They shouldn't be "disabled" should they?
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G3X: Pitch Trim/Roll trim motor control
- Thread starter LettersFromFlyoverCountry
- Start date
Bob,
You can use a Garmin AP servo as a trim servo. That’s not what you have!
absolutely should be disabled in your RV12. As other people said, this is for when you are using GSA28 servos as trim motors, like in certified installations.
Makes sense
Hey Josh, are we sure about this? I would definitely agree if Bob was asking about "Trim servo LRU enable" which is N/A for our RVs. But the RV-12 has a DC trim motor (Ray Allen) for which "Pitch trim motor control" would want to be enabled. I'm basing some assumptions on the thread title obviously!
Hey Matt,
Fair point! and thanks for giving me the chance to ammend my statement since i know you know the full answer here.
I was assuming that this question was geared towards the LRU configuration page since I get that exact question several times a week. That page should be left with tbe pitch and roll trim motors disabled.
Autotrim absolutely is a feature of the RV12s, so if the question was referencing the option on the Pitch Trim tab to enable control of the motor, then this can be enabled enabling auto trim.
Bob - if this question was directed at the option on the pitch trim tab under the trim configuration page then you can enable this feature. Enabling this will enable autotrim, allowing the autopilot to drive the trim system when the autopilot is engaged. If you do enable this feature PLEASE make sure you hit the test button on that page and check the direction of the auto trim controls. If this is set backwards then you could experience a trim runaway when the autopilot is on.
Hitting the test button will bring up two arrows on the screen. You need to hit the pitch up and down stick buttons on each stick and confirm that the correct corresponding arrow turns blue and that the motor is running the correct direction. If it is not, there will be an option in the trim configurations to reverse the auto trim direction. If you get confused please dont hesitate to reach out to me directly so I can help you!
How well does this actually work on an RV12? In my experience with G3X Touch AFCS most of the time it indicates Trim Up or Trim Down what is needed is a power adjustment not a trim change. I would not want AFCS to control my trim.
If this is in reference to AutoTrim why not? Works great on mine (if you are referencing about Autotrim)
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It works quite well actually when properly configured. The 12 is no different than any other aircraft in this regard. respectfuly, I am afraid you do not understand the dynamics involved here based on your comments.
Perhaps not but I'm willing to learn.
Would you please explain the dynamics involved in the transition from AP engaged cruise flight, to a coupled VS descent, then level off at target altitude.
Please include any trim or power changes required and explain how an auto trim system would react to any error in, and subsequent correct of, required power settings.
The purpose of auto trim is to keep the airplane in trim anytime the AP is engaged. If auto trim is enabled and properly configured and if you leave the AP engaged continuously in cruise, during the descent and at target altitude, the airplane will remain in trim (within a reasonable envelope) the entire time and there will be no trim up or down annunciations. It has nothing to do with power settings (that is 100% up to the pilot in an airplane without auto throttle), the AP servo senses how hard it is needing to continually push on the control surface and adjust the trim accordingly to reduce the continuous force required. While the AP is engaged, if you select a power setting that results in a trim change being required to minimize the force the AP needs to apply to the control surface, then auto trim will try its best to eliminate that force. This is the simple explanation, in reality there is more to the algorithm to keep things smooth.
