S-TEC 55x software / hardware mod for integration with G1000

[dvk]

We have had multiple issues with our Mooney Ovation 2 GX with S-TEC 55x autopilot for the last two years. Recently, the last symptom is a blank screen after showing the version number (7). Then, no button generates any action, and the display only shows TRIM ^ indicator when operating the electric trim. Previously, we had problems engaging the ALT mode, then FAIL when connecting GPSS, and others.

We are suspecting about the computer, and given that we are in a country where there is no STEC dealer, we are planning to buy a new STEC 55x computer. The question is about the required HARDWARE / SOFTWARE MODs that are required for this setup. We know that the STEC needs to be configured for steering with the KCS 55A protocol, and we know that are current unit has the HARDWARE MOD AP AR AJ and SOFTWARE MOD AE AF.

Do you know if, when looking for a new unit, we must get a computer with all those 5 or more? Or any of those are optional? Is there any documentation on them?

Keep in mind that we don't have access to a dealer to reconfigure the computer.

Thanks in advance!

[Bob Weber]

16 hours ago, dvk said:

We have had multiple issues with our Mooney Ovation 2 GX with S-TEC 55x autopilot for the last two years. Recently, the last symptom is a blank screen after showing the version number (7). Then, no button generates any action, and the display only shows TRIM ^ indicator when operating the electric trim. Previously, we had problems engaging the ALT mode, then FAIL when connecting GPSS, and others.

We are suspecting about the computer, and given that we are in a country where there is no STEC dealer, we are planning to buy a new STEC 55x computer. The question is about the required HARDWARE / SOFTWARE MODs that are required for this setup. We know that the STEC needs to be configured for steering with the KCS 55A protocol, and we know that are current unit has the HARDWARE MOD AP AR AJ and SOFTWARE MOD AE AF.

Do you know if, when looking for a new unit, we must get a computer with all those 5 or more? Or any of those are optional? Is there any documentation on them?

Keep in mind that we don't have access to a dealer to reconfigure the computer.

Thanks in advance!

I've got you covered,  just sent you an email.

[Ragsf15e]

1 hour ago, Bob Weber said:

I've got you covered,  just sent you an email.

Bob, that’s awesome, thanks for helping people out!

[dvk]

An update on our adventures with the S-TEC 55x in our Mooney Ovation 2 GX.

We finally found a technician in our country that has some of the tools needed to diagnose the module.

After 2 long months, they fixed some issues in the main board that had to do with pitch, then overhauled the pitch servo, gave the pitch cable the corresponding tension.

After that, they noted that there was a problem with the trim servo, overhauled it, but after that realized that there was a false contact that damaged the module of the STEC 55x board that controls TRIM. After that fix, the STEC 55x started working almost perfectly.

I say "almost" because we are still seeing some small porpoising (not more than +/- 100 fpm, and not diverging) when in ALT mode and VS. We tried turning off the electric TRIM switch, but it does the same symptom, so it looks it is not related to the TRIM servo, it looks like the pitch servo is lagging behind. Cable tension is fine, but it might be the case that either the internal accelerometer of the STEC is not working well (we understand it is used for small adjustments) or the pitch servo is not starting with small voltaje.

Any other advice or test that we can do?

Thanks a lot in advance!

[Graf_Aviator]

Hi!

How is your elevator trim setting in cruise flight?

I am asking because I had a similar problem. It was caused by an improperly rigged elevator.

In level flight the rudder was actually pitching up so the trim had to compensate with a lot of down pitch.
The trim gauge in the G1000 MFD was almost full down in level flight .

It is solved now, no more porpoising with my Stec55x. Trim is in the middle - And it’s faster too.

Graf


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[Graf_Aviator]

This is how it looked like during level flight. If you zoom in you see the weights at the front “hanging” down, control surface was up.
Now it is perfectly straight.






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[dvk]

As part of these tests, at some point I disconnected the electric trim, and tried with different trim settings. First with what looked like a trimmed setting for level flight, then like one full turn nose up, and then nose down. The behavior of the STEC was the same in all tests.

However, I noticed what you show in the picture about the elevator, and took a picture because I didn't know if that was normal. With the STEC on in ALT mode, the elevator is in a "nose up" attitude, like in your picture. I thought that when trimming nose up that will change, but it didn't.

I'm attaching a picture on the elevator position in the last flight, and the ELEV TRIM setting in the MFD.

 

 

[buddy]

1 hour ago, dvk said:

An update on our adventures with the S-TEC 55x in our Mooney Ovation 2 GX.

We finally found a technician in our country that has some of the tools needed to diagnose the module.

After 2 long months, they fixed some issues in the main board that had to do with pitch, then overhauled the pitch servo, gave the pitch cable the corresponding tension.

After that, they noted that there was a problem with the trim servo, overhauled it, but after that realized that there was a false contact that damaged the module of the STEC 55x board that controls TRIM. After that fix, the STEC 55x started working almost perfectly.

I say "almost" because we are still seeing some small porpoising (not more than +/- 100 fpm, and not diverging) when in ALT mode and VS. We tried turning off the electric TRIM switch, but it does the same symptom, so it looks it is not related to the TRIM servo, it looks like the pitch servo is lagging behind. Cable tension is fine, but it might be the case that either the internal accelerometer of the STEC is not working well (we understand it is used for small adjustments) or the pitch servo is not starting with small voltaje.

Any other advice or test that we can do?

Thanks a lot in advance!

Why is your elevator trim switch in the off position? The elevator trim switch needs to be on.

[Graf_Aviator]

Same as it was with my plane.

Just bend the trailing end of the control surface upwards a little bit.

I used two screw clamps and some pieces of wood to not damage the trailing end of the control surface. Also I used a digital protractor.

In my case it was something like 4 degrees, afterwards it was perfectly flat in level flight.



Basically your plane is aiming upwards the entire time and the trim is counteracting this with a downward pitch. And since the Mooney moves the entire end of the tail cone up and down for trim your control surface is not straight.

Happy to talk to you about this in detail. If you want you can PM me your number.

Graf


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[dvk]

6 minutes ago, buddy said:

Why is your elevator trim switch in the off position? The elevator trim switch needs to be on.

Because I was experimenting with the AP in ALT mode to see if there was a problem with the TRIM servo. I wanted to remove that variable.

[dvk]

11 minutes ago, Graf_Aviator said:

Same as it was with my plane.

Just bend the trailing end of the control surface upwards a little bit.

I used two screw clamps and some pieces of wood to not damage the trailing end of the control surface. Also I used a digital protractor.

In my case it was something like 3 degrees (2.7 to be exact) , afterwards it was perfectly flat in level flight.



Basically your plane is aiming upwards the entire time and the trim is counteracting this with a downward pitch. And since the Mooney moves the entire end of the tail cone up and down for trim your control surface is not straight.

Happy to talk to you about this in detail. If you want you can PM me your number.

Graf


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That's very interesting. And you say that you gained a very knots in cruise and improved the response of the ALT in the AP?

Do you also have an STEC 55x?

Thanks a lot, Graf!

[Graf_Aviator]

I do have an STEC 55x in my 2006 Ovation 2GX

The AP was porpoising like crazy when I had more weight in the back with more backward CG. At that time I was flying full down trim in cruise and there was no room left for the STEC to really adjust properly.

Like I said before now my trim is in the middle again as its supposed to be and the AP is doing a good job again.

It’s easy to try out. Let us know what you were able to accomplish.

Graf


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[dvk]

3 minutes ago, Graf_Aviator said:

I do have an STEC 55x in my 2006 Ovation 2GX

The AP was porpoising like crazy when I had more weight in the back with more backward CG. At that time I was flying full down trim in cruise and there was no room left for the STEC to really adjust properly.

Like I said before now my trim is in the middle again as its supposed to be and the AP is doing a good job again.

It’s easy to try out. Let us know what you were able to accomplish.

Graf


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Thanks a lot Graf for sharing your experience.

[PT20J]

Properly rigged, I believe airplanes with the bob weight (long bodies and the M20K) are in trim with the  elevator slightly trailing edge up. You can tell if you have a bob weight because the elevator will be full trailing edge down when sitting on the ground. Airplanes that have the trim assist bungees sit on the ground with the elevator in trail with the stabilizer if the trim is set to takeoff. M20Js trim in flight with the elevator slightly trailing edge down.