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RV12/Skyview trim

Pat Stewart

Well Known Member
On the 12 there is an elevator trim switch marked Up and down. When you push down the trim tab goes down, when you push up the tab goes up. I called Dynon and they said that is correct. i thought my harness was backwards so I fixed it until today when another builder ask me to look at his and it did the same thing.

My view is the trim button should drive the tab up when the down button is pushed meaning that down stands for pitch down and up stands for pitch up.
 
Should be opposite - -

The trim tab should operate the opposite of what the trim switch says. Up - down, down - up.
 
Agree however mine did not and now another 12 in my area did not so I called Dynon. They said down is down travel. Just curious if others had this issue.
 
Your post is a bit confusing...
You wrote that you called Dynon, and that you fixed it.

Does that mean it initially went down when you pushed up, and went up when you pushed down but you changed it because of what Dynon said?
If that is the case then you fixed it to be wrong.

If you use the PAP document to inspect the airplane prior to first flight it will lead you through the process of confirming that it is correct but what John said is right. Dynon told you wrong.
 
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I reversed the wiring on mine before my first flight thinking it was wired backwards. After seeing it again today I called Dynon. I know there wrong I just was curious about the wiring issue and if anyone else with a 12 has noticed this.
 
I reversed the wiring on mine before my first flight thinking it was wired backwards. After seeing it again today I called Dynon. I know there wrong I just was curious about the wiring issue and if anyone else with a 12 has noticed this.

Still not clear.... which way did it go when you thought it was backwards?
 
Mel's POST Mel is a DAR who knows the rules.
When down trim is pressed, the trim tab goes up. That makes the rear of the elevator go down which makes the tail go up, which makes the nose of the aircraft pitch down. Did I say that right?
 
I reversed the wiring on mine before my first flight thinking it was wired backwards. After seeing it again today I called Dynon. I know there wrong I just was curious about the wiring issue and if anyone else with a 12 has noticed this.

The only wiring issue that will occur is when the harness connections are made by the builder.

The trim servo has two white wires for the motor, so when they are connected to the harness at the back of the airplane there is no way to know which way the motor will go when up or down is selected on the switch.

Because of this, there is a procedure for checking the travel direction when the trim servo cable pins are inserted into the harness connector (I don't remember the Section or page)
If the travel is found reverse later on, then this procedure must have been skipped.

Regardless, if a builder will use the PAP to complete the final inspection, it will help them catch the error and correct it.
 
The only wiring issue that will occur is when the harness connections are made by the builder.

The trim servo has two white wires for the motor, so when they are connected to the harness at the back of the airplane there is no way to know which way the motor will go when up or down is selected on the switch.

Because of this, there is a procedure for checking the travel direction when the trim servo cable pins are inserted into the harness connector (I don't remember the Section or page)
If the travel is found reverse later on, then this procedure must have been skipped.

Regardless, if a builder will use the PAP to complete the final inspection, it will help them catch the error and correct it.

I think there is an error in the initial instructions of how to set the wires coming from the tailcone (using the cordless drill battery) which is later corrected in the PAP inspections. It seems a lot of builders end up having to reverse the two white wires to get the trim tab to travel in the correct direction.

Either that or we are using backwards cordless drill batteries!
 
I think there is an error in the initial instructions of how to set the wires coming from the tailcone (using the cordless drill battery) which is later corrected in the PAP inspections. It seems a lot of builders end up having to reverse the two white wires to get the trim tab to travel in the correct direction.

Either that or we are using backwards cordless drill batteries!

Thanks John.
That is the first I have heard of that... I will look into it.
 
I think there is an error in the initial instructions of how to set the wires coming from the tailcone (using the cordless drill battery) which is later corrected in the PAP inspections. It seems a lot of builders end up having to reverse the two white wires to get the trim tab to travel in the correct direction.

Either that or we are using backwards cordless drill batteries!

Thanks John.
That is the first I have heard of that... I will look into it.
 
Thanks, that's what I was looking for. We followed the instructions and new immediately that it was wrong, we just wanted to hear if anyone else had the problem. It was then made more complicated when Dynon tried to tell us that the down button meant the tab went down and up meant up. We are multi aircraft experienced builders and know how a trim tab works. Just curious if others ended up with the same issue.
 
Thanks, that's what I was looking for. We followed the instructions and new immediately that it was wrong, we just wanted to hear if anyone else had the problem. It was then made more complicated when Dynon tried to tell us that the down button meant the tab went down and up meant up. We are multi aircraft experienced builders and know how a trim tab works. Just curious if others ended up with the same issue.

I don't have the plans handy, but I did a video of the trim tab in operation on a working RV12 and then later the PAP covers it in detail....

The two white wires that you bring up from the trim motor into the wiring harness in the avionics section might have to be reversed.

Follow the PAP guidelines, and if your trim tab is moving the wrong way from what the PAP says, then you need to pull and reverse those two white wires.

There is also a fairly extensive paper with pics I think that comes in your final docs that covers setting the trim tab for the initial settings in Skyview - I found them to be accurate and have not had to do any adjustments since.

Additionally if you install the knob kit addition to the avionics package, there is an additional set up that needs to be done for the auto trim and I only had to do it one time and it works fine.
 
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Thanks John.
That is the first I have heard of that... I will look into it.

Hey it could always be builder error too....imagine that! I just noticed a lot of posts and blogs where folks had to reverse them white wires as they were finishing the PAP....so maybe....by that time you are so close to finish line you just shrug your shoulders and move on.
 
That's NOT a trim tab

It's an anti-servo tab on a stabilator and I believe it works backward. I'll check next week at the hangar.

Wayne 120241
 
It's an anti-servo tab on a stabilator and I believe it works backward. I'll check next week at the hangar.

Wayne 120241

It is an anti-servo tab and a trim tab (otherwise it would not need to be adjustable with a motor).

As mentioned and confirmed previously, when you push for nose up trim on the switch, the AST should move down, and vise-versa for nose down.
 
Scott, have you had a chance to confirm that the intstructions in Section 31B-04 are accurate?

We finally got a chance to check, and confirmed that DWG 31B-04 is not correct.

Step 2 should say..... Insert the wire labeled "Tab Up" into the 37-pin D-sub Pin 32. Then insert the remaining wire into Pin 31.

EDIT
The above is valid for an RV-12 that does not have a SV knobs module or G3X with autopilot module (either of which also has control of pitch trim)
These cases are still being investigated.
 
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Thanks Scott. I am glad to hear you are investigating those panels with AP control knobs. But it seems that if the AP is off and the pilot elects to use the Trim UP/Down switch on the switch panel, that the wiring at pin 31 and 32 would still have to be correct to obtain proper movement of the Trim Tab.
 
We finally got a chance to check, and confirmed that DWG 31B-04 is not correct.

Step 2 should say..... Insert the wire labeled "Tab Up" into the 37-pin D-sub Pin 32. Then insert the remaining wire into Pin 31.

EDIT
The above is valid for an RV-12 that does not have a SV knobs module or G3X with autopilot module (either of which also has control of pitch trim)
These cases are still being investigated.

I had to reverse the wires when doing the PAP checks, set up the trim for t/o, etc....later I followed the install wiring instructions for the a/p and knob panels and didn't have any problems, the airplane auto-trims fine and manually trims fine as well FWIW.
 
Ran into this also. Swapped the wires. Works correct now. I have the SV AV knobs and the setup readme eludes the direction is configurable. Haven't had the chance to test it yet since I need the.dfg file.
 
Yes wiring instructions are wrong

Yes , I too discovered there is a trim motor wiring error in the plans. I installed the Dynon AP Panel during the avionics install and wanted to verify the wiring was correct after inserting the trim motor wires into the fuselage connector but prior to closing up the connector .... so I would not need to open up the connector to make changes later.

When installing the Dynon AP Panel I wrote up a detailed report on my construction Blog of the trim motor's wiring error in the plans which can be seen at the following link:

http://www.dogaviation.com/2016/03/wiring-discrepancy-identified-in-trim.html

Happy Building,
 
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trim 31B-04

Scott in post #19, 11-24-2015, you state that it was confirmed that DWG 31B-04 is not correct. I can not find any Van's update under Service Bulletins, Notifications, or Revisions and Changes. Where else can I look for a revision of page 31b-04 and fig.!?
 
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