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Garmin GSA28 servo auto trim

A

alcladrv

Well Known Member
I'm trying to understand when you still have manual control of the elevator trim directly through the electric trim switch if the appropriate pins on the servo are connected to the servo and to the trim switch.

Does the servo need to have power to it, but not actually have the autopilot engaged to have manual trim control through the trim switch? Or, can the servo be completely unpowered and trim control merely passes through servo via the connected pins?

Thanks,

Mike
 
alcladrv said:
I'm trying to understand when you still have manual control of the elevator trim directly through the electric trim switch if the appropriate pins on the servo are connected to the servo and to the trim switch.

Does the servo need to have power to it, but not actually have the autopilot engaged to have manual trim control through the trim switch? Or, can the servo be completely unpowered and trim control merely passes through servo via the connected pins?

Thanks,

Mike
Click to expand...

We answered Mike's question offline, but wanted to post here as well in case others were waiting on an answer.

As shown on the drawing on page C-6 in the Rev. K G3X Installation Manual, the servo is installed inline with whatever you would normally use to drive your trim motors.

When the autopilot is engaged, the autopilot immediately takes control and trims up the airplane to zero the forces on the servos and keeps doing this as long as the autopilot is engaged.

When you disconnect the autopilot, you restore manual electric trim, but the servos still drive the trim motors and do speed scheduling per your configuration mode setup.

If you remove power from the servos (not normal) a relay drops, and you can continue to run the trim motors from your trim switch, albeit without speed scheduling.

Thanks,
Steve
 
Thanks for your response, Steve.

Rather than put the plane out of service for the duration of my Garmin autopilot installation, I planned to make steady progress toward the installation in shorter work periods.

I just finished mounting and wiring the GSA28 pitch servo. It will remain unpowered until I get the roll servo installed and the Canbus wire run. The elevator trim switch/servo motor wires now run through the pitch servo as depicted in the G3X installation manual and the trim servo works normally using the trim switch as it did before installing the pitch servo in the mix.

The plane remains airworthy and I'll move on to the roll servo during my next work session.

Mike
 
Trim position display G3X

G3X Team,

I understand how to wire the trim motors, but I'm still confused about displaying the trim indications on the GDU 375.

Below is a diagram from the install manual that shows wiring from a Ray Allen "trim position sensor". Does that mean I need a separate position sensor or is trim position already built into the Ray Allen motor?

I have the standard ray Allen trim motors with 5 wires. Two are for motor power. Are the other 3 wires on the trim motor the wires shown going into pins 18, 19, and 20 for elevator and 21, 22, and 23 for roll trim position? I'm hoping it'll be that easy without having to install a separate position sensor.



Thank You
 
Hi Bob,

The standard Ray Allen trim servos have the position sensor built in and indeed those are the three extra wires you are left with. You should have the secret decoder ring paperwork to help you sort the wire colors but if you don't it's available is here:

http://www.rayallencompany.com/RACmedia/instructionsT2andT3.pdf

You have a 50/50 shot of having the indicator exactly right the first time (just like the motor power wires and their directio), but don't worry because it's easy to change it with the G3X.

Hope that helps!

Cheers,
Stein
 
Good evening Bob,

Stein was slightly quicker on the draw, and he is correct about the GSA 28 and trim wiring.

One important point: since the Ray Allen trim motor wires are both the same color, it is easy to get them reversed. You want to be doubly sure that your trim switch, trim motor, and autopilot servo all have the same idea about which way is up and which way is down, so the pitch trim will run in the correct direction both when the servo is powered on and also when it is powered off (fail-safe mode). Therefore, be sure to closely follow the guidance in section 9.12.1 (servo wiring checkout) of the G3X installation manual.

As for the position sensor wiring, I believe the orange and blue wires on the Ray Allen servo are the power/ground connections, and the green wire is the signal output to the GEA 24 or GSU 73. As long as you hook it up this way, there will be no problems with reverse sensing since you will calibrate the trim position display as part of your post-installation checkout procedure (section 18.3.3).

- Matt
 
Position sensors

Thanks Stein that's what I was hoping was the answer.

About to power up the panel you guys built and I'm expecting the smoke to stay inside. Nice job
Bob
 
Wow

Wow,
An answer from Stein and while I'm thanking him I get an answer from Matt on the G3x team... All within 30 minutes of posting a question late on a Saturday night. I rushing out to buy a lottery ticket...
Thanks guys
 
Glad to help Bob... no charge for interrupting our regular Saturday night card game. ;)

- Matt
 
SteinAir said:
You have a 50/50 shot of having the indicator exactly right the first time (just like the motor power wires and their directio), but don't worry because it's easy to change it with the G3X.

Cheers,
Stein
Click to expand...

I just installed an infinity grip with 3 channel relay deck for a customer, I hooked up Ail/Elev/Flap motors, with a 50/50 chance you would think I might get at least one right.. I had to reverse all 3 :confused:

I don't bother with lotto tickets.
 
why the relay deck

Walt,
Are there Garmin AP servos (GSA 28) in the system you just wired? If so why did you use the relay deck? I plan on running the wires from the infinity grip trim switch direct to the servo. I only have one trim switch so I think I can do this. I'm in the receive and learn mode.......

Thanks
Bob
 
Inverted flight with G3X

I flew a Pitts S2C that had two slip/skid indicators. One for normal flight and one for inverted flight. Because I have both inverted fuel and oil systems, I'm curious how the G3X slip/skid indicator will react while in sustained inverted flight in my RV8. Did the Team X gurus program the slip/skid for inversion therapy? Curious minds want to know!

Thanks
Bob
 
bobmarkert said:
Walt,
Are there Garmin AP servos (GSA 28) in the system you just wired? If so why did you use the relay deck? I plan on running the wires from the infinity grip trim switch direct to the servo. I only have one trim switch so I think I can do this. I'm in the receive and learn mode.......

Thanks
Bob
Click to expand...

No AP servos involved.. but the Infinity needs a relay deck (or home made relay switching solution) to drive the trim/flap motors as the grip only uses single pole/throw switches which won't work to drive a motor both directions.
 
bobmarkert said:
I flew a Pitts S2C that had two slip/skid indicators. One for normal flight and one for inverted flight. Because I have both inverted fuel and oil systems, I'm curious how the G3X slip/skid indicator will react while in sustained inverted flight in my RV8. Did the Team X gurus program the slip/skid for inversion therapy? Curious minds want to know!
Click to expand...

Hello Bob,

Thanks for all your questions. The AHRS in the G3X system uses only aircraft body lateral acceleration to calculate the slip/skid ball position, so it should read correctly even in inverted flight.

- Matt
 
Inverted Flight

Wow! You look at the slip/skid indicator while flying inverted? I don't even look inside when flying inverted! I just hope that I remember to put the Doll's fuel selector on the left tank with the flop tube.
 
I also have the G3x-touch using the GSA 28 AP servo with the Ray Allen trim system. I see this has been discussed a lot however I remain unclear about connecting these up for the elevator function.

At the GSA 28 servo I have 2 green wires from connector position 13 and 14.
I understand these go to the Ray Allen servo motor. This servo has 5 wires:
1) white
2)white
3)orange
4)green
5)blue ...................................so which 2 of these connect to the GSA28??

Second issue: My AP servos connect thru a hub box to remainder of system and the cable bundle for this connection have 4 additional wires that are involved in the Ray Allen hook up.

These are green-white (2 of them) from pins 13 and 14
and orange-white (2 of them) from pins 11 and 12.......................not sure where these go either.

Would appreciate any advice getting this sorted out:confused:, Thanks G
 
simatos said:
I also have the G3x-touch using the GSA 28 AP servo with the Ray Allen trim system. I see this has been discussed a lot however I remain unclear about connecting these up for the elevator function.

At the GSA 28 servo I have 2 green wires from connector position 13 and 14.
I understand these go to the Ray Allen servo motor. This servo has 5 wires:
1) white
2)white
3)orange
4)green
5)blue ...................................so which 2 of these connect to the GSA28??

Second issue: My AP servos connect thru a hub box to remainder of system and the cable bundle for this connection have 4 additional wires that are involved in the Ray Allen hook up.

These are green-white (2 of them) from pins 13 and 14
and orange-white (2 of them) from pins 11 and 12.......................not sure where these go either.

Would appreciate any advice getting this sorted out:confused:, Thanks G
Click to expand...

Hello Gary,

The Ray Allen instructions identify the two white wires as the power/ground wires that drive the trim motor in/out, so these wires will connect to pins 13,14 on your GSA28 servo. If the trim motor runs in reverse when you are using manual electric trim, you can reverse the two white wires on pins 13,14.

Also shown in the Ray Allen instructions are the meaning of the orange, green, and blue wires. These are used to drive the trim motor position input. The orange is power from the GEA 24, green is signal, and blue is ground.

Using the pitch trim as an example, if you refer to page 24-6 in the Rev. P G3X Installation Manual, for the pitch trim position, the orange wire connects to pin 18, the green to pin 19, and the blue to pin 20.

Let us know if you have additional questions.

Thanks,
Steve
 
Steve Thank

Is there a drawing equivalent to the Rev P G3X manual (Page 24-6) in the G3X TOUCH manual??
 
You got to love Garmin Support / Team X guys, they are working even while eating Turkey :D
 
simatos said:
Steve Thank

Is there a drawing equivalent to the Rev P G3X manual (Page 24-6) in the G3X TOUCH manual??
Click to expand...

Hello Gary,

There is a single installation manual for both G3X and G3X Touch systems, and this the the Rev. P G3X Installation Manual.

The drawing on page 24-6 illustrates how to interface the Ray Allen trim position sensors to the GEA 24 which is used on both systems.

Thanks,
Steve
 
Steve,
OK that's great Im with the program, Thanks for your speedy reply. Getting close to flashing up the system, Cheers and happy holiday
Gary
 
So here?s my (not so bright) questions. Do I:
1 Branch off the two pitch trim motor wires as they pass by the pitch servo and connect to the servo then continue on to the trim switch?
2 Branch off the three wires at the trim position indicator, at the instrument panel, and connect them to GEA 24?
 
Dan,
If you mean branch off the way I think you do then NO.
1-The trim power goes to the servo then the servo powers the trim motor.
This way the servo can control speed of trim.
2- You will not need a separate trim indicator in the panel as the G3X will provide that indication on the PFD so the three indicator wires go directly to the GEA.
 
Think of the servo as being a closed relay and the trim works off a switch like usual. However the servo can break in and reduce the speed of trim, limit the time of trim and auto trim for the autopilot.
 
ka6dan & MarkW sorry to drop into the middle of your conversation, but I think I was where you were last week ka6dan and now you are asking how to wire in the MANUAL trim switch, is that correct?? If you look above, the Garmin folks describe the trim INDICATION hook up, the SERVO (GSA28) to trim motor hook up and like you the only thing we now need is where to wire the MANUAL trim switch. That is one thing I am also still unclear on. Perhaps Steve with Garmin may pipe in on the way to go with this. Thanks G
 
simatos said:
ka6dan & MarkW sorry to drop into the middle of your conversation, but I think I was where you were last week ka6dan and now you are asking how to wire in the MANUAL trim switch, is that correct?? If you look above, the Garmin folks describe the trim INDICATION hook up, the SERVO (GSA28) to trim motor hook up and like you the only thing we now need is where to wire the MANUAL trim switch. That is one thing I am also still unclear on. Perhaps Steve with Garmin may pipe in on the way to go with this. Thanks G
Click to expand...

Hello Gary,

Step 1: Start with a fully functioning manual electric trim system with trim switch, relay(as needed), and trim motor.

Step 2: Break into the 2 wires going to the trim motor and connect the two wires coming from the switch side to pins 11,12 on the GSA 28 servo.

Step 3: Connect the two wires going to the trim motor to pins 13,14 of the GSA 28 servo.

Auto-trim wiring installation complete.

Page 21-7 of the Rev. P G3X Installation manual includes diagrams that illustrate single and dual switch installations much better than we can here in words alone.

Please let us know if you still have questions.

Thanks,
Steve
 
GSA 28 pitch problems

Using the G3X non touch, GSA 28 autopilot I'm experiencing aggressive pitch up, and pitch down response when engaging the A/P. The G3X is telling me to trim down, then trim up so it's not holding any altitude much less climbing to a set altitude. When testing it on the ground the G3X toggle moves the control stick "pitch up" when I toggle it downward and vice versa, is that normal? If not, maybe it's "reversed" and needs to be changed. I did not build this 7 and don't know how it was wired but can go into the G3X menu to change settings. Any suggestions? Settings? Thanks! Mike
 
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