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G3X autotrim problem

Guilhermepilot

Guilhermepilot

Well Known Member
Hello capt's
My set up is single screen G3X with two garmin servos, pitch and roll, also have a alley electric trim, for some reason, my auto trim never worked (40 hrs by today)
The problems is

At level flight after a couple of minutes, the trim overrun pitch down until a press to dsc. I am flying with auto trim disable. And making corrections as needed via trim button
 
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Guilhermepilot said:
Hello capt's
My set up is single screen G3X with two garmin servos, pitch and roll, also have a alley electric trim, for some reason, my auto trim never worked (40 hrs by today)
The problems is

At level flight after a couple of minutes, the trim overrun pitch down until a press to dsc. I am flying with auto trim disable. And making corrections as needed via trim button
Click to expand...

Hello Guilherme,

We have to agree with Chris that perhaps your pitch trim motor is running in reverse when the autopilot is engaged and auto-trim is enabled.

First, a description of the trim architecture in your aircraft. There are three ways that trim operates.

Servos Powered Down (backup trim mode)
In this dirt simple backup mode a relay closes inside the GSA 28 servo and passes the trim motor wires directly through the servo. The wires connected to input pins 11,12 at the servo are directly connected to output pins 13,14.
​
Servos Powered Up, Autopilot Disengaged
This is the normal mode of operation when the autopilot is disengaged. The trim control inputs on pins 11,12 of the servo are read by the servo microprocessor, and speed scheduling is added by the servo to automatically drive the trim motor and vary the speed of the trim motor (using Pulse Width Modulation) to match the speed scheduling configuration.​
Servos Powered Up, Autopilot Engaged
This is the normal mode of operation when the autopilot is engaged. It is very similar to the previous mode except that the servo ignores the inputs and drives the trim motor based on out-of-trim torque sensing that it does on its own.​

Here is a simplified version of the steps explained in the G3X Installation Manual to configure/test your trim installation.

  1. Power off the servos.
  2. Use aircraft trim switches to run the trim motor. If the trim motor runs in the wrong direction, swap the trim motor wires at the control stick, at the servo on pins 11,12 (switch inputs), at the servo on pins 13,14 (trim motor drive wires), or at the trim motor itself.
  3. Verify that the trim now runs in the correct direction with the servos powered off.
  4. Apply power to the servos.
  5. Use the on screen controls on the servo configuration page to drive the trim motor for that servo.
  6. If trim motor runs in the wrong direction, change the trim motor direction setting on that page from Normal to Reverse (or Reverse to Normal if it is presently Reversed).
  7. Re-verify that the trim operates correctly in both the servo powered on and servo powered off conditions.

Let us know if you have questions.

Thanks,
Steve
 
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