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09-03-2018, 04:52 PM
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Join Date: Nov 2005
Location: sck ca
Posts: 64
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trio autopilot pitch issues
I have struggled for several years getting my trio ez pitch system to be usable.Does anyone have a picture or drawings of the pitch servo mount for a trio.It has been suggested thst there is flex in the servo mount causing oscillations and porpoising.FYI factory is very supportive.The roll system is flawless
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09-03-2018, 05:21 PM
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Join Date: Nov 2005
Location: AUSTRALIA
Posts: 749
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This is my experience with the Trio and my RV 9A - don’t know if it is relevant to the RV 8.
Installed as per the plans my Trio pitch servo was over sensitive and prone to oscillations and porpoising. I solved the problems by moving the servo push rod higher up the elevator bellcrank to the point just below where the two halves of the bellcrank widen to accommodate the elevator push rod. This effectively “lowers” the gearing of the servo. You may be able to achieve a similar result by moving the push rod on the servo arm inwards. If you try this make sure you comply with the warnings in the manual about not allowing the servo arm to over center or limit the movement of the elevator.
Fin.
Last edited by Finley Atherton : 09-03-2018 at 05:24 PM.
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09-03-2018, 07:06 PM
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Join Date: Feb 2005
Location: Bay Pines, FL (based @ KCLW)
Posts: 1,955
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Since you said you've been having the issue for several years...
Not sure if you have this issue, but this happened to me.
I purchased a used EZHold3 a few years ago & upon engaging, I had extreme oscillations & propoising. I worked with Trio to correct the issue without success.
Apparently, I had pulled the installation instructions off their website & they had the static & pitot ports reversed. They've since corrected the doc. If you're looking at an old doc you may have downloaded, it may be incorrect.
__________________
Danny "RoadRunner" Landry
Morphed RV7(formally 7A), N20DL, PnP Pilot
1190+ hours
2019 Donation Paid
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09-03-2018, 08:02 PM
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been here awhile
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Join Date: Dec 2004
Location: North Alabama
Posts: 4,301
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Quote:
Originally Posted by pilotdds
I have struggled for several years getting my trio ez pitch system to be usable.Does anyone have a picture or drawings of the pitch servo mount for a trio.It has been suggested thst there is flex in the servo mount causing oscillations and porpoising.FYI factory is very supportive.The roll system is flawless
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The pitch servo should work as well as the roll servo. Don't know if this is applicable to your RV-8 but here are photos of the servo in my RV-6:

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09-03-2018, 09:40 PM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by pilotdds
I have struggled for several years getting my trio ez pitch system to be usable.Does anyone have a picture or drawings of the pitch servo mount for a trio.It has been suggested thst there is flex in the servo mount causing oscillations and porpoising.FYI factory is very supportive.The roll system is flawless
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Does it look like this one? I designed it for them about 12 years ago, but I don't know if they subsequently distributed the drawings to RV-8 builders.
That's a stiffness check in the photo. The dial indicator said deflection was only 0.002" with the servo clutch at the slip point.

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Dan Horton
RV-8 SS
Barrett IO-390
Last edited by DanH : 09-05-2018 at 05:19 AM.
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09-03-2018, 09:41 PM
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Join Date: Feb 2007
Location: San Diego, CA
Posts: 1,670
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You haven't mentioned any attempt to change the gain settings in the software. The autopilot is very customizable using the various gain settings. Have you tried that?
I had to dial the gains down to get my Trio to work the way I wanted it to, especially for the pitch channel in turbulence.
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Pete Hunt, [San Diego] VAF #1069
RV-6, RV-6A, T-6G
ATP, CFII, A&P
2020 Donation+, Gladly Sent
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09-03-2018, 10:20 PM
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Join Date: Nov 2005
Location: sck ca
Posts: 64
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trio pitch issues
Yes I have reset the gain and deadband per the manual and Chucks instructions many times. The control units and the servos have been back to trio for testing and the pitot and static ports on the control unit have been verified and even vented to cabin pressure for one test.It did not seem to make a difference. Dan, Your mount looks very rigid how does the trio perform for you?I note your servo arm is mounted in the upright position .Thanks for the input.What was the thickness of the mount?
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09-03-2018, 11:13 PM
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Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,797
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I have a Trio Pro in a -10, and it is rock-solid. If you want to fly over to LVK I can pull the aft bulkhead off and you can see how mine is mounted.
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09-04-2018, 03:56 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by pilotdds
Dan, Your mount looks very rigid how does the trio perform for you?I note your servo arm is mounted in the upright position .Thanks for the input.What was the thickness of the mount?
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Flown it 800 hours now.
I can't locate the drawing on my hard drive.
No need to guess about mount stiffness; the check is easy. Set up a measurement device. Engage the servo. Pull the stick until the clutch slips. Read the measurement.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
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09-04-2018, 05:17 AM
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Join Date: Nov 2011
Location: Amelia, Va
Posts: 268
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Pitch
I have had this problem since I put in the Pro Pilot about 4 years ago. Tried everything. Trio says my RV-7A may be out of CG but is is not. They said to try to put 30 pounds in the front passenger side near the rudder pedals just to see. I did and no difference. I checked my install of the servo and it is correct.
I'm used to it by now. Kinda get a slight rock up and down on a CC flight.
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