I’m puzzled about the behavior of a Garmin GAD27 feeding roll trim information to a Ray Allen trim motor through a GSA28 roll servo. I find that I need to either cross wires compared to the Garmin documentation or tell the G3X Touch that the switch direction is reversed (although it is not) to make things work. I am curious to hear from others if you noticed the same thing, and of course to learn if I overlooked something.
The wiring has been done (and checked) to be exactly as suggested in the documentation. The “Roll Trim Switch Direction” is set to “Normal” and the “Roll Trim Motor Direction” is set to “Normal”.
In this setup, the pilot hat switch is connected to the GAD27 (1st connection), which sends power on two wires to the GSA28 servo (2nd connection). The servo then sends power to the Ray Allen trim motor (3rd connection).
1/ The pilot hat switch is connected to the GAD27. When I press the hat switch to the left, under “Configuration/System Information/ECS (GAD27)”, I see “Pilot Left”, as expected. Indeed, I checked that the “hat left switch” grounds Pin 28 (PILOT ROLL TRIM L) of the GAD27. So far, so good… but the plane rolls right. The problem must be somewhere else.
2/ When I press the hat switch to the left, under “Configuration/System Information/ROLL (GSA28)”, I see “Trim Input Roll Right”. Ha! I must have crossed wires from the GAD 27 to the roll servo. Well, after checking visually (wires of different colors, checked the wing root connector too), I can’t see any problem. I confirmed that with an Ohm meter, pins and a long test wire. Pin 9 (ROLL TRIM OUT 1) of the GAD27 is indeed connected to Pin 11 (TRIM IN 1) of the roll servo, and the return wire is wired according to Garmin documentation as well. Note that if I cross wires here compared to the Garmin documentation, all is well.
3/ As for the connection from the roll servo and the trim motor, when I press the “Roll Left” on-screen button under “Configuration/Trim/Roll Trim/Roll Trim Motor Movement/Test”, the plane rolls left. To me, this means that the wiring between roll servo and roll trim motor is correct.
To see if I had an internally mis-wired servo, I replaced it with the Garmin “GSA28 removal adaptor” which simply passes trim signals through. Same behavior, so the servo is not the problem. To see if I had an internally mis-wired GAD27, I borrowed another one. Same behavior! I also made sure that I did not swap ROLL TRIM POWER IN and Ground on the GAD27. As for my pitch trim, all is well.
G3Xpert kindly reviewed my schematics and loaded my configuration into their kiosk, and could not find any issue with either. They were not aware of the behavior reported here, hence my post.
The wiring has been done (and checked) to be exactly as suggested in the documentation. The “Roll Trim Switch Direction” is set to “Normal” and the “Roll Trim Motor Direction” is set to “Normal”.
In this setup, the pilot hat switch is connected to the GAD27 (1st connection), which sends power on two wires to the GSA28 servo (2nd connection). The servo then sends power to the Ray Allen trim motor (3rd connection).
1/ The pilot hat switch is connected to the GAD27. When I press the hat switch to the left, under “Configuration/System Information/ECS (GAD27)”, I see “Pilot Left”, as expected. Indeed, I checked that the “hat left switch” grounds Pin 28 (PILOT ROLL TRIM L) of the GAD27. So far, so good… but the plane rolls right. The problem must be somewhere else.
2/ When I press the hat switch to the left, under “Configuration/System Information/ROLL (GSA28)”, I see “Trim Input Roll Right”. Ha! I must have crossed wires from the GAD 27 to the roll servo. Well, after checking visually (wires of different colors, checked the wing root connector too), I can’t see any problem. I confirmed that with an Ohm meter, pins and a long test wire. Pin 9 (ROLL TRIM OUT 1) of the GAD27 is indeed connected to Pin 11 (TRIM IN 1) of the roll servo, and the return wire is wired according to Garmin documentation as well. Note that if I cross wires here compared to the Garmin documentation, all is well.
3/ As for the connection from the roll servo and the trim motor, when I press the “Roll Left” on-screen button under “Configuration/Trim/Roll Trim/Roll Trim Motor Movement/Test”, the plane rolls left. To me, this means that the wiring between roll servo and roll trim motor is correct.
To see if I had an internally mis-wired servo, I replaced it with the Garmin “GSA28 removal adaptor” which simply passes trim signals through. Same behavior, so the servo is not the problem. To see if I had an internally mis-wired GAD27, I borrowed another one. Same behavior! I also made sure that I did not swap ROLL TRIM POWER IN and Ground on the GAD27. As for my pitch trim, all is well.
G3Xpert kindly reviewed my schematics and loaded my configuration into their kiosk, and could not find any issue with either. They were not aware of the behavior reported here, hence my post.