January 27, 2020

Autopilot Servos Arrived

I received my Garmin GSA 28 servos on Saturday, so I’ll focus on some tasks this week related to the servos: making the pushrods, pinning and building the electrical connectors, and then installation of the servos. In reading about these servos, I learned a few things that I’m really happy about:

  • These servos can automatically control the elevator and aileron trim servos (so yes I’ll be connecting them to do that!), in addition to allowing manual control via a hat switch on the joystick grips
  • While the autopilot system will normally be fully-controlled by the G3X, this autopilot system can alternately be controlled by just a G5 backup PFD and a GMC 507 autopilot control panel, providing some redundancy
  • These servos use a brushless motor and a solenoid-activated engagement clutch, so when they’re disengaged they are virtually frictionless. This is a better/safer design (in my opinion) than competitive designs that use stepper motors and/or shear pins – in case of fault, you just pull power and the servo disconnects, period.
Block diagram showing a basic autopilot system using just the G5 PFD and and GMC 507 control panel
Inside of a GSA 28 autopilot servo

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