AP Panel Trim Problems

[MD11AV8R]

I just upgraded my panel to dual Skyview HDX displays (7" & 10") with the knob panel and the Autopilot control Panel. On my first flight with this new setup I did the ground checks of the trim and all seemed to work ok, but when I flew my first flight, on liftoff I encountered full nose up trim and trim not responding to the electric trim inputs. As you might guess I had my hands full horsing the beast around the traffic pattern to get it on the ground.
Back to the avionics shop I went in and described the problem. After checking everything out and ground checking the trim operation I attempted another takeoff and encountered the same problem- full up trim and no response from trim switch in either direction. Once back on the ground I taxied back to the avionics shop-AGAIN, shut down where we once again checked the trim, where it performed flawlessly.
We then decided to check the operation of the trim with the engine running, with one person standing outside to observe the movement while I activated the trim. The plan was for me to activate the trim in both directions, while the outside observer would give me a thumbs up or down to indicate the direction of movement. Initially the trim worked in one direction (up), but would not respond in the opposite direction. Eventually it quit responding altogether.
I returned the AP Controll panel to Dynon for repair, and today checked its operation before and after start before flight, and low and behold, the Trim worked great with the engine shut down, but once again I encountered the same problem as before with the engine running. I found that the way to get around this is to bypass the AP Panel with the trim, but then I do not have the Autotrim function or trim position indication.
My question is whether anyone else has experienced a similar problem, and if so how did they remedy the problem. Could this be a incorrect setting in skyview or do I have a defective AP Panel.
Frustrated in Jacksonville

 

[jakej]

I'd swap over the motor wires to Motor 2, that's a simple check to prove whether you do have a problem with the AP panel.  If it works with motor 2 then you most likely have a defective panel however if you get the same fault then maybe it could be another problem altogether.

 

[MD11AV8R]

Thanks for the reply. I will give that idea a try.

 

[Dynon]

Looking at your SV-AP-PANEL, we didn't find anything wrong here. Since this is a more complex problem, we should do some more in-depth personal troubleshooting with you (ideally via phone). A few thoughts though:

For a few reasons, this sounds a lot like you might have something that - to the system - looks like a stuck trim switch. The fact that it seems tied to engine could point to vibration in either a switch actuation, wiring, or grounding. A higher frequency intermittent tapping of a switch would run the trim similar to how a pressed button would. The module does have timeouts to stop button holds or cumulative time-on-button from continuing to run the trim, but you can still get out of trim before those stop the motor. When you have landed after one of these events, have you noticed whether the trim was at its actual endpoint? Or was it just very deflected?

Also, one other small thing - the trim motor control is entirely separate from trim position sensing circuit (your trim position sensor wire actually goes to entirely different place - the EMS module). So you should be able to bypass the panel from motor control, but retain your trim position indicator.

All of that said, give our support team a call at 425-402-0433 so that we can help you further. Reference your previous RMA number too so that the person you happen to talk to can get up to speed on your case.

 

[Bruno]

Hello Support

Is there a way to wire an Circuit Breaker in the system that could be pulled to disable the trim motor in the event of a Trim Run Away as above..

I'm in the process of installing the same system in my RV-4 and don't wanna play test pilot on the first take off with this system ON..

Thanks

Bruno

 

[dynonsupport]

Yes, as shown in the install manual, trim power comes from pin 9 and this needs current protection. If you disconnect power from this, the trim will not run.

Be aware that this means you will have NO trim control, not just lack of auto trim, so you'll get to fly your first flight with no trim capability. There is no external way to disable just the auto trim, but there is no need to as it will only run if the autopilot is engaged. Just don't turn on the AP on your first flight!

The failure above was caused by wiring issues, not an issue in the trim controller, and would have happened with a relay deck as well, so it's not really a unique failure with our product.

 

[Bruno]

Hello Support

Thank you for the info.

I haven't installed the Trim option ( 15 PIN Connector) yet, just the AP Panel and it is working just fine.

I will make sure to install the current protection when I wired the connector.

Bruno

 

[Johan_S]

Hallo support,
I am busy building a rv 7a and decided on Dynon system.
I also have a problem with the SV-AP-PANEL  (S/N 5757  )
My trim consist of 1 motor on the elevator ,  It is a Ray Allen T3-12-TS.
Since installation this servo would only move when the up pin is grounded (pin 3 or 5)
When the motor is connected as motor 1 (pins 7 & 8 ). No response when grounding
(pin 4 or 6)
I removed the wiring from the up / down switch and installed pins to the 15 pin plug directly.
After reading about the same problem other users experienced, I moved the pins on the 15 pin connector to motor 2. After doing this I found that the motor would only respond to grounding trim right( pin 10 and 12 )  again no reaction from trim left.
Any other advice would be appreciated.
Do you have agents in South Africa ?   
Regards
Johan

 

[Raymo]

Johan,

Make sure you do not have other trim relays in your system. The SV-AP-Panel provides for trim relay.

 

[Johan_S]

Hi Ray,
Thank you for the reply.
Aircraft still under construction, and i did all wiring, so no other relays.
The trim only work in one direction on both motors, i am hoping that it can be solved with one of the buttons on the front of the AP panel ??
Otherwise it must be one leg of the H bridges ??

 

[dynonsupport]

Johan,
It may very well be inside the AP controller, but one thing to try first. Are you sure the trim motor works both ways? The limit switches in the Ray Allen servos can fail in such a way that the servo will only move one way. You can use a 9V battery to move the servo and test very easily.

If that's working, then it likely is the AP panel. That will need to come back to the USA, we don't have repair facilities in SA.

 

[Johan_S]

Hi support,

If I swap polarity at the motor it runs the other way, the position indication on the SV also works well.

Seems like I will have to make a plan to ship it to you.

 

[Johan_S]

Support,

Can you please provide the international dialing code for your
telephone number 4254020433 I tried 01 but will not work.
Thank you

 

[Dynon]

We're in the US, so +1 425 402 0433 is what should work to reach us. I know that there may be some additional numbers that you need to dial to dial internationally from some countries (from the US, we need to prepend 011 before the foreign country code, for example), but other than that I'm not sure what else you would need to do. I know that I've successfully called home using +1 425 402 0433 when we're in Europe though.

 

[dynonsupport]

It might be more convenient to contact Dynon Support vie email. Support@dynonavionics.com.