My TruTrak autopilot has been flawless since I first put it in. However, it lacked certain integration with my GRT EFIS that kept me wanting a little more. No fault of TruTrak - it just knows how to talk RS232 to get GPS Track/course and ARINC.
GRT Had a "Notkosh" special on their AP servos that I took advantage of. They slave directly to my EFIS, and controlled directly from it. That means there should never be any discrepancy between what I tell my EFIS to do and my autopilot follows. The GRT servos are almost identical to the TruTrak servos, with the exception, of course, of the control head and the wiring.
Well, there are some physical differences. There are three screws on the roll servo that interfere with the TruTrak bracket. GRT has it's own bracket to deal with this, but I didn't buy it. So...solution B is to.....
Yup, take out the screw, re-bend the safety wire and make the hole free and clear for the bracket to attach to.
Voila, my solution.
Installed and safetied. Can you believe I thought this autopilot install could be done in a night? I am on night two now.
I will say the wiring is MUCH simpler. GRT uses a single RS232 port on their PFD to talk to both servos. They require an engage/disengage button wired to each servo individually, or both together (not covered in any documentation).
The pitch servo was simpler to install due to much better access.
Boom! Look at that professional safety wiring.
I needed to do some soldering of wires and running new wires to port 4 of the PDF. I must of done something right because as soon as I configured the EFIS's for the GRT AP Servos and turned them on, the input counter started counting up!
Here are the DEFAULT settings of the AP. I am still working on the setting that work for my setup.
Lower half of the defaults. Always good to know where you started at so you can get back there! Tonight I did a quick 0.5 flight to test it out. The GRT servos worked GREAT! I am very happy with so far, the AP seemed to work great right out of the gate.
I was definitely fooling myself thinking I could install this in a night. Sure, same servo dimensions, less wiring, how much work could it be? Well you know what they say about assumptions - it makes an ass out of you...and you! (me is you in this case!)
Last Modified: January 10, 2021