altitude encoder

[bd32322]

I have a very big suspicion that my altitude encoder is going. This is because the stec 30 alt altitude hold quit holding altitude although the servos are working. ATC showed me in a fast climb and then a descent, when I was nice and level. The garmin 430 sometimes says altitude input lost.

 

When I look at encoders in aircraft spruce, I see a box with one output (RS-232?) and probably one pneumatic input from the static source. Will that work in my case where 3 things are using the altitude information - namely transponder, gps, alt hold?

 

Can I just buy the cheapest encoder that is on the site there as long as it is TSOd?

This is the one I am looking a:

http://www.aircraft-spruce.com/catalog/avpages/amerikingencoder.php

 

Thanks

[N601RX]

Some things use serial input and others use parallel input. Some encoders output both. Anytime the encoder is replaced you also have to redo your 2 year cert.

[bd32322]

Thanks - I will check with whats on board.

My 2 year cert is coming up anyway - so its timely

[OR75]

the S-Tec 30 altitude hold should work independantly.

The "altitude" hold is actually a "pressure altitude" hold that the s-tec 30 gets from the pressure transducer.

 

 

 

As far as looking at what the encoder is seeing and what it is sending to the 430 (and if it is working or not), you can check the "pressure altitude" by going to the last page in the navigation mode. you may have to go in the setup so that it appears based on your default settings. If it is too different from what your altimeter setting is .... then your encoder is kaput or the wiring is acting.

 

My gut feel if it is a solid state type of encoder, it is likely the wiring. the GNS430 / transponder  / encoder are all wire connected    

[Rwsavory]

Stec 30 uses a pressure transducer for altitude hold, not the encoder. We had a similar issue with mode c, and it was determined to be the transponder. I would have your avionics shop look things over.

[Hank]

My 430 started showing altitude input lost; my G327 transponder would also show strange pressure altitude [often "0000"; sometimes -1000, or 22000 or some other random number]. ATC would tell me that my mode C was lost. then it would come back on.

 

Took her to the shop, surprise, the encoder was bad. Buy another one that matches your requirements, the guys in the shop will have several recommendations.

[N601RX]

I used a trans-cal encoder, but I was putting in a new system and selected it for size and the fact that it supported both serial and parallel output.  If your replacing a current encoder the cheapest option will be to use the same one that you already have so it is just a plug in replacement.

 

http://www.trans-cal.com/

[Mike A]

I had the pressure transducer for a Stec 30 go out on my cherokee. It would be chugging along then go to the down limit on the servos. Scared the heck out of me a couple times. If you look at it, it's a pretty cheap looking plastic piece. I'd check there for your autopilot problems.

[bd32322]

I had the pressure transducer for a Stec 30 go out on my cherokee. It would be chugging along then go to the down limit on the servos. Scared the heck out of me a couple times. If you look at it, it's a pretty cheap looking plastic piece. I'd check there for your autopilot problems.

Surprisingly that has never happened to me, which originally led me to believe the servos had quit, but the servos check out fine on the ground. Meaning, i engage alt hold and feel yoke pressure when moving the yoke forwards or backwards.

Its hard to tell whether the alt hold is really working because I have to trim before engaging it. And then it mostly maintains altitude probably because the aircraft is in trim, but then it starts drifting to more than 100 feet off commanded altitude and then I am sure it was never doing anything