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Stabiltor trim not working

T

Twinotter79

I'm New Here
Hello everyone,

This is my first post on VAF. I am just about to finish building an RV-12iS. The airplane has not flown, and I'm having an issue with the Stabilator trim not working. I have the Garmin G3X IFR package with Autopilot.

I have completed Safety Directive SD-0001 and have the new servo installed. The trim worked fine about a week ago, but now I can't get it to run in either direction from the trim switches on the sticks. Everything else on the electrical system seems to work fine.

Here are the actions I've taken to troubleshoot the problem:

1) The trim fuse is intact
2) The ships battery voltage is good at 13.5 volts
3) I've disconnected the D-sub connection at the servo, and successfully run the servo off a 12V external battery.
4) I've also run the servo successfully from the WH-P-30 at the D-sub connector at the AV-60000 power module with the external battery.
5) I am getting power to the control sticks, however the trim switches won't work.
6) I've adjusted the trim speed Pot to the full counter-clockwise position.
7) I've checked the tension on the AST actuator bolts and they can be turned by hand.

Reading some of the previous posts these trim issues seem to be an ongoing problem.

What am I missing here?

Thanks, John
 
Hi Bob, actually the way I read it, Counter-clockwise is supposed to be the fastest speed setting. I’ve been told to think about it as turning on a faucet.
 
Try applying power at the 9 pin connector at the base of the sticks. Also, put a meter on the trim pins and see if you get a completed circuit when you toggle the switch.

Could be the AV-6000 is bad.
 
Wouldn't hurt to try turning it fully the other direction.

The trim pathway is:
- Stick trim switches connect to the microcontroller in the AV-60000.
- Motor drive current goes out pins 1 and 2 of the 9-pin pitch trim connector on the AV-60000 to the pitch AP servo.
- The pitch servo routes that current back out its connector to pins 10 and 50 of the 50-pin connector on the AV-60000. (This is how you get auto-trim. The pitch servo is supposed to go into a bypass mode if it doesn't have power.)
- From there, the power goes through the AV-60000 again and back out pins 6 and 9 of the 9-pin connector, where it goes to the trim motor in the tail.

(Source: https://www.vansaircraft.com/wp-content/uploads/2022/10/WH-00134-2.pdf page 8)

What I would probably do is disconnect the 9-pin connector from the AV-60000 and measure pins 1 and 2 while operating the trim switches. If no voltage shows up there, then the AV-60000 itself is suspect, or the wiring from the control sticks to the AV-60000. If you do see voltage, then, find a way to connect pins 1 and 2 while measuring the voltage on pins 6 and 9. If that fails, the wiring to the pitch AP servo is suspect.

(Just some thoughts from reading the schematic. I have a legacy RV-12 so I can't speak from experience.)
 
Don't apply power to any circuit without knowing what voltage is required.
Some circuits require only 5 volts. Other circuits only look for a switch closure.
Applying the wrong voltage can damage expensive avionics.
 
FlyingDiver said:
Try applying power at the 9 pin connector at the base of the sticks. Also, put a meter on the trim pins and see if you get a completed circuit when you toggle the switch.

Could be the AV-6000 is bad.
Click to expand...

Mich48041 said:
Don't apply power to any circuit without knowing what voltage is required.
Some circuits require only 5 volts. Other circuits only look for a switch closure.
Applying the wrong voltage can damage expensive avionics.
Click to expand...

^ ^ ^ ^
Correct
Do not connect power to connections at the sticks.
The stick switches are actually just switching the connections to ground t cause the trim motor circuit to activate and send power to the trim servo motor.
 
Look at the back of the AV6000 for bad solder joints. If questionable, send pictures to Vans. We had a problem that did not surface until the plane flew 3 months ago for the first time. Trim would run away then stick. Other times it was unresponsive. A new board solved the problem.
 
Hello all,

First off, let me say thanks to all who have posted about this rather vexing problem.

UPDATE:
After many hours of checking wiring connections, and finding nothing wrong, I was at a loss as to how to proceed, as I could not get the trim servo to run at all. I felt I had checked everthing, including turning the trim speed adjustment full counter-clockwise and then clockwise several times to no avail. According to the Product Acceptance Procedures I have the trim set to the full counter-clockwise position which is full speed.

I have read many other posts which lead me to suspect the AV-60000.

I reviewed Service Bulletin 19-08-16 which was published on January 10th, 2020, and concerns a recall of the AV-60000 and AV-60009 If certain components are not fully soldered. This recall only concerns AV-60000's produced prior to September 30, 2019. My unit was produced on July 12, 2020, so the recall should not apply. Even so, all indications are pointing to the AV-60000.

As a last ditch effort (and a Hail Mary) I tried the trim again yesterday and lo and behold the TRIM RAN FINE! No issues at all - no intermittent problems - everything normal.

I'm in a quandry. I can't definitively locate the problem, but the AV60000 is highly suspect, and I can't trust that this issue won't reappear. Therefore, I believe the only course I have is to order a new AV-60000 and send the old unit in for testing.

I believe this is the fastest solution to get me in the air.

Thanks again - John Fontaine
 
"According to the Product Acceptance Procedures I have the trim set to the full counter-clockwise position which is full speed.":confused:

If viewing the AV-60000 from the knob side of the module (ref. attached photo), the maximum or full speed position is obtained by turning the blue knob fully clockwise.
 

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