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D180 Trim Calibration

bobg56

Well Known Member
Hey Guys, I had to send in my D180 to Dynon for a Firmware update and have noticed that my trim indication moves up and down a lot, sometimes it holds steady but mostly not. Dynon tech. support says I need to calibrate the trim system. I have also gone thru the seven pages of Vans D180 presets. I don't know what GP input was chosen before because I'm not the original builder/owner. I did take a photo of where the trim was before I sent the unit off to Dynon. I imagine the GP input can be found by looking at each one...anybody know how to do the calibration?...thanks
 
Yes, I have those pages from the D180 set up...and you say its at GP3, I'll give it a shot...thanks guys!
 
Bob - -

If I understand your issue, when I have had a problem with the indicator moving up and down without input, it has always been the connections at the tail. After 2 or 3 times in 9 years, I soldered them. Solid readings now.
 
If I can't get it to stop after recalibration I'll check that next..all my problems started after getting firmware update to 5.6, I had an auto pilot issue of porposing in pitch with led me to send pitch servo back to Dynon, that's a whole another story in itself... since then I'm having go thru all the initial settings which for the most part have not changed...I have to refigure the K factor for fuel flow and recal the trim, hopefully that will be it...hopefully....this Forum is a God Send!
 
This Forum is a God Send!

Yes, one of the best features of VAF is to help newcomers, especially those that may have bought an already-flying machine and are unfamiliar with the build process.

I bought my 12 from original builder with 48TT. I have over 1100 VAF posts - both asking for help and trying to help others... now mostly trying to help others.

Feels good to give back, or in some cases, pay forward.
 
Well I did the trim recal, no help, the indicator bug keeps on moving up and down the scale...I even reloaded the firmware for the D180, no joy...what I wound up doing is this...previously I had marked the LE of the stabilator to the fuselage when trimmed to T/O with a faired trim tab, I'll use this reference on my preflt. walk around...I have removed the indicator from the D180 because its annoying seeing it constantly in motion...I'm at Firmware Version 5.6 and yes Vans is only at 5.5...there is another story about that...so now everything is at 5.6, D180, AP 74, and Servos, EDC-10A...it seems every update fixes some problems but cause others, this has been making me nuts. Next decent weather I'm getting out to fly it, I had auto pilot issues which now I think are finally fixed, we shall see...
 
I have removed the indicator from the D180 because its annoying seeing it constantly in motion...

Suppose you land full stop and taxi back for takeoff... How will you know trim tab position????

bobg56 - You have 10 posts here in VAF and maybe short on RV-12 experience. Are you sure you want to remove trim tab indicator from D-180 screen?
 
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I'd rather not remove the trim indicator but its about useless, the bug keeps riding up and down...In the past when it worked I'd set it for T/O then I'd had to trim nose up on climb out a bit, then after landing I'd have to trim nose down to get it back to T/O, these were not huge changes. That's the thing with these firmware updates, it seems you keep trading off one problem for another which can be seen by the amount of versions they have for the D180 and I'm sure the Skyview has plenty as well. When I called Dynon about it they told me to do the recal. ..I guess I'll call them on Monday to see what else I can do. I don't think its loose wiring since this showed up right after up grading firmware.
 
Suppose you land full stop and taxi back for takeoff... How will you know trim tab position????
Hold the trim DOWN button for 5 seconds. That's what I do, since my trim indication is also highly erratic and essentially useless.
bobg56 - You have 10 posts here in VAF and maybe short on RV-12 experience. Are you sure you want to remove trim tab indicator from D-180 screen? Seems a little short-sighted...
I also would strongly encourage bobg56 to find and fix the actual root cause of the problem, not just ignore or deal with it. I know, I know, practice what you preach, right? I do plan to track down and fix my actual problem when the weather and my schedule permits. In the mean time, it's not a show-stopping issue. Our takeoff trim indicator has never been "right" since I bought the plane, to be honest, so I've always just used a five-count of down trim after landing to set it. However, since it's now pretty much completely busted, it's time to re-check and re-seat wiring, check connections, re-calibrate and see if we can't actually fix it.

And bobg56 -- it may be that loading new firmware was the cause of the issue. If I were in your position and it started acting up right after a firmware upgrade, I'd go back to the Van's supplied firmware first. There may be a reason they stuck with a specific version, and this may be it.
 
Hold the trim DOWN button for 5 seconds. That's what I do, since my trim indication is also highly erratic and essentially useless.

What if someday you get distracted, or rushed, and accidentally hold the trim UP button for 5 seconds by mistake???? Big ooops...

Very best thing is to fix root cause of all problems when they occur and ground the airplane as not airworthy until fixed.

You might want to read about this accident....http://www.vansairforce.com/community/showthread.php?t=97774
 
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That's the thing with these firmware updates, it seems you keep trading off one problem for another which can be seen by the amount of versions they have for the D180 and I'm sure the Skyview has plenty as well.

Bob --

I don't agree with your assessment of your trim display situation. Being an avid daily reader here on the forums for the last 7 years, I can't remember reading about a D180 software revision causing flaky trim display indications. However, I have read numerous posts where intermittent trim displays have ultimately been attributed to a wiring/connector issue and in a few instances the trim servo unit itself. Although I have a SkyView, I can honestly say I have not seen a Dynon software revision for the SkyView cause any major disruptions in the SkyView's functionality .... in fact, it has been just the opposite.

I have to agree with Jim on this one, removing the trim indication from the D180 display and not looking into the root cause of the problem is not the solution, nor in the best interest of safety ... which we should all be striving for.

Suggest beginning your trouble shooting by either looking at the connector on the back of the D180 or looking first at the tail cone which is easier to access ... so I would start there.

The trim wiring connections at the tail cone have been notorious for developing issues like the ones you mention or the trim motor not moving. (As a side note, the newer RV-12's use a different (much better) connector at this location which you can retrofit to if you find this location to be the culprit). Have somebody GENTLY move the wires around a little while you monitor the D180 and see if the display locks up nice and solid and then can be made flaky by moving the wire(s) at the connector at the tail cone. You may want to actually verify solid voltages at the trim motor side of the connector at the tail cone since it is really easy to do so. The white/blue wire should have a solid 5 volts measured to ground (this voltage comes from the D180 so if it is not rock solid follow the wiring back to the D180). The white/green wire is the actual trim position sense wire and the voltage on it will vary from a low voltage to close to 5 volts depending on the position of the trim motor ... however, the voltage should be constant when the trim motor is not moving. Operating the trim motor will change the voltage higher or lower depending on direction of motor movement ... but when stopped, the voltage should be rock solid. The white/orange wire is ground, to check that, switch the meter to the ohms scale you should read a very low resistance to air-frame ground. If the 5 volts on the white/blue wire is found to be solid but the there is an issue with bouncing voltages on the white/green wire (on the trim motor side of the connector) the trim motor assembly is your culprit (or a bad crimp on the pin for the white/green wire). If all the above checkouts OK, check the white/green wire on the tail cone side of the connector ... if the voltages are bouncing around the pins at the connector are the issue.

If the connector in the tail cone checks out OK, I would suggest removing the connector from the back of the D180 and check to make sure the pins associated with power to the trim unit and the position signal on GP3 are tight in the connector with no corrosion and don't easily push back if a little pressure is placed on them. Obviously this connector needed to be removed to send your D180 in for the upgrade so this connector would be the next best place to look for your trim issue. If removing, checking and reinserting the connector does not fix your issue and the 5 volts was rock solid at the tail cone, I would remove the connector's shell and have somebody slowly move the associated trim wire EMS-37/23 and see if there is any change on your display. Take a voltage reading from pin EMS-37/23 to ground. Whatever the voltage reading is, it should be rock solid ... then move the trim motor up or down ... as the motor moves, you will see the voltage on this pin change wherever you stop the motor the voltage on this pin should remain steady. If it is not, you have a bad connector pin between the tail cone and the D180 connector.

If the voltages on EMS-37/23 & are rock solid at the connector then there is either an issue with the connector on back of the D180 unit or an internal issue inside the D180.

Hope you find the above helpful.

And PLEASE ... don't fly with the trim indicator removed from your D-180 display. Because, even though you may know how to get around the trim display issue, that doesn't mean at some point in the future somebody else may need to fly your airplane and unknowingly become another NTSB statistic.

Good luck with your troubleshooting.
 
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Personal attacks such as calling someone "short-sighted" is in violation of posting rule number 7. Please delete that from your posts above.

Done... however, I'm entitled to my opinion. Safety should never be short-changed. Never...

Look at Lion Air Flight 610. Problem with pitch trim on flight prior to accident. Aircraft not airworthy on previous flight...
 
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Hey John, thanks for all that good info for T/S the trim problem. I'll get on it asap...the trim motor itself works without issues. I will follow your recommendations, also I'll call Dynon again. The reason I'm at 5.6 instead of 5.5 is that I had a bad auto pilot servo I sent to Dynon, they fixed it and sent it back with it at 5.6...I was not aware of Vans locking out the updates at 5.5 ...I updated the auto pilot system to 5.6 and had to send the D180 to Dynon to have it unlocked and brought to 5.6 because you can't lower the firmware back down, only up. This would have me removing my servos and AP74 to send back to Dynon. We (Dynon and myself) figured it would be best just to send in the D180...so now everything is at 5.6 and my trim indication is erratic...the D180 plug suggestion is the first thing I'll look at since maybe a pin got pushed back during removal/re installation...I thank all of you guys for your help...I've been an A&P for 40 years and I'm still learning things, especially when it comes to Experimental's, quite a bit different than my old C-170.
 
What if someday you get distracted, or rushed, and accidentally hold the trim UP button for 5 seconds by mistake???? Big ooops...
And not that big of a deal. The stick works quite well to control pitch while you correct the trim. Even if said trim is severely out of whack when you take off. You've never once in your life missed setting takeoff trim?
Very best thing is to fix root cause of all problems when they occur and ground the airplane as not airworthy until fixed.

You might want to read about this accident....http://www.vansairforce.com/community/showthread.php?t=97774
I did, and after ten pages I still saw nothing relevant to this discussion.

If there is a defect that presents a safety issue, I'll ground the airplane until it's fixed. A wonky RV-12 trim indicator does not, to me, cross that threshold. If it does for you, then great... you're more than welcome to do as you see fit. My trim indicator works occasionally, but it's not stable or reliable, so until I have some time and suitable weather to tear into things in our hangar, my co-owner and I are both well aware of its state, and fly accordingly.
 
The most likely problem is a bad connection as John G posted. If all of the connections seem to be good, then a 5K potentiometer could be substituted for the Ray Allen pot. Doing that will help to determine if the fault is wiring or inside of pitch trim servo.
 
What did you set your K Factor to btw ? I am in phase 1 testing and my fuel flow is waaaaaaay out !
 
You've never once in your life missed setting takeoff trim?

Haven't yet (knock on aluminum). Prior to the buying my RV-12 I owned and flew a J3-Cub for 23 years. Elevator trim (actually horiz stab incidence) is totally worthless on a Cub. Anytime you see a Cub on the ground, or in the air, the stab is trimmed full up. If you ever loose the up elevator cable on a Cub you're going to auger in - stab trim will not maintain a glide with/without power.

So now I'm flying a real airplane with full-functioning elevator trim and wing flaps to boot. I use a pre-takeoff checklist to remember to check these two items that I have not had the pleasure of using for all these years...
 
Haven't yet (knock on aluminum). Prior to the buying my RV-12 I owned and flew a J3-Cub for 23 years. Elevator trim (actually horiz stab incidence) is totally worthless on a Cub. Anytime you see a Cub on the ground, or in the air, the stab is trimmed full up. If you ever loose the up elevator cable on a Cub you're going to auger in - stab trim will not maintain a glide with/without power.

So now I'm flying a real airplane with full-functioning elevator trim and wing flaps to boot. I use a pre-takeoff checklist to remember to check these two items that I have not had the pleasure of using for all these years...
I use a pre-takeoff checklist as well... but nobody's perfect. Certainly not me. Anyway, I have taken off with trim set for landing. It takes about a second to realize what's going on and push, then (sheepishly, even if you're alone) reach for the trim switch and take the pressure off the stick.
 
Problem solved, it was a wire in the tail cone that was loose at the wire block...it was the excitation wire. Re secured it and tie wrapped the wires securely. The thing that gets me is that I was certain it was the update that did it since it worked fine before, some coincidence, now I'm going to go dance in the street to celebrate, I flew for about 1.5 hours today and everything was ship shape...nice!
 
Bob-

Sweet! Glad it was an easy fix and you are back to normal.

Those "legacy" connectors at the tail cone have been notorious for creating unwanted trim motor problems.

As previously mentioned, Van's has a much better connector available ... and a bracket to hold it, if I remember correctly.

If you begin having issues again and don't want to go the new connector route, you could always use male and female pins for a DB connector and place heat shrink over the pins after they are connected together.

Happy flying,
 
The "legacy" trim connectors were spades. The servo wires are very small gauge and the spades are made for bigger wire so it was difficult to get a good crimp. This is the first place to check when there are trim servo problems and you have these connectors.
i-jnzTVJL-L.jpg


There has since been two revisions to the connectors. The first revision provided for a Molex connector and the servo tray was revised to provide a slot for mounting the Molex. I believe this servo tray is compatible with the original servo.
i-3B4BLm6-L.png

i-hPzBMZQ-L.png

The Molex also has issues with being able to properly crimp the small wires to the Molex pins. The Molex connector has since been dropped.

The current revision (I think current) has a 9 pin D-sub for the connector. The D-sub pins can be better crimped to the small wires. Another servo tray is used now with a slot for the D-sub and this tray is not compatible with the earlier servo since there is also a newer version of the trim servo.
i-pBkVQjN-L.png

If you are wondering why I researched all this it's because I also have the legacy connectors and have periodically had connection issues with them. I would like to change them out to something better. I am thinking the best option is to solder the wires as JB suggests in an earlier post in this thread. Or as John suggests just use a 9-pin D-sub and wire tie it in place on your original servo tray. After preparing the D-sub wires and pins and checking function the plans call for sealing the back of the connectors with RTV.
 
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What was used on mine is a connector block, looks like something the phone company uses...I'm thinking I'll solder them then shrink wrap the connections....all I did for now was reconnect the loose wire and checked all the others by tightening the screws of the connector block and securing with tie wrap....I thank everyone who helped out with your suggestions !
 
The "legacy" trim connectors were spades..

Tony -

Thanks for setting the record straight regarding the trim motor's electrical connection revision history. I had forgotten that spade connectors were used on the very early RV-12's. My Bad.

My RV-12 has the Molex micro-fit connector ... so far no issues ... however, I did have the proper dies in my crimping tool for the micro pins. That said, at the first hint of trouble, I will switch over to D-sub pins.
 
Why even have a connector that can be unplugged? The trim servo is not something that is frequently removed, if ever. If it is ever replaced, an unpluggable connector is not any help because the wires on the new servo will require terminals to be attached. I soldered the wires together on my plane. The splices are hidden inside of the cushion clamp where they are well supported.
 
Thanks Joe - -

That is what I stated back on post #5. Never a problem again. Can cut or unsolder them if needed at some point. A pain when the indicator is moving around.
 
Why even have a connector that can be unplugged? The trim servo is not something that is frequently removed, if ever. If it is ever replaced, an unpluggable connector is not any help because the wires on the new servo will require terminals to be attached. I soldered the wires together on my plane. The splices are hidden inside of the cushion clamp where they are well supported.

Understanding the reason requires thinking about the certified nature of the RV-12, and some of the design requirements that go along with that.

The design, and plans (KAI) are in the context of a certified airplane that will be maintained by someone (A&P, Light Sport Repairman, etc.) that did not build it.
The service history of the trim servo is very good so replacement is a low probability, but airplanes also get damaged or require disassembly for a S.B. installation, etc.
In that type of situation, having a connector that assures proper operation after reassembly by someone that may not be super familiar with the RV-12 is just good engineering from a safety standpoint.
 
A lot of guys with "bigger" RV's don't use electrical connectors at the wing root. Wires for landing/nav lights, etc. are run into the fuselage and terminated full length. They figure the wings will never be removed...
 
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