The **GSA 375-R** is a high-performance, compact servo actuator manufactured by **Garmin**. It is primarily used within the Garmin G3X and G3X Touch electronic flight instrument systems (EFIS) for experimental and light sport aircraft to provide autopilot functionality. --- ### 1. Core Electronic Components The GSA 375-R is more than just a motor; it is a "smart" actuator that integrates mechanical power with complex control electronics. | Component | Description | Function | | :--- | :--- | :--- | | **Brushless DC Motor** | High-torque internal motor | Provides the physical force to move flight control surfaces. | | **Microprocessor** | Internal logic controller | Processes commands from the GMC (Autopilot Controller) and manages motor position. | | **Solenoid Clutch** | Electromagnetic engagement | Allows the autopilot to physically disconnect from the controls when disengaged or overridden. | | **CAN Bus Interface** | Digital communication port | The "nervous system" that links the servo to the G3X backbone. | | **Position Sensors** | Internal feedback loop | Constantly monitors the arm position to prevent over-extension or "runaway" scenarios. | --- ### 2. Technical Specifications Understanding the electrical requirements is critical for installation and troubleshooting. * **Voltage Range:** 14V or 28V systems (automatically adjusts). * **Communication Protocol:** Garmin CAN (Controller Area Network) bus. * **Weight:** Approximately 1.6 lbs (0.73 kg), making it ideal for weight-sensitive airframes. * **Torque Output:** Adjustable via software to match the specific airframe’s control resistance. --- ### 3. Key Electronic Features #### A. Smart Engagement (Clutch System) Unlike older servos that use shear pins, the GSA 375-R uses an **electromagnetic clutch**. When the autopilot is OFF, the clutch is de-energized, allowing the pilot to move the controls with zero resistance from the motor. When ON, the clutch locks the motor to the output arm. #### B. Slip Clutch Protection The electronics are programmed to allow a "pilot override." If the pilot manually forces the control stick, the internal slip clutch will give way without damaging the electronic gears or the motor. #### C. Integrated Trim Control The GSA 375-R can often act as a relay for the aircraft's pitch trim. This allows the autopilot to automatically trim the aircraft (Auto-Trim) so that there is no pressure on the stick when the autopilot is disengaged. --- ### 4. Wiring and Connector Layout The unit typically uses a high-density D-sub connector. The pinout generally includes: 1. **Power & Ground:** High current lines for motor operation. 2. **CAN HI/LO:** Data lines for communicating with the GDU (Display) and GSU (ADAHRS). 3. **CWS (Control Wheel Steering):** A discrete input that allows the pilot to temporarily hand-fly without disengaging the autopilot. ---