on the GoldenRod tip above...

Seems to work like the dad's light bulb, but with a touch of safety in mind...

It comes in larger sizes and mentions keeping it under the hood for engine storage...

Handles 500 ft'3. For <100watts...

Rules of thumb...

If the rH gets much above 50% anything that can rust, will. Below 20% is pretty dry. Above 80% there is a risk of rain when the hangar temps drop a few degrees...

A simple low cost rH meter in the plane can give you an idea how much of a challenge you are having and how affective your solution is working. Try that with a window free gun safe!

Best regards,

-a-